Tools and Methodologies to Manage Coastal and Marine Environments

**3**

**Chapter 1**

**Abstract**

**1. Introduction**

different orders of magnitude and scales.

natural protection systems.

Coastal Adaptation: Past

*José Simão Antunes do Carmo*

Behaviors, Contemporary

Management, and Future Options

In the recent past, coastal public works solutions were generally designed as engineering problems. By that time, prior to the 1980s, the primary goal of coastal works projects was to maximize safety, taking into account only engineering knowledge and existing economic constraints. Today, concerns are no longer limited to safety; lifestyle and quality of life have become essential ingredients in building a successful coastal works project. Other aspects of the project are also important, such as environmental impact, attractiveness, and sustainability. These additionalcomplexities are further aggravated by other pieces of the puzzle that need to be integrated into the overall design, such as the non-engineering and non-science aspects. A synthesis of recent concerns regarding coastal public works projects has, in fact, become much more difficult for engineers to manage due to new assumptions of value, social acceptance, and sustainability of these projects. In this context, it is common knowledge that decision-making on a coastal issue should be based on criteria such as technical effectiveness, costs, benefits, implementation, and monitoring. This chapter addresses coastal issues using a dual perspective of meeting current needs and ensuring future sustainability. Contemporary adapta-

tion measures and future accommodation options are also discussed.

coastal protection, adaptation strategies, future accommodation

**Keywords:** coastal issues, decision-making processes, public participation,

Coastal zones are interface regions between the mainland and the sea that are dominated by (1) processes that originate in the drainage basins of tributaries, (2) oceanographic and atmospheric processes, and (3) anthropogenic activities at

As recipient bodies, coastal areas not only receive the benefits of proper river basin management, but also suffer from the harm associated with or resulting from inefficient management processes. In particular, low water quality, sediment extraction, and sediment retention in structures implanted in the fluvial systems are the most evident factors that affect the use, natural resources, and activities that may occur in the coastal zones. The small amounts of sediment that flow into coastal areas are a matter of great concern to coastal managers, since this lack of sedimentation results in the disappearance or devaluation of beaches and the weakening of

## **Chapter 1**

## Coastal Adaptation: Past Behaviors, Contemporary Management, and Future Options

*José Simão Antunes do Carmo*

## **Abstract**

In the recent past, coastal public works solutions were generally designed as engineering problems. By that time, prior to the 1980s, the primary goal of coastal works projects was to maximize safety, taking into account only engineering knowledge and existing economic constraints. Today, concerns are no longer limited to safety; lifestyle and quality of life have become essential ingredients in building a successful coastal works project. Other aspects of the project are also important, such as environmental impact, attractiveness, and sustainability. These additionalcomplexities are further aggravated by other pieces of the puzzle that need to be integrated into the overall design, such as the non-engineering and non-science aspects. A synthesis of recent concerns regarding coastal public works projects has, in fact, become much more difficult for engineers to manage due to new assumptions of value, social acceptance, and sustainability of these projects. In this context, it is common knowledge that decision-making on a coastal issue should be based on criteria such as technical effectiveness, costs, benefits, implementation, and monitoring. This chapter addresses coastal issues using a dual perspective of meeting current needs and ensuring future sustainability. Contemporary adaptation measures and future accommodation options are also discussed.

**Keywords:** coastal issues, decision-making processes, public participation, coastal protection, adaptation strategies, future accommodation

## **1. Introduction**

Coastal zones are interface regions between the mainland and the sea that are dominated by (1) processes that originate in the drainage basins of tributaries, (2) oceanographic and atmospheric processes, and (3) anthropogenic activities at different orders of magnitude and scales.

As recipient bodies, coastal areas not only receive the benefits of proper river basin management, but also suffer from the harm associated with or resulting from inefficient management processes. In particular, low water quality, sediment extraction, and sediment retention in structures implanted in the fluvial systems are the most evident factors that affect the use, natural resources, and activities that may occur in the coastal zones. The small amounts of sediment that flow into coastal areas are a matter of great concern to coastal managers, since this lack of sedimentation results in the disappearance or devaluation of beaches and the weakening of natural protection systems.

To take into account these concerns and other concerns resulting from ongoing and future impacts from climate change, managers must approach coastal zones management different than they did in the past. Inadequate management methodologies are still common practices today in many countries that have fewer resources or less concern about global climate change.

We may learn from the past that most defensive measures have been more reactive than proactive. In addition, the intervention procedures in the coastal zones, whether for the purposes of valuation or implementation of protection measures, should be improved.

Until recently, much of the coastal engineering projects were almost exclusively based on experience. As discussed in Kamphuis [1], it was in this context that many of the coastal defense works were carried out and resulted in kilometers of breakwaters, sea walls, and groyne fields for defenses against flooding and urban fronts, recovery of degraded areas, and protection of heritage of great historical and cultural value.

It is common knowledge that hard engineering structures can be effective when properly designed and installed. However, because they are continuously subjected to events that in many cases exceed their design capacity, such structures require adequate and costly maintenance. On the other hand, it is also known that these structures tend to reduce erosion and the risk of flooding in one location, but increasing the risk in another.

Meanwhile, with the evolution of the numerical methods and the computational means, it has become possible to use increasingly sophisticated mathematical models to solve complex coastal engineering problems. The use of ever more powerful, less restrictive and more user-friendly computational models, along with physical modeling, is today a common practice in coastal engineering.

On the other hand, it is of utmost importance to involve interdisciplinary groups that cover different perspectives (such as policy makers, civil and environmental engineers, geologists, biologists, economists, sociologists, lawyers, etc.). These interdisciplinary groups should include local communities and stakeholders at different stages of project development, including design, building, and monitoring.

Indeed, public participation, including stakeholders, is considered as a key principle when planning and implementing conservation projects. The same view is shared by Hedelin et al. [2] and Barceló [3], who clarifies in an Elsevier editorial note *when people are ignored and conservation measures are put in, we see opposition, conflict and often failure. These problems require the best available evidence, and that includes having both natural and social scientists at the table*.

In this context, the guidelines on coastal defenses have changed. Contrary to the coastal defenses built in the past, contemporary adaptation measures include: artificial sand nourishments, possibly with additional sand support measures; building and rehabilitation of dunes; creation and restoration of wetlands; reinforcement or creation of submerged longitudinal bars; submerged breakwaters made of geotextile tubes; buffer zones; and land use restriction and zoning.

Other measures, which are less common, but may become essential in the near future, include: building on pilings; adaptation of drainage systems; building emergency flood shelters; and tidal houses, houseboats, and floating houses.

Reconciling current activities in the coastal zones with the maintenance of healthy ecosystems requires monitoring, systematic evaluation, and implementation of corrective measures. Indeed, it is generally understood and practice has shown that when planned, preventative adaptation will be more cost-effective and efficient in the long run than retroactive measures. Therefore, identifying and addressing needs and gaps in policies and planning will strengthen the adaptive capacity of regions and local communities.

**5**

*Coastal Adaptation: Past Behaviors, Contemporary Management, and Future Options*

In economic terms, coastal zones' natural wealth and the wide diversity of activities taking place make these regions the main source of revenue for many countries. In fact, coastal zones are currently (1) important areas of food production through agriculture, fishing, and aquaculture, (2) the main tourist destinations on all continents, (3) significant sources of mineral resources, including oil and natural gas, (4) foci of industrial development and transport, and (5) abundant reservoirs of

biodiversity and ecosystems, on which the functioning of the planet depends.

well-being of the residents throughout different times of the year.

However, some decreases in attractiveness or decreases in the demand rate have been observed. On one hand, these decreases will contribute to the maintenance and sustainability of coastal ecosystems, but such behavior can also result in socially

In fact, unfavorable circumstances in coastal zones include: (1) large concentrations of people and services in sensitive or risk areas, leading to artificialization of certain stretches; (2) insufficient or inefficient services (housing, security, health, catering, banks, leisure, bathing, etc.) to meet more needs during high-demand seasons; (3) scarcity (in quantity and quality) of water resources in seasons of increased demand and consumption; (4) great specialization of some economic activities, directed to very specific users and in very restricted periods of the year; (5) a poorly designed, non-existent, or very permissive arrangement of spaces with unbridled/abusive and uncontrolled occupations; (6) greater speculation, with uncontrolled costs and often incompatible with the quality of the services provided; (7) numerous situations of stress/confusion incompatible with rest (e.g., physical and mental recovery) that are sought; and (8) of least concern, the interests and

It is indispensable to ensure the availability of the amount and quality of water

The impact of saline intrusion on freshwater aquifers and the penetration of salt water in the estuaries will be substantially aggravated by global warming and the consequent rise in mean sea level. Due to excessive water consumption, coastal aquifers contamination by saltwater intrusion is already a reality in some southern European countries. Portugal is an example, particularly in the southern coastal

To cope with water scarcity in the months of greater tourist influx, in which the population reaches at least three times the resident population, two dams were built in the mid-twentieth century (Arade and Bravura). Subsequently, a third dam was built in the 1980s (Beliche), which was followed by the building of two more dams

The heights of these dams vary between 41 and over 90 m and with maximum

and 13.5 × 107

In addition, high pollutant loads discharged directly into the sea without any treatment or with an inadequate level of treatment contaminate or pollute the sea, thereby excluding these waters from bathing uses and natural resources conservation, with considerable environmental impacts. Often, changes in environmental factors give rise to qualitative changes in established ecosystems (e.g., specific

also suffer the effects of water shortages in the hottest months of the year, which

m3

[4]. However, these dams

in the 1990s (Funcho and Odeleite), and more recently a sixth (Odelouca).

resources needed. However, excessive consumption of water beyond sustainable availability can lead to irreversible degradation. Particularly worrying is the contamination of groundwater due to excess of water consumption from coastal aquifers, leading to exaggerated lowering of groundwater levels and the salinization of these waters. For example, **Figure 1** shows stains of the wells and boreholes that exist in the Algarve coastal zone (southern Portugal) and 17 aquifers (M1, M2,…,

*DOI: http://dx.doi.org/10.5772/intechopen.88123*

unsustainable conditions.

M17) with regional expression [4].

region of the Algarve (**Figure 1**).

storage capacities between 2.7 × 107

composition, biodiversity, etc.).

coincide with periods of higher consumption.

#### *Coastal Adaptation: Past Behaviors, Contemporary Management, and Future Options DOI: http://dx.doi.org/10.5772/intechopen.88123*

In economic terms, coastal zones' natural wealth and the wide diversity of activities taking place make these regions the main source of revenue for many countries. In fact, coastal zones are currently (1) important areas of food production through agriculture, fishing, and aquaculture, (2) the main tourist destinations on all continents, (3) significant sources of mineral resources, including oil and natural gas, (4) foci of industrial development and transport, and (5) abundant reservoirs of biodiversity and ecosystems, on which the functioning of the planet depends.

However, some decreases in attractiveness or decreases in the demand rate have been observed. On one hand, these decreases will contribute to the maintenance and sustainability of coastal ecosystems, but such behavior can also result in socially unsustainable conditions.

In fact, unfavorable circumstances in coastal zones include: (1) large concentrations of people and services in sensitive or risk areas, leading to artificialization of certain stretches; (2) insufficient or inefficient services (housing, security, health, catering, banks, leisure, bathing, etc.) to meet more needs during high-demand seasons; (3) scarcity (in quantity and quality) of water resources in seasons of increased demand and consumption; (4) great specialization of some economic activities, directed to very specific users and in very restricted periods of the year; (5) a poorly designed, non-existent, or very permissive arrangement of spaces with unbridled/abusive and uncontrolled occupations; (6) greater speculation, with uncontrolled costs and often incompatible with the quality of the services provided; (7) numerous situations of stress/confusion incompatible with rest (e.g., physical and mental recovery) that are sought; and (8) of least concern, the interests and well-being of the residents throughout different times of the year.

It is indispensable to ensure the availability of the amount and quality of water resources needed. However, excessive consumption of water beyond sustainable availability can lead to irreversible degradation. Particularly worrying is the contamination of groundwater due to excess of water consumption from coastal aquifers, leading to exaggerated lowering of groundwater levels and the salinization of these waters. For example, **Figure 1** shows stains of the wells and boreholes that exist in the Algarve coastal zone (southern Portugal) and 17 aquifers (M1, M2,…, M17) with regional expression [4].

The impact of saline intrusion on freshwater aquifers and the penetration of salt water in the estuaries will be substantially aggravated by global warming and the consequent rise in mean sea level. Due to excessive water consumption, coastal aquifers contamination by saltwater intrusion is already a reality in some southern European countries. Portugal is an example, particularly in the southern coastal region of the Algarve (**Figure 1**).

To cope with water scarcity in the months of greater tourist influx, in which the population reaches at least three times the resident population, two dams were built in the mid-twentieth century (Arade and Bravura). Subsequently, a third dam was built in the 1980s (Beliche), which was followed by the building of two more dams in the 1990s (Funcho and Odeleite), and more recently a sixth (Odelouca).

The heights of these dams vary between 41 and over 90 m and with maximum storage capacities between 2.7 × 107 and 13.5 × 107 m3 [4]. However, these dams also suffer the effects of water shortages in the hottest months of the year, which coincide with periods of higher consumption.

In addition, high pollutant loads discharged directly into the sea without any treatment or with an inadequate level of treatment contaminate or pollute the sea, thereby excluding these waters from bathing uses and natural resources conservation, with considerable environmental impacts. Often, changes in environmental factors give rise to qualitative changes in established ecosystems (e.g., specific composition, biodiversity, etc.).

*Coastal and Marine Environments - Physical Processes and Numerical Modelling*

or less concern about global climate change.

should be improved.

cultural value.

increasing the risk in another.

To take into account these concerns and other concerns resulting from ongoing and future impacts from climate change, managers must approach coastal zones management different than they did in the past. Inadequate management methodologies are still common practices today in many countries that have fewer resources

We may learn from the past that most defensive measures have been more reactive than proactive. In addition, the intervention procedures in the coastal zones, whether for the purposes of valuation or implementation of protection measures,

Until recently, much of the coastal engineering projects were almost exclusively

It is common knowledge that hard engineering structures can be effective when properly designed and installed. However, because they are continuously subjected to events that in many cases exceed their design capacity, such structures require adequate and costly maintenance. On the other hand, it is also known that these structures tend to reduce erosion and the risk of flooding in one location, but

Meanwhile, with the evolution of the numerical methods and the computational means, it has become possible to use increasingly sophisticated mathematical models to solve complex coastal engineering problems. The use of ever more powerful, less restrictive and more user-friendly computational models, along with physical

On the other hand, it is of utmost importance to involve interdisciplinary groups that cover different perspectives (such as policy makers, civil and environmental engineers, geologists, biologists, economists, sociologists, lawyers, etc.). These interdisciplinary groups should include local communities and stakeholders at different stages of project development, including design, building, and monitoring. Indeed, public participation, including stakeholders, is considered as a key principle when planning and implementing conservation projects. The same view is shared by Hedelin et al. [2] and Barceló [3], who clarifies in an Elsevier editorial note *when people are ignored and conservation measures are put in, we see opposition, conflict and often failure. These problems require the best available evidence, and that* 

In this context, the guidelines on coastal defenses have changed. Contrary to the coastal defenses built in the past, contemporary adaptation measures include: artificial sand nourishments, possibly with additional sand support measures; building and rehabilitation of dunes; creation and restoration of wetlands; reinforcement or creation of submerged longitudinal bars; submerged breakwaters made of geotex-

Other measures, which are less common, but may become essential in the near

future, include: building on pilings; adaptation of drainage systems; building emergency flood shelters; and tidal houses, houseboats, and floating houses. Reconciling current activities in the coastal zones with the maintenance of healthy ecosystems requires monitoring, systematic evaluation, and implementation of corrective measures. Indeed, it is generally understood and practice has shown that when planned, preventative adaptation will be more cost-effective and efficient in the long run than retroactive measures. Therefore, identifying and addressing needs and gaps in policies and planning will strengthen the adaptive

modeling, is today a common practice in coastal engineering.

*includes having both natural and social scientists at the table*.

tile tubes; buffer zones; and land use restriction and zoning.

capacity of regions and local communities.

based on experience. As discussed in Kamphuis [1], it was in this context that many of the coastal defense works were carried out and resulted in kilometers of breakwaters, sea walls, and groyne fields for defenses against flooding and urban fronts, recovery of degraded areas, and protection of heritage of great historical and

**4**

**Figure 1.**

*Well and borehole stains (blue points) and 17 aquifer systems (Mx) that exist with regional expression in Algarve, Portugal (Adapted from [4]).*

## **2. Traditional and contemporary decision-making procedures in coastal management processes**

From the procedural point of view, the implementation of works in the coastal zone followed a very simple procedure in a not too distant past. All interventions were focused on the project, which was entirely managed by an engineer. This engineer was responsible for everything and only had contacts with the entity responsible for coastal works. The contribution of experts from disciplinary areas with different perspectives did not exist or was very limited. In fact, until the 1980s, the construction of works in coastal zones essentially followed the schematic diagram shown in **Figure 2**.

At that time, the coastal public works were contracted and overseen by the project owner, usually a government entity or a construction/business company, who alone was responsible for project decisions, coastal work implementation, and monitoring of its behavior [1]. Coastal science at that time was essentially physical (hydrodynamics—waves, currents, tides, etc.).

In Portugal, some coastal public works projects that were executed in this context are noteworthy. Until the 1980s, the entire process was carried out in accordance with the procedures shown in **Figure 2**. The interventions were usually based

**7**

**Figure 3.**

*engineering projects (Courtesy of Lopes [5]).*

*Coastal Adaptation: Past Behaviors, Contemporary Management, and Future Options*

on a structural project and lacked impact studies, environmental concerns, public consultation, and intervention/incorporation of the input from local communities

**Figure 3** shows some of the interventions undertaken on the west coast of Portugal in the 1970s and 1980s and with subsequent structural reinforcement. Currently, the urban centers shown in this figure are residential areas at high vulnerability and risk, only maintained at the expense of hard engineering projects. It should be noted that the option for hard engineering projects was motivated by the general erosion trend of the Portuguese Atlantic coast and, in particular, by the defense of urban fronts. However, in general, these hard structures have had negative consequences along the Portuguese coast, as they have increased coastal erosion in remote areas by impeding the normal circulation of sediments. These projects also led to negative consequences locally as they led to urban expansions often occupying marginal areas as a result of false safety sensations provided by

In the 1980s, the development of more in-depth theoretical knowledge and the evolution of numerical methods and computer hardware occurred. These developments allowed engineers to develop and apply numerical models capable of describ-

It was in this context that the field of hydroinformatics emerged in the 1990s, which is a new scientific branch that links informatics tools, hydraulics, environmental concepts, and models with the overall objective of solving environmental problems in coastal waters. Examples of hydroinformatic environments created for this purpose are the modular structures described in Pinho et al. [6] and Deltares [7–9] (DELFT3D), which are capable of simulating hydrodynamic, morphody-

These modular structures and other highly complex two- and three-dimensional computational structures are now commonly used to solve real-world problems, particularly in coastal areas. Among the most common are: MIKE21 (https:// www.mikepoweredbydhi.com/products/mike-21), POM (http://www.ccpo.odu. edu/POMWEB/), ADCIRC (http://adcirc.org/), TELEMAC3D (http://www. opentelemac.org/), DELFT3D (https://oss.deltares.nl/web/delft3d), and CCHE3D

Meanwhile, as addressed in [1], concerns in coastal areas are no longer limited to safety issues: lifestyle and quality of life have become essential ingredients. Other aspects of the project have also become important, such as environmental impact, esthetics, and sustainability. The additional complexities were further aggravated by other aspects that needed to be integrated into the overall design, such as

*Urban seafronts protected by sea walls and groins. These residential areas are located at the western Portuguese coast (Mira on left and Esmoriz-Cortegaça on right) and are only maintained at the expense of hard* 

*DOI: http://dx.doi.org/10.5772/intechopen.88123*

and stakeholders.

such structures (**Figure 3**).

ing the physical processes with greater accuracy.

namic, and water quality processes.

(https://www.ncche.olemiss.edu/cche3d).

**Figure 2.** *Traditional decision-making process in coastal zone issues (Adapted from [1]).*

### *Coastal Adaptation: Past Behaviors, Contemporary Management, and Future Options DOI: http://dx.doi.org/10.5772/intechopen.88123*

on a structural project and lacked impact studies, environmental concerns, public consultation, and intervention/incorporation of the input from local communities and stakeholders.

**Figure 3** shows some of the interventions undertaken on the west coast of Portugal in the 1970s and 1980s and with subsequent structural reinforcement. Currently, the urban centers shown in this figure are residential areas at high vulnerability and risk, only maintained at the expense of hard engineering projects.

It should be noted that the option for hard engineering projects was motivated by the general erosion trend of the Portuguese Atlantic coast and, in particular, by the defense of urban fronts. However, in general, these hard structures have had negative consequences along the Portuguese coast, as they have increased coastal erosion in remote areas by impeding the normal circulation of sediments. These projects also led to negative consequences locally as they led to urban expansions often occupying marginal areas as a result of false safety sensations provided by such structures (**Figure 3**).

In the 1980s, the development of more in-depth theoretical knowledge and the evolution of numerical methods and computer hardware occurred. These developments allowed engineers to develop and apply numerical models capable of describing the physical processes with greater accuracy.

It was in this context that the field of hydroinformatics emerged in the 1990s, which is a new scientific branch that links informatics tools, hydraulics, environmental concepts, and models with the overall objective of solving environmental problems in coastal waters. Examples of hydroinformatic environments created for this purpose are the modular structures described in Pinho et al. [6] and Deltares [7–9] (DELFT3D), which are capable of simulating hydrodynamic, morphodynamic, and water quality processes.

These modular structures and other highly complex two- and three-dimensional computational structures are now commonly used to solve real-world problems, particularly in coastal areas. Among the most common are: MIKE21 (https:// www.mikepoweredbydhi.com/products/mike-21), POM (http://www.ccpo.odu. edu/POMWEB/), ADCIRC (http://adcirc.org/), TELEMAC3D (http://www. opentelemac.org/), DELFT3D (https://oss.deltares.nl/web/delft3d), and CCHE3D (https://www.ncche.olemiss.edu/cche3d).

Meanwhile, as addressed in [1], concerns in coastal areas are no longer limited to safety issues: lifestyle and quality of life have become essential ingredients. Other aspects of the project have also become important, such as environmental impact, esthetics, and sustainability. The additional complexities were further aggravated by other aspects that needed to be integrated into the overall design, such as

#### **Figure 3.**

*Urban seafronts protected by sea walls and groins. These residential areas are located at the western Portuguese coast (Mira on left and Esmoriz-Cortegaça on right) and are only maintained at the expense of hard engineering projects (Courtesy of Lopes [5]).*

*Coastal and Marine Environments - Physical Processes and Numerical Modelling*

**2. Traditional and contemporary decision-making procedures in coastal** 

*Well and borehole stains (blue points) and 17 aquifer systems (Mx) that exist with regional expression in* 

From the procedural point of view, the implementation of works in the coastal zone followed a very simple procedure in a not too distant past. All interventions were focused on the project, which was entirely managed by an engineer. This engineer was responsible for everything and only had contacts with the entity responsible for coastal works. The contribution of experts from disciplinary areas with different perspectives did not exist or was very limited. In fact, until the 1980s, the construction of works in coastal zones essentially followed the schematic

At that time, the coastal public works were contracted and overseen by the project owner, usually a government entity or a construction/business company, who alone was responsible for project decisions, coastal work implementation, and monitoring of its behavior [1]. Coastal science at that time was essentially physical

In Portugal, some coastal public works projects that were executed in this context are noteworthy. Until the 1980s, the entire process was carried out in accordance with the procedures shown in **Figure 2**. The interventions were usually based

**management processes**

*Algarve, Portugal (Adapted from [4]).*

**Figure 1.**

diagram shown in **Figure 2**.

(hydrodynamics—waves, currents, tides, etc.).

**6**

**Figure 2.**

*Traditional decision-making process in coastal zone issues (Adapted from [1]).*

non-engineering and non-science concerns. Examples of these concerns include socio-economic aspects and quality of life, involving leisure, tourism, sporting practices, fishing industries, water quality, etc.

These emerging sociological realities needed to be addressed, as well as the voices of actors and interest groups that would like their input incorporated into the project design. In fact, a synthesis of these recent concerns has become much more difficult to manage since this new reality is based on assumptions of value, social acceptance, and sustainability. The interrelationships presented in **Figure 4** show the current complexity inherent to the contemporary management process of the coastal zone.

The organizational chart shown in **Figure 4** shows that to integrate all social and technical requirements and to facilitate an optimum solution, coastal managers must organize and maintain clear communication between the various actors.

As is clear from preceding discussion, two distinct realities stand out from the traditional and contemporary approaches to the coastal planning and management issues. On one hand, the need to utilize more scientific and technological knowledge into addressing coastal issues is recognized. Therefore, specialists from different disciplines enrich the structural component of engineering design. On the other hand, the need to involve public agents, entities, interest groups, and local communities is recognized in order to ensure the necessary support and social component of the structural component.

These concepts synthesize the current manner of addressing with the coastal issues. The interactivity between both the physical-environmental and socioeconomic systems is at the interface of the well-known concept of Integrated Coastal Zone Management, which requires the integration of different disciplinary expertise from local, societal, and practical knowledge within coastal planning and decision-making processes.

**9**

**Figure 6.**

*respectively (Adapted from [12]).*

**Figure 5.**

*Coastal Adaptation: Past Behaviors, Contemporary Management, and Future Options*

**Figure 5** shows how these systems complement each other for the success of an intervention located in the coastal zone. The structural component (or resistant structure) suffers the physical effects of the processes and is fundamentally of the technical-scientific and environmental domain (PES). The socio-economic component (SES) forms the base of support of the resistant structure and is the domain of

The need to involve researchers from different disciplinary areas in the conceptualization and development phases of an intervention program in the coastal zone has been recognized in several coastal interventions carried out on the Portuguese coast. The same has occurred with the need to involve public institutions, local communities, users, and citizens in general in the process of socio-

In this context, the intervention carried out at Costa da Caparica [11], which is an extensive well-attended bathing area, located near Lisbon, Portugal, shown in

*Typical coastal system composed of a resistant structure and its base of support (Adapted from [10]).*

*Views of Costa da Caparica beach, close to Lisbon, Portugal, deprived of sand in 2006 (Courtesy of Alveirinho Dias), and the beach and its marginal strip after the last major intervention in 2014, on the left and right,* 

*DOI: http://dx.doi.org/10.5772/intechopen.88123*

institutions, stakeholders, and citizens.

**Figure 6**, was particularly relevant.

economic consultation.

#### **Figure 4.**

*Contemporary decision-making process in coastal zone issues (Adapted from [1]).*

*Coastal Adaptation: Past Behaviors, Contemporary Management, and Future Options DOI: http://dx.doi.org/10.5772/intechopen.88123*

**Figure 5** shows how these systems complement each other for the success of an intervention located in the coastal zone. The structural component (or resistant structure) suffers the physical effects of the processes and is fundamentally of the technical-scientific and environmental domain (PES). The socio-economic component (SES) forms the base of support of the resistant structure and is the domain of institutions, stakeholders, and citizens.

The need to involve researchers from different disciplinary areas in the conceptualization and development phases of an intervention program in the coastal zone has been recognized in several coastal interventions carried out on the Portuguese coast. The same has occurred with the need to involve public institutions, local communities, users, and citizens in general in the process of socioeconomic consultation.

In this context, the intervention carried out at Costa da Caparica [11], which is an extensive well-attended bathing area, located near Lisbon, Portugal, shown in **Figure 6**, was particularly relevant.

#### **Figure 5.**

*Coastal and Marine Environments - Physical Processes and Numerical Modelling*

practices, fishing industries, water quality, etc.

coastal zone.

of the structural component.

decision-making processes.

non-engineering and non-science concerns. Examples of these concerns include socio-economic aspects and quality of life, involving leisure, tourism, sporting

These emerging sociological realities needed to be addressed, as well as the voices of actors and interest groups that would like their input incorporated into the project design. In fact, a synthesis of these recent concerns has become much more difficult to manage since this new reality is based on assumptions of value, social acceptance, and sustainability. The interrelationships presented in **Figure 4** show the current complexity inherent to the contemporary management process of the

The organizational chart shown in **Figure 4** shows that to integrate all social and technical requirements and to facilitate an optimum solution, coastal managers must organize and maintain clear communication between the various actors. As is clear from preceding discussion, two distinct realities stand out from the traditional and contemporary approaches to the coastal planning and management issues. On one hand, the need to utilize more scientific and technological knowledge into addressing coastal issues is recognized. Therefore, specialists from different disciplines enrich the structural component of engineering design. On the other hand, the need to involve public agents, entities, interest groups, and local communities is recognized in order to ensure the necessary support and social component

These concepts synthesize the current manner of addressing with the coastal issues. The interactivity between both the physical-environmental and socioeconomic systems is at the interface of the well-known concept of Integrated Coastal Zone Management, which requires the integration of different disciplinary expertise from local, societal, and practical knowledge within coastal planning and

**8**

**Figure 4.**

*Contemporary decision-making process in coastal zone issues (Adapted from [1]).*

*Typical coastal system composed of a resistant structure and its base of support (Adapted from [10]).*

#### **Figure 6.**

*Views of Costa da Caparica beach, close to Lisbon, Portugal, deprived of sand in 2006 (Courtesy of Alveirinho Dias), and the beach and its marginal strip after the last major intervention in 2014, on the left and right, respectively (Adapted from [12]).*

## **3. Levels of operation and public participation in coastal issues decisions**

As is clear from the foregoing considerations, the inclusion of different disciplinary groups is of the utmost importance for the success of any intervention program in the coastal zone. In fact, contemporary assessment processes are based on vulnerability indexes or coastal sensitivity, which are functions of several variables or physical parameters that require a diversified knowledge base that has a depth that goes beyond the pure domain of engineering.

In order to be successful, managers must consider not only physical processes and economic interests, but also the opinions and participation of citizens, stakeholders, and local communities in any planning process, conservation project, and coastal development. Public participation is paramount to ensure the development and sustainability of any coastal zone. The use of management strategies that address and consider public perception of the environmental risks, erosion effects, cyclones, tidal surges, and floods is appropriate.

However, the inclusion of entities and people to have a passive attitude is not enough. Managers must also reflect on the level of participation of the agents involved. As is reported in Guimarães et al. [13], seven levels of participation can be defined: passive, in which participants are informed of what will happen; informatory, which provides answers to participants' questions; consultation, where the participants are consulted and their perspectives are heard; incentives, in which people participate for incentives; functional, in which groups are formed that aim to achieve defined objectives; interactive, in which people participate in joint analyses to define actions; and finally, mobilizing participation, in which people participate by taking initiatives independently of external institutions. These levels of participation correspond to different levels of interaction and can be considered distinct stages of the decision-making process.

This brief analysis highlights the need to involve many actors when implementing procedures in order to produce well-accepted and sufficiently credible decisionmaking vulnerability and risk assessment projects in the coastal zone. However, these procedures will only succeed with as much consensus as possible, which should be useful for integrated planning and management of the coastal zone; thus, these procedures serve to establish priorities for intervention.

Truly shared management corresponds to the levels of involvement with a high degree of interaction, which encourages various types of participation, simultaneously functional, interactive, and mobilizing. For this reason, it is essential to establish trusting relationships that must be supported with dialog and a discourse among the different groups involved in the decision-making process. This relational procedure is primarily based on three dimensions: integrate, interact, and inform, as is schematically shown in **Figure 7**.

The process begins by identifying the intervention needs, which are accomplished by defining the type and design of the project. The intervention needs are noted during the implementation period of the coastal work and continue with the monitoring of the structure and surrounding space.

In all of the stages, various stakeholders should be involved and heard in the decision-making process. Decision makers should consider stakeholders an integral part of the plan to remain informed, motivated, and active during the various phases of definition, implementation, and monitoring of the proposed project.

The creation and maintenance of a healthy, multi-functional system requires strong collaboration between broadly skilled technicians, public and private entities, local authorities, residents, non-governmental organizations (NGOs), stakeholders, and citizens (**Figure 4**).

**11**

**Figure 7.**

*Coastal Adaptation: Past Behaviors, Contemporary Management, and Future Options*

In the process of developing a coastal intervention, setting commitments that result in the integration and involvement of all potential stakeholders is essential for a manager to be successful in the decision-making process. With this same goal, sensitizing the agents involved to the opportunities, potential failures, and lower

A permanent interaction is also essential to establish a framework for reciprocal cooperation between all parties. This interaction will provide clear and transparent information on the possible options, in order to ensure that all parties equally accept, share, and assume the expected benefits, costs, and risks involved with the project.

Contemporary coastal managers are concerned with the preservation and enjoyment of coastal zones. Proper use, assessment, and monitoring of natural resources are important goals for preservation. However, to what extent will the current tourist densification in coastal zones be compatible with the sustainability of coastal zones? Will the complementary effects of global climate change lead to significant

In fact, the following facts are true: (1) two-thirds of the world's megacities are located on the coast, and more than half of the population of the 22 European Member States (that have a coastline) live less than 50 km from the sea [14] and (2) these narrow coastal strips correspond to only approximately 10% of the living space on Earth. According to Berger [15], one billion people could live along the

Population growth and economic development are critical factors for change in coastal zones, which generate high pressure on ecosystems and natural resources due to increased use and proliferation of services. According to European Environment Agency [16], between 1995 and 2025, the projected urbanization of the coastal zone on some coasts of the Mediterranean shows a built occupation increasing from 55 to 73% in Spain, 24 to 34% in France, and 38 to 45% in Italy. Failure to reverse this situation will inevitably lead to ecosystem collapse, which will occur more or less rapidly depending on the evolution/intensification of the following factors: (1) lack of pleasant spaces, leading to unbridled/abusive

individual gains in favor of the collective benefit is also important.

*Three key-dimensions for the success of the Integrated Coastal Zone Management.*

**4. Prospects for future accommodation in coastal areas**

changes in the current demand for the coastal zones?

coasts, at or below 10-m elevations, by the year 2060.

*DOI: http://dx.doi.org/10.5772/intechopen.88123*

*Coastal Adaptation: Past Behaviors, Contemporary Management, and Future Options DOI: http://dx.doi.org/10.5772/intechopen.88123*

**Figure 7.** *Three key-dimensions for the success of the Integrated Coastal Zone Management.*

In the process of developing a coastal intervention, setting commitments that result in the integration and involvement of all potential stakeholders is essential for a manager to be successful in the decision-making process. With this same goal, sensitizing the agents involved to the opportunities, potential failures, and lower individual gains in favor of the collective benefit is also important.

A permanent interaction is also essential to establish a framework for reciprocal cooperation between all parties. This interaction will provide clear and transparent information on the possible options, in order to ensure that all parties equally accept, share, and assume the expected benefits, costs, and risks involved with the project.

## **4. Prospects for future accommodation in coastal areas**

Contemporary coastal managers are concerned with the preservation and enjoyment of coastal zones. Proper use, assessment, and monitoring of natural resources are important goals for preservation. However, to what extent will the current tourist densification in coastal zones be compatible with the sustainability of coastal zones? Will the complementary effects of global climate change lead to significant changes in the current demand for the coastal zones?

In fact, the following facts are true: (1) two-thirds of the world's megacities are located on the coast, and more than half of the population of the 22 European Member States (that have a coastline) live less than 50 km from the sea [14] and (2) these narrow coastal strips correspond to only approximately 10% of the living space on Earth. According to Berger [15], one billion people could live along the coasts, at or below 10-m elevations, by the year 2060.

Population growth and economic development are critical factors for change in coastal zones, which generate high pressure on ecosystems and natural resources due to increased use and proliferation of services. According to European Environment Agency [16], between 1995 and 2025, the projected urbanization of the coastal zone on some coasts of the Mediterranean shows a built occupation increasing from 55 to 73% in Spain, 24 to 34% in France, and 38 to 45% in Italy.

Failure to reverse this situation will inevitably lead to ecosystem collapse, which will occur more or less rapidly depending on the evolution/intensification of the following factors: (1) lack of pleasant spaces, leading to unbridled/abusive

*Coastal and Marine Environments - Physical Processes and Numerical Modelling*

depth that goes beyond the pure domain of engineering.

cyclones, tidal surges, and floods is appropriate.

stages of the decision-making process.

as is schematically shown in **Figure 7**.

holders, and citizens (**Figure 4**).

monitoring of the structure and surrounding space.

these procedures serve to establish priorities for intervention.

**3. Levels of operation and public participation in coastal issues decisions**

As is clear from the foregoing considerations, the inclusion of different disciplinary groups is of the utmost importance for the success of any intervention program in the coastal zone. In fact, contemporary assessment processes are based on vulnerability indexes or coastal sensitivity, which are functions of several variables or physical parameters that require a diversified knowledge base that has a

In order to be successful, managers must consider not only physical processes and economic interests, but also the opinions and participation of citizens, stakeholders, and local communities in any planning process, conservation project, and coastal development. Public participation is paramount to ensure the development and sustainability of any coastal zone. The use of management strategies that address and consider public perception of the environmental risks, erosion effects,

However, the inclusion of entities and people to have a passive attitude is not enough. Managers must also reflect on the level of participation of the agents involved. As is reported in Guimarães et al. [13], seven levels of participation can be defined: passive, in which participants are informed of what will happen; informatory, which provides answers to participants' questions; consultation, where the participants are consulted and their perspectives are heard; incentives, in which people participate for incentives; functional, in which groups are formed that aim to achieve defined objectives; interactive, in which people participate in joint analyses to define actions; and finally, mobilizing participation, in which people participate by taking initiatives independently of external institutions. These levels of participation correspond to different levels of interaction and can be considered distinct

This brief analysis highlights the need to involve many actors when implementing procedures in order to produce well-accepted and sufficiently credible decisionmaking vulnerability and risk assessment projects in the coastal zone. However, these procedures will only succeed with as much consensus as possible, which should be useful for integrated planning and management of the coastal zone; thus,

Truly shared management corresponds to the levels of involvement with a high degree of interaction, which encourages various types of participation, simultaneously functional, interactive, and mobilizing. For this reason, it is essential to establish trusting relationships that must be supported with dialog and a discourse among the different groups involved in the decision-making process. This relational procedure is primarily based on three dimensions: integrate, interact, and inform,

The process begins by identifying the intervention needs, which are accomplished by defining the type and design of the project. The intervention needs are noted during the implementation period of the coastal work and continue with the

In all of the stages, various stakeholders should be involved and heard in the decision-making process. Decision makers should consider stakeholders an integral part of the plan to remain informed, motivated, and active during the various phases of definition, implementation, and monitoring of the proposed project. The creation and maintenance of a healthy, multi-functional system requires strong collaboration between broadly skilled technicians, public and private entities, local authorities, residents, non-governmental organizations (NGOs), stake-

**10**

and uncontrolled occupations; (2) depletion of water resources (in quantity and quality); (3) inefficiency of services (security, health, catering, leisure, socializing, etc.); (4) increased speculation, with unbearable costs, and (5) aggravation of conflicts and insecurity.

In the meantime, maintaining coastal zone esthetics and sustainability in areas of increasing risk will only be possible through regular interventions, in accordance with the guidelines expressed in the previous points. Long-lasting sustainability can be achieved by implementing interventions that effectively reduce wave energy prior to reaching the coastline.

In fact, it is possible to guide the waves propagation by acting on the bathymetry in areas of the continental shelf, where the waves propagate in intermediate- and shallow-water conditions, forcing waves to rotate (refraction effect) and to break in positions away from the coastline; thus, preventing all of the wave energy from being discharged on the beach and/or in other natural defense systems, such as dunes. To preserve coastal dunes and stabilize the coastal foundation properly, one strategy recommends the use of artificial nourishments, possibly complemented by additional protections to prevent sand losses, such as longitudinal detached submerged breakwaters made of geotextile material. The goal of this strategy is to protect the coast in an environmentally friendly and esthetically pleasing manner. Examples of effective actions that protect the coast in this manner are presented in Oh and Shin [17] and Taal et al. [18].

It is important to note that coastal zone defense programs should adopt protection principles based on preventive actions of wave behavior, that is, interventions must be carried out from the ocean to the coast.

On this issue, the Leirosa case study has been an example of learning. This sand dune system has been the scene of three major dune rehabilitation interventions in the past 15 years. The first involved the reconstruction of the sand dunes followed by re-vegetation [19]; see **Figure 8**.

The second intervention consisted of installing geotextile containers filled with sand [20, 21], and the last one was implemented to stabilize the existing geotextilereinforced sand dune system in the area where some encapsulated sand layers, mainly the bottom three, had partially opened up [22, 23]; see **Figure 9**.

This protection strategy allowed this stretch of the coast to remain more or less stable until 2014. However, the Hercules and Stephanie storms that struck the Portuguese coast in 2014 caused deep damages in this dune system, thus increasing the weaknesses that existed.

These events have taught us that the measures taken to protect the beach and dune system of Leirosa would not be sufficient, so we put forward a proposal to install a multi-functional submerged structure with characteristics to (1) protect

**Figure 8.** *Rehabilitated stretch of the Leirosa sand dunes system, from May to September 2000 (Adapted from [12]).*

**13**

**Figure 10.**

*Coastal Adaptation: Past Behaviors, Contemporary Management, and Future Options*

the coastal zone, dissipating energy of waves, (2) create a calmer sea on the lee side of the structure, and (3) increase the surfing possibilities in the Leirosa area of Portugal. In addition, it should be noted that coastal defense structures incorporating multi-functionalities are, in general, well-accepted by stakeholders [24]. Still according to Evans et al. [24], stakeholders recognize that the benefits to society

*General aspect of some bottom geotextile layers after the high tides late in the winter of 2006, in April* 

The proposed structure for Leirosa was tested for two reef geometries with different reef angles (45 and 66°) [25, 26]. Wave data were obtained from a DATAWELL directional wave buoy located about 5 km off the coastline, position 40° 03′ 22″ N 8° 57′ 22″ W, at 25 m water depth. Average significant heights (HS) and wave peak directions (TZ) for 3-h intervals were recorded over a period of 9 months. Values of the peak period and wave direction distributions for different

Since these data series are very short, the records shown in **Figure 10** were compared to longer series (12 years) of average wave heights and peak periods obtained at a station located in Figueira da Foz, about 15 km to the north of Leirosa. These data were transposed to the wave buoy installed near Leirosa using the coastal wave model SWAN. Comparisons of frequency histograms for significant wave heights

Taking into account the results shown in **Figure 11**, where pronounced differences are noted especially in the wave periods, two design wave conditions were tested: typical storm conditions on the Portuguese west coast (wave height H = 4:0 m, period T = 15 s), and common conditions on this coast (H = 1:5 m, T = 9 s). Accordingly, the four scenarios C1–C4 shown in **Table 1** were simulated.

*Local wave data obtained from a DATAWELL directional wave buoy, at 25 m water depth: TZ-HS and* 

provided by such structures could attract public and private funding.

and peak periods obtained by both methods are shown in **Figure 11**.

*DOI: http://dx.doi.org/10.5772/intechopen.88123*

**Figure 9.**

*(Adapted from [12]).*

wave heights are shown in **Figure 10**.

*DIR-HS relationships, on the left and right, respectively.*

*Coastal Adaptation: Past Behaviors, Contemporary Management, and Future Options DOI: http://dx.doi.org/10.5772/intechopen.88123*

#### **Figure 9.**

*Coastal and Marine Environments - Physical Processes and Numerical Modelling*

conflicts and insecurity.

prior to reaching the coastline.

Oh and Shin [17] and Taal et al. [18].

by re-vegetation [19]; see **Figure 8**.

the weaknesses that existed.

must be carried out from the ocean to the coast.

and uncontrolled occupations; (2) depletion of water resources (in quantity and quality); (3) inefficiency of services (security, health, catering, leisure, socializing, etc.); (4) increased speculation, with unbearable costs, and (5) aggravation of

In the meantime, maintaining coastal zone esthetics and sustainability in areas of increasing risk will only be possible through regular interventions, in accordance with the guidelines expressed in the previous points. Long-lasting sustainability can be achieved by implementing interventions that effectively reduce wave energy

In fact, it is possible to guide the waves propagation by acting on the bathymetry in areas of the continental shelf, where the waves propagate in intermediate- and shallow-water conditions, forcing waves to rotate (refraction effect) and to break in positions away from the coastline; thus, preventing all of the wave energy from being discharged on the beach and/or in other natural defense systems, such as dunes. To preserve coastal dunes and stabilize the coastal foundation properly, one strategy recommends the use of artificial nourishments, possibly complemented by additional protections to prevent sand losses, such as longitudinal detached submerged breakwaters made of geotextile material. The goal of this strategy is to protect the coast in an environmentally friendly and esthetically pleasing manner. Examples of effective actions that protect the coast in this manner are presented in

It is important to note that coastal zone defense programs should adopt protection principles based on preventive actions of wave behavior, that is, interventions

On this issue, the Leirosa case study has been an example of learning. This sand dune system has been the scene of three major dune rehabilitation interventions in the past 15 years. The first involved the reconstruction of the sand dunes followed

The second intervention consisted of installing geotextile containers filled with sand [20, 21], and the last one was implemented to stabilize the existing geotextilereinforced sand dune system in the area where some encapsulated sand layers, mainly the bottom three, had partially opened up [22, 23]; see **Figure 9**.

This protection strategy allowed this stretch of the coast to remain more or less stable until 2014. However, the Hercules and Stephanie storms that struck the Portuguese coast in 2014 caused deep damages in this dune system, thus increasing

These events have taught us that the measures taken to protect the beach and dune system of Leirosa would not be sufficient, so we put forward a proposal to install a multi-functional submerged structure with characteristics to (1) protect

*Rehabilitated stretch of the Leirosa sand dunes system, from May to September 2000 (Adapted from [12]).*

**12**

**Figure 8.**

*General aspect of some bottom geotextile layers after the high tides late in the winter of 2006, in April (Adapted from [12]).*

the coastal zone, dissipating energy of waves, (2) create a calmer sea on the lee side of the structure, and (3) increase the surfing possibilities in the Leirosa area of Portugal. In addition, it should be noted that coastal defense structures incorporating multi-functionalities are, in general, well-accepted by stakeholders [24]. Still according to Evans et al. [24], stakeholders recognize that the benefits to society provided by such structures could attract public and private funding.

The proposed structure for Leirosa was tested for two reef geometries with different reef angles (45 and 66°) [25, 26]. Wave data were obtained from a DATAWELL directional wave buoy located about 5 km off the coastline, position 40° 03′ 22″ N 8° 57′ 22″ W, at 25 m water depth. Average significant heights (HS) and wave peak directions (TZ) for 3-h intervals were recorded over a period of 9 months. Values of the peak period and wave direction distributions for different wave heights are shown in **Figure 10**.

Since these data series are very short, the records shown in **Figure 10** were compared to longer series (12 years) of average wave heights and peak periods obtained at a station located in Figueira da Foz, about 15 km to the north of Leirosa. These data were transposed to the wave buoy installed near Leirosa using the coastal wave model SWAN. Comparisons of frequency histograms for significant wave heights and peak periods obtained by both methods are shown in **Figure 11**.

Taking into account the results shown in **Figure 11**, where pronounced differences are noted especially in the wave periods, two design wave conditions were tested: typical storm conditions on the Portuguese west coast (wave height H = 4:0 m, period T = 15 s), and common conditions on this coast (H = 1:5 m, T = 9 s). Accordingly, the four scenarios C1–C4 shown in **Table 1** were simulated.

#### **Figure 10.**

*Local wave data obtained from a DATAWELL directional wave buoy, at 25 m water depth: TZ-HS and DIR-HS relationships, on the left and right, respectively.*

#### **Figure 11.**

*Frequency histograms for significant wave heights and peak periods. (a) Significant height, HS. (b) Peek period, TP.*

In order to propagate the incident wave, a Boussinesq type model, COULWAVE [27] was used. **Figure 12** shows numerical results of wave heights and the wave breaking line for the common wave conditions and a reef angle = 45° (C1 test, **Table 1**).

**Figure 12** shows the good performance of an artificial submerged reef taking advantage of the wave refraction effect. This structure also causes wave to break in the water mass (away from the coastline). Therefore, it is possible not only to increase the width of the beach (new position of the breaker line), but also take advantage of the generated wave characteristics (shoaling effects) for sports practices. This structure can be designed to meet current conditions and, if necessary, be further strengthened to take into account possible changes in coastal dynamics.

At a later stage, earlier actions will no longer be effective, possibly as the result of ongoing climate change. This change may lead to an increased demand for accommodation alternatives in coastal areas. In areas of greater scarcity and risk,

**15**

century.

**Figure 12.**

**Table 1.**

*Coastal Adaptation: Past Behaviors, Contemporary Management, and Future Options*

*Reef, wave, and mesh characteristics used for the four simulated scenarios [26].*

**Scenario Reef angle (°) H (m) T (s) Points per wavelength Grid size (m) Time step (s)** C1 45 1.5 9 43 2.14 0.09288 C2 45 4.0 13 60 2.77 0.11999 C3 66 1.5 9 43 2.14 0.09288 C4 66 4.0 13 70 2.37 0.10285

countries such as the USA, the UK, India, Indonesia, Philippines, Thailand, and

*Wave heights and wave breaking line around the reef area (reef angle = 45°; wave height H = 1.5 m, and period* 

In essence, it is the resumption of very old defense principles (e.g., stilts), although with potentially different motivations; however, these same flood defense purposes constructions are not new. As shown in **Figure 13**, the coastal areas of countries with extensive lowlands, such as Portugal, have constructions that were already adopted as flood defense options in the second half of the nineteenth

With the same goal of flood defense, demand and housing construction has grown significantly in several coastal regions of the world. For example, many houses are built on pilings along the west coast of the USA. **Figure 14** shows a set of houses of this type built on Malibu beach, California, USA, with waves crashing underneath the houses. **Figure 15** shows two luxurious waterfront homes built on

More examples, among many others, are shown in https://www.homestratosphere.com/houses-built-on-stilts/. However, these structures require some care because, as noted in Park et al. [29], the structure elevation is a critical variable

many others already have elevated constructions on pilings.

pilings over the water, also in the USA coast.

*T = 9.0 s, as C1 test, Table 1) (Adapted from [26]).*

*DOI: http://dx.doi.org/10.5772/intechopen.88123*


*Coastal Adaptation: Past Behaviors, Contemporary Management, and Future Options DOI: http://dx.doi.org/10.5772/intechopen.88123*

#### **Table 1.**

*Coastal and Marine Environments - Physical Processes and Numerical Modelling*

In order to propagate the incident wave, a Boussinesq type model, COULWAVE [27] was used. **Figure 12** shows numerical results of wave heights and the wave breaking line for the common wave conditions and a reef angle = 45° (C1 test, **Table 1**). **Figure 12** shows the good performance of an artificial submerged reef taking advantage of the wave refraction effect. This structure also causes wave to break in the water mass (away from the coastline). Therefore, it is possible not only to increase the width of the beach (new position of the breaker line), but also take advantage of the generated wave characteristics (shoaling effects) for sports practices. This structure can be designed to meet current conditions and, if necessary, be further strengthened to take into account possible changes in coastal dynamics. At a later stage, earlier actions will no longer be effective, possibly as the result

*Frequency histograms for significant wave heights and peak periods. (a) Significant height, HS. (b) Peek* 

of ongoing climate change. This change may lead to an increased demand for accommodation alternatives in coastal areas. In areas of greater scarcity and risk,

**14**

**Figure 11.**

*period, TP.*

*Reef, wave, and mesh characteristics used for the four simulated scenarios [26].*

#### **Figure 12.**

*Wave heights and wave breaking line around the reef area (reef angle = 45°; wave height H = 1.5 m, and period T = 9.0 s, as C1 test, Table 1) (Adapted from [26]).*

countries such as the USA, the UK, India, Indonesia, Philippines, Thailand, and many others already have elevated constructions on pilings.

In essence, it is the resumption of very old defense principles (e.g., stilts), although with potentially different motivations; however, these same flood defense purposes constructions are not new. As shown in **Figure 13**, the coastal areas of countries with extensive lowlands, such as Portugal, have constructions that were already adopted as flood defense options in the second half of the nineteenth century.

With the same goal of flood defense, demand and housing construction has grown significantly in several coastal regions of the world. For example, many houses are built on pilings along the west coast of the USA. **Figure 14** shows a set of houses of this type built on Malibu beach, California, USA, with waves crashing underneath the houses. **Figure 15** shows two luxurious waterfront homes built on pilings over the water, also in the USA coast.

More examples, among many others, are shown in https://www.homestratosphere.com/houses-built-on-stilts/. However, these structures require some care because, as noted in Park et al. [29], the structure elevation is a critical variable

#### **Figure 13.**

*Flood-proof piling houses built on the coast of Tocha-Mira, Portugal, in the mid-nineteenth century (Adapted from [28]).*

#### **Figure 14.**

*Houses on Malibu beach built on pilings with waves crashing underneath the houses (https://www. homestratosphere.com/houses-built-on-stilts/).*

#### **Figure 15.**

*Two luxurious waterfront homes built on pilings over the water in the USA (https://www.homestratosphere. com/houses-built-on-stilts/).*

affecting property damage and loss; they show that vertical or horizontal force caused by a given set of wave conditions may increase or decrease depending on the structure's elevation above the water level. Guidelines on how to design and build safer and less vulnerable housing to reduce the risk of life and property in coastal areas can be found in Coulbourne et al. [30].

More recently, a significant increase of floating houses and houseboats has been noted. Facilities of this kind are multiplying throughout the world, including

**17**

*Coastal Adaptation: Past Behaviors, Contemporary Management, and Future Options*

the sets of houseboats at De Omval, Amsterdam, on the river Amstel (just downstream from De Omval), the 60 houseboats situated on the north side of the River Thames, on Battersea Reach, and the harbor at Bembridge, with approximately 25

*Types of floating houses, as future widespread adaptation measure to address coastal hazards and climate* 

An increasing demand for this type of housing and a reduction of current living conditions in coastal areas are foreseeable, especially from the middle of the present century. As a consequence of global climate change, it is also foreseeable that an increase of integrated neighborhoods (including houseboats) in the coastal cities may occur. Alternatively, independent urban poles exclusively composed of houseboats, tidal houses, and floating houses like those shown in

Coastal areas are now places of attraction for large masses. Coastal managers have a growing interest in implementing effective management that meets current needs, while also taking into account the need to sustainably manage natural resources for future generations. To satisfy these requirements, alternative solutions that safeguard the sustainability of the environment, tourism social resources, and

Contemporary coastal management relies on the basis of integration and account-

ability of all stakeholders, including local communities, investors, technicians, specialists (from different disciplinary areas), and managers in the processes of conceptualization, decision-making, implementation, and monitoring of any intervention program in the coastal zone. Coastal management should aim to sensitize all stakeholders to the intervention needs, hazards, and inherent risks. Stakeholders and managers should discuss collegially the possible solutions and corresponding costs and participate in decision-making processes, accepting in this way a potential failure. The phases of implementation and monitoring should be shared in such a way that everyone is proud of the success of the intervention or be motivated to accept and correct failure. However, if multiple interest groups are involved and these groups have conflicting interests, complexities can manifest themselves even in the acceptance and approval of processes, often resulting in conflicting voices [31]. These conflicts may be an additional problem, which may lead to only some of the

services in the coastal zones will have to be considered.

stakeholders supporting the process.

*DOI: http://dx.doi.org/10.5772/intechopen.88123*

houseboats [12].

**Figure 16.**

**Figure 16** may increase.

*change (Google, unknown author and date).*

**5. Conclusions**

*Coastal Adaptation: Past Behaviors, Contemporary Management, and Future Options DOI: http://dx.doi.org/10.5772/intechopen.88123*

#### **Figure 16.**

*Coastal and Marine Environments - Physical Processes and Numerical Modelling*

*Houses on Malibu beach built on pilings with waves crashing underneath the houses (https://www.*

*Flood-proof piling houses built on the coast of Tocha-Mira, Portugal, in the mid-nineteenth century (Adapted* 

*Two luxurious waterfront homes built on pilings over the water in the USA (https://www.homestratosphere.*

affecting property damage and loss; they show that vertical or horizontal force caused by a given set of wave conditions may increase or decrease depending on the structure's elevation above the water level. Guidelines on how to design and build safer and less vulnerable housing to reduce the risk of life and property in coastal

More recently, a significant increase of floating houses and houseboats has been noted. Facilities of this kind are multiplying throughout the world, including

**16**

**Figure 14.**

**Figure 13.**

*from [28]).*

**Figure 15.**

*com/houses-built-on-stilts/).*

areas can be found in Coulbourne et al. [30].

*homestratosphere.com/houses-built-on-stilts/).*

*Types of floating houses, as future widespread adaptation measure to address coastal hazards and climate change (Google, unknown author and date).*

the sets of houseboats at De Omval, Amsterdam, on the river Amstel (just downstream from De Omval), the 60 houseboats situated on the north side of the River Thames, on Battersea Reach, and the harbor at Bembridge, with approximately 25 houseboats [12].

An increasing demand for this type of housing and a reduction of current living conditions in coastal areas are foreseeable, especially from the middle of the present century. As a consequence of global climate change, it is also foreseeable that an increase of integrated neighborhoods (including houseboats) in the coastal cities may occur. Alternatively, independent urban poles exclusively composed of houseboats, tidal houses, and floating houses like those shown in **Figure 16** may increase.

### **5. Conclusions**

Coastal areas are now places of attraction for large masses. Coastal managers have a growing interest in implementing effective management that meets current needs, while also taking into account the need to sustainably manage natural resources for future generations. To satisfy these requirements, alternative solutions that safeguard the sustainability of the environment, tourism social resources, and services in the coastal zones will have to be considered.

Contemporary coastal management relies on the basis of integration and accountability of all stakeholders, including local communities, investors, technicians, specialists (from different disciplinary areas), and managers in the processes of conceptualization, decision-making, implementation, and monitoring of any intervention program in the coastal zone. Coastal management should aim to sensitize all stakeholders to the intervention needs, hazards, and inherent risks. Stakeholders and managers should discuss collegially the possible solutions and corresponding costs and participate in decision-making processes, accepting in this way a potential failure.

The phases of implementation and monitoring should be shared in such a way that everyone is proud of the success of the intervention or be motivated to accept and correct failure. However, if multiple interest groups are involved and these groups have conflicting interests, complexities can manifest themselves even in the acceptance and approval of processes, often resulting in conflicting voices [31]. These conflicts may be an additional problem, which may lead to only some of the stakeholders supporting the process.

Several factors will contribute to the need for adapting management procedures: global warming, consequent rise in mean sea levels, increased frequency, and intensification of storms, especially beginning in the middle of the present century [32]. These impacts from global warming will require other forms of accommodation in coastal areas.

At some point, it will no longer be possible to maintain the effectiveness of the protection measures in the high-risk areas. The effort to continue living in vulnerable areas, possibly even with high loss rates, will remain for some time, but there will come a time when the risk will no longer be acceptable and much of the effort will focus on retreating from these areas. At that time, local communities will eventually accept that retreat to a safer place is necessary. The question of "How long will the location where we retreated be a safer place?" will always remain. The costs involved in maintaining the effectiveness of protection measures in high-risk areas may also be an additional problem.

Measures of protection and accommodation will be adapted to the circumstances. The need to model the seabed on the continental shelf (at depths of 5–10 m), by redirecting the propagation of waves and forcing them to break onto the water mass (away from the coastline) is increasingly recognized. Consequently, by preventing waves from discharging much of their energy onto beaches and dune systems, natural protection systems will be less exposed.

Possible solutions to erosion include artificial sand nourishments with installation of submerged coastal control structures, such as submerged longitudinal bars, using sand-filled geotextile tubes as sand containment supports, as in Oh and Shin [17]. Another possible solution consists in the installation of submerged multi-functional artificial reefs equally with the use of geotextiles in tubular form, of which is example the Narrowneck reef installed in the Gold Coast, Australia, in response to the increasing occurrences of beach erosion [33].

Accommodation measures that use aquatic environments have long been a reality. More recently, the number tidal houses, houseboats, and floating houses are increasing. A wide variety of houseboat options are available, both in terms of features and dimensions.

The contemporary reality still allows resistance to adverse conditions with relatively soft adaptation solutions; however, most forecasts point to significant changes within a few decades [32]. High concentrations of population and services in coastal areas, increasing difficulties in finding safe and pleasant spaces and the expected flooding of many lowlands as a result of global climate change are favorable conditions for the search and installation of accommodation alternatives.

As endnotes, it is recommended the involvement of people (residents, citizens, stakeholders, and others), technical support and government in the actions to be developed under the following guidelines:


**19**

**Author details**

José Simão Antunes do Carmo

\*Address all correspondence to: jsacarmo@de.uc.pt

provided the original work is properly cited.

Department of Civil Engineering, University of Coimbra, Coimbra, Portugal

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

*Coastal Adaptation: Past Behaviors, Contemporary Management, and Future Options*

*DOI: http://dx.doi.org/10.5772/intechopen.88123*

*Coastal Adaptation: Past Behaviors, Contemporary Management, and Future Options DOI: http://dx.doi.org/10.5772/intechopen.88123*

## **Author details**

*Coastal and Marine Environments - Physical Processes and Numerical Modelling*

tion in coastal areas.

features and dimensions.

developed under the following guidelines:

community or a city's entire strategy.

long-term local strategies.

areas may also be an additional problem.

systems, natural protection systems will be less exposed.

response to the increasing occurrences of beach erosion [33].

Several factors will contribute to the need for adapting management procedures:

At some point, it will no longer be possible to maintain the effectiveness of the protection measures in the high-risk areas. The effort to continue living in vulnerable areas, possibly even with high loss rates, will remain for some time, but there will come a time when the risk will no longer be acceptable and much of the effort will focus on retreating from these areas. At that time, local communities will eventually accept that retreat to a safer place is necessary. The question of "How long will the location where we retreated be a safer place?" will always remain. The costs involved in maintaining the effectiveness of protection measures in high-risk

Measures of protection and accommodation will be adapted to the circumstances. The need to model the seabed on the continental shelf (at depths of 5–10 m), by redirecting the propagation of waves and forcing them to break onto the water mass (away from the coastline) is increasingly recognized. Consequently, by preventing waves from discharging much of their energy onto beaches and dune

Possible solutions to erosion include artificial sand nourishments with installation of submerged coastal control structures, such as submerged longitudinal bars, using sand-filled geotextile tubes as sand containment supports, as in Oh and Shin [17]. Another possible solution consists in the installation of submerged multi-functional artificial reefs equally with the use of geotextiles in tubular form, of which is example the Narrowneck reef installed in the Gold Coast, Australia, in

Accommodation measures that use aquatic environments have long been a reality. More recently, the number tidal houses, houseboats, and floating houses are increasing. A wide variety of houseboat options are available, both in terms of

The contemporary reality still allows resistance to adverse conditions with relatively soft adaptation solutions; however, most forecasts point to significant changes within a few decades [32]. High concentrations of population and services in coastal areas, increasing difficulties in finding safe and pleasant spaces and the expected flooding of many lowlands as a result of global climate change are favorable conditions for the search and installation of accommodation alternatives.

As endnotes, it is recommended the involvement of people (residents, citizens, stakeholders, and others), technical support and government in the actions to be

• Multi-functional flood defense infrastructures can be developed and should be

become more resilient and flood resistant, and should be part of an integrated

• The planning systems should encourage integrated solutions and innovative

• Barriers are not enough as flood defenses—existing and new houses can

implemented for the benefit of local people and businesses.

global warming, consequent rise in mean sea levels, increased frequency, and intensification of storms, especially beginning in the middle of the present century [32]. These impacts from global warming will require other forms of accommoda-

**18**

José Simão Antunes do Carmo Department of Civil Engineering, University of Coimbra, Coimbra, Portugal

\*Address all correspondence to: jsacarmo@de.uc.pt

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

## **References**

[1] Kamphuis JW. Costal science, engineering and management. In: Proceedings of the Canadian Coastal Conference 2005; Dartmouth, Nova Scotia, Canada; 2005. 9p

[2] Hedelin B, Evers M, Alkan-Olsson J, Jonsson A. Participatory modelling for sustainable development: Key issues derived from five cases of natural resource and disaster risk management. Environmental Science and Policy. 2017;**76**:185-196. DOI: 10.1016/j. envsci.2017.07.001

[3] Barceló D. Researching New Ways to Connect People to Nature: A Special Collection for #WorldEnvironmentDay. Editor's Note. 2017. https:// www.elsevier.com/connect/ researching-new-ways-to-connectpeople-to-nature-a-special-collectionfor-worldenvironmentday

[4] Nunes L, Monteiro JP, Cunha MC, Vieira J, Lucas H, Ribeiro L. The water crisis in southern Portugal: how did we get there and how should we solve it. WIT Transactions on Ecology and the Environment. 2006;**99**:435-444. DOI: 10.2495/RAV060431

[5] Lopes AM. Information systems applied to the integration of knowledge in coastal management of the Central Region. In: Colloquium on Coastal Management: Vulnerabilities and Risks in the Central Region; Portugal: University of Aveiro, November 26, 2010

[6] Pinho JLS, Vieira JMP, Antunes do Carmo JS. Hydroinformatic environment for coastal waters hydrodynamics and water quality modelling. Journal of Advances in Engineering Software. 2004;**35**:205-222. DOI: 10.1016/j.advengsoft.2004.01.001

[7] Deltares. User Manual Delft3D-FLOW. Hydro-Morphodynamics,

Version: 3.15.34158. The Netherlands: Deltares; 2014. https://oss.deltares.nl/ documents/183920/185723/Delft3D-FLOW\_User\_Manual.pdf

[8] Deltares. User Manual Delft3D-WAVE. Hydro-Morphodynamics. Simulation of Short-Crested Waves with SWAN. Version: 3.05. The Netherlands: Deltares; 2019. https://content.oss. deltares.nl/delft3d/manuals/Delft3D-WAVE\_User\_Manual.pdf

[9] Deltares. User Manual D-Water Quality. Water quality and Aquatic Ecology. Version: 5.06. The Netherlands: Deltares; 2019. https://content.oss. deltares.nl/delft3d/manuals/D-Water\_ Quality\_PLCT\_User\_Manual.pdf

[10] Kamphuis JW. Coastal engineering education and coastal models. Coastal Engineering Proceedings. 2012;**33**:30. DOI: 10.9753/icce.v33.management.30. 7p. ISSN: 2156-1028

[11] Veloso-Gomes F, Costa J, Rodrigues A, Taveira-Pinto F, Pais-Barbosa J, Neves L. Costa da Caparica artificial sand nourishment and coastal dynamics. ICS2009 Proceedings. Journal of Coastal Research. 2009;**SI56**:678-682

[12] Antunes do Carmo JS. Climate change, adaptation measures and integrated coastal zone management: The new protection paradigm for the Portuguese coastal zone. Journal of Coastal Research. 2018;**34**(3):687-703. DOI: 10.2112/ JCOASTRES-D-16-00165.1

[13] Guimarães MH, Dentinho T, Boski T. Application of the Q methodology in the promotion of dialogue among agents interested in the management of Praia da Vitória Bay, Terceira, Azores. In: VI Congress on Planning and Management of Coastal Areas of Portuguese Speaking Countries, Boavista Island, Cape Verde; 2011 (in Portuguese)

**21**

62p

pp. 381-384

4; CD-Rom: 0 415 39433 3

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*Coastal Adaptation: Past Behaviors, Contemporary Management, and Future Options*

a sanddune system. WIT Transactions on Ecology and the Environment. 2006;**88**:195-204. DOI: 10.2495/

[22] Antunes do Carmo JS, Reis CS, Freitas H. Rehabilitation of a geotextilereinforced sand dune. Journal of Coastal

[23] Antunes do Carmo JS, Reis CS, Freitas H. Working with nature by protecting sand dunes: Lessons learned. Journal of Coastal Research. 2010;**6**(6):1068-1078. DOI: 10.2112/

[24] Evans AJ, Garrod B, Firth LB, Hawkins SJ, Morris-Webb ES, Goudge H, et al. Stakeholder priorities for multifunctional coastal defence developments and steps to effective implementation.

Marine Policy. 2017;**75**:143-155

[26] Mendonça A, Fortes CJ, Capitão R, Neves MG, Moura T, Antunes do Carmo JS. Wave hydrodynamics around a multifunctional artificial reef at Leirosa. Journal of Coastal Conservation. 2012;**16**:543-553. DOI: 10.1007/

s11852-012-0196-1

[25] Mendonça A, Fortes CJ, Capitão R, Neves MG, Antunes do Carmo JS, Moura T. Hydrodynamics around an artificial surfing reef at Leirosa, Portugal. Journal of Waterway, Port, Coastal, and Ocean Engineering. 2012a;**138**(3):226-235. DOI: 10.1061/ (ASCE)WW.1943-5460.0000128

[27] Lynett PJ, Liu PL-F. Modeling wave generation, evolution, and interaction with depth-integrated, dispersive wave equations. In: COULWAVE Code Manual. NY, USA: Cornell University; 2008. Long and intermediate wave modeling package, v. 2.0. https://pdfs. semanticscholar.org/f07d/a390c4590b88

0607037be8d900538f42c992.pdf

[28] Alveirinho Dias, J.M., Ferreira, Ó.M.F.C., Pereira A.P.R.R., 1994.

Research, SI. 2009;**56**:282-286

JCOASTRES-D-10-00022.1

CENV060191

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[14] Neumann B, Vafeidis AT, Zimmermann J, Nicholls RJ. Future coastal population growth and exposure to sea-level rise and coastal flooding—A global assessment. PLoS One. 2015;**10**(3):e0118571. DOI: 10.1371/

[15] Berger M. Coastal Populations Grow—And Will Continue To—As Sea Levels Rise. Environment. 2015. Available from: https://weather.com/ science/environment/news/coastalpopulations-grow-sea-levels-rise

[16] EEA. The changing faces of Europe's

[17] Oh YI, Shin EC. Using submerged geotextile tubes in the protection of the E. Korean shore. Coastal Engineering. 2006;**53**:879-895. DOI: 10.1016/j.

Vertegaal CTM, Wijsman JWM, Van der Valk L, Tonnon PK. Development of Sand Motor. Concise Report Describing the First Four Years of the Monitoring and Evaluation Programme (MEP). Delft, The Netherlands: Deltares; 2016.

[19] Reis CS, Freitas H. Rehabilitation of the Leirosa sand dunes. In: EuroCoast-Portugal Association, editor. Littoral 2002, Porto; Vol. III. September 22-26, 2002. Porto, Portugal; 2002.

[20] Reis CS, Freitas H, Antunes do Carmo JS. Leirosa sand dunes: A case study on coastal protection. In: Proceedings of the IMAM - Maritime Transportation and Exploitation of Ocean and Coastal Resources, Lisboa; de September 26-30. Taylor & Francis/BALKEMA; 2005. pp. 1469-1474. ISBN: Vol. 2: 0 415 39374

coastal areas. EEA Report No. 6;

Copenhagen; 2006. 112p

coastaleng.2006.06.005

[18] Taal MD, Löffler MAM,

journal.pone.0118571

*Coastal Adaptation: Past Behaviors, Contemporary Management, and Future Options DOI: http://dx.doi.org/10.5772/intechopen.88123*

[14] Neumann B, Vafeidis AT, Zimmermann J, Nicholls RJ. Future coastal population growth and exposure to sea-level rise and coastal flooding—A global assessment. PLoS One. 2015;**10**(3):e0118571. DOI: 10.1371/ journal.pone.0118571

[15] Berger M. Coastal Populations Grow—And Will Continue To—As Sea Levels Rise. Environment. 2015. Available from: https://weather.com/ science/environment/news/coastalpopulations-grow-sea-levels-rise

[16] EEA. The changing faces of Europe's coastal areas. EEA Report No. 6; Copenhagen; 2006. 112p

[17] Oh YI, Shin EC. Using submerged geotextile tubes in the protection of the E. Korean shore. Coastal Engineering. 2006;**53**:879-895. DOI: 10.1016/j. coastaleng.2006.06.005

[18] Taal MD, Löffler MAM, Vertegaal CTM, Wijsman JWM, Van der Valk L, Tonnon PK. Development of Sand Motor. Concise Report Describing the First Four Years of the Monitoring and Evaluation Programme (MEP). Delft, The Netherlands: Deltares; 2016. 62p

[19] Reis CS, Freitas H. Rehabilitation of the Leirosa sand dunes. In: EuroCoast-Portugal Association, editor. Littoral 2002, Porto; Vol. III. September 22-26, 2002. Porto, Portugal; 2002. pp. 381-384

[20] Reis CS, Freitas H, Antunes do Carmo JS. Leirosa sand dunes: A case study on coastal protection. In: Proceedings of the IMAM - Maritime Transportation and Exploitation of Ocean and Coastal Resources, Lisboa; de September 26-30. Taylor & Francis/BALKEMA; 2005. pp. 1469-1474. ISBN: Vol. 2: 0 415 39374 4; CD-Rom: 0 415 39433 3

[21] Antunes do Carmo JS, Reis CS, Freitas H. Successful rehabilitation of a sanddune system. WIT Transactions on Ecology and the Environment. 2006;**88**:195-204. DOI: 10.2495/ CENV060191

[22] Antunes do Carmo JS, Reis CS, Freitas H. Rehabilitation of a geotextilereinforced sand dune. Journal of Coastal Research, SI. 2009;**56**:282-286

[23] Antunes do Carmo JS, Reis CS, Freitas H. Working with nature by protecting sand dunes: Lessons learned. Journal of Coastal Research. 2010;**6**(6):1068-1078. DOI: 10.2112/ JCOASTRES-D-10-00022.1

[24] Evans AJ, Garrod B, Firth LB, Hawkins SJ, Morris-Webb ES, Goudge H, et al. Stakeholder priorities for multifunctional coastal defence developments and steps to effective implementation. Marine Policy. 2017;**75**:143-155

[25] Mendonça A, Fortes CJ, Capitão R, Neves MG, Antunes do Carmo JS, Moura T. Hydrodynamics around an artificial surfing reef at Leirosa, Portugal. Journal of Waterway, Port, Coastal, and Ocean Engineering. 2012a;**138**(3):226-235. DOI: 10.1061/ (ASCE)WW.1943-5460.0000128

[26] Mendonça A, Fortes CJ, Capitão R, Neves MG, Moura T, Antunes do Carmo JS. Wave hydrodynamics around a multifunctional artificial reef at Leirosa. Journal of Coastal Conservation. 2012;**16**:543-553. DOI: 10.1007/ s11852-012-0196-1

[27] Lynett PJ, Liu PL-F. Modeling wave generation, evolution, and interaction with depth-integrated, dispersive wave equations. In: COULWAVE Code Manual. NY, USA: Cornell University; 2008. Long and intermediate wave modeling package, v. 2.0. https://pdfs. semanticscholar.org/f07d/a390c4590b88 0607037be8d900538f42c992.pdf

[28] Alveirinho Dias, J.M., Ferreira, Ó.M.F.C., Pereira A.P.R.R., 1994.

**20**

2010

*Coastal and Marine Environments - Physical Processes and Numerical Modelling*

Version: 3.15.34158. The Netherlands: Deltares; 2014. https://oss.deltares.nl/ documents/183920/185723/Delft3D-

[8] Deltares. User Manual Delft3D-WAVE. Hydro-Morphodynamics. Simulation of Short-Crested Waves with SWAN. Version: 3.05. The Netherlands: Deltares; 2019. https://content.oss. deltares.nl/delft3d/manuals/Delft3D-

[9] Deltares. User Manual D-Water Quality. Water quality and Aquatic Ecology. Version: 5.06. The Netherlands: Deltares; 2019. https://content.oss. deltares.nl/delft3d/manuals/D-Water\_ Quality\_PLCT\_User\_Manual.pdf

[10] Kamphuis JW. Coastal engineering education and coastal models. Coastal Engineering Proceedings. 2012;**33**:30. DOI: 10.9753/icce.v33.management.30.

FLOW\_User\_Manual.pdf

WAVE\_User\_Manual.pdf

7p. ISSN: 2156-1028

[11] Veloso-Gomes F, Costa J, Rodrigues A, Taveira-Pinto F, Pais-Barbosa J, Neves L. Costa da Caparica artificial sand nourishment and coastal dynamics. ICS2009 Proceedings. Journal of Coastal Research. 2009;**SI56**:678-682

[12] Antunes do Carmo JS. Climate change, adaptation measures and integrated coastal zone management:

[13] Guimarães MH, Dentinho T, Boski T. Application of the Q methodology in the promotion of dialogue among agents interested in the management of Praia da Vitória Bay, Terceira, Azores. In: VI Congress on Planning and Management of Coastal Areas of Portuguese Speaking Countries, Boavista Island, Cape Verde;

The new protection paradigm for the Portuguese coastal zone. Journal of Coastal Research. 2018;**34**(3):687-703. DOI: 10.2112/

JCOASTRES-D-16-00165.1

2011 (in Portuguese)

[1] Kamphuis JW. Costal science, engineering and management. In: Proceedings of the Canadian Coastal Conference 2005; Dartmouth, Nova

[2] Hedelin B, Evers M, Alkan-Olsson J, Jonsson A. Participatory modelling for sustainable development: Key issues derived from five cases of natural resource and disaster risk management. Environmental Science and Policy. 2017;**76**:185-196. DOI: 10.1016/j.

[3] Barceló D. Researching New Ways to Connect People to Nature: A Special Collection for #WorldEnvironmentDay.

[4] Nunes L, Monteiro JP, Cunha MC, Vieira J, Lucas H, Ribeiro L. The water crisis in southern Portugal: how did we get there and how should we solve it. WIT Transactions on Ecology and the Environment. 2006;**99**:435-444. DOI:

[5] Lopes AM. Information systems applied to the integration of knowledge in coastal management of the Central Region. In: Colloquium on Coastal Management: Vulnerabilities and Risks in the Central Region; Portugal: University of Aveiro, November 26,

[6] Pinho JLS, Vieira JMP, Antunes do Carmo JS. Hydroinformatic environment for coastal waters hydrodynamics and water quality modelling. Journal of Advances in Engineering Software. 2004;**35**:205-222. DOI: 10.1016/j.advengsoft.2004.01.001

[7] Deltares. User Manual Delft3D-FLOW. Hydro-Morphodynamics,

Editor's Note. 2017. https:// www.elsevier.com/connect/ researching-new-ways-to-connectpeople-to-nature-a-special-collection-

for-worldenvironmentday

10.2495/RAV060431

Scotia, Canada; 2005. 9p

**References**

envsci.2017.07.001

Chapter 2

Abstract

are presented.

1. Introduction

23

Perspective

Numerical Modeling Tools

Hydrodynamics: A User

Applied to Estuarine and Coastal

Isabel Iglesias, Paulo Avilez-Valente, José Luís Pinho, Ana Bio,

José Manuel Vieira, Luísa Bastos and Fernando Veloso-Gomes

Estuarine and coastal areas have been intensively studied given their complexity, ecological, and societal value and the importance of their ecosystem

characterization of these areas, which is achievable complementing the comprehensive field measurements with numerical models solutions. Based on a detailed comparison between two close-by, but extremely different, Portuguese estuaries (the Douro and Minho estuaries), this chapter intends to discuss how accurately numerical modeling tools can provide relevant information for a variety of coastal zones. They can be very useful for various applications in the planning and management fields, such as coastal and infrastructures protection, harbor activities, fisheries, tourism, and coastal population safety, thus supporting an effective and integrated estuarine and coastal management, which must consider both the safety of the populations and the sustainability of the marine ecosystems and services. In particular, the capacity of the numerical models to give a detailed characterization of morpho-hydrodynamic processes, as well as assess and predict the effects of anthropogenic interventions, extreme events and climate change effects,

services. Estuarine and coastal management must be based on a sound

Keywords: estuaries and coasts, hydrodynamics, field measurements,

The Coastal Zone is strategically important from environmental, economic, and societal points-of-view. Coastal zones are densely populated, concentrating human settlements, leisure activities, fisheries, and other marine industries. In the last decades, the population, economic assets, and urbanizations in the coastal zones have experienced a rapid growth, and a continuous increase of population in these regions is expected for the near future [1, 2]. The intensification of anthropic activities in coastal regions can boost their vulnerability to extreme events and, consequently, augment damages, cause injuries, and even loss of lives. In the

numerical modeling, coastal zones management

Estudo Sintético de Diagnóstico da Geomorfologia e da Dinâmica Sedimentar dos Troços Costeiros entre Espinho e Nazaré (e\_book). Portugal. Available from: http://w3.ualg. pt/~jdias/JAD/eb\_EspinhoNazare.html (in Portuguese) Portugal. Available from: http://w3.ualg.pt/~jdias/JAD/ eb\_EspinhoNazare.html

[29] Park H, Tomiczek T, Cox DT, van de Lindt JW, Lomonaco P. Experimental modeling of horizontal and vertical wave forces on an elevated coastal structure. Coastal Engineering. 2017;**128**:58-74. DOI: 10.1016/j. coastaleng.2017.08.001

[30] Coulbourne B, Haupt M, Sundberg S, Low DK, Yeung J, Squerciati J. Recommended residential construction for coastal areas. In: Building on Strong and Safe Foundations. 2nd ed. 2009. US Federal Emergency Management, FEMA P-550, 242 p. ISBN-13: 978-1484818657, ISBN-10: 1484818652

[31] Kamphuis JW. Introduction to coastal engineering and management. In: Advances Series on Ocean Engineering. 2nd ed. Vol. 30. Singapore: World Scientific Publishing; 2010. 525p. ISBN-13: 978-981-283-484-3

[32] IPCC. Synthesis report summary for policymakers. In: Core Writing Team, Pachauri RK, Meyer LA, editors. Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC); Geneva, Switzerland; 2014. 32p

[33] Jackson LA, Tomlinson R, Corbett B, Strauss D. Long term performance of a submerged coastal control structure: A case study of the Narrowneck multifunctional artificial reef. In: 33rd Conference on Coastal Engineering; Santander, Spain; Vol. 54; 2012. 13p

## Chapter 2

*Coastal and Marine Environments - Physical Processes and Numerical Modelling*

Estudo Sintético de Diagnóstico da Geomorfologia e da Dinâmica Sedimentar dos Troços Costeiros entre Espinho e Nazaré (e\_book). Portugal. Available from: http://w3.ualg. pt/~jdias/JAD/eb\_EspinhoNazare.html (in Portuguese) Portugal. Available from: http://w3.ualg.pt/~jdias/JAD/

eb\_EspinhoNazare.html

coastaleng.2017.08.001

10: 1484818652

[30] Coulbourne B, Haupt M, Sundberg S, Low DK, Yeung J,

construction for coastal areas. In: Building on Strong and Safe Foundations. 2nd ed. 2009. US Federal Emergency Management, FEMA P-550, 242 p. ISBN-13: 978-1484818657, ISBN-

[31] Kamphuis JW. Introduction to coastal engineering and management.

Engineering. 2nd ed. Vol. 30. Singapore: World Scientific Publishing; 2010. 525p.

[32] IPCC. Synthesis report summary for policymakers. In: Core Writing Team, Pachauri RK, Meyer LA, editors. Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC); Geneva,

[33] Jackson LA, Tomlinson R, Corbett B, Strauss D. Long term performance of a submerged coastal control structure: A case study of the Narrowneck multifunctional artificial reef. In: 33rd Conference on Coastal Engineering; Santander, Spain; Vol. 54; 2012. 13p

In: Advances Series on Ocean

ISBN-13: 978-981-283-484-3

Switzerland; 2014. 32p

Squerciati J. Recommended residential

[29] Park H, Tomiczek T, Cox DT, van de Lindt JW, Lomonaco P. Experimental modeling of horizontal and vertical wave forces on an elevated coastal structure. Coastal Engineering. 2017;**128**:58-74. DOI: 10.1016/j.

**22**

## Numerical Modeling Tools Applied to Estuarine and Coastal Hydrodynamics: A User Perspective

Isabel Iglesias, Paulo Avilez-Valente, José Luís Pinho, Ana Bio, José Manuel Vieira, Luísa Bastos and Fernando Veloso-Gomes

## Abstract

Estuarine and coastal areas have been intensively studied given their complexity, ecological, and societal value and the importance of their ecosystem services. Estuarine and coastal management must be based on a sound characterization of these areas, which is achievable complementing the comprehensive field measurements with numerical models solutions. Based on a detailed comparison between two close-by, but extremely different, Portuguese estuaries (the Douro and Minho estuaries), this chapter intends to discuss how accurately numerical modeling tools can provide relevant information for a variety of coastal zones. They can be very useful for various applications in the planning and management fields, such as coastal and infrastructures protection, harbor activities, fisheries, tourism, and coastal population safety, thus supporting an effective and integrated estuarine and coastal management, which must consider both the safety of the populations and the sustainability of the marine ecosystems and services. In particular, the capacity of the numerical models to give a detailed characterization of morpho-hydrodynamic processes, as well as assess and predict the effects of anthropogenic interventions, extreme events and climate change effects, are presented.

Keywords: estuaries and coasts, hydrodynamics, field measurements, numerical modeling, coastal zones management

## 1. Introduction

The Coastal Zone is strategically important from environmental, economic, and societal points-of-view. Coastal zones are densely populated, concentrating human settlements, leisure activities, fisheries, and other marine industries. In the last decades, the population, economic assets, and urbanizations in the coastal zones have experienced a rapid growth, and a continuous increase of population in these regions is expected for the near future [1, 2]. The intensification of anthropic activities in coastal regions can boost their vulnerability to extreme events and, consequently, augment damages, cause injuries, and even loss of lives. In the

present context of climate changes, an increase in the frequency and strength of extreme events have been reported [2], with potentially severe consequences for both society and environment, affecting human health and infrastructures, and resulting in the loss of property and habitats [3, 4]. For example, a loss of 70% of the coastal wetlands by 2080 is predicted due to a combination of sea-level rise, intensification of coastal urbanization, and increase of constructions for flood defense [5, 6]. Wetlands are highly productive areas, essential not only for fisheries and nature conservation, but also as a natural protection against floods. Their loss can have high socio-economic costs. Thus, extreme events, climate change conditions, and anthropogenic activities can put at risk the Coastal Zone's prolific flora and fauna and the ecosystem services they provide (e.g., food, fisheries, tourism, cultural services, energy, water abstraction, raw materials, water desalination/treatment, climate, and natural hazard regulation).

monitoring methodologies should be pursued to improve our knowledge

Numerical Modeling Tools Applied to Estuarine and Coastal Hydrodynamics: A User Perspective

are essential to properly assess the effect of each forcing driver, accurately

Considerable effort has been made to provide the most accurate estimations for the complex estuarine/coastal circulation, using either simple box models or complex numerical model suites. With the development of high-resolution numerical modeling systems, essential decision-making support instruments became available for an effective and integrated marine and coastal management. Numerical models

representing the dynamical processes of estuarine/coastal systems [10]. Their input can be manipulated to represent the impact of changes in initial and boundary conditions, topo-bathymetric features, and coastal structures [12]. They can help to overcome the lack of field observations and measurements, allowing a full characterization of the morpho-hydrodynamic, chemical, and biological behavior of coastal regions, and providing valuable information to promote population, services

The current modeling tools available for coastal and estuarine studies allow an almost complete representation of the physical conditions of these areas. There is a large variety of models and techniques. The numerical techniques can be based on several methods, such as finite element, finite difference, finite volume, boundary element, or Eulerian-Lagrangian. The time integration algorithms can be explicit, implicit, semi-implicit, or characteristic-based. The functions can be of the first, second, or higher order, and the spatial dimensions can be one-dimensional (either in the horizontal plane 1DH or in the vertical 1DV), two-dimensional depth integrated (2DH) or lateral integrated (2DV), or three-dimensional (3D) [15, 16]. It is therefore important to properly select the adequate numerical model tool for the specific problem(s) the user wants to solve. This selection should be made in each case considering a compromise between the available data for model calibration and validation, the objectives of the model simulations and the available computational

The most powerful modeling suites currently available (Delft3D, open TELEMAC-MASCARET, SWASH, ROMS, MOHID, SELFE, ADCIRC, Tuflow-FV, FVCOM, Mike21, etc.) are able to simulate several physical processes and environmental actions, such as flood/ebb cycles, bathymetry dynamics, friction, river discharge, water levels dynamics, currents velocity, wind action, waves, density effects, sediment transport, or Coriolis force, among others. Normally, numerical tools to model these processes are available in different and separate modules that the user can select depending on the desired complexity of the solutions. Modeling suites can also contain additional modules that allow the characterization of biological and ecological processes that are fundamental for water quality assessment, recurring to both Lagrangian and Eulerian transport approaches, including larvae migration, ecological status, nutrients concentration, pollutant evolution, etc. But, even these biogeochemical modules are completely dependent on the results obtained by the modules that represent the hydrodynamic patterns. The hydrodynamic conditions (water levels, currents velocities, temperature, and salinity) resulting, for example, from the complex interaction between tides, waves, storm surge, wave set-up, and river discharge, will define the main transportation patterns of sediments, larvae and pollutants with a direct effect on the ecosystems. Most of the numerical models applied to coastal and estuarine regions can be

implemented in 2DH/V or 3D configurations. 2DH simulations simplify the

2. Numerical models and the ensembles technique

about those processes.

DOI: http://dx.doi.org/10.5772/intechopen.85521

and ecosystems safety [13, 14].

resources.

25

In this context, there is a need for scientific and technical information available to decision-makers, to support a sustainable coastal management, and avoid serious damages and higher losses for the littoral populations and coastal environments [7, 8]. This information is crucial to implement early warning systems and find solutions to reduce the negative impacts associated with extreme events (floods, droughts, storm surges, and coastal storms), climate change, and man-made interventions in the Coastal Zone. These can help to reduce exposure and vulnerability, mitigate the associated risks and promote the adaptation and the resilience of the communities to the potential adverse impacts, even though risks cannot be fully mitigated.

Effective protection of the Coastal Zone requires a comprehensive understanding of its morpho-hydrodynamic processes, as well as of the effects of these processes on the territory and the ecosystems. Coasts are land-ocean transition areas and, therefore, Coastal Zone assessment must consider land-ocean interactions, including estuaries and marine areas [9]. Meteorological, oceanographic, morphological, chemical, and biological parameters, obtained through in-situ measurement campaigns, are key descriptors to represent and understand the present state and the main evolution trends of the estuarine and coastal systems. However, field campaigns are usually expensive, often difficult and not always effective. As a consequence, there is a lack of continuous and long-term observations, being these regions generally under-sampled and poorly understood [10]. This limited knowledge, related with the lack of systematic monitoring and interface system complexity, leads to a high degree of uncertainty about the expectable effects of future scenarios associated with man-made interventions, climate change, and extreme events.

A complete estuarine/coastal dynamics characterization and, particularly, the assessment of future conditions, could be achieved through results obtained with numerical models [7, 11]. These models provide predictions of future trends and outcomes for different scenarios, hence supporting the implementation of sustainable action plans. Nevertheless, it should be noticed that field data is crucial for proper implementation of numerical models. Measured data are needed to define the models' initial states, forcing conditions, and static computation of calibration parameters values, or its dynamic computation using data assimilation techniques. Field data are also required to assess the numerical models performance comparing model results to measurements. So, despite the fact that advanced numerical models are excellent tools to understand the Coastal Zone behavior, comprehensive periodic or continuous monitoring campaigns in estuarine and coastal regions are still crucial to ensure the effectiveness of model application. Moreover, some of the complex morpho-hydrodynamic processes that take place in the coastal environment are still poorly understood. The combination of numerical and field

monitoring methodologies should be pursued to improve our knowledge about those processes.

## 2. Numerical models and the ensembles technique

present context of climate changes, an increase in the frequency and strength of extreme events have been reported [2], with potentially severe consequences for both society and environment, affecting human health and infrastructures, and resulting in the loss of property and habitats [3, 4]. For example, a loss of 70% of the coastal wetlands by 2080 is predicted due to a combination of sea-level rise, intensification of coastal urbanization, and increase of constructions for flood defense [5, 6]. Wetlands are highly productive areas, essential not only for fisheries and nature conservation, but also as a natural protection against floods. Their loss can have high socio-economic costs. Thus, extreme events, climate change conditions, and anthropogenic activities can put at risk the Coastal Zone's prolific flora and fauna and the ecosystem services they provide (e.g., food, fisheries, tourism, cultural services, energy, water abstraction, raw materials, water desalination/treat-

Coastal and Marine Environments - Physical Processes and Numerical Modelling

In this context, there is a need for scientific and technical information available to decision-makers, to support a sustainable coastal management, and avoid serious damages and higher losses for the littoral populations and coastal environments [7, 8]. This information is crucial to implement early warning systems and find solutions to reduce the negative impacts associated with extreme events (floods, droughts, storm surges, and coastal storms), climate change, and man-made interventions in the Coastal Zone. These can help to reduce exposure and vulnerability, mitigate the associated risks and promote the adaptation and the resilience of the communities to the potential adverse impacts, even though risks cannot be

Effective protection of the Coastal Zone requires a comprehensive understanding of its morpho-hydrodynamic processes, as well as of the effects of these processes on the territory and the ecosystems. Coasts are land-ocean transition areas and, therefore, Coastal Zone assessment must consider land-ocean interactions, including estuaries and marine areas [9]. Meteorological, oceanographic, morphological, chemical, and biological parameters, obtained through in-situ measurement campaigns, are key descriptors to represent and understand the present state and the main evolution trends of the estuarine and coastal systems. However, field campaigns are usually expensive, often difficult and not always effective. As a consequence, there is a lack of continuous and long-term observations, being these regions generally under-sampled and poorly understood [10]. This limited knowledge, related with the lack of systematic monitoring and interface system complexity, leads to a high degree of uncertainty about the expectable effects of future scenarios associated with man-made interventions, climate change, and

A complete estuarine/coastal dynamics characterization and, particularly, the assessment of future conditions, could be achieved through results obtained with numerical models [7, 11]. These models provide predictions of future trends and outcomes for different scenarios, hence supporting the implementation of sustainable action plans. Nevertheless, it should be noticed that field data is crucial for proper implementation of numerical models. Measured data are needed to define the models' initial states, forcing conditions, and static computation of calibration parameters values, or its dynamic computation using data assimilation techniques. Field data are also required to assess the numerical models performance comparing model results to measurements. So, despite the fact that advanced numerical models are excellent tools to understand the Coastal Zone behavior, comprehensive periodic or continuous monitoring campaigns in estuarine and coastal regions are still crucial to ensure the effectiveness of model application. Moreover, some of the complex morpho-hydrodynamic processes that take place in the coastal environment are still poorly understood. The combination of numerical and field

ment, climate, and natural hazard regulation).

fully mitigated.

extreme events.

24

Considerable effort has been made to provide the most accurate estimations for the complex estuarine/coastal circulation, using either simple box models or complex numerical model suites. With the development of high-resolution numerical modeling systems, essential decision-making support instruments became available for an effective and integrated marine and coastal management. Numerical models are essential to properly assess the effect of each forcing driver, accurately representing the dynamical processes of estuarine/coastal systems [10]. Their input can be manipulated to represent the impact of changes in initial and boundary conditions, topo-bathymetric features, and coastal structures [12]. They can help to overcome the lack of field observations and measurements, allowing a full characterization of the morpho-hydrodynamic, chemical, and biological behavior of coastal regions, and providing valuable information to promote population, services and ecosystems safety [13, 14].

The current modeling tools available for coastal and estuarine studies allow an almost complete representation of the physical conditions of these areas. There is a large variety of models and techniques. The numerical techniques can be based on several methods, such as finite element, finite difference, finite volume, boundary element, or Eulerian-Lagrangian. The time integration algorithms can be explicit, implicit, semi-implicit, or characteristic-based. The functions can be of the first, second, or higher order, and the spatial dimensions can be one-dimensional (either in the horizontal plane 1DH or in the vertical 1DV), two-dimensional depth integrated (2DH) or lateral integrated (2DV), or three-dimensional (3D) [15, 16]. It is therefore important to properly select the adequate numerical model tool for the specific problem(s) the user wants to solve. This selection should be made in each case considering a compromise between the available data for model calibration and validation, the objectives of the model simulations and the available computational resources.

The most powerful modeling suites currently available (Delft3D, open TELEMAC-MASCARET, SWASH, ROMS, MOHID, SELFE, ADCIRC, Tuflow-FV, FVCOM, Mike21, etc.) are able to simulate several physical processes and environmental actions, such as flood/ebb cycles, bathymetry dynamics, friction, river discharge, water levels dynamics, currents velocity, wind action, waves, density effects, sediment transport, or Coriolis force, among others. Normally, numerical tools to model these processes are available in different and separate modules that the user can select depending on the desired complexity of the solutions. Modeling suites can also contain additional modules that allow the characterization of biological and ecological processes that are fundamental for water quality assessment, recurring to both Lagrangian and Eulerian transport approaches, including larvae migration, ecological status, nutrients concentration, pollutant evolution, etc. But, even these biogeochemical modules are completely dependent on the results obtained by the modules that represent the hydrodynamic patterns. The hydrodynamic conditions (water levels, currents velocities, temperature, and salinity) resulting, for example, from the complex interaction between tides, waves, storm surge, wave set-up, and river discharge, will define the main transportation patterns of sediments, larvae and pollutants with a direct effect on the ecosystems.

Most of the numerical models applied to coastal and estuarine regions can be implemented in 2DH/V or 3D configurations. 2DH simulations simplify the

computational requirements by solving the shallow water equations. It has been demonstrated that this kind of models can accurately reproduce current velocity, flood extent, and water levels, being useful to complement risk assessment tools and early warning systems, because less computational resources are required and the numerical solutions are much faster obtained. Several authors used 2DH models with satisfactory results [14, 17–24], though 3D models are required to properly represent several processes, like vertical stratification, vertical current profiles, turbulent mixing processes, sediment transport, turbidity, water quality, effects of salinity, and temperature gradients on river plumes or salt-wedge estuarine configurations [25–28].

overestimation of Delft3D and open TELEMAC-MASCARET, respectively, were observed for surface elevation for nonflood scenarios. For historical floods, the two models obtained very similar results, despite using different numerical approximations. The different numerical approximations of Mike 21 FM, Delft3D, and Delft3D FM were tested by Symonds et al. [24], confirming that despite the differences in the grids configuration, all the approaches accurately predict hydrodynamic conditions in complex estuarine regions. They also demonstrate that the unstructured

Numerical Modeling Tools Applied to Estuarine and Coastal Hydrodynamics: A User Perspective

There is, hence, a wide range of numerical models that can be applied to estua-

rine/coastal zones to proper characterize these complex areas and gain a deep understanding of their hydrodynamic characteristics. Through the implementation of numerical algorithms, the circulation in these systems can be reproduced and different hydrodynamic processes can be represented. And knowledge about the hydrodynamic patterns influenced by bottom morphological changes may allow assessment and forecasting of the effects of hazardous and extreme events, anthropogenic intervention, or climate change. Hydrodynamic modeling has therefore been the focus of a large number of previous works in estuarine environments

Nowadays, the available powerful computational resources and complex numerical model suites allow the implementation of high-resolution studies

with accurate results. Some examples are the works of Dias et al. [50] and Jones and Davies [46] for estuarine tides, Pinho and Vieira [44] for estuarine salt-water intrusion, Robins and Davies [21] and Sutherland et al. [43] for estuarine

and coastal morpho-hydrodynamic behavior, Pinho et al. [45] and Iglesias et al. [14] for estuarine flood studies, Pinho et al. [51] for coastal waters hydrodynamics and water quality, Antunes do Carmo et al. [16] for agitation in harbors, Antunes do Carmo and Seabra-Santos [30] for coastal protection, and Monteiro et al. [22] for coastal circulation and river plumes. However, every modeling system has its own advantages and limitations, and model solutions will display uncertainties related with errors, calibration parameters, or model assumptions and forcing functions. Given the need for accurate forecasts, finding and implementing new solutions to avoid such errors is crucial. A single model can have biases, high variability, or inaccuracies related with the specification of initial conditions or the representation of physical processes in the models, causing large uncertainties in numerical prediction systems that can affect the reliability of the obtained

results [52]. So, why not use several models to reduce uncertainties?

recently, in estuarine hydrodynamics [14].

27

few as two [53]. Ensemble is a French word that means "set," "cluster," or

The ensembles technique is based on the combination of several numerical models solutions and can improve the forecast results when compared to a single model-based approach, even if the number of members in the models ensemble is as

"together" and usually refers to a unit or group of complementary parts that contribute to a single effect [54]. Ensemble modeling is a method that consists of running two or more related numerical models with the same conditions and then synthesizing the results into a single solution. This single solution will improve the accuracy of the final forecast, compared to the solutions provided by each model. It has been demonstrated that combining models generally increases the skill, reliability, and consistency of model forecasts [55], and ensemble simulations are currently applied in atmospheric and climate sciences to predict meteorological behavior and climate change effects ([56, 57]; IPCC: https://www.ipcc.ch/), being also used in other sectors, such as public health [58], agriculture [59], and more

Two types of ensembles can be defined: single-model and multi-model ensembles. The single-model ensemble is based on a single model that is run several times with very slight differences in the initial and/or boundary conditions, producing

models present a higher computational efficiency.

DOI: http://dx.doi.org/10.5772/intechopen.85521

[11, 14, 17, 21, 22, 40–50].

Regarding the equations and their approximations, 3D models are normally based on the Navier-Stokes equations or its depth-integrated version, the shallow water equations, which are applicable when the horizontal scale is much greater than the vertical scale. The shallow water equations applied to 1DH or 2DH problems are also known as Saint-Venant equations [29]. Despite their wide applicability, shallow water equations are not able to properly represent small relative amplitude waves propagating in shallow water conditions, which is of upmost importance to simulate the superposition between waves and currents, the effects of the waves on the sediment transport, the waves interaction with the bottom, or other wave processes, as shoaling, reflection, refraction, diffraction and decomposition [16, 30]. For this purpose, more sophisticated models are needed, like the ones of Boussinesq, Korteweg de Vries, Serre, or Green-Naghdi. These models include additional terms that take into account the nonhydrostatic effects of free surface curvature. Boussinesq equations [31, 32] are derived from the Navier-Stokes equations by depth-averaging them considering the pressure as nonhydrostatic [33]. Boussinesq-type equations can account nonlinear and dispersive effects considering various degrees of accuracy. The Korteweg de Vries equation, which was first introduced by Boussinesq and rediscovered by Korteweg and de Vries [32, 34] describes weakly nonlinear shallow water waves, allowing the representation of solitary wave solutions [35]. However, it must be considered that the wave dynamic becomes strongly nonlinear in the final stages of shoaling, particularly in the surf and swash zones. To properly represent this phenomenon and provide a correct description of the waves up to the breaking point, fully nonlinear equations should be considered, as the Serre or Green-Naghdi equations. Serre equations [36], also known as the Su-Gardner equations, are deduced from the fundamental equations of fluid mechanics, but taking into account the incompressibility of the fluid, the vertical uniformity of the velocity field and the conservation laws [16]. Finally, Green-Naghdi nonlinear equations [37] considers the 3D water-wave problem with a free surface and a variable bottom, and taking into account that the fluid can be rotational [38].

A comparison between the effectivity of different models and approximations is a really difficult task if the models are not implemented for the same region and considering the same initial/forcing conditions. Nevertheless, there are already some works where the capabilities of different numerical models are compared. Walstra et al. [39] applied the PISCES and the Delft3D models to coastal environments, depicting a general good overall agreement of both models, except for Delft3D under low wave conditions and for PISCES when a flow generated by the breaking of the waves on the shoal is presented. Rahman and Venugopal [25] compared 3D versions of open TELEMAC-MASCARET and Delft3D to represent the hydrodynamic conditions of the Pentland Firth and also the tidal regime energy in that area. Open TELEMAC-MASCARET seems to show the best consistency with the field data, although Delft3D also obtained good results for water level variations. The same models but in a 2DH version were selected by Iglesias et al. [14] to model floods at the Douro estuary. A small underestimation and

#### Numerical Modeling Tools Applied to Estuarine and Coastal Hydrodynamics: A User Perspective DOI: http://dx.doi.org/10.5772/intechopen.85521

overestimation of Delft3D and open TELEMAC-MASCARET, respectively, were observed for surface elevation for nonflood scenarios. For historical floods, the two models obtained very similar results, despite using different numerical approximations. The different numerical approximations of Mike 21 FM, Delft3D, and Delft3D FM were tested by Symonds et al. [24], confirming that despite the differences in the grids configuration, all the approaches accurately predict hydrodynamic conditions in complex estuarine regions. They also demonstrate that the unstructured models present a higher computational efficiency.

There is, hence, a wide range of numerical models that can be applied to estuarine/coastal zones to proper characterize these complex areas and gain a deep understanding of their hydrodynamic characteristics. Through the implementation of numerical algorithms, the circulation in these systems can be reproduced and different hydrodynamic processes can be represented. And knowledge about the hydrodynamic patterns influenced by bottom morphological changes may allow assessment and forecasting of the effects of hazardous and extreme events, anthropogenic intervention, or climate change. Hydrodynamic modeling has therefore been the focus of a large number of previous works in estuarine environments [11, 14, 17, 21, 22, 40–50].

Nowadays, the available powerful computational resources and complex numerical model suites allow the implementation of high-resolution studies with accurate results. Some examples are the works of Dias et al. [50] and Jones and Davies [46] for estuarine tides, Pinho and Vieira [44] for estuarine salt-water intrusion, Robins and Davies [21] and Sutherland et al. [43] for estuarine and coastal morpho-hydrodynamic behavior, Pinho et al. [45] and Iglesias et al. [14] for estuarine flood studies, Pinho et al. [51] for coastal waters hydrodynamics and water quality, Antunes do Carmo et al. [16] for agitation in harbors, Antunes do Carmo and Seabra-Santos [30] for coastal protection, and Monteiro et al. [22] for coastal circulation and river plumes. However, every modeling system has its own advantages and limitations, and model solutions will display uncertainties related with errors, calibration parameters, or model assumptions and forcing functions. Given the need for accurate forecasts, finding and implementing new solutions to avoid such errors is crucial. A single model can have biases, high variability, or inaccuracies related with the specification of initial conditions or the representation of physical processes in the models, causing large uncertainties in numerical prediction systems that can affect the reliability of the obtained results [52]. So, why not use several models to reduce uncertainties?

The ensembles technique is based on the combination of several numerical models solutions and can improve the forecast results when compared to a single model-based approach, even if the number of members in the models ensemble is as few as two [53]. Ensemble is a French word that means "set," "cluster," or "together" and usually refers to a unit or group of complementary parts that contribute to a single effect [54]. Ensemble modeling is a method that consists of running two or more related numerical models with the same conditions and then synthesizing the results into a single solution. This single solution will improve the accuracy of the final forecast, compared to the solutions provided by each model. It has been demonstrated that combining models generally increases the skill, reliability, and consistency of model forecasts [55], and ensemble simulations are currently applied in atmospheric and climate sciences to predict meteorological behavior and climate change effects ([56, 57]; IPCC: https://www.ipcc.ch/), being also used in other sectors, such as public health [58], agriculture [59], and more recently, in estuarine hydrodynamics [14].

Two types of ensembles can be defined: single-model and multi-model ensembles. The single-model ensemble is based on a single model that is run several times with very slight differences in the initial and/or boundary conditions, producing

computational requirements by solving the shallow water equations. It has been demonstrated that this kind of models can accurately reproduce current velocity, flood extent, and water levels, being useful to complement risk assessment tools and early warning systems, because less computational resources are required and the numerical solutions are much faster obtained. Several authors used 2DH models with satisfactory results [14, 17–24], though 3D models are required to properly represent several processes, like vertical stratification, vertical current profiles, turbulent mixing processes, sediment transport, turbidity, water quality, effects of salinity, and temperature gradients on river plumes or salt-wedge estuarine

Coastal and Marine Environments - Physical Processes and Numerical Modelling

Regarding the equations and their approximations, 3D models are normally based on the Navier-Stokes equations or its depth-integrated version, the shallow water equations, which are applicable when the horizontal scale is much greater than the vertical scale. The shallow water equations applied to 1DH or 2DH problems are also known as Saint-Venant equations [29]. Despite their wide applicability, shallow water equations are not able to properly represent small relative amplitude waves propagating in shallow water conditions, which is of upmost importance to simulate the superposition between waves and currents, the effects of the waves on the sediment transport, the waves interaction with the bottom, or other wave processes, as shoaling, reflection, refraction, diffraction and decomposition [16, 30]. For this purpose, more sophisticated models are needed, like the ones of Boussinesq, Korteweg de Vries, Serre, or Green-Naghdi. These models include additional terms that take into account the nonhydrostatic effects of free surface curvature. Boussinesq equations [31, 32] are derived from the Navier-Stokes equations by depth-averaging them considering the pressure as nonhydrostatic [33]. Boussinesq-type equations can account nonlinear and dispersive effects considering various degrees of accuracy. The Korteweg de Vries equation, which was first introduced by Boussinesq and rediscovered by Korteweg and de Vries [32, 34] describes weakly nonlinear shallow water waves, allowing the representation of solitary wave solutions [35]. However, it must be considered that the wave dynamic becomes strongly nonlinear in the final stages of shoaling, particularly in the surf and swash zones. To properly represent this phenomenon and provide a correct description of the waves up to the breaking point, fully nonlinear equations should be considered, as the Serre or Green-Naghdi equations. Serre equations [36], also known as the Su-Gardner equations, are deduced from the fundamental equations of fluid mechanics, but taking into account the incompressibility of the fluid, the vertical uniformity of the velocity field and the conservation laws [16]. Finally, Green-Naghdi nonlinear equations [37] considers the 3D water-wave problem with a free surface and a variable bottom, and taking into account that the fluid can be

A comparison between the effectivity of different models and approximations is a really difficult task if the models are not implemented for the same region and considering the same initial/forcing conditions. Nevertheless, there are already some works where the capabilities of different numerical models are compared. Walstra et al. [39] applied the PISCES and the Delft3D models to coastal environments, depicting a general good overall agreement of both models, except for Delft3D under low wave conditions and for PISCES when a flow generated by the breaking of the waves on the shoal is presented. Rahman and Venugopal [25] compared 3D versions of open TELEMAC-MASCARET and Delft3D to represent the hydrodynamic conditions of the Pentland Firth and also the tidal regime energy in that area. Open TELEMAC-MASCARET seems to show the best consistency with the field data, although Delft3D also obtained good results for water level variations. The same models but in a 2DH version were selected by Iglesias et al.

[14] to model floods at the Douro estuary. A small underestimation and

configurations [25–28].

rotational [38].

26

different simulation results. The multi-model ensemble, as its name suggests, considers different numerical models that present different structural complexities. Each model is run using the same initial and boundary conditions. The multi-model ensemble clearly outperforms both single models and the single-model ensemble [60–62].

To combine the outputs of different models, several statistical techniques can be applied, considering the mean, the median, a linear regression, weighted average, or linear programming techniques, among others [52, 57, 63–65]. Computing the mean of the ensemble members' outputs is one of the most used methods; using the mean, the effect of combining models to reduce errors can be expressed in terms of bias and variance [54]. The bias is used to measure the extent to which the ensemble result, averaged over the ensemble members, differs from the target function. The variance can be defined as the extent to which the considered ensemble models disagree [66]. Being the root mean square error (RMSE), the sum of the model variance, and square of the bias, the model's ensemble suitability can be expressed in terms of the mean RMSE of the ensemble members [14].

The ensembles technique can thus be used to improve single models forecasts, reduce their uncertainty, and provide the most accurate results for a variety of sectors, as previously mentioned. This is the main objective of the EsCo-Ensembles project, a FCT (Fundação para a Ciência e a Tecnologia, Portugal) funded project that intends to use a numerical models ensemble to simulate estuarine hydrodynamic patterns in the face of anthropic interventions, extreme events, and climate changes. In this project, the ensembles technique will be applied to two of the main estuaries of the Portuguese coast: the Douro and Minho estuaries.

## 3. A Portuguese case study: Douro and Minho estuaries

The need for an accurate forecasting based on numerical models becomes clear when the Douro and Minho estuarine regions are analyzed. Although these estuaries, located in the western coast of the Iberian Peninsula, are separated by a distance of less than 100 km (Figure 1), their dynamics and environmental conditions are completely different (Table 1). Despite presenting similar seasonal river flow regimes (Figure 2), with minimum values in summer and maximum values in the rainy winter season, flow values and patterns differ. For the Minho river, between 1970 and 2018, a maximum daily mean river flow of 4600 m<sup>3</sup> /s was measured at Frieira dam; whereas the Douro presented a maximum daily mean river flow of 10,990 m<sup>3</sup> /s at Crestuma-Lever dam between 1986 and 2018. The difference between these two systems is also evident when river flood peak discharges associated with different return periods are estimated (Table 2). The different river discharge patterns suffice to support the need for a focused and local hydrodynamic characterization of the two estuaries when trying to avoid future risks related with human interventions (dredging, ports, alterations in the estuarine banks, designing of breakwaters, etc.), extreme events such as coastal and estuarine floods or storm surges, sea-level rise and the increase in the number and/or intensity of extreme events associated with climate change predictions. However, a comparison of the main estuaries characteristics and bathymetric conditions (Table 1 and Figures 1 and 3), reinforces this necessity. For the river flood peak discharges analysis, we assumed that the probability distribution for extreme flow events follows a Gumbel law [67]. Daily mean river flow data was provided by the SNIRH-Sistema Nacional de Informação de Recursos Hídricos (https://snirh.apambiente.pt/), measured between 1986 and 2018 at the Crestuma-Lever dam, and by Confederación Hidrográfica Miño-Sil (https://www.chminosil.es/es/), measured between 1970 and 2018 at the

Frieira dam. It should be noted that the presented extreme values refer to average daily extremes, since annual instantaneous peak values were not available. Thus,

Douro Minho

) 97,603 17,080

Estuarine limit Artificial (dam) Natural (limit of tide penetration)

Minho and Douro estuaries' location and bathymetry (in metres—vertical datum MSL-mean sea level). The

Numerical Modeling Tools Applied to Estuarine and Coastal Hydrodynamics: A User Perspective

DOI: http://dx.doi.org/10.5772/intechopen.85521

River length (km) 927 300 Estuarine mouth Artificial (breakwaters) Natural (rocks)

horizontal coordinates of the bathymetric maps are in datum PT-TM06/ETRS89.

Estuarine extension (km) 21 35 Estuarine river flow Artificial (dam) Artificial (dam) Mean depth (m) 13.8 7.6 Maximum estuarine width (m) 1,300 2,100 Minimum estuarine width (m) 135 160

The bathymetric map for the Minho estuary (Figure 1) was constructed using several topographic and bathymetric data sets: topographic data provided by the Portuguese Direção Geral do Território (DGT; http://www.dgterritorio.pt/) as a Digital Terrain Model (DTM) obtained from a nation-wide altimetric survey carried

higher flood peak extremes are expected for both estuaries.

Hydrographic basin (km<sup>2</sup>

Main characteristics of each considered estuary.

Table 1.

29

Figure 1.

Numerical Modeling Tools Applied to Estuarine and Coastal Hydrodynamics: A User Perspective DOI: http://dx.doi.org/10.5772/intechopen.85521

#### Figure 1.

different simulation results. The multi-model ensemble, as its name suggests, considers different numerical models that present different structural

Coastal and Marine Environments - Physical Processes and Numerical Modelling

expressed in terms of the mean RMSE of the ensemble members [14].

estuaries of the Portuguese coast: the Douro and Minho estuaries.

3. A Portuguese case study: Douro and Minho estuaries

1970 and 2018, a maximum daily mean river flow of 4600 m<sup>3</sup>

10,990 m<sup>3</sup>

28

patterns in the face of anthropic interventions, extreme events, and climate changes. In this project, the ensembles technique will be applied to two of the main

single-model ensemble [60–62].

complexities. Each model is run using the same initial and boundary conditions. The multi-model ensemble clearly outperforms both single models and the

To combine the outputs of different models, several statistical techniques can be applied, considering the mean, the median, a linear regression, weighted average, or linear programming techniques, among others [52, 57, 63–65]. Computing the mean of the ensemble members' outputs is one of the most used methods; using the mean, the effect of combining models to reduce errors can be expressed in terms of bias and variance [54]. The bias is used to measure the extent to which the ensemble result, averaged over the ensemble members, differs from the target function. The variance can be defined as the extent to which the considered ensemble models disagree [66]. Being the root mean square error (RMSE), the sum of the model variance, and square of the bias, the model's ensemble suitability can be

The ensembles technique can thus be used to improve single models forecasts, reduce their uncertainty, and provide the most accurate results for a variety of sectors, as previously mentioned. This is the main objective of the EsCo-Ensembles project, a FCT (Fundação para a Ciência e a Tecnologia, Portugal) funded project that intends to use a numerical models ensemble to simulate estuarine hydrodynamic

The need for an accurate forecasting based on numerical models becomes clear when the Douro and Minho estuarine regions are analyzed. Although these estuaries, located in the western coast of the Iberian Peninsula, are separated by a distance of less than 100 km (Figure 1), their dynamics and environmental conditions are completely different (Table 1). Despite presenting similar seasonal river flow regimes (Figure 2), with minimum values in summer and maximum values in the rainy winter season, flow values and patterns differ. For the Minho river, between

Frieira dam; whereas the Douro presented a maximum daily mean river flow of

Daily mean river flow data was provided by the SNIRH-Sistema Nacional de Informação de Recursos Hídricos (https://snirh.apambiente.pt/), measured between 1986 and 2018 at the Crestuma-Lever dam, and by Confederación Hidrográfica Miño-Sil (https://www.chminosil.es/es/), measured between 1970 and 2018 at the

/s at Crestuma-Lever dam between 1986 and 2018. The difference between these two systems is also evident when river flood peak discharges associated with different return periods are estimated (Table 2). The different river discharge patterns suffice to support the need for a focused and local hydrodynamic characterization of the two estuaries when trying to avoid future risks related with human interventions (dredging, ports, alterations in the estuarine banks, designing of breakwaters, etc.), extreme events such as coastal and estuarine floods or storm surges, sea-level rise and the increase in the number and/or intensity of extreme events associated with climate change predictions. However, a comparison of the main estuaries characteristics and bathymetric conditions (Table 1 and Figures 1 and 3), reinforces this necessity. For the river flood peak discharges analysis, we assumed that the probability distribution for extreme flow events follows a Gumbel law [67].

/s was measured at

Minho and Douro estuaries' location and bathymetry (in metres—vertical datum MSL-mean sea level). The horizontal coordinates of the bathymetric maps are in datum PT-TM06/ETRS89.


#### Table 1.

Main characteristics of each considered estuary.

Frieira dam. It should be noted that the presented extreme values refer to average daily extremes, since annual instantaneous peak values were not available. Thus, higher flood peak extremes are expected for both estuaries.

The bathymetric map for the Minho estuary (Figure 1) was constructed using several topographic and bathymetric data sets: topographic data provided by the Portuguese Direção Geral do Território (DGT; http://www.dgterritorio.pt/) as a Digital Terrain Model (DTM) obtained from a nation-wide altimetric survey carried

bathymetric survey performed by the IH. The sand spit topography was taken from a 2015 topographical survey [68], and the adjacent coastal bathymetry was obtained from the Bathymetric Model of Douro (IH). For both estuaries, additional ocean bathymetric data was extracted from the GEBCO database [69], and the different

Numerical Modeling Tools Applied to Estuarine and Coastal Hydrodynamics: A User Perspective

The Douro River is one of the major rivers of the Iberian Peninsula. It flows from the Sierra de Urbion, in Spain, to the Atlantic Ocean, in northern Portugal, ending in an urban estuary surrounded by two major cities: Porto and Vila Nova de Gaia (Figure 1). The Douro is a highly dynamic narrow estuary with torrential regimes that produce strong currents and recurrent severe floods that cause serious damage to the riverine populations and navigation problems [68, 72]. Its dynamics is mainly forced by freshwater flows, being very dependent on highly variable natural conditions and on the hydropower production schedule of the Crestuma-Lever dam and of the other 50 national and international river basin dams. For flow rates above

/s, the river water masses rush to the sea and seawater intrusion is

morphodynamics is conditioned by natural (wind, rainfall, river flow, waves, tides and storm surges) and human (breakwaters and dams construction, sand extraction, and dredging) processes [68, 75, 76]. To prevent erosion of the sand spit or its excessive migration into the navigation channel, maintaining both navigability and bank protection, a new detached breakwater was built parallel to the head of the sandbar, and the existing northern breakwater was extended. These structures, concluded in 2008, interfere with local sedimentary and hydrodynamic patterns, significantly increasing the area and volume of the sand spit in a relatively short period (10 years) [68, 77]. Historical records reveal ruptures or partial destruction of the sandbar during river flood events, allowing for a rapid discharge of excess

Minho and Douro estuaries' bathymetric profile for the estuarine central axis (in metres—vertical datum

which acquires a salt-wedge configuration [73]. This has a strong effect on the freshwater residence time, which can vary from 8 h to more than 2 weeks [74]. The bathymetric configuration of the Douro estuary presents an irregular distribution with depths generally varying between 0 and 10 m (Figures 1 and 3). Depths up to 28 m can be found associated with narrower sections, outer bends, and former sites of sediments extraction [72]. At the southern margin of the estuary's mouth lies a wetland (São Paio Bay) and an estuarine sand spit (Cabedelo) that partially obstructs the river mouth, protecting the estuary from the ocean's storm waves. This sand spit is made up of fluvial and maritime sediments, and its

/s, the ocean water enters the estuary,

data sets considered were interpolated using a Kriging algorithm [70, 71].

800 m<sup>3</sup>

Figure 3.

31

MSL-mean sea level).

prevented. For flow rates below 800 m<sup>3</sup>

DOI: http://dx.doi.org/10.5772/intechopen.85521

#### Figure 2.

Box plots representing the monthly minimum (lower whisker), lower quartile (25%, bottom box limit), median (red line), upper quartile (75%, top box limit), and maximum (upper whisker) daily mean river flow values of the Douro and Minho rivers flows, from 1986 to 2018 and from 1970 to 2018, respectively. Data source: SNIRH (https://snirh.apambiente.pt/) and Confederación Hidrográfica Miño-Sil (https://www.ch minosil.es/es/).


#### Table 2.

River flood average daily extreme discharges (Q) associated with different return periods (T).

on in 2011 with a LiDAR (light detection and ranging); and bathymetric data provided by the Portuguese Instituto Hidrográfico (IH; http://www.hidrografico.pt/), obtained in 2006. The Douro bathymetry (Figure 1) was extracted from a 2009

#### Numerical Modeling Tools Applied to Estuarine and Coastal Hydrodynamics: A User Perspective DOI: http://dx.doi.org/10.5772/intechopen.85521

bathymetric survey performed by the IH. The sand spit topography was taken from a 2015 topographical survey [68], and the adjacent coastal bathymetry was obtained from the Bathymetric Model of Douro (IH). For both estuaries, additional ocean bathymetric data was extracted from the GEBCO database [69], and the different data sets considered were interpolated using a Kriging algorithm [70, 71].

The Douro River is one of the major rivers of the Iberian Peninsula. It flows from the Sierra de Urbion, in Spain, to the Atlantic Ocean, in northern Portugal, ending in an urban estuary surrounded by two major cities: Porto and Vila Nova de Gaia (Figure 1). The Douro is a highly dynamic narrow estuary with torrential regimes that produce strong currents and recurrent severe floods that cause serious damage to the riverine populations and navigation problems [68, 72]. Its dynamics is mainly forced by freshwater flows, being very dependent on highly variable natural conditions and on the hydropower production schedule of the Crestuma-Lever dam and of the other 50 national and international river basin dams. For flow rates above 800 m<sup>3</sup> /s, the river water masses rush to the sea and seawater intrusion is prevented. For flow rates below 800 m<sup>3</sup> /s, the ocean water enters the estuary, which acquires a salt-wedge configuration [73]. This has a strong effect on the freshwater residence time, which can vary from 8 h to more than 2 weeks [74]. The bathymetric configuration of the Douro estuary presents an irregular distribution with depths generally varying between 0 and 10 m (Figures 1 and 3). Depths up to 28 m can be found associated with narrower sections, outer bends, and former sites of sediments extraction [72]. At the southern margin of the estuary's mouth lies a wetland (São Paio Bay) and an estuarine sand spit (Cabedelo) that partially obstructs the river mouth, protecting the estuary from the ocean's storm waves. This sand spit is made up of fluvial and maritime sediments, and its morphodynamics is conditioned by natural (wind, rainfall, river flow, waves, tides and storm surges) and human (breakwaters and dams construction, sand extraction, and dredging) processes [68, 75, 76]. To prevent erosion of the sand spit or its excessive migration into the navigation channel, maintaining both navigability and bank protection, a new detached breakwater was built parallel to the head of the sandbar, and the existing northern breakwater was extended. These structures, concluded in 2008, interfere with local sedimentary and hydrodynamic patterns, significantly increasing the area and volume of the sand spit in a relatively short period (10 years) [68, 77]. Historical records reveal ruptures or partial destruction of the sandbar during river flood events, allowing for a rapid discharge of excess

#### Figure 3.

Minho and Douro estuaries' bathymetric profile for the estuarine central axis (in metres—vertical datum MSL-mean sea level).

on in 2011 with a LiDAR (light detection and ranging); and bathymetric data provided by the Portuguese Instituto Hidrográfico (IH; http://www.hidrografico.pt/), obtained in 2006. The Douro bathymetry (Figure 1) was extracted from a 2009

River flood average daily extreme discharges (Q) associated with different return periods (T).

Box plots representing the monthly minimum (lower whisker), lower quartile (25%, bottom box limit), median (red line), upper quartile (75%, top box limit), and maximum (upper whisker) daily mean river flow values of the Douro and Minho rivers flows, from 1986 to 2018 and from 1970 to 2018, respectively. Data source: SNIRH (https://snirh.apambiente.pt/) and Confederación Hidrográfica Miño-Sil (https://www.ch

Coastal and Marine Environments - Physical Processes and Numerical Modelling

 7,655 3,308 9,215 3,944 11,235 4,767 12,748 5,383 14,256 5,998 16,246 6,809 17,749 7,421

/s) Q Minho (m3

/s)

T (years) Q Douro (m3

Figure 2.

minosil.es/es/).

Table 2.

30

water and reducing the risk of urban flooding [68]. Now, with a stronger sandbar, its rupture is less probable and the effect of a flood is likely to be harsher, both in terms of economic losses and structural damage [14].

strangulation or intense variations of bathymetry, and various islands and sandbars that emerge during low tide [85, 93]. Also, during the low water level period of spring tides, the connection between the estuary and the sea is restricted to two shallow channels, causing serious problems for navigation. Dredging campaigns are often carried out to keep the navigation channel open, with possible implications for the morphological evolution of the estuary and adjacent coastal areas [94], and

Numerical Modeling Tools Applied to Estuarine and Coastal Hydrodynamics: A User Perspective

In terms of numerical modeling, there is a lack of publications for this estuary, probably due to the scarcity of in-situ data to force and calibrate the numerical models and validate their accuracy. Sousa et al. [95] and Pereira [13] implemented two hydrodynamic numerical models (MOHID and Delft3D) for the Minho estuary surroundings. In spite of obtaining interesting results in the validation processes with data from the Minho estuary measurement stations, those studies focused on representing the interaction between the waters of the Minho river and the Galician rias or the Lima estuary, respectively, and do not present a detailed and complete analysis of the estuarine hydrodynamics. Delgado [94] and Portela [92] also built some numerical modeling tools for the Minho estuary. Their studies focused mainly

Nevertheless, several conclusions about the morpho-hydrodynamic behavior of the Minho estuary can be inferred from previous works. The estuarine processes may be dominated by the river flow or by the tide depending on the magnitude of these two forcing parameters. Extreme river flows can change the circulation pattern within the entire estuarine and coastal region, restricting the entrance of oceanic water to the mouth of the estuary. In such cases, the tide acts as a resistance to the fluvial flow. Current velocities of the ebb are higher than the velocity during flood, which produces a higher duration of the ebb. This effect is stronger for low river flows. As expected, currents exhibit higher velocities in the narrower sections, particularly at the mouth of the estuary, but they are also stronger during spring tides than during neap tides. The described hydrodynamic patterns will have a direct effect on sediment transport, which is directly proportional to the strength of the flow and the amplitude of the tide. Similar conclusions were obtained by Iglesias et al. [96] using realistic river flow and tide scenarios. Their numerical solutions show a tide dominated estuary, with a visible tidal effect even for extreme river flows. For low river flow conditions, a large part of the estuarine region is dry, becoming exposed to the wind action. In this situation, river flow is confined to two shallow channels in the estuarine area. During high flow conditions, most of the estuary is flooded, with intense currents throughout the estuarine region, except in the widest part upstream from the river mouth, where the estuary widens and the

The characteristics of an estuarine region depend on numerous drivers that define not only the estuarine behavior, but also its ecosystems and human settlement distribution. In this chapter, these relationships, and differences between estuaries, are highlighted, comparing two near-by but completely different estuarine regions of the northern Portuguese coast. The comparison reinforces the need to analyze each region separately, considering the specific configuration of each estuary for the definition of management protocols, to minimize any potential

The Douro estuary is an urban estuary, where effects of extreme events, anthropic activities, and climate changes will mostly generate problems in urban

vulnerability and to allow mitigation of risks and hazardous effects.

on the estuarine sediment transport for a few theoretical scenarios.

cross-sectional area increases significantly.

4. Discussion and conclusions

33

for bottom habitats.

DOI: http://dx.doi.org/10.5772/intechopen.85521

There are some previous works that aimed to reproduce the Douro estuary dynamics using numerical models. Silva [78] implemented a 2D depth-averaged (2DH) hydrodynamic model for the lower estuarine area, to represent the effect of several engineering works on the main currents configuration. Using the 1994 configuration, he found that relatively small alterations of the estuarine mouth conditions can produce marked changes in the currents strength and direction for normal winter conditions (river flow 1000 m<sup>3</sup> /s). The impact of the structures at the estuary's mouth on hydrodynamics, salt-water intrusion, and sediment transport was also presented by Pinho et al. [79], considering several scenarios of mean river flow. Their solutions, which were obtained using two coupled models: one for hydrodynamics and another for sediment transport, revealed maximum current velocities and maximum erosion at the estuarine mouth between the breakwaters. Similar patterns were obtained by Portela [72] and Iglesias et al. [14]. Particularly, Iglesias et al. [14] implemented two different numerical models for the Douro river to depict the effect of the sand spit in the floods water levels, demonstrating that the new breakwaters configuration and the strengthening of the sand spit will probably produce an increase in high-water levels during flood conditions, with expected severe impacts on the estuary banks. River floods were also simulated by Araújo et al. [80]. However, their work was focused on numerical model meshes development rather than on the socio-economical impacts of floods. Other related research are the modeling works of Azevedo et al. [81, 82], which related the estuary's hydrodynamic behavior with contaminant dispersion, biogeochemistry, and primary production, and the work of Mendes et al. [83], which evaluated the potential effect of sea-level rise in the Douro estuary.

The Minho River is an international river as well; it separates Spain and Portugal in its last 70 km, flowing into the Atlantic Ocean between A Guarda (Spain) and Caminha (Portugal). The Minho estuary is a very shallow water body, with a mean depth of 4 m, but regions close to 20-m depth can be found associated with a narrowing of the main channel, that increases flow velocities and, consequently, erosion (Figures 1 and 3) [84, 85]. Estuarine flows are mainly controlled by the Frieira dam, whose reservoir feeds a hydroelectric power plant located 80 km upstream from the estuary mouth. Due to the low river flow values (see Figure 2), the average water residence time in this estuary is 1.5 days [86]. The tributaries of the Minho between Frieira and the estuarine mouth can provide some additional freshwater to the estuary, but they have a minor influence given their small drainage basins.

One of the most important characteristics of the Minho estuarine region is its large diversity of habitats and its importance for the nursery and feeding of marine species and for ecosystem functioning [87, 88]. For this reason, this estuary is protected by Portuguese and Spanish conservation statutes, preserving a low level of industrialization. Despite the fact that the Minho ecosystem has been intensively studied in terms of its morpho-hydrodynamic characteristics, water quality, biodiversity, populations, and pollution, its dynamics is still essentially unknown [89, 90]. One of this estuary's main problems is the strong siltation related with high sediment deposition and low currents velocities, which are due to flow rate smoothing by the dam, and the consequent reduction of the frequency and intensity of floods [91, 92]. Being the hydrographic zero the level of the lowest astronomical tide, which is 2 m below the local mean sea level, the area above the hydrographic zero between the river mouth, and 14 km upstream represents about 70% of the total area, indicating a high degree of sedimentation. The morphodynamic patterns generated by silting produced several bathymetric constraints to navigation, such as

#### Numerical Modeling Tools Applied to Estuarine and Coastal Hydrodynamics: A User Perspective DOI: http://dx.doi.org/10.5772/intechopen.85521

strangulation or intense variations of bathymetry, and various islands and sandbars that emerge during low tide [85, 93]. Also, during the low water level period of spring tides, the connection between the estuary and the sea is restricted to two shallow channels, causing serious problems for navigation. Dredging campaigns are often carried out to keep the navigation channel open, with possible implications for the morphological evolution of the estuary and adjacent coastal areas [94], and for bottom habitats.

In terms of numerical modeling, there is a lack of publications for this estuary, probably due to the scarcity of in-situ data to force and calibrate the numerical models and validate their accuracy. Sousa et al. [95] and Pereira [13] implemented two hydrodynamic numerical models (MOHID and Delft3D) for the Minho estuary surroundings. In spite of obtaining interesting results in the validation processes with data from the Minho estuary measurement stations, those studies focused on representing the interaction between the waters of the Minho river and the Galician rias or the Lima estuary, respectively, and do not present a detailed and complete analysis of the estuarine hydrodynamics. Delgado [94] and Portela [92] also built some numerical modeling tools for the Minho estuary. Their studies focused mainly on the estuarine sediment transport for a few theoretical scenarios.

Nevertheless, several conclusions about the morpho-hydrodynamic behavior of the Minho estuary can be inferred from previous works. The estuarine processes may be dominated by the river flow or by the tide depending on the magnitude of these two forcing parameters. Extreme river flows can change the circulation pattern within the entire estuarine and coastal region, restricting the entrance of oceanic water to the mouth of the estuary. In such cases, the tide acts as a resistance to the fluvial flow. Current velocities of the ebb are higher than the velocity during flood, which produces a higher duration of the ebb. This effect is stronger for low river flows. As expected, currents exhibit higher velocities in the narrower sections, particularly at the mouth of the estuary, but they are also stronger during spring tides than during neap tides. The described hydrodynamic patterns will have a direct effect on sediment transport, which is directly proportional to the strength of the flow and the amplitude of the tide. Similar conclusions were obtained by Iglesias et al. [96] using realistic river flow and tide scenarios. Their numerical solutions show a tide dominated estuary, with a visible tidal effect even for extreme river flows. For low river flow conditions, a large part of the estuarine region is dry, becoming exposed to the wind action. In this situation, river flow is confined to two shallow channels in the estuarine area. During high flow conditions, most of the estuary is flooded, with intense currents throughout the estuarine region, except in the widest part upstream from the river mouth, where the estuary widens and the cross-sectional area increases significantly.

## 4. Discussion and conclusions

The characteristics of an estuarine region depend on numerous drivers that define not only the estuarine behavior, but also its ecosystems and human settlement distribution. In this chapter, these relationships, and differences between estuaries, are highlighted, comparing two near-by but completely different estuarine regions of the northern Portuguese coast. The comparison reinforces the need to analyze each region separately, considering the specific configuration of each estuary for the definition of management protocols, to minimize any potential vulnerability and to allow mitigation of risks and hazardous effects.

The Douro estuary is an urban estuary, where effects of extreme events, anthropic activities, and climate changes will mostly generate problems in urban

water and reducing the risk of urban flooding [68]. Now, with a stronger sandbar, its rupture is less probable and the effect of a flood is likely to be harsher, both in

Coastal and Marine Environments - Physical Processes and Numerical Modelling

There are some previous works that aimed to reproduce the Douro estuary dynamics using numerical models. Silva [78] implemented a 2D depth-averaged (2DH) hydrodynamic model for the lower estuarine area, to represent the effect of several engineering works on the main currents configuration. Using the 1994 configuration, he found that relatively small alterations of the estuarine mouth conditions can produce marked changes in the currents strength and direction for

the estuary's mouth on hydrodynamics, salt-water intrusion, and sediment transport was also presented by Pinho et al. [79], considering several scenarios of mean river flow. Their solutions, which were obtained using two coupled models: one for hydrodynamics and another for sediment transport, revealed maximum current velocities and maximum erosion at the estuarine mouth between the breakwaters. Similar patterns were obtained by Portela [72] and Iglesias et al. [14]. Particularly, Iglesias et al. [14] implemented two different numerical models for the Douro river to depict the effect of the sand spit in the floods water levels, demonstrating that the new breakwaters configuration and the strengthening of the sand spit will probably produce an increase in high-water levels during flood conditions, with expected severe impacts on the estuary banks. River floods were also simulated by Araújo et al. [80]. However, their work was focused on numerical model meshes development rather than on the socio-economical impacts of floods. Other related research are the modeling works of Azevedo et al. [81, 82], which related the estuary's hydrodynamic behavior with contaminant dispersion, biogeochemistry, and primary production, and the work of Mendes et al. [83], which evaluated the

The Minho River is an international river as well; it separates Spain and Portugal in

One of the most important characteristics of the Minho estuarine region is its large diversity of habitats and its importance for the nursery and feeding of marine species and for ecosystem functioning [87, 88]. For this reason, this estuary is protected by Portuguese and Spanish conservation statutes, preserving a low level of industrialization. Despite the fact that the Minho ecosystem has been intensively studied in terms of its morpho-hydrodynamic characteristics, water quality, biodiversity, populations, and pollution, its dynamics is still essentially unknown [89, 90]. One of this estuary's main problems is the strong siltation related with high

sediment deposition and low currents velocities, which are due to flow rate

32

smoothing by the dam, and the consequent reduction of the frequency and intensity of floods [91, 92]. Being the hydrographic zero the level of the lowest astronomical tide, which is 2 m below the local mean sea level, the area above the hydrographic zero between the river mouth, and 14 km upstream represents about 70% of the total area, indicating a high degree of sedimentation. The morphodynamic patterns generated by silting produced several bathymetric constraints to navigation, such as

its last 70 km, flowing into the Atlantic Ocean between A Guarda (Spain) and Caminha (Portugal). The Minho estuary is a very shallow water body, with a mean depth of 4 m, but regions close to 20-m depth can be found associated with a narrowing of the main channel, that increases flow velocities and, consequently, erosion (Figures 1 and 3) [84, 85]. Estuarine flows are mainly controlled by the Frieira dam, whose reservoir feeds a hydroelectric power plant located 80 km upstream from the estuary mouth. Due to the low river flow values (see Figure 2), the average water residence time in this estuary is 1.5 days [86]. The tributaries of the Minho between Frieira and the estuarine mouth can provide some additional freshwater to the estuary, but they have a minor influence given their small drainage basins.

/s). The impact of the structures at

terms of economic losses and structural damage [14].

normal winter conditions (river flow 1000 m<sup>3</sup>

potential effect of sea-level rise in the Douro estuary.

environments, reflected in structural damages, economic losses, and impacts on tourism and navigation activities. In the Minho estuary, the same phenomena will have different impacts, mostly affecting ecosystems and biodiversity, due to habitat loss and the migration and loss of autochthonous species. In comparison to the Douro estuary, the Minho presents a smaller concentration of population and human activities on its banks. Thus, economic impacts will mainly be caused by changes in the fishing and tourism activities.

inaccuracies in the numerical results, a models ensemble will be produced for the final forecasting. The EsCo-Ensembles project will provide valuable information about the NW Portuguese coastal zone to authorities, stakeholders, inhabitants, and society in general. Project results will contribute to the development of strategies for a sustainable management of estuarine and coastal areas affected by anthropogenic pressures, providing key information to develop protocols and mitigation strategies, to protect natural resources, population and infrastructures, and to potentiate new maritime infrastructures and coastal defense works adapted to future harmful

Numerical Modeling Tools Applied to Estuarine and Coastal Hydrodynamics: A User Perspective

This research was partially supported by the Strategic Funding UID/Multi/ 04423/2013 through national funds provided by FCT—Foundation for Science and Technology and European Regional Development Fund (ERDF). This contribution has also been funded by project EsCo-Ensembles (PTDC/ECI-EGC/30877/2017), co-funded by NORTE2020, Portugal 2020, and the European Union through the

\*, Paulo Avilez-Valente1,2, José Luís Pinho3

2 Faculty of Engineering, University of Porto (FEUP), Porto, Portugal

4 Faculty of Sciences, University of Porto (FCUP), Porto, Portugal

\*Address all correspondence to: iiglesias@ciimar.up.pt

1 Interdisciplinary Centre of Marine and Environmental Research (CIIMAR),

3 Center of the Territory, Environment and Construction (CTAC), University of

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

, Luísa Bastos1,4 and Fernando Veloso-Gomes1,2

, Ana Bio<sup>1</sup>

,

events and climate change conditions.

DOI: http://dx.doi.org/10.5772/intechopen.85521

ERDF, and by FCT through national funds.

University of Porto, Matosinhos, Portugal

provided the original work is properly cited.

Acknowledgements

Author details

José Manuel Vieira<sup>3</sup>

Minho, Braga, Portugal

35

Isabel Iglesias<sup>1</sup>

The modeling tools that have been developed so far, and which were described above, although extremely useful, need to be further developed. In the case of the Douro estuary, a complete hydrodynamic characterization, which considers the present topo-bathymetric configuration is still needed to fully unravel the estuarine dynamics, assess evolution trends, forecast future developments, including the effects of possible future human interventions, as well as to estimate the risks of flooding and the effect of sea-level rise associated with global warming. The numerical models developed for the Minho estuary are clearly insufficient for a complete characterization of this complex region, as well as for a reliable forecast of, for instance, hazardous events effects. Numerical models, capable of representing the estuarine stratification and its links with tide, river flow, and waves, are key tools to understand the distribution of biota and the functioning of the ecosystem, and to anticipate possible future conditions considering climate change and sea-level rise conditions. In addition, numerical models capable of representing the transport of larvae, pollutant, and sediments in a realistic way are crucial to describe estuarine trends, assess effects of anthropogenic intervention, quantify water residence times and sedimentary/erosive processes, as well as anticipate the effect of extreme river flows.

Next to stressing the relevance of performing regional modeling studies, this chapter also provides a thorough characterization of different available models, techniques, and physical processes simulations, including comparisons of several models performances, underlining the importance of choosing the modeling tool that best suits the numerical problem at hand and the computational means available to the user.

All these facts highlight the relevance of research projects dedicated to improve numerical modeling tools that provide a deeper understanding of the estuarine and coastal zones and represent the dynamics of the systems over time (past and present situations). One example is the project EsCo-Ensembles—Estuarine and coastal numerical modeling ensembles for anthropogenic, extreme events and climate change scenarios. This project aims to apply a new methodology based on models ensembles to build forecast and warning systems for estuarine/coastal regions. Two or more model outputs will be combined to obtain more accurate results that properly represent actual estuarine behavior as well as future trends, allowing for identification and mapping of the most sensitive areas. Modeling results will help to preserve and protect the estuarine/coastal regions and to mitigate the damages related with hazardous events, anthropogenic interventions, and climate change. Although extremely reliable, numerical models are prone to errors related to bathymetric and topographic assumptions, grid construction, spatial and temporal resolution, and to initial and forcing conditions, as well. As an example, there is not a clear trend for sea-level rise at the Portuguese coast. For different locations and periods, several authors report values of 1.3 [97], 1.9 [98], or even 0.7 mm/year [99], which does not agree with the global mean sea level rise of 1–2 mm/year, although locally, sea level can present increasing or decreasing trends [2]. To properly represent the effect of sea-level rise over the hydrodynamic conditions for a particular region, all these trends should be carefully evaluated and properly integrated into the numerical models. However, to avoid a large amount of input options, which can lead to

Numerical Modeling Tools Applied to Estuarine and Coastal Hydrodynamics: A User Perspective DOI: http://dx.doi.org/10.5772/intechopen.85521

inaccuracies in the numerical results, a models ensemble will be produced for the final forecasting. The EsCo-Ensembles project will provide valuable information about the NW Portuguese coastal zone to authorities, stakeholders, inhabitants, and society in general. Project results will contribute to the development of strategies for a sustainable management of estuarine and coastal areas affected by anthropogenic pressures, providing key information to develop protocols and mitigation strategies, to protect natural resources, population and infrastructures, and to potentiate new maritime infrastructures and coastal defense works adapted to future harmful events and climate change conditions.

## Acknowledgements

environments, reflected in structural damages, economic losses, and impacts on tourism and navigation activities. In the Minho estuary, the same phenomena will have different impacts, mostly affecting ecosystems and biodiversity, due to habitat loss and the migration and loss of autochthonous species. In comparison to the Douro estuary, the Minho presents a smaller concentration of population and human activities on its banks. Thus, economic impacts will mainly be caused by

Coastal and Marine Environments - Physical Processes and Numerical Modelling

The modeling tools that have been developed so far, and which were described above, although extremely useful, need to be further developed. In the case of the Douro estuary, a complete hydrodynamic characterization, which considers the present topo-bathymetric configuration is still needed to fully unravel the estuarine dynamics, assess evolution trends, forecast future developments, including the effects of possible future human interventions, as well as to estimate the risks of flooding and the effect of sea-level rise associated with global warming. The numerical models developed for the Minho estuary are clearly insufficient for a complete characterization of this complex region, as well as for a reliable forecast

of, for instance, hazardous events effects. Numerical models, capable of representing the estuarine stratification and its links with tide, river flow, and waves, are key tools to understand the distribution of biota and the functioning of the ecosystem, and to anticipate possible future conditions considering climate change and sea-level rise conditions. In addition, numerical models capable of representing the transport of larvae, pollutant, and sediments in a realistic way are crucial to describe estuarine trends, assess effects of anthropogenic intervention, quantify water residence times and sedimentary/erosive processes, as well as antic-

Next to stressing the relevance of performing regional modeling studies, this chapter also provides a thorough characterization of different available models, techniques, and physical processes simulations, including comparisons of several models performances, underlining the importance of choosing the modeling tool that best suits the numerical problem at hand and the computational means avail-

All these facts highlight the relevance of research projects dedicated to improve numerical modeling tools that provide a deeper understanding of the estuarine and coastal zones and represent the dynamics of the systems over time (past and present situations). One example is the project EsCo-Ensembles—Estuarine and coastal numerical modeling ensembles for anthropogenic, extreme events and climate change scenarios. This project aims to apply a new methodology based on models ensembles to build forecast and warning systems for estuarine/coastal regions. Two or more model outputs will be combined to obtain more accurate results that properly represent actual estuarine behavior as well as future trends, allowing for identification and mapping of the most sensitive areas. Modeling results will help to preserve and protect the estuarine/coastal regions and to mitigate the damages related with hazardous events, anthropogenic interventions, and climate change. Although extremely reliable, numerical models are prone to errors related to bathymetric and topographic assumptions, grid construction, spatial and temporal resolution, and to initial and forcing conditions, as well. As an example, there is not a clear trend for sea-level rise at the Portuguese coast. For different locations and periods, several authors report values of 1.3 [97], 1.9 [98], or even 0.7 mm/year [99], which does not agree with the global mean sea level rise of 1–2 mm/year, although locally, sea level can present increasing or decreasing trends [2]. To properly represent the effect of sea-level rise over the hydrodynamic conditions for a particular region, all these trends should be carefully evaluated and properly integrated into the numerical models. However, to avoid a large amount of input options, which can lead to

changes in the fishing and tourism activities.

ipate the effect of extreme river flows.

able to the user.

34

This research was partially supported by the Strategic Funding UID/Multi/ 04423/2013 through national funds provided by FCT—Foundation for Science and Technology and European Regional Development Fund (ERDF). This contribution has also been funded by project EsCo-Ensembles (PTDC/ECI-EGC/30877/2017), co-funded by NORTE2020, Portugal 2020, and the European Union through the ERDF, and by FCT through national funds.

## Author details

Isabel Iglesias<sup>1</sup> \*, Paulo Avilez-Valente1,2, José Luís Pinho3 , Ana Bio<sup>1</sup> , José Manuel Vieira<sup>3</sup> , Luísa Bastos1,4 and Fernando Veloso-Gomes1,2

1 Interdisciplinary Centre of Marine and Environmental Research (CIIMAR), University of Porto, Matosinhos, Portugal

2 Faculty of Engineering, University of Porto (FEUP), Porto, Portugal

3 Center of the Territory, Environment and Construction (CTAC), University of Minho, Braga, Portugal

4 Faculty of Sciences, University of Porto (FCUP), Porto, Portugal

\*Address all correspondence to: iiglesias@ciimar.up.pt

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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37

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2012. 3-21 p

2014;95(3):377-386

265-287

9(1):S69-S87

69-86

36

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[5] Nicholls RJ, Hoozemans FMJ, Marchand M. Increasing flood risk and wetland losses due to global sea-level rise: Regional and global analyses. Global Environmental Change. 1999;

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Science. 2009;66:1497-1507

Management Association. 2017;64(4):

Journal of the Air & Waste

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Coastal and Marine Environments - Physical Processes and Numerical Modelling

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Universidade de Aveiro; 2016

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Magazine. 1895;36(5):422-443

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019–02-14]

1953;8:374-388

19:1-19

38

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Numerical Modeling Tools Applied to Estuarine and Coastal Hydrodynamics: A User Perspective DOI: http://dx.doi.org/10.5772/intechopen.85521

[80] Araújo MAVC, Mazzolari A, Trigo-Teixeira A. An object oriented mesh generator: Application to flooding in the Douro estuary. Journal of Coastal Research. 2013;65(65):642-647

[64] Roy Bhowmik SK, Durai VR. Application of multimodel ensemble techniques for real time district level rainfall forecasts in short range time scale over Indian region. Meteorology and Atmospheric Physics. 2010;106:

[72] Portela LI. Sediment transport and morphodynamics of the Douro River estuary. Geo-Marine Letters. 2008;

[73] Azevedo IC, Duarte PM, Bordalo AA. Understanding spatial and temporal

[74] Vieira MEC, Bordalo AA. The Douro estuary (Portugal): A mesotidal salt wedge. Oceanologica Acta. 2000;23(5):

[75] Santos I, Teodoro A, Taveira-Pinto F. Análise da evolução morfológica da restinga do rio Douro. In: 5as Jornadas de Hidráulica, Recursos Hídricos e Ambiente. Vol. 2010. Porto. p. 14

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Integração de metodologias no estabelecimento de um programa de monitorização costeira para avaliação de risco. In: VII Conferência Nacional de Cartografia e Geodesia. 2011. p. 11

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[78] Silva A. Implementação de um modelo hidromorfológico para a Barra

[79] Pinho J, Vieira J, Neves D. Efeito das obras da embocadura na hidrodinâmica, intrusão salina e dinâmica sedimentar do estuário do Rio Douro. In: 10o Congresso da Água. Alvor. 2010

do Douro: Contribuição para a compreensão do sistema. In: 3<sup>o</sup> Congresso da Água. Lisboa; 1996

2011;64(64):1740-1744

Gonçalves H, Veloso-Gomes F, Taveira-Pinto F. Extraction of Cabedelo sand spit area (Douro estuary) from satellite images through image processing techniques. Journal of Coastal Research.

dynamics of key environmental characteristics in a mesotidal Atlantic estuary (Douro, NW Portugal). Estuarine, Coastal and Shelf Science.

2008;76(3):620-633

585-594

28(2):77-86

Coastal and Marine Environments - Physical Processes and Numerical Modelling

[65] Ajami NK, Duan Q, Gao X,

[66] Krogh A, Vedelsby J. Neural network ensembles, cross validation, and active learning. In: Advances in Neural Information Processing Systems

[67] Loaiciga HA, Leipnik RB. Analysis of extreme hydrologic events with Gumbel distributions: Marginal and

Environmental Research and Risk Assessment. 1999;13:251-259

[68] Bastos L, Bio A, Pinho JLS, Granja H, Jorge da Silva A. Dynamics of the Douro estuary sand spit before and after breakwater construction. Estuarine, Coastal and Shelf Science. 2012;109:

[69] Becker JJ, Sandwell DT, Smith WHF, Braud J, Binder B, Depner J, et al. Global bathymetry and elevation data at 30 arc seconds resolution: SRTM30\_ PLUS. Marine Geodesy. 2009;32(4):

[70] Krige DG. A Statistical Approach to some Mine Valuations and Allied Problems at the Witwatersrand

[Thesis]. University of Witwatersrand;

geostatistics. Economic Geology. 1963;

[71] Matheron G. Principles of

7. Vol. 7. 1995. pp. 231-238

additive cases. Sthocastic

Sorooshian S. Multimodel combination techniques for analysis of hydrological simulations: Application to distributed model Intercomparison project results. Journal of Hydrometeorology. 2006;7:

19-35

755-768

53-69

355-571

1951

40

58:1246-1266

[81] Azevedo IC, Bordalo AA, Duarte PM. Influence of river discharge patterns on the hydrodynamics and potential contaminant dispersion in the Douro estuary (Portugal). Water Research. 2010;44(10):3133-3146

[82] Azevedo IC, Bordalo AA, Duarte P. Influence of freshwater inflow variability on the Douro estuary primary productivity: A modelling study. Ecological Modelling. 2014;272: 1-15

[83] Mendes R, Vaz N, Dias JM. Potential impacts of the mean sea level rise on the hydrodynamics of the Douro river estuary. Journal of Coastal Research. 2013;165(65):1951-1956

[84] Freitas V, Costa-Dias S, Campos J, Bio A, Santos P, Antunes C. Patterns in abundance and distribution of juvenile flounder, Platichthys flesus, in Minho estuary (NW Iberian Peninsula). Aquatic Ecology. 2009;43(4):1143-1153

[85] Reis JL, Martinho AS, Pires-Silva AA, Silva AJ. Assessing the influence of the river discharge on the Minho estuary tidal regime. Journal of Coastal Research. 2009;2009(56):1405-1409

[86] Ferreira J, Abreu P, Bettencourt A, Bricker S, Marques J, Melo J, et al. Monitoring Plan for Portuguese Coastal Waters. Water Quality and Ecology. Development of Guidelines for the Applications of the European Union Water Framework Directive; 2005. p. 141

[87] Domínguez García MD, Horlings L, Swagemakers P, Simón Fernández X. Place branding and endogenous rural development. Departure points for

developing an inner brand of the river Minho estuary. Place Branding and Public Diplomacy. 2013;9(2):124-140

[88] Ribeiro DC, Costa S, Guilhermino L. A framework to assess the vulnerability of estuarine systems for use in ecological risk assessment. Ocean and Coastal Management. 2016;119:267-277

[89] Gonçalves A, Marques J. LTER Minho estuary [internet]. In LTER-ESTUARIES-Portugal. Avaliable from: https://data.lter-europe.net/deims/site/ lter\_eu\_pt\_011 [Accessed: 2019-02-14]

[90] Zacarias NG, DaSilva AJ. Tide propagation in the Minho River estuary (Portugal). In: 43rd Estuarine & Coastal Sciences Association – International Symposium. 2008

[91] Delgado A, Taveira-Pinto F, Silva R. Hydrodynamic and morphodynamic preliminar simulation of river Minho estuary. In: 6a Jornadas de Hidráulica, Recursos Hídricos e Ambiente. 2011. pp. 113-126

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[93] Zacarias NG. Influência da batimetria e do caudal fluvial na propagação da maré no estuário do rio Minho. Technical report, Universidade de Évora; 2007. p. 81

[94] Delgado A. Caracterização hidrodinâmica e sedimentar do estuário do rio Minho. [Thesis]. Universidade do Porto; 2011

[95] Sousa MC, Vaz N, Alvarez I, Gomez-Gesteira M, Dias JM. Modeling the Minho River plume intrusion into the rias Baixas (NW Iberian Peninsula). Continental Shelf Research. 2014;85: 30-41

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**43**

Section 2

Coastal Dynamics

and Ongoing Climate

Processes in Coastal and

Marine Environments

## Section 2
