**1. Introduction**

Sandy coastlines are dynamic environments that are continuously modified in response to wave, tidal, and eolian processes. Sediment is in constant flux amongst the nearshore, foreshore, and backshore (**Figure 1**). Over short time scales (i.e., hours to months), individual storm events and seasonal variability in wave and wind energy result in topographic adjustments [1]. For example, characteristic 'winter' or 'summer' profiles can develop where sediment movement between zones can be cyclically removed, stored, and/or returned [2, 3] (**Figure 1**). The 'winter' profile develops in periods of higher wave energy where sediment is removed from the backshore (i.e., through beach and foredune scarping) and stored in nearshore sand bars [2, 3]. As wave energy decreases, sediment can be returned landward through welding of nearshore sand bars onto the foreshore and deposition

#### *Spatial Variability in Environmental Science - Patterns, Processes, and Analyses*

**Figure 1.**

*This idealized diagram depicts the seasonal variability of across shore profiles, landforms, and vegetation that can develop during periods of increased (i.e., winter profile) or decreased (i.e., summer profile) wave energy.*

of berm deposits on the beach [2, 3], leading to embryo dune development and foredune recovery [4] (e.g., 'summer' profile; **Figure 1**).

Small scale topographic variability is subsumed by larger scale controls on coastal dynamics [1, 5, 6] except in the presence of an alongshore variable framework geology [7]. However, changes in wave climate [8] and eustatic sea level [9] have the potential to disrupt the current balance between erosional and depositional processes. These climatic changes could lead to increased water levels during storm events and the potential for sediment to be transported inland through breaching [10, 11], overwash [12] or the development of blowouts [13, 14]. Sediment deposited landward of the foredune would be effectively removed from the cyclical 'seasonal' recovery state, and could lead to increased erosion, fragmentation, and landward retreat of the foredune [15, 16]. This disruption of sediment supply could also accelerate the transgression of the coastline as it responds to future changes in sea level [9]. Thus, the ability of foredunes to recover following storm events will have implications on both the short- and longer-term resiliency of sandy coastlines [17, 18].

limit transport potential and initiate dune building (e.g., [22]). If these conditions persist, dune recovery can occur through ramp building and embryo dunes can develop seaward of the established foredune [15]. Following major erosion events, full dune recovery may take years to complete [17, 23] and is controlled by fre-

*A foredune scarp observed at Brackley Beach, Prince Edward Island National Park, following the post-tropical storm Dorian in September 2019. This image shows that significant erosion of the stoss slope resulted in the formation of a steep and continuous scarp, alongshore. Other storm impacts, including a flattened across shore*

The impact of a storm and the relatively slow recovery tend to be considered a two-dimensional, cross-shore phenomenon in which the storm impact depends only on the height of the storm surge relative to the elevation of the dune crest (e.g., [24, 25]). However, the foredune line is not uniform and can exhibit considerable variability in height, volume, and alongshore extent [12, 26, 27]. As noted, the exact location of dune erosion and overwash penetration depends on the correspondence of alongshore variations in the incident forcing and on existing gaps and low-lying areas along the dune line [28–31]. Understanding the variability of the beach-dune systems is essential to understanding the response of sandy coastlines to changes in storm activity and sea level rise, and it is important to the development of appropriate sampling strategies for field studies of sediment transport exchange amongst

Climatic change over the coming decades, including increased storminess [8] or sea level rise [9], have the potential to modify current beach-dune interactions. For example, an increased frequency of storm surge events can lead to barrier island systems of low elevation and discontinuous dunes that, in turn, increase the potential for island inundation and breaching [17]. However, a low frequency of storm surge can limit sediment transfer to the backbarrier as overwash leading to island drowning in response to an increase in sea level [32], unless sediment transfer is accomplished by blowouts [13, 14]. Monitoring the resiliency of sandy coastlines is, therefore, critical to our understanding on how these systems will respond to larger scale sedimentological and climatic perturbations. To address this challenge, advances in surveying technology including unmanned aerial vehicles (UAVs) and light detection and ranging (LiDAR) systems are able to provide robust geo-spatial data sets that will enhance repeat survey strategies of these dynamic

quency of high magnitude events [17].

*profile and elevated wrack line, are also visible.*

*Monitoring Storm Impacts on Sandy Coastlines with UAVs*

*DOI: http://dx.doi.org/10.5772/intechopen.91459*

**Figure 2.**

the nearshore, beach and dune (e.g., [31]).

environments.

**69**

Following significant storm events or storm seasons, periods of increased wave energy often leads to the development of a foredune scarp (**Figure 2**). The ability of the foredune to recover, or return to its pre-storm morphology, is then controlled primarily by the sequence and relationship between eolian transport potential and sediment supply [4]. Initially, sediment eroded from the foredune by elevated storm surge and wave run up can be deposited directly onto the beach or further seaward into nearshore bar structures [2, 3]. As the beach slope relaxes to a characteristic 'winter' or flattened beach profile (**Figure 2**), the low sloping surface promotes rapid boundary layer development during on shore winds and increases sediment flux potential [19], with minimal slope controlled limitations on flux magnitude [20]. Elevated wrack lines (**Figure 2**), exposed lag deposits, and large woody debris that may be present following storm events can temporarily trap sediment blown into the beach-dune boundary (e.g., see [6]).

Over seasonal or annual time scales, sediment stored in nearshore bars can begin migrating landward during periods of reduced wave energy [2, 3]. An increase in sediment supply into the foreshore can result in the formation of multiple berm ridges that are deposited above high tide and swash lines, increasing beach width [3]. This results in a larger supply of dry erodible sediment in the backshore which is less affected by tidal or swash driven surface moisture constraints on eolian transport [21]. Finally, vegetation recolonization at the beach-dune boundary can

#### **Figure 2.**

of berm deposits on the beach [2, 3], leading to embryo dune development and

*This idealized diagram depicts the seasonal variability of across shore profiles, landforms, and vegetation that can develop during periods of increased (i.e., winter profile) or decreased (i.e., summer profile) wave energy.*

*Spatial Variability in Environmental Science - Patterns, Processes, and Analyses*

Small scale topographic variability is subsumed by larger scale controls on coastal dynamics [1, 5, 6] except in the presence of an alongshore variable framework geology [7]. However, changes in wave climate [8] and eustatic sea level [9] have the potential to disrupt the current balance between erosional and depositional processes. These climatic changes could lead to increased water levels during storm events and the potential for sediment to be transported inland through breaching [10, 11], overwash [12] or the development of blowouts [13, 14]. Sediment deposited landward of the foredune would be effectively removed from the cyclical 'seasonal' recovery state, and could lead to increased erosion, fragmentation, and landward retreat of the foredune [15, 16]. This disruption of sediment supply could also accelerate the transgression of the coastline as it responds to future changes in sea level [9]. Thus, the ability of foredunes to recover following storm events will have implications on both the short- and longer-term resiliency

Following significant storm events or storm seasons, periods of increased wave energy often leads to the development of a foredune scarp (**Figure 2**). The ability of the foredune to recover, or return to its pre-storm morphology, is then controlled primarily by the sequence and relationship between eolian transport potential and sediment supply [4]. Initially, sediment eroded from the foredune by elevated storm surge and wave run up can be deposited directly onto the beach or further seaward into nearshore bar structures [2, 3]. As the beach slope relaxes to a characteristic 'winter' or flattened beach profile (**Figure 2**), the low sloping surface promotes rapid boundary layer development during on shore winds and increases sediment flux potential [19], with minimal slope controlled limitations on flux magnitude [20]. Elevated wrack lines (**Figure 2**), exposed lag deposits, and large woody debris that may be present following storm events can temporarily trap

Over seasonal or annual time scales, sediment stored in nearshore bars can begin migrating landward during periods of reduced wave energy [2, 3]. An increase in sediment supply into the foreshore can result in the formation of multiple berm ridges that are deposited above high tide and swash lines, increasing beach width [3]. This results in a larger supply of dry erodible sediment in the backshore which is less affected by tidal or swash driven surface moisture constraints on eolian transport [21]. Finally, vegetation recolonization at the beach-dune boundary can

foredune recovery [4] (e.g., 'summer' profile; **Figure 1**).

sediment blown into the beach-dune boundary (e.g., see [6]).

of sandy coastlines [17, 18].

**68**

**Figure 1.**

*A foredune scarp observed at Brackley Beach, Prince Edward Island National Park, following the post-tropical storm Dorian in September 2019. This image shows that significant erosion of the stoss slope resulted in the formation of a steep and continuous scarp, alongshore. Other storm impacts, including a flattened across shore profile and elevated wrack line, are also visible.*

limit transport potential and initiate dune building (e.g., [22]). If these conditions persist, dune recovery can occur through ramp building and embryo dunes can develop seaward of the established foredune [15]. Following major erosion events, full dune recovery may take years to complete [17, 23] and is controlled by frequency of high magnitude events [17].

The impact of a storm and the relatively slow recovery tend to be considered a two-dimensional, cross-shore phenomenon in which the storm impact depends only on the height of the storm surge relative to the elevation of the dune crest (e.g., [24, 25]). However, the foredune line is not uniform and can exhibit considerable variability in height, volume, and alongshore extent [12, 26, 27]. As noted, the exact location of dune erosion and overwash penetration depends on the correspondence of alongshore variations in the incident forcing and on existing gaps and low-lying areas along the dune line [28–31]. Understanding the variability of the beach-dune systems is essential to understanding the response of sandy coastlines to changes in storm activity and sea level rise, and it is important to the development of appropriate sampling strategies for field studies of sediment transport exchange amongst the nearshore, beach and dune (e.g., [31]).

Climatic change over the coming decades, including increased storminess [8] or sea level rise [9], have the potential to modify current beach-dune interactions. For example, an increased frequency of storm surge events can lead to barrier island systems of low elevation and discontinuous dunes that, in turn, increase the potential for island inundation and breaching [17]. However, a low frequency of storm surge can limit sediment transfer to the backbarrier as overwash leading to island drowning in response to an increase in sea level [32], unless sediment transfer is accomplished by blowouts [13, 14]. Monitoring the resiliency of sandy coastlines is, therefore, critical to our understanding on how these systems will respond to larger scale sedimentological and climatic perturbations. To address this challenge, advances in surveying technology including unmanned aerial vehicles (UAVs) and light detection and ranging (LiDAR) systems are able to provide robust geo-spatial data sets that will enhance repeat survey strategies of these dynamic environments.
