**1. Introduction**

Algae blooms within coastal estuarine systems have been a threat to vital key ecosystem components causing the degradation of ecological integrity. With non-point source pollution being a primary concern, using geographic information system (GIS) approaches to assess the impacts is effective for stormwater management. Therefore, with the use of land use/land cover (LC/LU), soil, and elevation data, the Potential Runoff Coefficient (PRC) and runoff depth were calculated for the IRL and Halifax River watershed. The analysis consisted of manipulating the geospatial data to derive the potential runoff coefficients and runoff depths.

Considering the contributing factors of surface runoff, the overall goal of the study is to estimate the quantities of runoff within the Indian River Lagoon (IRL) watershed based on a method that encompasses those parameters. The findings can also address whether such method and similar approaches can indicate locations of algae blooms, and aid in stormwater/watershed management. The objectives of this study are listed respectively; **Objective 1:** to calculate the potential runoff coefficients within the IRL watershed. The values will be based on the satellite image classification and validation for land cover/land use, elevation data, and soil data of the study area. **Objective 2:** to calculate the runoff depth of the IRL watershed over an eleven-year duration (2006–2011) using the derived value of the runoff coefficients and rainfall data provided by National Oceanic and Atmospheric Administration National Weather Service (NOAA NWS) River Forecast Centers (RFCs) collected from the Hydrologic Rainfall Analysis Project (HRAP). The outcome will represent the actual quantity of rainfall that was converted to runoff for the year. **Objective 3:** to visually assess if there is a geographic correlation of surface runoff and algae concentrations during months of the 2011 super algal bloom. The finished products can aid in gaining coastal resilience to help adapt to storms, flooding events, and parameters can be used to determine suitability for stormwater parks and infrastructure. The data acquired from the public GIS databases include ground-truthed information and remotely sensed data which were carefully interpreted and validated by professionals.

#### **1.1 The Indian River Lagoon system**

The Indian River Lagoon (IRL), spanning ~40% of Florida's east coast, is one of the nation's biggest and most biodiverse estuaries. The IRL consists of barrier islands separating its water from Atlantic Ocean [1]. The exchange of the IRL water with the ocean occurs naturally at Ponce De Leon Inlet in New Smyrna Beach, and Jupiter Inlet near West Palm Beach. The other man-made inlets include Sebastian Inlet, Fort Pierce Inlet, Port Canaveral, and St. Lucie inlet. The estuary stretches 251 km along the east coast of Florida with numerous tributaries [2]. The IRL system is made up of three sub lagoons that include the Mosquito Lagoon, which is in the northern section, the Banana River, and the IRL (**Figure 1**). The natural sources of freshwater for the IRL include Crane Creek (Melbourne, FL), Eau Gallie River, St. Lucie River, St. Sebastian River, and Turkey Creek. A secondary natural source of freshwater in the IRL is the Tomoka River which is located west of the lagoon running north connecting to the Halifax River then eventually the Mosquito Lagoon. Although the Tomoka River is not directly connected to the IRL or in its watershed, the Halifax River (**Figure 1**) is partially connected to the northern lagoon at Ponce Inlet and therefore its watershed is included in this study. The IRL and Halifax River watershed contains ~40 cities. The developed urban land comprises impervious surfaces and residential communities that primarily contain turf grass.

In the summer of 2011, a super algal bloom event occurred in the IRL which reached a high biovolume of dinoflagellate *Pyrodinium bahamense var. bahamense* (33.9 × 106 μm3 mL<sup>−</sup><sup>1</sup> ) with mean chlorophyll *a* concentrations (6.2–16.4 μg/L) that positively correlated with total nitrogen and total phosphorus levels that exceeded historical levels in various locations [3]. Following the massive algae bloom, there have been recurrent blooms consisting of green macroalgae such as *Chaetomorpha* sp. since 2013 [4, 5]. As a result of the 2011 super algal bloom, the coverage of seagrass within the IRL drastically declined from the loss of photosynthetic light by the surface algae [6]. Although fluctuations in seagrass bed percent cover in the lagoon have been understood as a part of a natural cycle of decline and recovery as seagrass abundance,

**121**

**Figure 1.**

*A GIS-Based Approach for Determining Potential Runoff Coefficient and Runoff Depth…*

scientists suspect that nonpoint source pollution via surface runoff may have had a

*A map of Indian River Lagoon and Halifax River, Florida. The Indian River Lagoon is composed of three waterbodies: the Mosquito Lagoon, Indian River, and the Banana Lagoon. The inset map provides a reference* 

Surface runoff is water from rain or snowmelt that travels over the land before entering nearby waterbodies. Stormwater flowing across surrounding land transports various pollutants, and ultimately contributes to non-point source pollution. Surface runoff negatively affects many aquatic ecosystems as the runoff transports pollutants and other substances into waterbodies, which can alter turbidity, phosphorus and nitrogen concentrations, and organic matter content in receiving waterbodies [9]. The effects of surface runoff can also be intensified by climate change in specific regions that may have highly developed land and altered hydrology from the addition of artificial stormwater structures that modify the flow of water [10]. Human activities have been shown to have a stronger impact on runoff than climate

significant impact on the recent recurring algal blooms in the lagoon [7, 8].

change, but both stressors significantly impacts runoff quantities [10].

**1.2 Surface runoff and runoff models**

*for the location of the lagoon in Florida.*

*DOI: http://dx.doi.org/10.5772/intechopen.87163*

*A GIS-Based Approach for Determining Potential Runoff Coefficient and Runoff Depth… DOI: http://dx.doi.org/10.5772/intechopen.87163*

#### **Figure 1.**

*Lagoon Environments around the World - A Scientific Perspective*

Considering the contributing factors of surface runoff, the overall goal of the study is to estimate the quantities of runoff within the Indian River Lagoon (IRL) watershed based on a method that encompasses those parameters. The findings can also address whether such method and similar approaches can indicate locations of algae blooms, and aid in stormwater/watershed management. The objectives of this study are listed respectively; **Objective 1:** to calculate the potential runoff coefficients within the IRL watershed. The values will be based on the satellite image classification and validation for land cover/land use, elevation data, and soil data of the study area. **Objective 2:** to calculate the runoff depth of the IRL watershed over an eleven-year duration (2006–2011) using the derived value of the runoff coefficients and rainfall data provided by National Oceanic and Atmospheric Administration National Weather Service (NOAA NWS) River Forecast Centers (RFCs) collected from the Hydrologic Rainfall Analysis Project (HRAP). The outcome will represent the actual quantity of rainfall that was converted to runoff for the year. **Objective 3:** to visually assess if there is a geographic correlation of surface runoff and algae concentrations during months of the 2011 super algal bloom. The finished products can aid in gaining coastal resilience to help adapt to storms, flooding events, and parameters can be used to determine suitability for stormwater parks and infrastructure. The data acquired from the public GIS databases include ground-truthed information and remotely sensed

data which were carefully interpreted and validated by professionals.

The Indian River Lagoon (IRL), spanning ~40% of Florida's east coast, is one of the nation's biggest and most biodiverse estuaries. The IRL consists of barrier islands separating its water from Atlantic Ocean [1]. The exchange of the IRL water with the ocean occurs naturally at Ponce De Leon Inlet in New Smyrna Beach, and Jupiter Inlet near West Palm Beach. The other man-made inlets include Sebastian Inlet, Fort Pierce Inlet, Port Canaveral, and St. Lucie inlet. The estuary stretches 251 km along the east coast of Florida with numerous tributaries [2]. The IRL system is made up of three sub lagoons that include the Mosquito Lagoon, which is in the northern section, the Banana River, and the IRL (**Figure 1**). The natural sources of freshwater for the IRL include Crane Creek (Melbourne, FL), Eau Gallie River, St. Lucie River, St. Sebastian River, and Turkey Creek. A secondary natural source of freshwater in the IRL is the Tomoka River which is located west of the lagoon running north connecting to the Halifax River then eventually the Mosquito Lagoon. Although the Tomoka River is not directly connected to the IRL or in its watershed, the Halifax River (**Figure 1**) is partially connected to the northern lagoon at Ponce Inlet and therefore its watershed is included in this study. The IRL and Halifax River watershed contains ~40 cities. The developed urban land comprises impervious surfaces and residential communities that primarily contain

In the summer of 2011, a super algal bloom event occurred in the IRL which reached a high biovolume of dinoflagellate *Pyrodinium bahamense var. bahamense*

positively correlated with total nitrogen and total phosphorus levels that exceeded historical levels in various locations [3]. Following the massive algae bloom, there have been recurrent blooms consisting of green macroalgae such as *Chaetomorpha* sp. since 2013 [4, 5]. As a result of the 2011 super algal bloom, the coverage of seagrass within the IRL drastically declined from the loss of photosynthetic light by the surface algae [6]. Although fluctuations in seagrass bed percent cover in the lagoon have been understood as a part of a natural cycle of decline and recovery as seagrass abundance,

) with mean chlorophyll *a* concentrations (6.2–16.4 μg/L) that

**1.1 The Indian River Lagoon system**

**120**

turf grass.

(33.9 × 106 μm3

mL<sup>−</sup><sup>1</sup>

*A map of Indian River Lagoon and Halifax River, Florida. The Indian River Lagoon is composed of three waterbodies: the Mosquito Lagoon, Indian River, and the Banana Lagoon. The inset map provides a reference for the location of the lagoon in Florida.*

scientists suspect that nonpoint source pollution via surface runoff may have had a significant impact on the recent recurring algal blooms in the lagoon [7, 8].
