**4. Results**

## **4.1 LC/LU classification**

There are six LC/LU classes delineated from the supervised classification. The land that mostly consists of agriculture occurs in the southern section of the watershed. The overall accuracy of the LC/LU classification image was 0.82, and the lowest accuracies were in the impervious (User accuracy of 0.65) and bare soil (0.53) classes. This may have been due to the spectral similarity between bare sand along the coast and impervious surfaces such as roof tops. The reference points that appeared to exist in unhealthy brown vegetation were misclassified as bare soil. The kappa coefficient for the LC/LU image was 0.77, with an overall average of 0.82.

#### **4.2 Slope**

The slope for the study area was assigned a quantile classification to exclude the effects from outliers in the digital elevation map. The elevation in the state of Florida is relatively flat with an average slope of ~0.47 m per pixel. The areas of high percent slope are manmade structure such as buildings, walls, or homes in developed areas. Some manmade structures with unusually high slopes were identified as the outliers. The other cities have slopes ranging from 0.50 to 1.79 average percent.

#### **4.3 Soil**

The soil texture classification for central east Florida consists of mostly fine with Myakka Fine Sand as a native soil, covering more than 1.5 million acres of land, and

**127**

**Figure 2.**

*watersheds, FL.*

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

labeled as the Florida Official State Soil [34]. The soil data were reclassified into the 12 different textures within the USDA Soil Texture Triangle to accurately implement the values: sand, loamy sand, sandy loam, silt loam, sandy clay loam, silty clay loam, sandy clay, silty clay, and clay. The total study area was composed of 67.7%

The PRC values range from 3 to 100% (**Figure 2**). The PRCs are higher in runoff

The precipitation data in the IRL watershed from 2006 to 2016 were divided into four quarters with each quarter representing the average of three-month intervals: January–March, April–June, July–September, and October–December. Although the quarterly intervals do not accurately align with seasons, the data are segmented to show the temporal shifts of the rainfall pattern in this area. The IRL watershed precipitation is usually the lowest within the first quarter averaging ~5.48 cm. As the seasonal rainfall increases in spring and summer moving from 10.03 cm in second quarter to 15.55 cm in the third quarter. The rainfall decreases towards the

*Map displaying the potential runoff coefficients (PRC; %) for the Indian River Lagoon and Halifax River* 

values in developed areas that are in close proximity to the coastal waterbodies of the IRL and Halifax River. The spatial resolution (10 m) of the image shows a detailed delineation of the manmade infrastructure within urban coastal communi-

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

sand, 4.5% loamy sand, and 8.7% silty clay.

ties such as roads, buildings, homes, and airports.

end of the year with an average of 5.58 cm.

**4.4 PRC**

**4.5 Precipitation**

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

labeled as the Florida Official State Soil [34]. The soil data were reclassified into the 12 different textures within the USDA Soil Texture Triangle to accurately implement the values: sand, loamy sand, sandy loam, silt loam, sandy clay loam, silty clay loam, sandy clay, silty clay, and clay. The total study area was composed of 67.7% sand, 4.5% loamy sand, and 8.7% silty clay.
