**5.4 Runoff depth during the 2011 super algal bloom**

The IRL ecosystem recently suffered from a recurrence of algae blooms since 2011 which are heavily influenced by anthropogenic stressors within its watershed, such as surrounding developed land with possible higher surface runoff [8]. Based on a visual comparison; the runoff depth was higher prior to the algal bloom events between 2011 and 2016 particularly near the areas of recorded high Chlorophyll *a* concentrations (**Figures 3**–**6**). It is important to note that the monthly runoff reflects precipitation estimates collected at the end of the month. Therefore, the runoff depth map for March should be visually compared to the chlorophyll *a* concentrations in April 2011.

Although there is no available MERIS NDCI calculations collected throughout the summer, there was an increase of runoff to 10–18 cm in May and June for the Banana River (**Figures 5** and **6**). The increase may explain the 48.62 μg/L spike in chlorophyll a May 2011 from April 2011. Based on the estimated concentrations by MERIS NDCI and water quality samples from SJRWMD, the algal bloom became higher on the 14 September 2011 with the highest concentrations in October [29].

**135**

**Figure 8.**

*area.*

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

The runoff depth for October 2011 showed the high runoff with values above 15 cm in the southern IRL and Northern IRL. Subsequently, concentrations of chlorophyll a gradually decreased throughout October, and further dropped in November and December. Results also indicate that there were also smaller contributions of runoff during those months with decreasing trends. Visual comparisons between the chlorophyll *a* and runoff depth indicate that there may be a correlation positive association between the two variables for 2011. However, further analysis including

*The map above shows the geographically weighted regression locally weighted coefficients throughout the study* 

Delineation of PRCs and runoff depths can provide a geographic depiction for assessing lands of interest to implement sustainable developmental designs and structures. In this study, runoff coefficients were calculated for each pixel regardless of surrounding pixel values. Therefore, computational methods used in this study to determine runoff depth were not assessed using methods to incorporate Directly Connected Impervious Areas (DCIA). DCIAs are areas that are considered

statistical measures should be performed to assess the relationship.

**5.5 Implication for coastal water management**

*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*
