Figure 3. Map of coastal North Carolina HUC12 watershed areas that were used to summarize land use change between 2019 and 2001. The watersheds in this map are colored by the SGA name that the watershed is closest to and therefore associated with. Study area map was created in R version 4.1.0 with the ‘sf’ version 0.9 package.
Percent changes within each consolidated LULC class for all coastal watershed areas from 2001 to 2019 were calculated in R version 4.1.0. Water quality stations were then related to watersheds based on distance, with stations being assigned to the nearest watershed. Because of the variation in flow volumes of contributing tributaries to these estuaries it is difficult to generalize the exact transport distance of non-point sources of FCs in coastal systems. It is known that FCs are generally sourced from surrounding watersheds and their survivability in the water is dependent on a wide range of environmental factors (Weiskel et al., 1996; Cho et al., 2016; Korajkic et al., 2019). For context, Weiskel et al. (1996) demonstrated that even point source discharges of FC being diluted to near-background levels within 15 meters of the source (Weiskel et al. 1996). Each station’s distance to shoreline was also calculated, which was done through nearest feature geoprocessing in R using the estuarine shoreline data layer from the NCDMF Estuarine Shoreline Mapping Project (NC Division of Coastal Management, 2007).