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).