Figure 4 . Map of the 20-year FC trends for all 466 water
quality stations (points) along North Carolina’s coast alongside the
developed change percentage of the HUC12 watershed areas (purple fill).
The points representing the water quality station FC trends are colored
by the τFC value with the red and orange colors
illustrating the positive trends in FC concentrations while the green
and blue colors indicate a negative trend in FC concentrations. These
points are also sized by the magnitude of their βFCvalues (i.e., larger points represent steeper slopes in the FC trends
and smaller points represent more gently sloping FC trends). The light
purple watershed areas represent smaller proportions of developed land
increase whereas dark purple areas represent a more intense increase in
developed land proportions from 2001 to 2019; white, unfilled areas
between watersheds correspond to watersheds that do not directly connect
to a waterway. This map was created in R version 4.1.0 with ‘sf’ version
0.9 package.
The Pearson correlation coefficients for the water quality and
environmental trends along the full coastal area are summarized in Table
1. These correlations include the relationships between
τFC, βFC, τSal,
βSal, τPrecip, βPrecip,
developed land percentage, barren land percentage, wetlands land
percentage, vegetated land percentage, cultivated land percentage, and
distance to shore. We observed a clear negative relationship between
both τFC & βFC and τSal& βSal (r values from -0.281 to -0.304). There was a
weak positive relationship between βFC and
τPrecip & βPrecip. The positive
relationship between τSal & βSal and
all land use classifications with wetlands had the strongest positive
coefficients (r = 0.393 and r = 0.401, respectively). Distance to shore
was weakly correlated with overall FC trends.