Headwater catchments: Estimating surface drainage extent across North Carolina and correlations between landuse, near stream, and water quality indicators in the Piedmont physiographic region.

摘要

Headwater drainages are an important part of larger river networks because of their linkage to the surrounding landscape. Most of the drainages are not shown as blue-lines on the commonly used USGS 1:24,000 scale topographic map series, especially in finely dissected terrain. In a preliminary study, the traditional contour crenulation (T-CC) method was used to map-measure drainage lengths in seven first-order blue-line (FO-BL) drainage areas located in the Piedmont (P) physiographic region of North Carolina (NC). They were compared to field-measured lengths. Results indicated a strong correlation between the lengths (R = 0.98). Results also indicated strong correlations between lengths and areas for both methods (Field Measured, R = 0.99 and T-CC, R = 0.97). Drainage densities (Dds) for each method were compared using ANOVA and Tukey-Kramer procedures. Mean field-measured and T-CC Dds were not significantly different. Both were significantly greater than the mean FO-BL Dd.; The preliminary study was expanded and included 122 randomly selected FO-BL catchments across five topographically diverse physiographic regions. Results indicated that catchment size and map contour intervals were also important factors in predicting T-CC lengths from areas. T-CC length prediction equations were tested in the Piedmont and Mountain regions. T-CC and predicted Dds were compared. Results indicated that mean T-CC and predicted Dds were not significantly different for either region. By region, the T-CC lengths were 2 to 4 times greater than FO-BL lengths.; Macroinvertebrates family taxa richness (FTR) and Hilsenhoff family biotic index (FBI) values were used to assess the near-stream habitat and average runoff condition of 33 headwater catchments located in the upper Neuse River basin of NC. Near-stream habitat condition (HR) was rated using elements of the US Environmental Protection Agency (US EPA) Rapid Bioassessment Protocols; bank stability, bank vegetation protection, riparian zone width, and riparian zone vegetation structure. Catchment runoff condition was estimated using the US Department of Agriculture (USDA), Natural Resources Conservation Service (NRCS) curve number (CN) method. Three reference sites were selected to represent small, medium, and large size-class reference conditions. Catchment areas and the four assessment variables (CN, HR, FTR, and FBI) were normally distributed within each of the catchment size-classes, as were the CN and FBI variables for the 33 catchments combined. (Abstract shortened by UMI.)