Bankfull Curves for the Temperate Rainforests in the Southern Appalachian Mountains of Western North Carolina

Bankfull hydraulic geometry relationships, also called regional curves, relate bankfull stream channel dimensions and discharge to watershed drainage area. This paper describes results of bankfull curve relationships developed for the temperate rainforests of the Southern Appalachian Mountains primarily on Western North Carolina Mountain streams in the Southeastern United States. Gauge stations for small and larger catchments were selected with a range of 10 to 50 years of continuous or peak discharge measurements, no major impoundments, no significant change in land use over the past 10 years, and impervious cover ranges of <20%. Cross-sectional and longitudinal surveys were measured at each study reach to determine channel dimension, pattern, and profile information. Log-Pearson Type III distributions were used to analyze annual peak discharge data for nine small watersheds sites gauged by the United States Department of Agriculture (USDA), Forest Service, Southern Research Station, Coweeta Hydrologic Laboratory and for eleven larger watersheds gauged by the United States Geological Survey (USGS). Power function relationships were developed using regression analyses for bankfull discharge, channel cross-sectional area, mean depth, and width as functions of watershed drainage area.