Hydrologic and Water Quality Analysis of a Regenerative Stormwater Conveyance (RSC) in the North Carolina Piedmont

摘要

Installed in an eroded channel, regenerative stormwater conveyance (RSC) is a grade-control and retention practice that connects a series of pools with boulder riffles and a subsurface sand layer. RSCs are designed to detain and slowly release storm events smaller than 1 in and recreate a headwater stream environment. An eroded headcut draining a 6.8 acre developed watershed in Durham, North Carolina was retrofitted with a RSC in November 2014. An upstream/downstream monitoring study is currently inthe data collection phase using flow paced storm event sampling for a full suite of water quality parameters. Statistical analysis of differences between upstream, mid-structure, and downstream monitoring locations will be compared for peak flow, volume,pollutant concentration, and pollutant load. Initial results indicate intersection of a seasonally high water table limiting pool drawdown and causing outflow volumes to exceed inflow volumes by 24%. Peak flow rates have been reduced by 41% along the length of the RSC for storm events smaller than 0.5 in, however, due to the limited storage capacity, peak flow rates have increased by 16% for storm events greater than 0.5 in. Preliminary analyses of nutrient concentrations indicate potentially significant decreases in total nitrogen concentrations along the length of the RSC but not total phosphorous and total suspended sediment, possibly due to slow bank stabilization after construction. Upon completion, study results will be provided to state regulators for use in determining RSC accreditation and to the design community for use in improving future RSC design and maintenance.