Relating Stormwater Control Measure (SCM) Discharge Design Standards to Stream Erosion in Piedmont North Carolina: Case Studies in Raleigh and Chapel Hill, North Carolina

摘要

As rural watersheds become urbanized, the percent imperviousness increases, altering the hydraulics of stormwater runoff. To restore urbanized watersheds, stormwater control measures-(SCMs) are often implemented and designed through water quality measures to return peak flow attenuation to a pre-developed state; however, the affect of release rates on the geomorphic stability of streams are often neglected. The SCMs reduce peak flow rates, but increase duration of sub-bankfull flows within channels, extending periods of erosion. Nineteen rural reference streams along with PCSWMM were used to 1) develop a power regression equation controlling maximum release rate of SCMs based on critical shear stresses of bed sediment and 2) develop annual allowable erosional hours and excess stream power standards. These standards were then applied to 2 urbanized watersheds, House Creek in Raleigh, NC and Tanyard Branch in Chapel Hill, NC to assess the practicality of using the developed standards in an urbanized watershed and determine the geomorphic impact of using LID practices instead of a wet pond on a stream.