Stormwater Performance Measures and Metrics

Abstract

A major challenge in the management of urban stormwater is defining appropriate metrics for success. The ideals of measures and metrics are continuously evolving. Stormwater control measures provide the link between the existing conditions of the watershed and the desired hydrologic and water-quality characteristics leaving the watershed. The selection, design, construction, and maintenance of the stormwater control measures (SCMs) will determine how well they meet specific desired performance metrics. The Chesapeake Bay Program provides credit for pollutant removal for the implementation of SCMs in retrofit situations based on performance curves estimated from SCM data. One of the simplest and most desired targets is a threshold pollutant concentration for in-stream water quality. To synthesize the pollutant duration curve, the sample concentrations, with their respective durations, are ranked highest to lowest.