Characterizing hydrologic response in urban watersheds: a case study of Philadelphia, Pennsylvania

Abstract

An analysis of hydrologic response in Philadelphia, Pennsylvania is conducted using rain and discharge data from August and September, 2011. Runoff ratio, response time, unit area peak discharge and the temporal accumulation of rain and runoff are used to quantify hydrologic response. Eight different watersheds are analyzed, and the geospatial differences amongst them allow correlations between these response metrics and both basin area and basin development. It is found that the fraction of developed land in Philadelphia watersheds influences response time and peak discharge; more developed, urbanized basins exhibit shorter response times and higher peak discharges than basins with a smaller fraction of developed lands. Storms are predicted to become stronger with rising sea surface temperatures, and as the city of Philadelphia becomes more developed, especially in currently moderately-developed watersheds, flood potential will increase.