Baltimore Ecosystem Study Institute of Ecosystem Studies

2011 BES Annual Meeting Presentation and Poster Abstracts

Stormwater management and hydrologic response in BES watersheds
Miller, Andrew

Stormwater management (SWM) did not exist in Baltimore watersheds during the period when most inner-ring suburbs were developed, but was gradually introduced beginning in the 1980's. SWM structures are now pervasive features of the landscape in areas developed over the past 30 years. The purpose of these structures is to mitigate the hydrologic consequences of intensive urban development. However there are many confounding factors affecting hydrologic response to precipitation events and the aggregate effect of a network of SWM structures at the watershed scale is not necessarily the same as the damping effect of a single structure on the hydrologic response of its source area. This study utilizes BES watersheds as natural experiments, comparing small developed watersheds in close proximity to each other with similar percent impervious cover and differences in the percent of drainage area controlled by SWM. Watershed comparisons include Scotts Level (drainage area = 8.6 km2, 32.9% impervious, 10.5% SWM) and Gwynns Falls near Delight (drainage area = 10.5 km2, 28.5% impervious, 42.7% SWM); and Dead Run headwater tributaries DR1 (1.2 km2, 67% impervious, 48.1% SWM), DR2 (1.9 km2, 49.1% impervious, 30.5% SWM) and DR (1.6 km2, 45.9% impervious, 2.9% SWM). Analyses include comparison of flow duration curves for unit runoff rates, quickflow hydrographs associated with individual storms, and characteristic shapes of unit hydrograph response to short-duration pulse rainfall. Results suggest that SWM may have a damping effect in some cases but is not necessarily the dominant influence on watershed hydrologic response.