Uniform TitleAn analysis of the SCS method in the simulation of stormwater disconnection in an urban watershed
NameAlthouse, Eileen M. (author), Obropta, Christopher (chair), Uchrin, Christopher (internal member), Vowinkel, Eric (outside member), Althouse, Eileen M. (author), Rutgers University, Graduate School-New Brunswick,
DescriptionSmall storms can have adverse affects on downstream water quality in urbanizing
watersheds because impervious surfaces convey greater volumes of runoff and lead to largerstorm flows than under natural conditions (Booth 1990; Beard and Chang 1979). Therefore
management of the water quality storm (1.25" of rain over 2 hours) has been targeted in water quality initiatives. This study examined whether reducing the effective impervious area that contributes runoff during the water quality storm by disconnecting it from the stormwater conveyance system could be a viable stormwater management solution in existing residential areas. Disconnection was examined in the Pompeston Creek Watershed, Burlington County, New Jersey on the lot, subdivision, and watershed scale. A calibrated HEC-HMS model of the watershed was used for the watershed scale analysis. The SCS equations to were applied to simulate disconnection by routing runoff from the disconnected impervious surface over an adjacent impervious surface. The 2, 10, and 100-year storms were examined in addition to the water quality storm. Three primary conclusions were made: 1) the composite curve number method, and therefore the composite curve numbers given in TR-55, under-predicts small storm runoff when compared to the volume weighted method because the composite curve number does not account for the runoff conveyed by directly connected impervious surfaces in urbanizing areas; 2) by disconnecting the runoff
from the impervious areas by routing it over the pervious area, the runoff volume can be reduced for the water quality storm; 3) the effectiveness of disconnection in mitigating the runoff volumes relies on the infiltration capacity of the pervious area. Both the extent of the under-prediction of the composite curve number and the relative volume reduction achieved by disconnection decrease as storm depth increases. The adjustment of the basin curve number during model calibration for small observed storm events suggested that the original composite curve number method was inadequate in predicting runoff in the watershed scale model for small storms. Basin-wide reductions in runoff volumes with the application of basin-wide disconnection were consistent with the reductions predicted on the smaller scales.
These results have a direct application to regional stormwater management planning as
disconnection can be a suitable retrofit for the management of the small storm in existing
NoteIncludes bibliographical references (p. 162-165).
CollectionGraduate School - New Brunswick Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.