City of Alexandria Taylor Runoff Analysis

A. Morton Thomas and Associates, Inc. 10710 Midlothian Turnpike, Suite 202 Richmond, Virginia 23235

Donald Rissmeyer 804-276-6231

October 2007 – June 2008

A. Morton Thomas and Associates were hired by the City of Alexandria to prepare a xpswmm model for a hydrology and hydraulics evaluation of flooding downstream of the Duke Street Bridge. Xpswmm was selected as the model because of the combination of open channel and closed pipe in the Taylor Run basin. The existing HEC-RAS model was imported into xpswmm and the pipe and manhole information was imported from the City’s Geographical Information System (GIS) database. The City was evaluating converted a portion of the stream from open channel to closed box culverts. Using xpswmm’s scenario manager, we were able to compare the existing open channel system with the proposed closed box culvert system for the 1-year, 2-year, 5 year, 10-year, 25 year, 50-year and 100-year recurrence interval storms.