Virginia Avenue Drainage & Stormwater Management Retrofit Study

As the City Engineer for the City of Seaford, Delaware, GMB worked with the City to provide alternatives to address flooding problems along Virginia Avenue and in adjacent communities.

GMB performed a flood analysis for the East Virginia Avenue watershed, which includes, several residential subdivisions, the Western Sussex Boys & Girls Club, Seaford High School, the Shipley State Service Center and a portion of Route 13A. The goal of the consulting effort was to provide recommended solutions to ongoing flooding problems which have forced the evacuation of residents from their homes during heavy rainfalls. 

GMB analyzed the existing closed pipe conveyance system and stormwater management/pond systems using Boss International’s StormNET software.  StormNET is a hydrodynamic model which can calculate the impact that rising or falling hydraulic grade lines in the receiving drainage system will have on discharge rates and water surface elevations within the private stormwater management facilities. Model input included a combination of LIDAR data and field collected survey points.

In evaluating the existing drainage system, GMB recognized opportunities to retrofit new BMP’s and upgrade existing BMP’s.  Flow was directed to a new wet pond, which serves as a forebay to a complex created wetland system.  An existing overgrown dry basin was converted to a wetland system with channel and floodplain, and an existing wet pond was converted to a shallow wetland system.

The project was funded by the Delaware Clean Water Advisory Council, as well as the Delaware Department of Natural Resources & Environmental Control.