Gully Run Floodplain Study

Taylor Wiseman & Taylor (TWT) performed a detailed floodplain analysis for Gully Run along 1,300 LF of an open 12’ wide by 6’ high concrete and stone drainage channel. The analysis included sections covered by an existing building and two driveways, and the waterway that passes through a concrete arch culvert under Belmont Avenue in Lower Merion Township, PA.

The study involved analyzing over 1,050 acres in a highly-urbanized area. Upstream and downstream portions of Gully Run are completely enclosed in a concrete culvert.  The downstream end of the study began at a 7’ diameter culvert that leads to the Schuylkill River.

An analysis, utilizing the SCS TR-55 and US Army Corps of Engineers HEC-RAS methodologies and respective software, 1,200 LF upstream of the subject site, a natural impoundment area created by a roadway culvert, was analyzed to determine available downstream flows reaching the site.

The study demonstrated that 100-year storm flows are contained within the concrete channel and development of the site was possible.