The study was directed by Flood Control District staff and supported by Claunch & Miller Inc., engineering consultants, and focused on the hydraulic capacity and constraints of Poor Farm Ditch. Poor Farm Ditch provides drainage to approximately 1,330 acres of highly developed watershed. The analysis considered stormwater flow that would be generated by both 10 percent (10-year) and 1 percent (100-year) rainfall events. Because of the channel’s close interface with Brays Bayou, and the ongoing federal flood damage reduction project (“Project Brays”) sponsored by the U.S. Army Corps of Engineers and the Flood Control District, the study had to consider stormwater detention volume needed to mitigate the potential impacts on Brays Bayou resulting from identified improvements on this tributary channel.
Key findings from the Regional Study included the following:
- Poor Farm Ditch upstream of University Boulevard has adequate capacity to convey runoff from a 1 percent (100-year) storm event.
- Poor Farm Ditch downstream of Bellaire Boulevard to the confluence with Brays Bayou has 57 percent excess capacity to convey runoff from a 1 percent (100-year) storm event.
- The reach of Poor Farm Ditch between University and Bellaire boulevards is not adequate and would need to be enlarged by as much as 75 percent to convey runoff from a 1 percent (100-year) storm event.
- The Bellaire Boulevard bridge needed to be widened because it was a constraint to stormwater conveyance. This bridge was later modified in 2012.
The study concluded that, despite making the improvements to the reach of Poor Farm Ditch between University and Bellaire boulevards, the channel downstream of Bellaire Boulevard had more than adequate capacity to contain the increased flow within banks. No additional stormwater mitigation was necessary.
However, the study also concluded it would be necessary to mitigate the impacts of the proposed Poor Farm Ditch improvements on Brays Bayou by providing stormwater detention along Brays Bayou. It was estimated that 43 acre-feet of mitigation was necessary to mitigate impacts of the proposed Poor Farm Ditch improvements.