Flood Mitigation Using Channelization and Detention Given Changing Rainfall Conditions in Houston

Houston, Texas, has highly engineered its waterways to reduce flooding. However, this has been shown to be inadequate during recent storms in 2015 through 2017, including Hurricane Harvey. This study analyzed the efficacy of a large-scale structural mitigation project, Project Brays, on reducing flood levels in the Brays Bayou watershed given updated rainfall standards released in 2018. In addition, we investigated the water surface elevation (WSE) reduction of three detention basins that were constructed as a part of this mitigation project. We propose other possible detention basins to mitigate flood hazard in the highly flood-prone regions of the watershed. We found that Project Brays will decrease WSE in the upstream half of the watershed by around 1.2 m at the expense of increasing WSE by 0.52 m downstream. Additional detention basins could further decrease WSE by an average of 0.1 m over the area impacted during the Atlas 14 100-year storm. These impacts are very localized directly downstream of the detention locations and are no longer seen after approximately 300 m. Future mitigation should contain more localized detention directly upstream of flood-prone areas to provide additional targeted reductions in floodplain extent. Project Brays is a case study that demonstrates how future climate scenarios may be necessary for the large-scale design works of the future, given that such projects often take decades to construct and it is not typically standard practice to design for climate conditions potentially existing upon completion.