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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. [ABSTRACT FROM AUTHOR]

Addicks and Barker reservoirs were built in the 1940s to protect downtown Houston from flooding and have generally worked very well until 2017 when Hurricane Harvey devastated much of Houston and surroundings with up to 40 inches (102 cm) of rainfall causing flooding of 154,000 homes in over 22 watersheds in Houston/Harris County alone. However, the story of how Addicks and Barker flooded upstream residential areas from a hydrologic standpoint is a harsh lesson in flood infrastructure policy and funding. This failure to protect both downstream properties in Buffalo Bayou and upstream areas behind the dams ended up with tens of thousands of flooded homes and properties, with many having flood waters for over 10 days. This paper explores the main causes for the flooding and addresses the hydrologic issues upstream in both reservoirs. The main causes of flooding were not just related to a massive rainfall event, but also explosive urban expansion of land use upstream of reservoirs, altered and updated reservoir design issues, and lack of governmental action in the years leading up to the disaster. Potential long‐term solutions to the flooding and design problems are addressed in this article as well. [ABSTRACT FROM AUTHOR]

A physics-based, distributed hydrologic model (Vfto) was used to evaluate the effects of urbanization and detention storage on watershed stream flows with grid cells as small as 0.09 k[m.sup.2] (22 acres). The analysis was performed for the Little Cypress Creek watershed in Houston, Texas. Hypothetical development and flood mitigation scenarios in the upstream, midstream, and downstream portions of the creek were analyzed for their impacts on peak flows for the 100-year design storm. Local ponds and regional reservoirs were compared for their ability to bring downstream flows back to existing conditions at all points along the creek. Analysis showed that downstream flows would be most effectively mitigated when storm water detention volumes and release rates are imposed with an awareness of locations relative to watershed headwaters of a referenced outlet point. This is in contrast to many existing policies that are uniformly applied across a watershed. DOI: 10.1061/(ASCE)WR.1943-5452.0000066 CE Database subject headings: Land use; Reservoirs; Floods; Hydrologic models; Urban areas; Water storage; Watersheds. Author keywords: Land use; Detention reservoirs; Flood control; Hydrologic models.

Issues discussed concern the technological improvements in flood warning systems for urban areas, focusing on the use of geographic information systems, the internet, and advanced radar to predict floods. Topics addressed include the inadequacies of many flood prediction systems in urban areas, equipment to measure real-time rainfall, and computer models that evaluate storm intensities and flooding probability.