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Stormwater flooding has inundated the area along Deer Creek between Hanley Road and South Brentwood Boulevard 26 times since 1957, creating significant public safety issues and causing property damage.
The Deer Creek Flood Mitigation project includes the planning, design and construction of improvements to the Deer Creek channel and floodplain to alleviate ongoing flooding problems and protect properties from frequent flooding. These updates will also provide a greater opportunity for businesses to move to the area.
Floodplain restoration is the process of fully or partially restoring low-lying areas next to streambanks to their original conditions, so that they’re able to accommodate larger overflows of water after large or intense storms.
The floodplain area along Deer Creek has been previously filled and developed, and has subsequently experienced flooding problems. This project will restore some natural floodplain areas along Deer Creek to serve their natural flood control and habitat functions. The end result will consist of low-lying areas with natural vegetation that will be dry most of the time, but allowed to flood following large or intense storms.
The City of Brentwood has adopted FEMA guidelines for floodplain regulations, which do not allow for raising low-lying land in flood-prone areas, a practice that has been found to actually increase overall flood risk. These regulations can be found in the City of Brentwood’s Floodplain Ordinance.
The area that floods in Brentwood along Deer Creek is a location where the natural floodplain along the creek was filled in and developed (approximately 100 years ago). Since that time, the nearly 37-square-mile watershed area upstream has fully developed, increasing the amount of impervious areas (primarily buildings and pavement) and the rate at which stormwater runoff reaches Deer Creek. In Brentwood, the Deer Creek channel slope flattens out and the velocities in the channel slow down at the confluence with Black Creek, and this is an area where the flow of water can get backed up, much like traffic gets backed up on a highway.
Flooding is planned to be eliminated along the Manchester Road corridor, between Brentwood Boulevard and Hanley Road.
A map of the proposed changes in floodplain for Deer Creek and Black Creek is available at this link.
The floodplain bench will be designed to drain toward the creek to avoid wet spots from forming and becoming stagnant. When the floodplain bench area is flooded, the water will generally be deep and not stay in the area for long periods of time. Any green infrastructure will have an underdrain to drain the water until the area is dry following rain events. The City will also utilize a fountain or other feature to keep the pond’s water moving, ensuring water does not remain stagnant.
The goal in the project's design and engineering is to produce no rise in Deer Creek water surface elevation for neighboring communities.
The Metropolitan St. Louis Sewer District (MSD) is working through its Project Clear to minimize combined sewer overflows into Deer Creek. MSD is undertaking these efforts separately from the Brentwood Bound project.