F-56 Detention and Retention Upper Cypress and Addicks

F-56 Detention and Retention Upper Cypress and Addicks


Recent Action

February 26, 2019 – Harris County Commissioners Court authorized a $360,000 agreement with an engineering firm for a feasibility investigation in support of this project

September 25, 2018 -- Harris County Commissioners Court authorized negotiations with an engineering firm to conduct an engineering investigation in support of this project

September 25, 2018 – Harris County Commissioners Court authorized and initiated this project


This project included a feasibility investigation to determine whether creating multiple shallow stormwater detention and retention areas on private agricultural or open property in the upper Cypress and Addicks Reservoir watersheds would reduce flooding risks in the Addicks Reservoir and upper Cypress Creek watersheds.

These areas, which would be surrounded by low 3-4-foot earthen berms – rather than created by excavation – would temporarily hold back stormwater until it naturally drained and evaporated, or was manually pumped dry. The berms, which could be distributed on the properties of willing landowners throughout the upper Cypress Creek watershed, would not interfere with the land’s other uses.

Drainage in the Addick Reservoir watershed is complicated by the fact that, during storm events in the upper northwest areas of the county exceeding a 10-percent (10-year) event, runoff overflows from the upper Cypress Creek watershed and travels overland (south) into the tributary watersheds draining into the Addicks and Barker reservoirs. These include Langham, Bear and South Mayde creeks. This unique hydrological condition is referred to as the “Cypress Creek Overflow.”

This is a natural condition caused by the particular topography of northwest Harris County and the upper Cypress Creek area. This condition predates urban development and was taken into consideration when the Addicks and Barker reservoirs were constructed in the 1940s.

The feasibility investigation found that nearly 700 parcels in the project area could be candidates for the shallow storage concept, potentially holding an estimated 26,000 acre-feet of runoff during a 1 percent (100-year) rain event (using Atlas 14 rain data.) This equates to 40 percent of the Cypress Creek Overflow from Cypress Creek into the Addicks Reservoir watershed, and is comparable to the capacity of some reservoir concepts discussed in the Cypress Creek Overflow Management Plan.

The feasibility investigation also found that the shallow storage concept also would have an impact on the peak flowrate along Cypress Creek between the Grand Parkway and Highway 290, and would offer benefits in both regional and local drainage.

Feasibility Investigation Report