The Harris County Flood Control District has identified two possible plans in an ongoing discussion about overflow management in the Cypress Creek area. A draft report with details on both plans will be submitted to the Texas Water Development Board later this year.
Flooding concerns revolve around significant storms that cause Cypress Creek to overflow, with that overflow eventually making its way to the Addicks Reservoir. Although floods in the Cypress Creek and Addicks Reservoir watersheds do not occur often, HCFCD is looking for ways to prepare for future development in west Harris County, which is expected to make flooding more of an issue.
"The reservoirs have very large capacity, but the capacity is limited," said Dena Green, study manager in HCFCD's engineering and construction division. "If too much water is released, it can impact the folks living downstream along Buffalo Bayou. If not enough is released, it can affect those upstream of the reservoir."
HCFCD records show overflowing has occurred five times since 1990. The size of a overflow is measured based on how likely it is to occur within a year. A 1-percent annual storm is the amount of rain having a 1 percent chance of being equaled or exceeded in a given year, according to the CCFCC. Green said Cypress Creek overflow happens somewhere between 5- and 10-year storms.
Projections from the Region H Water Planning Group show the population in the study area rising from 312,000 people to 550,000 people by 2070. Green estimates 30,000–40,000 acres of land will be developed to support that population.
"Flood control has had indications from developers that they are interested in developing in the area where the overflow occurs currently," she said.
Both proposed concepts employ a combination of storage and conveyance components, said Burton Johnson, a consultant working on the project. They were both developed with the concept of Probable Maximum Precipitation in mind—the statistically plausible worst-case event from the standpoint of a fully developed watershed.
The Mound Creek plan would cost around $276.5 million and involves building a storage area at Mound Creek with collection channels to funnel overflow to Bear Creek. The Katy Hockley/North Cypress plan involves creating a larger storage area surrounding Cypress Creek. This plan would cost $369.4 million.
Possible ways to raise money for the project include partnering with area organizations such as the Katy Prairie Conservancy on land acquisition and charging impact fees to developers who build in the area.
Details on the plans are still being fine-tuned. Officials plan to work with Harris County commissioners and hold a public meeting this summer to gather more input.
