Ongoing efforts to manage stormwater overflow from Cypress Creek to the Addicks Reservoir watershed continued with a public meeting Sept. 28 hosted by the Harris County Flood Control District.

HCFCD presented details on the two proposed regional concept plans designed to manage the overflow. A grant awarded by the Texas Water Development Board was used to conduct the research, and a draft report detailing the two plans will be submitted to TWDB at the end of October.

Eventually, the two plans will be narrowed down to one, which will be proposed to Harris County Commissioners Court for approval. In the meantime, HCFCD is collecting public comments on the plans through Oct. 25.

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—once every five-to-ten years on average—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."

Projections from the Region H Water Planning Group show the population in the study area rising from 312,000 people to around 550,000 people by 2060. Green estimates 30,000–40,000 acres of land will be developed to support that population.

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 $271 million and involves building a reservoir for storage at Mound Creek with collection channels to funnel overflow to Bear Creek, which would be widened. The Katy Hockley/North Cypress plan involves creating reservoir in both the Upper Cypress and Addicks watershed to capture flow along Cypress Creek with outlets to Bear Creek and Cypress Creek. This plan would cost around $369 million.

The Mound Creek plan uses less land with a greater inundation depth and features a shorter drain time. The Katy/Hockley plan provides more storage, creates more conservation land and has a greater opportunity for financial contributions from partner organizations based on early funding studies.

In a separate but related initiative, HCFCD is preparing supplemental guidelines for overflow management. These proposed recommendations, which involve increasing minimum detention rates and adjusting how runoff is calculated in the study area, will be submitted to Harris County Commissioners Court for consideration.

Comments from the public can be submitted by email, through the study website or by mail to Dena Green at the HCFCD office at 9900 Northwest Freeway.

Next steps involve submitting a draft report to TWDB in late October, then going to commissioners court to seek approval of the Regional Overflow Management Concept Plan in December. Following approval, HCFCD officials will investigate further into funding strategies before submitting a final report to TWDB in the first quarter of 2015.