Cypress Creek Overflow Management Plan

Western and northwestern Harris County is anticipated to experience a surge of land development activities in the near future. According to Region H Regional Water Planning studies, the population of the study area, currently about 340,000, is anticipated to nearly double in the next 50 years. 

This area drains into the two major reservoirs on the west side of Harris County, Addicks and Barker, which are designed to mitigate flooding in the downtown Houston area. The trend in land development will convert many acres of prairie land and rice farms into a suburban environment. Drainage is complicated by the fact that when storm events exceeding a 10-year event occur in the upper northwest areas of the county, runoff overflows from the Cypress Creek watershed into the tributary watersheds draining into the Addicks and Barker reservoirs. 

The expanse of area includes almost 400 square miles, or 1/6 of the entire Harris County. To maintain orderly development of the area, and to avoid future drainage problems caused by lack of overall planning, it is necessary to take a comprehensive look at how a drainage plan and appropriate public policy can be implemented to minimize flood risk. This planning effort must balance the competing types of land use interests: preservation, business interests, and environmental mitigation needs. The planning effort also must examine the applicability of existing drainage criteria and make appropriate changes in light of the constraints; develop a sound implementation strategy that recognizes and protects the interested parties; and is economically viable to implement. 

In September of 2011, the Harris County Flood Control District organized a steering committee of key stakeholders to identify the array of issues associated with the competing land interests and drainage issues in the study area. The steering committee includes representatives from Bayou Preservation Association, City of Houston, Harris County, Katy Prairie Conservancy, US Army Corps of Engineers, Waller County, West Houston Association, and the Flood Control District. 

The objective of this effort was to establish a set of policies, technical criteria and guidelines that will allow the Flood Control District and Harris County to plan for and implement programs that reduce flood risks that are reflective of the unique hydrologic conditions in upper Cypress Creek and the drainage areas upstream of Addicks and Barker reservoirs. The principal product of this effort will be a series of design guidelines and an implementation plan for moving forward.

1. Gain consensus among key stakeholder groups representing business, environment, regulatory and other quality-of-life interests of the facts relating to flooding, flood volumes, flood peaks, and flood risk. 

2. Gain an understanding of the needs and objectives of the interested parties as it relates to land preservation, environmental mitigation, and land development. 

3. Develop a consensus plan to reduce flood risks that incorporates the needs and objectives of all of the key stakeholder groups based on the collective interests involved and that is supported by all parties. 

4. Establish interim criteria while adoption of the final consensus plan is ongoing. 

5. Design a business plan to implement the strategies defined including the roles and responsibilities of all of the parties involved. 

6. Gain adoption of the consensus and business plans by Commissioners Court.

The study took a comprehensive look at the aspects of the flooding problem and its solution(s). Aspects of the study were categorized into engineering, environmental, business/financial, and communication disciplines. Scope of Work elements included the following. 

Task 1: Quantifying and Delineating Flood Risk to define the quantity, areal extent and depth of flooding associated with the Cypress Creek overflow and the locally generated runoff. 

Task 2: Identifying Mitigation Strategies 

• To estimate the size of storage/conveyance facilities necessary to respond to changing land uses from undeveloped (prairie) to suburban use. 
• To evaluate the sizing and practicality of implementing alternative strategies to manage the volume and peak rate of runoff in the study area, including runoff in Cypress Creek and the Addicks watershed, in both Waller County and Harris County. 

Task 3: Benefits of Prairie Restoration for Flood Control to determine the flood retardation benefits associated with prairie grasslands, in terms of both infiltration and time of concentration. 

Task 4: Identifying critical conservation areas to define those tracts of land that, for reasons of unique flood management potential or environmental habitat or wetland characteristics, would be preferred to remain as open space for environmental restoration. 

Task 5: Cost/Benefit Analysis to determine the value in establishing a regional drainage plan for the watershed(s), and to quantify that value in terms of avoided costs and benefits to the community. 

Task 6: Project Financing and cost Pro Forma to develop alternative strategies for financing a regional plan and identifying what roles and responsibilities public, private, and non-profit interests would commit to work together to implement any strategy. 

Task 7: Public Outreach Program to communicate to the public the scope of activities being considered by this planning effort and to solicit suggestions that may be incorporated into the planning study. 

Task 8: Final Report to summarize the findings of all investigations into a final report for adoption by Harris County Commissioners Court and potentially Waller County Commissioners Court. 

The study effort was completed in October 2014, and the Flood Control District submitted the draft Cypress Creek Overflow Management Plan study report to the Texas Water Development Board (TWBD) at that time. After a review period, the TWBD accepted the report in September 2015.

Between December 2014 and December 2015, the Flood Control District hosted seven stakeholder workshops about the draft Supplemental Guidelines and Criteria to provide background information about why the criteria are needed, and to determine areas of concern and suggested revisions to the document. The workshops were well attended by several stakeholders, including the West Houston Association (WHA), Greater Houston Builders Association (GHBA), the American Council of Engineering Companies (ACEC), and the Harris County Public Infrastructure Department (HCPID). The goal was to work toward consensus on the guidelines and criteria, and we feel that we achieved that, as well as developing a deeper understanding of landowner and development concerns regarding real-world implementation of the requirements outlined in the guidelines. 

Harris County Commissioners Court adopted the Supplemental Guidelines and Criteria in March 2016, and they are now part of the Flood Control District's Policy Criteria and Procedures Manual.

Currently, the U.S. Army Corps of Engineers is considering the Cypress Creek Overflow Management Plan study and its recommendations as part of the Corps-led Buffalo Bayou and Tributaries Resiliency Study, which began in October 2018. 

Prairie Vegetation Rainfall/Runoff Study 

As part of the "Prairie Vegetation Rainfall/Runoff" study that was conducted within the larger Cypress Creek Overflow study, the Flood Control District continues to gather rainfall and runoff data from three different types of monitoring sites in the study area: developed property, agricultural and range land property, and native prairie. That data will be evaluated and compared with the initial analysis conducted during the study effort, and the results will be posted when the study is complete.