Lower Clear Creek and Dickinson Bayou Regional Drainage Solutions
In mid-2021 a phase 1 study regarding regional flood mitigation along both Clear Creek and Dickinson Bayou was completed. This initial study focused on riverine flooding specifically, and was intended to provide a detailed view of the current landscape in the watersheds to include changes in development and natural grade. We want to highlight that there were possible solutions to solve flooding in the region and did so by setting a baseline target of reducing water elevation at the I-45 crossings by 3ft during heavy rain events. This goal can be achieved in both watersheds, albeit with very costly projects. Provided is a picture of where we are today—nearly two years after the phase 1 study was completed—and how we are moving forward.
The proposed Clear Creek Alternatives achieve 2ft of reduction in water surface elevation at SH3, to over 3ft in reduction upstream through Friendswood. The three alternatives for Clear Creek, which include tunnels, are achieved with a preliminary budget of $1.25B. Each of these alternatives consists of a system of 5-7 projects (conveyance improvements and detention) that combine to reduce flood risk for thousands of properties. You can see some of the project locations below, noting red is an increase in water due to improvements (i.e. a pond installed in that location) and blue-purple is a decrease in water. Note project labeled “6” as we will revisit it later.
The approach to Dickinson Bayou was quickly summed up by one project alternative. Other alternatives did not provide the necessary benefit to the hardest hit areas surrounding downtown Dickinson. The most meaningful alternative, which provides a 2-3+ft reduction in water surface elevation throughout the majority of downtown Dickinson, involves upstream detention and an 11,000 CFS diversion channel from Dickinson Bayou to discharge in the area of SH 146. This watershed has repeated flood risk even with smaller (10, 50-year) rain events and the proposed projects would reduce flood risk for 1,000 properties during a 10-year event, 2,000 properties in a 50-year event, 2,200 in a 100-year event and 2,000 in a 500-year event. The array of proposed projects for Dickinson Bayou are achieved with a preliminary budget of $500M.
Overall Project Strategies
With an estimated combined budget of $1.75 billion, it is apparent that funding will be an obstacle. It is not feasible to expect local governments in these areas to provide funds to cover this cost, so other options involving State and Federal funding need to be explored. The primary funding mechanism for this study is a program directed by the US Army Corp of Engineers (USACE) and funded by Congress. This program is funded via the Water Resources Development Act (WRDA) and we are happy to say that the project was included in the final approved bill along with 94 other Corps feasibility studies. Being included in WRDA is a driver for reapplication in future years to receive construction funding. To prove to USACE and the federal government that the projects are valid and functional, we need to go through a feasibility study, which will expand upon the work that was done between 2019-2021. There are multiple criteria for approval, but the main goal is proving that the project(s) provide a benefit-cost ratio (BCR) of more than 1, that is, the cost to perform the work is less than the benefit created. Unfortunately, the development within these two watersheds makes achieving the required BCR difficult. Residential properties pale (cost-wise) in comparison to the more heavily industrialized areas further up the ship channel. Our consultants are working diligently to try and quantify the social-economic impacts of these events in such a way that they can be translated into an economic benefit. For example, not being able to live in your house for weeks during repairs, or the inability to go back to work. But these factors don’t easily translate to a dollar amount, compared to insurance claim totals, which are typically needed to calculate BCR.
The project feasibility study, at a cost of $3M, was authorized in the WRDA 2022 bill; however, authorization doesn’t equal appropriation (funding). In this case, the project is funded with a 50/50 split between local sponsors and USACE, therefore we need $1.5 million in federal funding allocated to the project to proceed. City staff submitted a “Community Project Funding Request” through Congressman Weber’s office for consideration in mid-March, with the expectation of an answer by early summer. If funding is secured, we can proceed with the next phase of the project. One thing to note regarding expectations: It must be stated that these solutions are likely to take 5-10 years before implementation, if everything goes well.
There are various other coordination activities happening which can fund different parts of the plan:
- Section 205 (flood mitigation) of the Continuing Authorities Program (CAP) through USACE funds projects up to $10M. The project mentioned previously in the Clear Creek Section (#6 on the map) was submitted to USACE for inclusion in this program. This project is a high-water bypass along Clear Creek at FM270 to move water more efficiently through this intersection by avoiding the bridge crossing as well as the large oxbow in the creek. The project approval follows a similar process to the WRDA above and a feasibility study needs to be completed to prove the benefit of the project. The project was accepted into the program, and we are hoping to receive final approval in mid-June. This program takes approximately 3 years to reach construction if all goes as planned.
- All previously mentioned programs require funding via a local match. This can be achieved via state or other non-federal sponsors. To date, the project has been identified as a Tier 1 project for both the Houston-Galveston Area Council (H-GAC) and as part of the Texas General Land Office (GLO) Coastal Resiliency Master Plan. In addition to these two organizations, the study and all project concepts have been included in the draft version of the first ever Texas State Flood Plan being developed by the Texas Water Development Board.
There are multiple options moving forward to proceed with these projects, but they all ultimately depend on a combination of interagency funding that local government’s alone can’t reasonably achieve. Currently, there is a strong sense of regional support from the Dickinson Bayou Watershed Steering Committee, the Clear Creek Watershed Steering Committee, Harris County Flood Control District, Galveston County, League City, Friendswood, Dickinson, Pearland, Webster, El Lago, Nassau Bay, Taylor Lake Village, Santa Fe, and multiple Drainage Districts within Galveston County. We plan to continue to keep all interested parties informed as well as advocate for additional support.