This project will focus on recovery and resiliency through detailed analysis, modeling, and mapping of existing flood risk and developing proposed alternatives to provide long term risk reduction within the community. The study will include survey data collection through bathymetric, terrestrial, and aerial surveys, mapping jurisdictional boundaries with reference to ditch / outfall capacity and rights-of-way, hydrologic and hydraulic studies, capital improvement plan development with detailed maps, identification of problem areas, and recommended priority of projects for future flood mitigation.

The contract between the GLO and Liberty County was executed on January 9, 2024 and the Master Drainage Plan (MDP) was began by LJA Engineering, Inc. (LJA) on March 12, 2024. The project is estimated to be completed by Fall 2027.

Project Management

The MDP is scheduled to take 3.5 years to complete with surveying taking 1.5 years, the modeling analysis to take 1.5 years and the reporting to take around 9 months. The communication effort will be spread throughout the project schedule as needed.

Survey

Initial schedule is to perform the necessary surveying efforts over the first 12-18 months, including installation of approximately 200 benchmark monuments across the County, detailed terrestrial survey for channel cross section, structure crossings (culverts and bridges) and other important geometric details that need to be incorporated into the hydraulic models. Collection of updated LiDAR aerial survey has been coordinated with the H-GAC as part of their recent flights in Jan / Feb 2024 and bathymetric survey of the channel geometry below water with sonar will be completed once the monumentation efforts are complete and ready for use.

H&H Engineering

Detailed model development of the Hydrologic and Hydraulic conditions will be performed for the approximate ten (10) drainage areas across the county. Utilizing the US Army Corps of Engineers modeling software HEC-HMS and HEC-RAS, LJA will evaluate existing conditions to identify flood risk and problem areas and then develop proposed alternative improvements with a prioritization of needs. This effort will also include preliminary cost estimates and benefit / impact metrics for use in a Benefit Cost Analysis (BCA).

Communications

Throughout the project, public communication will be critical in understanding the existing issues and local problems across the County as well as presenting the existing condition findings to help calibrate / validate the modeling results, and then discuss the proposed recommended alternatives and prioritization for inclusion in the Capital Improvement Plan (CIP). These efforts will include presentations to Commissioners Court at strategic milestones and public meetings for additional coordination with stakeholders and local residents.

Reporting

The development of the MDP will include interim technical memos to Liberty County for cursory review for Data Collection, Survey, Existing Conditions, and the Alternative Analysis efforts. The final report will be a compiled package of these Technical Memos for review by the County and the GLO and will include any feedback or comments received by the County and stakeholders. Additional reporting will include updated flood risk maps and an update to the Drainage Criteria Manual to help manage future developments across the County.