Harris County, which contains the City of Houston, has suffered numerous catastrophic floods over the years, and the public demanded progress in terms of flood risk communication and flood damage reduction. This demand was evidenced on August 25, 2018, when Harris County voters overwhelmingly supported a $2.5 billion bond program. 

The public wanted to rebuild sustainable communities. They need high-quality, detailed flood risk and hazard maps that were easily accessed and understood. Most importantly, they needed to develop a better understanding of flood risks in order to make key life decisions such as when and where to buy a home, and the flood insurance premiums for that home (all Harris County residents are encouraged to buy flood insurance). In order to provide this vital information, the Harris County Flood Control District and County leadership have determined that updated Flood Insurance Rate Maps were needed for Harris County, and the District worked with the Federal Emergency Management Agency to develop a Map Activity Statement to guide the development of updated Risk Map products for all of Harris County’s 22 major watersheds. 

HDR was selected to provide professional engineering, project management and control and quality control services to support HCFCD in delivering these important products for the citizens of Harris County. A highly qualified team of engineering firms and drainage professionals was assembled to complete this effort, with HDR serving as the prime consultant with primary responsibility for project management, oversight and quality control. In that role, the project team, which included Pape-Dawson Engineers, Inc., Walter P. Moore and Associates, Inc., Crouch Environmental Services, Inc., and Kleinschmidt, oversaw the efforts of other consultants selected by HCFCD to perform floodplain modeling and mapping services. 

In addition, we were responsible for floodplain modeling and mapping services for selected watersheds. Hydraulic modeling involved linked 1D/2D HEC-RAS models, with hydrograph inputs developed using HEC-HMS. A number of innovative approaches and techniques were utilized in this study, including rain-on-grid analyses aimed at identifying flood risks that traditional floodplain studies do not take into account. Floodplain mapping products included non-National Flood Insurance Program layers that contain information specific to Harris County and representative of the types of flooding experienced in this portion of the Gulf Coastal Plain.

The project was completed in two phases. Phase I involved studies of 11 watersheds located in the northern and western portions of Harris County with Phase II including studies of the remaining 11 watersheds located in the southern and eastern portions of the county. The project study duration for modeling and draft mapping products was approximately three years, with an additional two to three years allocated for developing and perfecting the new FEMA Flood Insurance Rate Maps and ancillary work products, including an updated Harris County Flood Insurance Study Report.