TWDB Flood Planning: Developing a Statewide Flood Quilt
The TWDB has embarked upon a regional flood planning process, modeled on the successful regional water planning process. As a starting point to assess statewide flood hazards, TWDB assembled a statewide “floodplain quilt,” consisting of multiple sources of floodplain data including National Flood Hazard Layers (pending and preliminary detail and approximate studies), Base Level Engineering (BLE), and digitized paper FIRMS. Given a large portion of the state does not yet have floodplain maps, TWDB contracted with Halff who partnered with Aqua Strategies in collaboration with Fathom to develop a “cursory floodplain” dataset to append the State’s floodplain quilt.
The intention of the Fathom “rapid assessment” flood data is to “fill the gaps” where flood risk data is unavailable. The Fathom “cursory floodplain” dataset includes pluvial, fluvial and coastal flood risk produced using models developed at 30-meter resolution for the entire state of Texas, for return periods of 5-, 10-, 100- and 500-years. The 30-meter produced Fathom models incorporate TWDB provided LiDAR data in all areas of the state with model results hydrologically mapped at a 3-meter resolution.
The state’s “floodplain quilt” combined with the statewide “cursory floodplain” are being used by regional flood planning groups to identify and establish Flood Management Evaluations, Strategies, Projects for their regions. In addition, there are opportunities for the regional flood planning groups to work with the regional water planning groups on strategies that benefit both groups.
Representatives from Halff Associates, who managed the Fathom project and who are serving as the consultants for regional flood planning groups, will be presenting at a TWCA webinar.