TWDB’s Statewide Base Level Engineering Strengthens Texas’ Flood Resilience
Krista Melnar
Stormwater Practice Leader
Garrett Johnston
The Texas Water Development Board (TWDB) has made exceptional progress in providing broader and more accessible resources for Texas communities looking to improve their flood resilience before, during and after disasters.
The Board recently shared how statewide Base Level Engineering (BLE) modeling and mapping is expanding available flood risk information – providing flood hazard data for all 268,000 square miles of Texas. To provide complete statewide coverage over the past five years, TWDB developed new floodplain maps for nearly one-third of Texas and improved maps for other portions of the state where data was outdated or incomplete. This statewide effort complements detailed Federal Emergency Management Agency (FEMA) maps and local community studies to create a broader foundation for planning and preparedness.
Our Freese and Nichols stormwater team is among five consultant groups that partnered with TWDB to develop the new BLE data products, alongside Halff, AECOM, AtkinsRéalis and Stantec.
The statewide BLE program received the Gold Medal at the 2025 American Council of Engineering Companies (ACEC) Texas Engineering Excellence Awards, recognizing the scale and public value of this effort.
Why Complete Data Matters for Flood Disaster Resilience
The BLE data developed in this program complements FEMA’s Flood Insurance Rate Maps by providing flood depth information and identifying flood risk beyond FEMA’s study limits. For much of the state, BLE is the only available modeled flood risk data source, which can help Texas communities evaluate flood risk and regulate development in alignment with local ordinances. In some areas, including FEMA Zone A* areas and certain Zone AE** areas where BLE is more conservative, communities may consider BLE as the best available data.
“Many Texas communities have had to rely on outdated or incomplete floodplain maps to assess risk, particularly in West Texas. These new models and maps help fill those gaps and supplement detailed data available elsewhere,” said Garrett Johnston, Freese and Nichols’ National Technical Leader for Stormwater and a BLE project team member.
“The Texas Water Development Board has shown strong leadership in advancing comprehensive, statewide flood planning. Their BLE initiative provides a solid foundation that supports the broader effort to reduce flood risk across the state.”
How to Access and Use BLE Data
Today, Texans can access BLE maps, models, and other information through FEMA’s Estimated Base Flood Elevation (BFE) Viewer. The status of TWDB’s BLE studies is available on TWDB’s Texas BLE Status Dashboard. These intuitive tools allow communities and property owners to explore flood depths and areas of potential flood risk, while also providing full access to models and technical reports for engineers and planners.
The value of BLE data extends across the full disaster cycle:
- Planning: It can help communities screen risk, guide development and permitting decisions and identify where a more detailed study may be needed
- Response: It can support situational awareness and help officials evaluate vulnerable areas and potential impacts
- Recovery: It can help local leaders prioritize next steps, identify areas for further analysis, and support rebuilding decisions, such as where and how high to rebuild
- Mitigation: It can inform project development, floodplain management and long-term efforts to reduce future risk
No single dataset can solve every flood challenge. But statewide BLE gives Texas communities consistent, accessible flood hazard information that can support decisions before, during, and after disasters. With this investment, TWDB has strengthened the tools available to help Texans understand risk, plan wisely and reduce future flood losses for years to come.
Zone Definitions
Zone A and AE are High-Risk Flood Areas (100-Year-Flood events)
*Zone A: Areas with an annual 1% chance of flooding with no depths or base flood elevation provided on FEMA maps
**Zone AE: Areas with an annual 1% chance of flooding with detailed flood data, including base flood elevations on FEMA maps
Krista Melnar, PE, CFM, PMP, leads the Stormwater Practice and is based in Austin.
Garrett Johnston, PE, CFM, GISP, leads National Technical Excellence for the Stormwater practice and is based in Austin.