The flood risk information developed through MAAPnext will help local governments, engineers, and developers make better-informed decisions about where and how to build safely once FEMA releases official flood maps.

Communities can use this data to plan future growth, guide infrastructure investments, and identify areas where flood mitigation projects will have the greatest impact. Builders and planners will have access to clearer, more accurate flood information, helping ensure that new structures meet modern standards for safety and resilience.

This information empowers everyone, from homeowners to policy makers, to take proactive steps that reduce flood damage and improve long-term community resilience.

FEMA is anticipated to release the Preliminary Flood Insurance Rate Maps (FIRMs) for Harris County after completion of its federal review and publishing process. Following the release, FEMA will initiate a formal public review and appeal period.

Learn more about the FEMA map review process

Flood models are computer simulations that show how water moves during a storm. MAAPnext uses hybrid 1D (one-dimensional) and 2D (two-dimensional) models to better capture complex flooding conditions.

• 1D modeling looks at how water moves along a defined path such as a bayou, ditch, or creek. It measures depth and flow speed along a single channel. 
• 2D modeling simulates how water spreads across the surface — over streets, yards, and open areas — to represent flooding that can occur away from main channels in a realistic manner.

By combining both methods, MAAPnext can show how rainfall and runoff interact across thecounty, resulting in more complete and realistic flood risk information.

Rainfall and elevation are two of the most critical inputs in flood modeling. The updated rainfall data from NOAA’s Atlas 14 reflects more recent observations and provides revised rainfall frequency estimates for Harris County based on updated statistical analyses.

Similarly, new LiDAR elevation data, collected in 2018, offers a much more detailed 3D view of the county’s surface, including roads, neighborhoods, and drainage channels. This enhanced data helps engineers and modelers simulate water flow more precisely, improving the accuracy of flood maps and reducing uncertainty about where and how flooding may occur.

The project integrates local data, cutting-edge modeling, and technology that were not available in earlier studies, such as updated rainfall estimates from NOAA’s Atlas 14 and high-resolution LiDAR terrain data. These improvements provide a clearer, more detailed, and more realistic picture of flood risk across every part of Harris County.

MAAPnext uses updated data available for this mapping effort. The updated flood risk information is based on several major data sources, including updated rainfall information from NOAA Atlas 14, 2018 terrain/LiDAR data, 2018 impervious cover and land use data, new 1D/2D hydrologic and hydraulic modeling, historical storm information, and completed projects that were available for incorporation into the modeling.

MAAPnext is intended to provide a more complete picture of flood risk across Harris County, including riverine flooding from bayous and creeks, coastal flooding, and community flooding that can occur when intense rainfall overwhelms local drainage systems such as streets, storm sewers, and roadside ditches.

However, no flood map can include every real-time or future condition. MAAPnext does not automatically reflect projects that are still planned, under design, under construction, or completed after the project’s modeling cutoff unless those projects were submitted, reviewed, and incorporated into the mapping process. It also does not replace site-specific engineering, local drainage studies, finished-floor elevation surveys, or official determinations made by FEMA, a lender, an insurance provider, or a local floodplain administrator.

If a resident or community believes there is newer technical information that should be considered, that information may be submitted during the appropriate FEMA review process once the Preliminary Flood Insurance Rate Maps are released for public review.