The Dallas County Map Modernization study began in September, 2004. The goal of the project is to produce Digital Flood Insurance Rate Maps (DFIRMs) for the entire county. Preliminary maps will be available in the Fall of 2006, and the final DFIRMs will become available in 2007.

Dallas County covers a total area of 908 square miles. There are 25 distinct cities and towns in the county that participate in the National Flood Insurance Program. The 2004 population of the county is estimated to be 2,296,000. All land in the county drains to the Trinity River and its tributaries. Currently, there are 986 miles of FEMA-studied rivers and streams for Dallas County.

The flood of record occurred in 1908. During the 1908 flood, the Trinity River was reported to have attained a depth of 52.6 feet, and to have been 2 miles wide in places. Flooding continues to be a problem in the County. Most recently, southern areas of the county received more than a foot of rainfall overnight on July 28-29, 2004.