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Floodplain Mapping

Status of Floodplain Mapping in Texas (July 2009)Texas Water Development Board (TWDB) became a Cooperating Technical Partner (CTP) with FEMA in October 2000. In the 80th State Legislature the TWDB was named the state agency tasked with coordinating the National Flood Insurance Program (NFIP) within the state in 2007. The NFIP and Floodplain mapping is administered by the Texas Water Development Board and in conjunction with the Texas Natural Resources Information System-the state's clearinghouse for digital maps and geographic data.

FEMA Map Modernization

FEMA's Map modernization (Map Mod) Program officially ended with FY08 mapping assignments and did not map the entire state. The purpose of the Floodplain Mapping group within TNRIS is to work with its partners and support a program to increase local awareness and ownership of flood hazard maps. This effort will result in homeowners, business owners, State and local government officials, and other citizens of Texas receiving more accurate flood hazard and risk information. This process will start with prioritizing floodplain mapping needs statewide.

Data Sets

Data sets are being developed regularly including the Texas High Water Marks. The Texas High Water Marks show the water surface elevations (WSEL) of flooding events around the state. Texas Highwater marks are available in different platforms that include Geo-spatial PDFs, gis files, webservices, and Google Fusion Tables.

Another data set is Texas Low Water Crossings. Knowing where your low water crossings helps define flood risk in your area.

A component of floodplain accuracy is the limitations of the elevation data used to define the floodplain. Various elevation data sets were used to create the floodplains in Texas however it is up to the user of the floodplains to understand how the floodplains were defined. Knowing how the elevation data set compares to other datasets such as survey data helps to put the limitations of the elevation data into perspective. Comparing elevation datasets is another tool the Floodplain mapping services group offers and can be found here.

The group offers technical assistance on understanding your floodplain maps and helps to make floodplains more accessible by offering geospatial pdfs (right-click and 'save link as' to download) of your communities floodplains.

Map Service Center

TNRIS archives, maintains, and distributes the largest collection of current and historical spatial geographic data sets for the State of Texas. The collection of maps, photos, documents and other spatial datasets have been contributed from multiple sources.
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