What is a Floodplain?

A floodplain is a geographic area subject to flooding and/or land adjacent to a waterway necessary to contain a flood. Floodplains can be associated with rivers, lakes, streams, channels, or even small creeks that are normally dry most of the year. There are two types of floodplains we generally deal with:

  • . 25 year floodplain: an area subject to flooding as a result of the occurrence of a 25 year storm event - a storm that has a 4% chance of occurring in any given year.
  • 100 year floodplain: an area subject to flooding as a result of the occurrence of a 100 year storm event - a storm that has a 1% chance of occurring in any given year.

See also the Federal Emergency Management Agency (FEMA) web site for more information on floodplains and floodplain management.

Floodplain Regulations in Williamson County

Floodplain regulations are enforced to protect public safety and health. In addition, they encourage sound engineering practices and efficient floodplain management techniques. All construction in Williamson County must adhere to federal floodplain regulations. Regulations are established by the Federal Government and implemented by the Federal Emergency Management Agency (FEMA). The County Engineer's Office is responsible for examining construction for compliance with local and federal floodplain regulations.

Evaluating and Permitting Floodplains

County Engineer's Office is the designated floodplain administrator for Williamson County. Official floodplain maps for the County are available for viewing in our office at 3151 S.E. Inner Loop, Suite B, Georgetown, TX, 78626. Floodplain permitting within various cities in Williamson County is handled by those cities directly.

Currently, residents may come to the County Engineer's Office for consultation to determine whether any specific location is within the floodplain. Alternatively, FEMA maintains a website (http://store.msc.fema.gov) where you can view the same maps. Per county ordinance, a Certificate of Compliance is required for all structures or other developments outside of a FEMA-mapped floodplain in unincorporated areas of the county. The Certificate of Compliance verifies that no FEMA-mapped 100 year floodplain exists in the area of proposed development.

Floodplain Development Permit

If your property is in the floodplain, you will need to elevate the structure higher than the base flood elevation. A floodplain permit will be required. To receive a permit, residents must obtain a permit application packet. Included in the packet are instructions and the forms necessary for the floodplain development permit:

To complete this process, you must hire a surveyor to certify the elevation of the structure and complete the elevation certificate. Completion of the process qualifies the home for the National Flood Insurance Program (NFIP). Development within the flood way is prohibited except with extensive engineering and flood proofing. The Williamson County Flood Damage Prevention Ordinancecontains the full text of regulations.

If you have questions, please contact the County Engineer's Office at (512) 943-3330.

Important Note: As of November 1, 2005, County Engineer's Office stopped issuing the 3-part form entitled the “Williamson County Floodplain Management Program Elevation Certificate” and began asking applicants to have their surveyors or engineers use the “Federal Emergency Management Agency (FEMA) National Flood Insurance Program Elevation Certificate” (FEMA Form No. 81-31) relating to new permit applications.

FEMA Map Service Center and Flood Map Store
Digital versions and images of flood maps are now available for viewing and printing from the on-line FEMA Flood Map Store at: http://msc.fema.gov/. This on-line store provides paper, scanned images on CD-ROM, and downloads of maps. The Flood Map Store allows users to create a FIRMette at no cost. A FIRMette is a section of the flood hazard map at 100% scale that can be printed on standard paper sizes (8.5 x 11, 8.5 x 14, and 11 x 17).