New floodplain maps for Travis, Williamson and parts of Burnet counties are set to take effect Sept. 26, and floodplain administrators advise property owners in affected areas to buy flood insurance before the effective date.

Property owners who purchase flood insurance prior to the effective date of the maps may lock in more favorable flood insurance rates and keep their premiums as low as possible. It takes 30 days for flood insurance to take effect once it has been purchased.

The maps are the result of a five-year effort by local cities, counties and the Federal Emergency Management Agency (FEMA) to use the most up-to-date hydrological studies, topography and technical information to reassess flood risks.

Many current maps are more than 30 years old and are based on outdated or insufficient data and models.

The maps are used to determine whether flood insurance is required by mortgage companies and loan institutions. Local communities are required to adopt and enforce the new maps in their building ordinances for residents to be eligible for the lower-cost, federally available flood insurance.

The new maps also provide property owners the degree of flood risk to existing and proposed buildings and guide local community planners on where it is safe to build.

Hundreds of properties will be affected by the new floodplain maps, including more than 550 homes and businesses around Lake Travis. Based on the new maps, properties may move in or out of the floodplain.

The most dramatic impact will be a 6-foot increase of the 100-year floodplain of Lake Travis from 716 feet above mean sea level (msl) to approximately 722 feet msl. (A “100-year flood” refers to a magnitude of flood that has a 1 percent chance of occurring in any year.)

To view copies of the Preliminary Flood Insurance Rate Maps for Travis County, check the City of Austin’s Web site at www.ci.austin.tx.us/watershed/flood_fema_pmappdf.htm#current. Click on the Index map to locate the appropriate map panel for your property.

City of Austin residents may view maps at www.cityofaustin.org/watershed/floodplain_newmap.htm.

Information about FEMA’s National Flood Insurance Program and the impacts of new maps to home and business owners can be viewed at www.fema.gov.

More flood insurance information can be found on the National Flood Insurance Program’s FloodSmart Web site at www.floodsmart.gov/floodsmart.