A large flood on the lower Colorado River could cause $338 million in economic damages from Lake Buchanan through Matagorda County, according to a study by the U.S. Army Corps of Engineers. The study shows that potential flood damages, particularly around Lake Travis, are greater than previously thought. This fact sheet reports on findings from the first phase of the Lower Colorado River Basin Study.

What is the source and purpose of gathering this information?
The U.S. Congress approved the Corps of Engineers study based on requests by the City of Austin and LCRA, representing cities and counties in the river basin that want to find solutions to flood damage problems. The study partners -- LCRA, Austin, Sunset Valley, Travis County and Wharton -- want to improve knowledge of flooding in the basin and identify ways to reduce property damage and loss of life. A major finding of the study, first reported in April 2002, showed that Lake Travis would rise nearly 6 feet higher during a 100-year flood than the official figure adopted in the 1970s. Based on that dramatic difference, the study was expanded to specifically address the 100-year flood elevation on Lake Travis.

What kind of property damage would a large flood cause?

According to the report, a 100-year flood, if it occurred throughout the basin, could damage 12,400 homes and businesses, creating an economic loss of more than $388 million including vehicles and crop damages.

A 500-year flood, an even more catastrophic event, would damage more than 29,000 homes and businesses in addition to vehicles and crops at a cost of $1.9 billion. Hydrologists use terms such as 100-year and 500-year to describe different sizes of catastrophic flooding.

What makes this information new?
For most of the Colorado River downstream of Austin, this is the first comprehensive survey of property at risk of flooding. Also, on Lake Travis, the flood study indicates that a 100-year flood would reach a level nearly 6 feet higher than previously thought -- 722 feet above mean sea level (ft. msl.) instead of 716 ft. msl. Thus, a 100-year flood would affect about 550 more structures than previously thought.

How will the study partners respond to the new information about damage risks?
The study partners will evaluate a number of alternatives for reducing the risk or magnitude of flood damages. The possible responses identified so far include:

• Take no action.
• Raise official floodplain levels, which are established by the Federal Emergency Management Agency (FEMA). FEMA works in cooperation with individual communities to study floodplains and remap them according to the most recent data. A FEMA remapping study is under way in Travis County.
• Buy and remove structures from the floodplains to reduce the potential for damages.

The Corps of Engineers will examine the consequences of each alternative, including the economic and environmental costs and benefits, and split the study costs with local partners. The partners will help choose the most effective and practical courses of action and seek funding to implement them. In addition to basinwide flooding issues, individual communities have specific issues. The Corps of Engineers and LCRA are working with Wharton, Bastrop and Travis counties and the City of Austin on studies to address their particular flood issues.

How long will it take to choose and carry out a course of action?
It will take at least two to three years to assess the costs and benefits of the alternatives. After deciding on a course of action, the partners will need additional time to obtain congressional approval and federal funding for any projects that the solution may involve, and to make any changes involving the Corps of Engineers, FEMA or other federal agencies. Although the risk to life and property and rapid urbanization make quick action vital, determining the best course of action will take time and careful consideration. Each alternative could present substantial and conflicting consequences for basin residents that would need to be addressed.

Does this study affect my flood insurance or building requirements?
The study itself does not change the officially designated 100-year floodplain on FEMA Flood Insurance Rate Maps or local floodplain building ordinances. However, flood officials strongly recommend that property owners take the study results into account when making decisions about structural elevation and flood insurance coverage. Contact your local floodplain administrator to determine whether a particular property is in the 100-year floodplain and to discuss flood protection options. Contact information for local floodplain administrators can be found at www.tnrcc.state.tx.us/permitting/waterperm/wrpa/fpa.pdf. If FEMA raises the designated 100-year floodplain, there may be flood insurance rate benefits to property owners in the newly-designated floodplain if flood insurance is obtained and maintained prior to the change. For more information about FEMA flood insurance regulations, contact Carl Watts at the FEMA Region VI office, (940) 898-5128, or Diana Herrera with the FEMA National Flood Insurance Program, (281) 829-6880.

Where can I get more information about the Corps of Engineers study?
Contact Elston Eckhardt of the Corps of Engineers at (817) 886-1681 or by e-mail at Elston.D.Eckhardt@swf02.usace.army.mil.

Where can I get more information about the FEMA floodplain mapping study of Travis County?
Contact Mike Moya or T. Lynn Lovell, project consultants at Halff Associates, at (817) 847-1422 or by e-mail at mmoya@halff.com or llovell@halff.com.

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