Onion Creek Flood Risk Reduction

Project Locations

• Lower Onion Creek, near William Cannon and Pleasant Valley
• Upper Onion Creek, in the Onion Creek Neighborhood, near Pinehurst and Wild Dunes Drives

Map of Project Locations

Overview

Onion Creek is vulnerable to flooding due to the size and characteristics of the watershed. At 344 square miles, it is Austin’s largest watershed. The creek catches water from a large area, resulting in high flows and a wide floodplain.

The neighborhoods along Onion Creek were built in the 1970s, before we understood the breadth and depth of the creek’s floodplain. After the houses were built, new floodplain maps showed the potential for severe flooding.

For lower and upper Onion Creek, buyouts are the most effective way to protect the public and first responders from flood risks. There have been three studies evaluating flooding along Onion Creek. These studies have all found many drawbacks to other types of solutions, resulting in the recommendation for buyouts.

Studies

• Executive Summary for the Onion Creek Floodplain Modeling and Mapping Report below, Halff Associates, Inc., 2017
• Onion Creek Floodplain Modeling and Mapping, Phase 2 – Risk Identification and Mitigation, Halff Associates, Inc., 2017
• Lower Colorado River Basin County Interim Feasibility Study Technical Report - Appendix H, U.S. Army Corps of Engineers, 2013
• Lower Colorado River Basin Phase I, Texas, Interim Feasibility Report, U.S. Army Corps of Engineers, 2006
• Lower Colorado River Basin Phase I, Texas, Interim Feasibility Report - Appendices, U.S. Army Corps of Engineers, 2006
• Onion Creek Flood Control Study, Loomis & Moore, 1997

Flood Safety

Another flood will occur in this area. To prepare, we encourage residents of this area to take the following steps:

1. Consider purchasing flood insurance for both the structure and the contents. Renters can purchase policies too. Contact your insurance agent.
2. Stay informed by signing up for Warn Central Texas.
3. Have an emergency plan. Please keep in mind that you may be safer staying at your home, on your roof, if necessary, than trying to escape a flood in your vehicle. Most fatalities during floods happen in vehicles.
4. Make an emergency kit.
5. Get to know your neighbors. They are often the ones who can respond first in an emergency.