Onion Creek is Austin’s largest watershed and is particularly vulnerable to flooding. We have several projects to reduce the risk of flooding along Onion Creek.
Lower Onion Creek, Corps Project, near William Cannon and Pleasant Valley
Lower Onion Creek, 25 and 100-year project areas, near William Cannon and Pleasant Valley
Upper Onion Creek, in the Onion Creek Neighborhood, near Pinehurst and Wild Dunes Drives
Map of Project Locations
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.
As of January 2018, we have purchased 808 properties in the lower Onion Creek project areas and seven in the Upper Onion Creek project area.
Executive Summary for the Onion Creek Floodplain Modeling and Mapping Report below, Halff Associates, Inc., 2017
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.