The city has updated its floodplain regulations to protect the public from flooding. This was in response to the National Weather Service study of historical rainfall called Atlas 14. This study shows that Central Texas is more likely to experience larger storms than previously thought.


Austin regulates new development, redevelopment and remodeling in the floodplain. These regulations are meant to protect Austinites from flooding and reduce public expense in the aftermath of a flood.

Austin also requires developers to include drainage pipes, detention ponds and/or other drainage infrastructure in their projects. The drainage criteria tell developers the proper size their drainage infrastructure needs to be. We are in the process of changing the drainage criteria at this time.

Floodplain Regulation Changes

Download a summary of the changes or the ordinance.

The revised floodplain regulations have five main components. There are other changes to the floodplain regulations in addition to these main components that are discussed in the summary document, above.

  • They redefine the 100-year floodplain as the current 500-year floodplain to regulate development. This change means that the floodplain regulations will apply to more properties. Property owners and businesses in the interim 100-year floodplain have new restrictions if they want to develop, expand, remodel or improve their properties. We estimate that there are approximately 7,200 buildings in the interim 100-year floodplain.
  • They include a new exception that will allow for the administrative approval for redevelopment of a residential building in the floodplain that reduces flood risk. In the past, this often required approval by the Austin City Council.
  • They include an expansion to an existing exception that allows for a building to encroach on the 100-year floodplain of the Colorado River downstream of Longhorn Dam and along Lady Bird Lake to also include Lake Austin and parts of Lake Travis.
  • They increase the freeboard requirement for buildings from 1 foot to 2 feet. Freeboard is the height above the floodplain that a building must be constructed.
  • They allow staff to administratively waive the safe access requirement for residents who want to build an addition to their homes as long as the improvements are not considered a substantial improvement, satisfy the freeboard requirement and do not adversely impact flood levels.