We are in the process of changing our floodplain regulations in light of a National Weather Service study of historical rainfall.
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. We have started the process to change these regulations.
Austin also requires developers to include drainage pipes, detention ponds and/or other drainage infrastructure in their projects. The drainage criteria tell developers what options they have and how big their drainage infrastructure needs to be. We will be changing the drainage criteria in a separate process.
It uses an interim 100-year floodplain, based on 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 would have new restrictions if they want to develop, expand, remodel or improve their properties. We estimate that there are approximately 3,600 buildings and 4,400 acress added in the interim 100-year floodplain.
It includes a new exception that will allow for the administrative approval for redevelopment of a residential building in the floodplain that reduces flood risk. Currently, this often requires approval by the Austin City Council.
It proposes to expand 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.
It proposes an increase in the freeboard requirement for buildings from 1 foot to 2 feet.
Guidance Document for Long-Term Planning
We have created a guidance document that provides long-term planning recommendations to the development community to assist them during this regulation and rules change period. The document discusses timing and applicability of the floodplain regulations and changes to the Drainage Criteria Manual. For long-term planning, it provides recommendations for floodplain delineations, peak flow rates, storm drain design and bridges and culverts. Download the guidance document.
These changes are being proposed in light of a National Weather Service study of historical rainfall. This study is called Atlas 14. It shows that large storms are more likely than previously realized. In the next few years, we plan to submit revised floodplain maps to FEMA based on this study. The future 100-year floodplain should be similar to the current 500-year floodplain. The proposed changes discussed on this page will update our regulations and criteria faster than the floodplains can be revised.
Stakeholder meetings began in July 2018 and are ongoing.
Public meetings were held in September and October 2018.
Public hearings about the proposed regulations will be conducted by the Zoning and Platting Commission, Environmental Commission, Planning Commission and the Austin City Council. These hearings will begin in January 2019.
Following all public hearings, the Austin City Council will consider adopting the proposed regulations.