December 13, 2018

City of Austin Employs Three Step Approach to Atlas 14

The HBA Advocacy Forum focused on Atlas 14, the national effort to update floodplains based on rainfall accumulations from 1961-2017. There are 4000 structures (homes, buildings, etc) in the floodplan, as currently defined. It is expected this will jump to 7,200 using the Atlas 14 guidelines. Still, this only describes 3% of the total structures in Travis County, so the total impact is relatively low.  

The City of Austin is employing a three-step process to approach Atlas 14.

  1. Land Development Code Changes
    1. Revise Floodplain definitions (definition of 100yr=500yr; 25yr=100yr)
    2. Create redevelopment exception
    3. Expand the Colorado River Exception to include Lake Austin and parts of Lake Travis.
    4. Increase the freeboard requirement from 1ft to 2ft.
  2. Drainage Criteria Manual Revisions: rainfall rates determine floodplains, size of storm drain pipes, inlets, and ditches, retention pond size.
  3. Floodplain Study and Mapping Updates: They will use Consultants. It will be a 2-3 year process, then FEMA, who does not have their own budget to study the floodplains, will use their recommendations to approve and update the flood insurance maps (approximately 1 year). 

Staff will continue to review plans based on current codes. This will remain the practice until the City Council adopts the Preliminary Code. There is an administrative exception process for visitability already in place.   

Our speakers suggested those interested in learning more check out the following links: