Austin Speeds Up Timeline For Adopting Changes To Drainage Rules

Jul 1, 2019

The City of Austin is expected to consider changes to the land development code and drainage rules by the end of the year, speeding up its timeline to mitigate increased flood risk in the area.  

“The sooner these regulations get put into effect, the more we’re protecting the public from flood hazards that we have known to occur,” Kevin Shunk, the city's floodplain administrator, said.

Last year, a federal study of historic rainfall data, known as Atlas 14, found a 30 percent increase in the amount of rain that can fall in a 24-hour period in the Austin area. 

The city's Watershed Protection Department has recommended adopting interim changes to the land development code to prevent further development in areas designated at greater flood risk. It proposes redefining 100-year floodplains as 25-year floodplains, and 500-year floodplains as 100-year floodplains.

The department proposed incentivizing residential development to make structures more flood-resistant, extending a Colorado River building exception to Lake Austin and parts of Lake Travis, and requiring the lowest floor of buildings in the 100-year floodplain to be at least 2 feet off the ground. 

The city will also be revising rainfall values used to build different types of drainage infrastructure, like storm pipes. 

“We have a new understanding of flood risk and there’s a lot more buildings, a lot more roadways and a lot more drainage systems that don’t have the capacity to drain the amount of water that we’re expecting now,” Shunk said.

City staff sped up the process of revising drainage rules; they'll now be adopted within three months after the interim redefinition of the floodplains.

The Watershed Protection Department is re-studying and re-mapping floodplains with the updated data from Atlas 14. Studies are expected to take at least two years and will be used to make new flood insurance maps.

The department said over the past year it has mailed about 24,000 postcards to residents in the redefined floodplain areas and held more than 80 public meetings.

The Austin City Council is expected to consider proposed changes to the land use code in October and adopt new drainage rules in December.