The study, called Atlas 14, was conducted by the National Oceanic and Atmospheric Administration and is the first of its kind since 1961. Using updated rainfall intensity data, the NOAA has redefined critical storm events.
Previously, a 100-year storm in Travis County would consist of 10 inches of rain in 24 hours. Using the updated data, a 100-year-storm now consists of 13 inches in the same period.
Despite the release of this study, it will take years for the Federal Emergency Management Agency to update its flood insurance rate maps, according to a summary prepared by Stacey Scheffel, flood plain administrator for Travis County.
In the interim, county commissioners have chosen to adopt the higher standards that reflect the new Atlas 14 data.
Because the county has relied on FEMA flood insurance rate maps in the past, the process to update local rates is “still unclear,” per Scheffel’s summary.
Adopting Atlas 14 standards will increase costs for developers, landowners and the county.
In November, commissioners voted to spend an additional $22 million to ensure 2017 bond and critical safety projects are compliant with the updated flood plain standards.
“It is more cost effective and prudent to build the infrastructure based on the Atlas 14 data than to retrofit it later, or in response to an event,” Scheffel wrote.