Atlas 14 Volume 11 (Texas) data to be published in October 2018

The National Oceanic and Atmospheric Administration (NOAA) has undergone an effort to update precipitation frequency estimates across the United States using historical data. This historical data is current through 2017 and includes major storm events, such as Hurricane Harvey.
As these estimates are developed, they are published in NOAA Atlas 14. Volume 11 of Atlas 14 covers the entire state of Texas and NOAA expects to make those estimates public in October 2018.

Once published, each local entity and floodplain administrator will have an opportunity to review, adopt and update local drainage requirements and floodplain maps.

What are Austin and San Antonio doing to prepare?

Both the City of Austin and the City of San Antonio, along with many other local counties and cities, have indicated that they will adopt Atlas 14 Volume 11 as the new standard in determining rainfall intensities. Public meetings have been held and information bulletins have been published by both entities in preparation for the changes.

Proposed Timing of Changes

The remainder of 2018 will be used by both the City of San Antonio and the City of Austin to review the published data and revise development regulations in response. Both entities expect to adopt and implement the new rainfall intensities and associated changes in regulations in early 2019. Once adopted, the local floodplain administrators can begin re-analyzing and re-mapping the 100-year FEMA floodplain, a process that will likely take 2 – 4 years to complete.

How do you prepare?

Since the final rainfall intensities have not been published, it is not possible to determine the specific effect that the adoption of Atlas 14 will have on any specific property or project. However, it is certain that the size of new drainage facilities will increase and that the FEMA 100-year floodplain area will increase. It is estimated that the new FEMA 100-year floodplain limits will resemble the current 500-year floodplain limits in many areas. Consu