The River Authority uses comprehensive planning, precision protection, strategic partnership, and community preparedness to help communities throughout the San Antonio River Basin reduce the devastating effects of flooding.
Draft Floodplain FAQs
Why is the San Antonio River Authority updating floodplain maps in Bexar County?
The San Antonio River Authority (River Authority) has interlocal agreements with Bexar County, City of San Antonio, and 19 suburban cities within Bexar County to maintain the floodplain maps for their jurisdictions. The River Authority is also a Cooperating Technical Partner with the Federal Emergency Management Agency (FEMA). Through this partnership, FEMA recognizes the River Authority’s floodplain mapping role, performed on behalf of the local communities.
Day-to-day, the floodplain maps are maintained through Letters of Map Revision. Letters of Map Revision are small-scale floodplain map updates and usually cover small areas like lots or individual neighborhoods. These revisions typically reflect changes to the floodplain that result from construction activity. Less frequently, widespread updates covering an entire county are needed to keep the floodplain mapping data current.
Why is there a widespread update to the floodplain maps now?
There is new rainfall, land use, and topography data that affects all of Bexar County. The last study of the floodplains in Bexar County used terrain and land use data from around 2004 and rainfall estimates based on data from the 1960’s. This was the best available data at that time. Since that time enough information and data is available to warrant an update of the floodplain maps. Updated information includes the National Oceanic and Atmospheric Administration’s (NOAA) estimates of how much rain will fall in large storms, the Texas Natural Resources Information System’s (TNRIS) ground surface elevation data, and the River Authority’s land use data. These inputs for the new floodplain mapping study were developed and collected from 2017 to 2019. The engineering studies to develop the draft floodplains have been underway since 2019.
When will the new floodplains go into effect?
We estimate the new floodplain maps will become effective in 18-24 months. The River Authority provides draft floodplains to FEMA, and FEMA continues the process of formalizing the floodplain map panels. FEMA will issue Preliminary Flood Insurance Rate Maps (FIRMS) and then provide the public a 90-day appeals and comment period. Effective FIRMS will be published after responses are reviewed and incorporated. The River Authority is starting the public engagement process early to provide the community with ample time to review and provide comments on the maps.
The engineering data is being made available immediately on the River Authority’s Digital Data and Modeling Repository (D2MR) website for use as “Best Available Data.” D2MR website is a well-known and used tool within the development engineering community.
What does this mean for residents and business owners in and around the updated floodplains?
Bexar County and all the cities in Bexar County have special regulations for activities inside the floodplain intended to reduce flood risk to life and property. Residents and business owners will need to coordinate with their jurisdiction’s floodplain administrator to obtain a permit for construction or building improvements.
If a property owner has a federally backed mortgage on a property in the floodplain, they will be required to purchase flood insurance. Based on data from the National Flood Insurance Program from August 31, 2022, the average annual cost for flood insurance premium and associated fees in Bexar County is $783.45. The average coverage including building and contents is $285,505. For more information about flood insurance, property owners can speak with their home insurance provider, keeping in mind that flood insurance is separate from home insurance.
How can I submit an appeal?
When the Preliminary Flood Insurance Rate Maps and Flood Insurance Study Report are published, there will be a 90-day appeal period. During this period, any owner or lessee of real property may file an appeal with their municipality’s floodplain administrator.
Learn More About Flood Risk
Why does it flood?
We live in a region known as Flash Flood Alley. It stretches from Del Rio in southwest Texas, east to San Antonio and follows the IH-35 corridor north through the Dallas-Fort Worth metroplex. Heavy rainfall and drainage off this landscape, also known as the Balcones Escarpment, combine to make this part of Texas one of the most flood-prone regions in North America.
Flash Flood Alley
In the San Antonio River Basin of South Texas, steep terrain, shallow soils, and narrow river channels send runoff quickly downhill. The result is deep, fast, and erosive flood waters. These destructive forces have the potential to penetrate communities downstream, threatening lives and property throughout the basin.
The San Antonio River Authority is meeting the challenge head-on with a multi-level approach to flood risk management.
Hover or touch the map below to view the counties in Texas that are part of “Flash Flood Alley.”
Flooding History in San Antonio
San Antonio River Authority Partnerships
Working together with other government organizations is a crucial component of effective flood risk management. The River Authority promotes partnerships to both regional governments and officials, and state and federal agencies. By harnessing shared information, knowledge, and other resources, communities can plan more effectively and efficiently.
Flood planning, protection, and prevention can be costly. Much of what the River Authority has been able to accomplish would not be possible without the support, resources, and cooperation of local governments, state and federal agencies, floodplain administrators, and stakeholders. Their expertise helps our team better identify flood risk not only in the San Antonio River watershed, but throughout the region. The River Authority utilizes these relationships and resources at every level to efficiently implement effective flood risk management. Look below to see the River Authority’s partners in managing flood risk throughout the San Antonio River Basin.