Storms like the one that dropped up to 13 inches of rain in Bexar County over the Memorial Day weekend are a sobering reminder that we live in Flash Flood Alley. The unique combination of geology, geography and climate in south central Texas can cause storms and catastrophic flooding as seen in 1998, 2002 and on May 25. The San Antonio River Authority (SARA), along with the Federal Emergency Management Agency (FEMA), is working on a program that will help government agencies and residents in Bexar County better understand and prepare for flood risks.
SARA will host a public meeting to kick off its Risk Mapping, Assessment, and Planning (Risk MAP) effort for the Upper San Antonio River Watershed on Thursday, June 6 at 6 p.m. at SARA’s main office, 100 East Guenther Street. The public is invited to learn about Risk MAP and provide input on existing and potential flood risks in the Upper San Antonio River Watershed.
“The May 25 storm is the latest reminder of the impact of flash flooding in the San Antonio River Watershed,” said SARA General Manager Suzanne Scott. “The innovative Risk MAP program through FEMA will provide another important tool to communicate flood risk and help protect lives and property.”
Risk MAP is a FEMA program that provides communities with updated flood hazard information and risk assessment tools they can use to enhance their mitigation plans to better protect their citizens. Through more accurate flood maps, risk assessment tools and outreach support, Risk MAP builds on Map Modernization—the effort that produced Digital Flood Insurance Rate Maps (DFIRM) for Bexar County—and strengthens local ability to make informed decisions about reducing risk. Risk MAP uses a watershed-based study approach that allows for the understanding of risks in a more comprehensive way.
FEMA has allocated $712,500 to SARA, FEMA’s local Cooperating Technical Partner, to develop non-regulatory Risk MAP products for the Upper San Antonio River Watershed, which includes the San Antonio River, Olmos Creek, the Westside Creeks and Salado Creek. SARA will focus on flood damage centers previously identified through SARA’s watershed master planning process and develop products that will help residents, business owners and local governments better understand their level of flood risk.“As Cooperating Technical Partner with FEMA, SARA will manage the project to create useful mapping products with the most up-to-date terrain and flood modeling data available,” said SARA Watershed Engineering Manager Russell Persyn. “These maps will show not just the extents of potential flooding, but many of the risks associated with flood events.”
Some of these non-regulatory products include maps showing depth of flooding within the floodplain; velocity of flood water flows; annual chance of flooding ranging from 10 percent to 0.2 percent; and probability of flooding over a 30-year period. While these products aren’t intended for regulatory use, they can be used by local governments and citizens for public education about risk and to drive mitigation actions such as development of capital projects or emergency action plans.
The Risk MAP process for the Upper San Antonio River Watershed will be completed within one year. SARA will host several opportunities for the public to provide input on the Risk MAP effort, including an interactive website to be launched at the kick-off public meeting. SARA is also working with FEMA to begin Risk MAP studies in the Medina River and Cibolo Creek watersheds.
Residents of Bexar County can view the DFIRMs containing the current one percent annual chance (100-year) floodplains online at www.BexarFloodFacts.org.