San Antonio River Authority Tackles Flooding As Helsinki Hails Storms

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It’s not a groundbreaking pronouncement, but the message at the seventh European Conference on Severe Storms being held in Helsinki, Finland, this week is to hold on for more storms.

global warming bookFor some time, Texans have heard (and recently have begun to feel) that climate change heralds a drier, hotter world. While citing “considerable uncertainty” in the complex earth processes that govern evaporation and rainfall, George Ward writes in the second edition of The Impact of Global Warming on Texas that “Global warming is expected to increase the intensity of the hydrologic cycle.” With air temperatures expected to rise by 3.6 degrees Fahrenheit by 2050, rainfall in the state is expected to decrease by about 5 percent.

While stronger hurricanes are expected, predicting inland thunderstorm weather is trickier business. While some have suggested that future precipitation in Texas will be delivered suddenly in increasingly violent storms, today Paul Brown reports for Climate News Network that the Helsinki pronouncement is that “more intense thunderstorms combined with damaging winds” are indeed on the menu.

“However because thunderstorms are small in size on the scale of existing climate models it is not possible to tell whether they will also lead to more tornadoes and larger size hail – two of the most damaging problems associated with severe storms,” Brown writes.

However the water comes, it’s of interest to San Antonians recently reminded of the power of water when more than 10 inches of rain pounded the city during the second wettest day on record. Storms May 25 were blamed for three deaths and $10 million in property damage.

Here’s a flood simulation from SARA, part of their May 2013 flood analysis:

Beginning at 6 p.m. Thursday, the San Antonio River Authority is holding a public hearing on “Risk Mapping, Assessment, and Planning” (Risk MAP) efforts along the Upper San Antonio River Watershed being conducted by SARA and and FEMA to better predict the impact of such storms on the ground.

“The May 25 storm is the latest reminder of the impact of flash flooding in the San Antonio River Watershed,” SARA General Manager Suzanne Scott said in a prepared release. “The innovative Risk MAP program through FEMA will provide another important tool to communicate flood risk and help protect lives and property.”

For those who are interested in possibly attending, here is the rest of the release about Risk MAP:

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 http://www.BexarFloodFacts.org.

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