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One month after the destructive flooding of Texas Hill Country rivers led to multiple deaths and tens of millions of dollars in property damage, scientists, regional water management leaders, and academics are still weighing the consequences and the prospect of future severe weather events in Texas.
The frequency and severity of weather events ranging from the recent flooding along the Llano, Colorado, Trinity, and Blanco rivers, as well as devastating flooding from Hurricane Harvey, have left communities ill-prepared, with experts and elected officials pondering the future impact in a state where climate change is not universally accepted by top state officials and lawmakers, and where a continuing population boom and urban development pose major challenges.
More than 100 scientists, students, and concerned citizens gathered at the LBJ Theatre at Texas State University for a Nov. 15 panel discussion, part of the 35th annual Texas Water Symposium, a quarterly event co-organized by the Hill Country Alliance and its sponsors. Moderated by Rivard Report Publisher and Editor Robert Rivard, the evening’s program was titled “The Future of Flooding in Texas: How do we protect life and property in the face of extreme weather events?”
The event was the sixth in the series, staged in collaboration with the university’s Department of Geography and the Meadows Center for Water and the Environment.
Mindy Conyers, state flood assessment coordinator at the Texas Water Development Board, a position created by the Texas Legislature in 2017, said recent destructive weather events led the Texas Water Development Board to create the State Flood Assessment, a document now being drafted that is designed to guide statewide flood planning efforts and increase the ability of cities and smaller communities to better measure and mitigate flood risks.
Raymond Slade Jr., a certified professional hydrologist who retired after a long career in Texas with the U.S. Geological Survey, quoted Gilbert F. White, a prominent 20th-century geographer and father of flood plain management: “Floods are merely a hazard, mankind is the disaster.”
White argued, often fruitlessly, that the best way to prevent flood hazards is to prohibit development on flood plains. Slade told audience members that government could “spend a nickel now” purchasing and protecting flood prone areas or “spend a dollar later” on response and recovery.
The 100-year flood construct – a flood with a 1 percent chance of occurring in any given year – is no longer sufficient for land-use planning, he said, noting that over the past decade, flood peaks have increased by 40 percent on the Guadalupe River, 125 percent on the Blanco River, and 162 percent on the San Marcos River.
Michael Moya, vice president and water resource leader at Halff & Associates, cited National Oceanic and Atmospheric Administration (NOAA) data that states historically calculated 100-year flood models are now occurring closer to once every 25 years, meaning such flooding is four times more likely to occur than previously predicted.
Texas has experienced nine flood disasters costing more than $1 billion, Moya said. Since 2010, 18 storms have exceeded the so-called 100-year storm classification. Eight of these floods were declared federal disasters.
Moya said most homeowners insure their homes against fire but do not purchase flood insurance, which he recommended even for homes not located in traditional flood plains. The likelihood of flood damage is far higher than fire damage, he noted.
Improved flood frequency statistics are based on longer weather records and updated methods for calculating flood risk from precipitation data. Hydrologists and meteorologists originally developed many of the long-used values with only 30-50 years of weather records, using the 1961 federal standard referred to as Technical Paper 40, published by the former Weather Bureau. The updated process published this year by NOAA – and referred to in brief as NOAA Atlas 14 – specifically for Texas uses nearly 100 years of data and multiple, sophisticated calculations.
These newly released rainfall frequency and recurrence intervals will be used by scientists, engineers, and developers to inform the Federal Emergency Management Agency’s (FEMA) Flood Insurance Rate Maps used in flood hazard mapping and land use planning. However, some panelists voiced concern that FEMA flood maps themselves still will not show full flood risk. Many flood scenarios could occur even if not predicted by contemporary mapping and modeling.
All of the panelists agreed there is a need for greater community awareness and education, but they also noted the reluctance of political leaders to approve expanded flood plain maps that generate homeowner complaints that their property is being reduced in market value because of increased flood risk.
In response to Hurricane Harvey, Houston’s newly accepted development standards require rebuilding above the 500-year flood plain.
“With storm intensity increasing we can only expect a 1,000-year flood is already in the making, so where should the development line be drawn?” Rivard asked.
Stephen Graham, assistant general manager of the San Antonio River Authority, said the increased intensity of storms requires new measures for mitigation and more sophisticated modeling to anticipate risk and outcomes. Graham said the River Authority’s strategies have changed. Engineers no longer believe they can build their way out of flood risk and mitigation.
New approaches include preserving green spaces for mitigation, wetland and riparian restoration; collecting rainwater; launching community education programs; planting pollinator gardens; and designing flood control to also include economic development and recreation considerations. The 13-mile long San Antonio River linear park in the city, formerly concrete ditches in many places, is a good example of how new approaches produce a communitywide benefit.
The panel supported several key takeaways. Flood mitigation requires a variety of solutions from “green to gray” infrastructure, including protecting land in the headwaters to absorb rainfall events, preventing development in floodplains, capturing rainwater in highly impervious settings, and building infrastructure to store and convey floodwaters through urban and rural areas.
A primary goal for floodwater management, voiced more than once, is to “slow it down, spread it out, and let it soak in.”
Slade humorously described what he called the “Hydro-illogical Cycle,” with alternating droughts and floods provoking predictable human behavior patterns that move from awareness and alarm to concern and, ultimately, apathy. That pattern needs to change, he said, or the consequences will be even more loss of life and property damage.
More information on the Texas Water Symposium is available here. The panel discussion will be broadcast on Texas Public Radio at 9:30 p.m. Sunday.