Engineers: Development regulations needed to fight floods

Greg Bowen | The Herald Zeitung | October 12, 2010

SEGUIN — Tough regulations to cut stormwater runoff from new housing subdivisions and commercial developments are being recommended by an engineering firm that looked at ways to reduce flooding along flood-prone Alligator Creek east of New Braunfels.

Lance Klein, with M&S Engineering of Spring Branch, told a crowd estimated at 50 that construction projects — such as stormwater detention ponds, widening of the creek’s channel or upsizing culverts under bridges — are not cost-effective enough to garner the federal dollars needed to make them affordable for local governments. Klein made his comments Tuesday evening during a meeting of Geronimo and Alligator Creeks Watershed Partnership, a group of citizens, cities, counties, and state and federal agencies working to develop a plan for the protection of the watershed, which stretches from New Braunfels to Seguin. Klein said a stormwater detention pond big enough to reduce flooding on Alligator Creek by a single foot — some areas along the creek were under five feet of water during the June 9 flood, observers said — would cost an estimated $17-19 million, but would protect only 170 homes along Alligator Creek.

The benefit wasn’t there based on the reduction of damage

– Lance Klein

Federal agencies typically will not help fund a project unless the dollar amount in benefits is higher than the dollar amount spent on a project, he said. The only other options for flood control, Klein said, are “non-structural,” including the adoption and enforcement of more stringent standards for development. Some options, he said, would be to limit the encroachment of structures into flood-prone areas and to require buildings to be elevated above the level of flooding.

Klein and M&S also are recommending installation of flood early warning systems, automatic gates across problem stream crossings that close when floodwaters rise, and buyouts of structures that flood frequently. He said the $330,000 flood study plan, which began two years ago, will be reviewed by the partnership’s oversight committee, which could recommend additional studies before the report goes to the Texas Water Development Board by the end of the year.

The partnership is also dealing with water quality issues in the creeks. A watershed protection plan now under development will recommend ways to reduce the elevated levels of bacteria in the creeks as well as cutting problems with “nutrient enrichment” caused by too-high levels of nitrogen, likely due to inflows of chemical fertilizers, which can result in algal blooms and excessive growth of aquatic vegetation. Alligator Creek begins in southeastern Comal County, just above Interstate 35. It runs southeast, traveling through a rapidly developing area of the Austin-San Antonio corridor. Typically dry, springflows enter Alligator Creek before it flows into Geronimo Creek near Seguin. Geronimo Creek in turn flows to the Guadalupe River. The two creeks form an almost 70-square-mile watershed in Comal and Guadalupe counties within the larger Guadalupe River Basin. The upper portion of the Alligator Creek watershed lies in the extra-territorial jurisdiction, or ETJ, of the city of New Braunfels. The lower portion of the Geronimo Creek watershed is in the Seguin’s ETJ.

According to the partnership, as development and population growth continue, the percentage of urban land use will rise and play an increasingly important role in the hydrology and water quality of the creeks. Partners in the effort include New Braunfels, Comal County, New Braunfels Utilities, Seguin, Guadalupe County, Guadalupe-Blanco River Authority, Comal-Guadalupe Soil and Water Conservation District, Plum Creek Watershed Partnership, Texas State Soil and Water Conservation Board, Texas Agrilife Extension Service, Texas Commission on Environmental Quality, Texas Water Resources Institute, National Resources Conservation Service, and U.S. Environmental Protection Agency.

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