U.S. Army Corps of Engineers

In a separate partnership, LCRA joined with Travis County, the City of Austin and the U.S. Army Corps of Engineers (the Corps) to initiate a federal Flood Control Study of the Lower Colorado River. As the initial part of this study, the partnership will develop new hydrologic and hydraulic computer models of the main stem of the river and of a major tributary, Onion Creek. Using these models, together with extensive environmental and economic analyses of the basin, the partnership will then be able to accurately identify flood prone areas in the basin and efficiently evaluate cost-effective flood plain management alternatives.

The total cost of the study effort is estimated at $7.8 million and was scheduled to be completed in five years. The models developed during the initial efforts by the Corps were used by the Corps and other local engineers involved in the study to identify the areas at the highest risk for suffering economic losses, and determine should a flood occur in the future. In this manner, the study partners hoped to be able to develop flood control projects which provide the greatest benefit to the most amount of people. The new models were also used by the LCRA and FEMA during the preparation of the new Flood Insurance Rate Maps.

In addition, the Corps of Engineers administers the Section 404 “dredge and fill” permitting program under the Clean Water Act. The Act regulated activities within the floodplain, including those that impact wetlands, that may increase flood potential. According to a United States Geological Survey (USGS) wetland inventory of Texas, about half of the wetlands in Texas have been lost to development. This has about the same effect as removing thousands of flood-control dams. These wetlands not only capture and retain runoff and floodwaters, they also filter contaminants and recharge aquifers. Federal regulations require all applicants to avoid unnecessary impacts to wetlands and to minimize and mitigate unavoidable impacts. Coordination between the Corps permitting activities and floodplain management goals could result in the protection of wetlands critical to flood reduction.

 

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