ASABE Technical Library - Abstract

Abstract. From 1954 to 2001, the Natural Resources Conservation Service (NRCS), formerly Soil Conservation Service (SCS), built 150 flood control dams in Virginia. These structures were installed under the Pilot Watershed Program of 1953; Public Law 78-534 (PL-534), the Flood Control Act of 1944; and Public Law 83-566 (PL-566), the Watershed Protection and Flood Prevention Act of 1954. The cost of installing these structures was over $151 million. Over time, the benefits have far exceeded the initial investment. In many cases, the economic benefits of having the dams in place are greater now than when the dams were installed. However, these dams are aging. In 2000, Congress passed the Small Watershed Rehabilitation Amendments to the Watershed Protection and Flood Prevention Act. Since 2005, Virginia NRCS has rehabilitated nine dams and has seven additional dams in various stages of planning, design, and construction. NRCS has also received requests for Federal assistance on ten more dams. Dams considered for this program no longer meet State Dam Safety requirements due to changes in evaluation criteria or hazard class. During the planning process, NRCS considered options for addressing the initial problem and for addressing all other issues identified in the site assessment. After rehabilitation, all of the components of the dam must be in compliance with current NRCS criteria. This often involves modifications to the principal spillway, auxiliary spillway, and embankment. For the nine completed rehabilitation projects, innovative solutions have been used to upgrade the vegetated earth auxiliary spillways to meet the required criteria for integrity, stability, and capacity. The original spillway designs and most of the rehabilitation solutions were based upon the research conducted by the USDA Agricultural Research Service (ARS) Hydraulic Engineering Laboratory in Stillwater, Oklahoma. An evaluation of the performance of these structures demonstrates the effectiveness of the partnership between ARS and NRCS to collaborate on design, construction methods, and effective implementation of economical solutions. As the dams that are part of our national infrastructure continue to age, NRCS and other entities responsible for the safety of these dams will be looking to the ARS Hydraulics Laboratory to continue to develop and improve the tools that we use.