DAVID D. DUNN, U.S. Geological Survey, 8011 Cameron Road, Austin, Texas 78754, USA

Sediment from the main channel of the lower Brazos River in Texas has been utilized extensively as a source of sand for construction of infrastructure in southeast Texas. Concern has arisen recently over the influence of this sediment removal on the transport of sediment to the Gulf of Mexico from the Brazos River, and ultimately, its influence on beach erosion in the Sargents Beach area of the Texas coast. The U.S. Geological Survey (USGS), in cooperation with the Texas Parks and Wildlife Department (TPWD) and the University of Texas Bureau of Economic Geology (BEG), is conducting an analysis of historical streamflow and sediment-transport data to estimate the effects of main-channel sand and gravel removal on sand delivery to the Gulf of Mexico. The effects of numerous upstream reservoirs and changes in land-use practices in the Brazos River basin will be accounted for in the analysis. The localized effects of a typical dredging operation will also be analyzed by measuring the flow field and sediment-transport characteristics upstream, through, and downstream of the dredging operation. The hydraulic effects of this operation will be shown with a series of velocity vector maps and comparisons of upstream, mid-reach, and downstream sediment measurements.