Principal Investigator: Dan M. Skolds (Georgia Institute of Technology)
Principal Investigator: Terry W. Sturm (Georgia Tech)
Sponsor: GWRI
Start Date: 1985-06-01; Completion Date: 1986-06-01;
Keywords: Bed load, Dams, Degradation, Rivers, Scour, Sediment
Description:
The effects of man’s activities on an alluvial river are investigated in this research. Specifically, streambed adjustments downstream of a dam constructed on a wide alluvial river are studied experimentally in a laboratory model of an existing alluvial river. The experimental results show that both scour and fill occur in the river bed downstream of the dam as the result of an alluvial bar moving through the system. The bar originates from the local scour hole just downstream of the outlet structure. The channel becomes choked on one side by the bar, while scour occurs on the opposite side of the channel. A numerical model using the streamtube approach is developed to enable prediction of both scour and fill in the same river cross section. The numerical model is tested for sensitivity to the upstream boundary condition, the sediment porosity, the sediment transport relation, and the numerical time step. When compared with the experimental results, the numerical model results agree with the observed scour and fill trends, but the magnitudes are underpredicted. The streamtube approach was found to be a viable technique for investigating two-dimensional streambed adjustments, but additional refinements related to the fundamental problems of transverse velocity distribution and widening due to streambank failure are needed as these problems are illuminated by further research.