USE OF ROTATING SIDE-SCAN SONAR TO MEASURE BEDLOAD

Experiments in the 1960's demonstrated that the rate of sediment transport represented by migrating bedforms gives a more accurate measure of bedload transport than rates predicted from flow measurements. Rotating side-scan sonar can be used in the field to measure the rate of bedform migration and to calculate bedload transport rates. A rotating side-scan sonar system was deployed in the Colorado River in Grand Canyon for this purpose. For two sites where total load was measured using a depth-integrating sampler, approximately 5% and 0.3% of the sand transport was bedload involved in bedform migration; the other 95-99.7% occurred as suspended load that bypassed the bedforms.