Measuring stream discharge by non-contact methods: A proof-of-concept experiment

This report describes an experiment to make a completely non-contact open-c hannel discharge measurement. A van-mounted, pulsed doppler (10GHz) radar c ollected surface-velocity data across the 183-m wide Skagit River, Washingt on at a USGS streamgaging station using Bragg scattering from short waves p roduced by turbulent boils on the surface of the river. Surface velocities were converted to mean velocities for 25 sub-sections by assuming a normal open-channel velocity profile (surface velocity times 0.85). Channel cross- sectional area was measured using a 100 MHz ground-penetrating radar antenn a suspended from a cableway car over the river. Seven acoustic doppler curr ent profiler discharge measurements and a conventional current-meter discha rge :measurement were also made. Three non-contact discharge measurements c ompleted in about a 1-hour period were within 1 % of the gaging station rat ing curve discharge values. With further refinements, it is thought that op en-channel flow can be measured reliably by non-contact methods.