Performance assessment of H Flumes under extreme approach flow conditions

H Flumes were designed by the Soil Conservation Service group of the U.S. Department of Agriculture and came into widespread use in the 1930s to measure runoff in small agricultural watersheds and experimental plots. Rating tables for the head-discharge relationships were prepared based on the calibration of these devices, and calibration equations were subsequently developed. The H Flume is specified to have an opening with sloping sides in the lateral and upstream direction. Laterally the opening has a 6 to 1 slope, and in the flow direction the opening has a 2 to 1 slope.