Testing a handheld radar to measure water velocity at the surface of channels

Abstract

Among the non-contact instruments to measure water velocity in open channels, two handheld radars are available on the market since ten years. Due to the lack of information about these instruments, one model was tested in the laboratory and in the field. The radar was able to estimate the velocity of a water surface within [p = 0.95] ± 0.3 m/s at medium velocities (from 0.3 to 3 m/s) and within ± 10 % of the measured value at large velocities (up to at least 6 m/s). Although this is not very accurate, the ease of using handheld radars still makes them attractive to quickly estimate discharge at gauging stations, safely determine water velocity during a flood and investigate how water flows under difficult access conditions. Nevertheless, the tested radar was tending to underestimate the water velocity, above all when it was looking downstream. More studies are necessary to know why. © 2014 Société Hydrotechnique de France .