ASABE Technical Library - Abstract

Abstract. Mountainous soils often contain large amounts of gravels, to impact infiltration, runoff and soil erosion. The flow velocity within gravels is of great importance on researches of water erosion process in rocky mountainous areas. Laboratory experiments were undertaken to study the flow velocity within gravels with the Electrolyte Tracer Method. Dye tracer method was used to measure the leading edge velocity. The gravels of about 2 cm in diameter were used to fill to a thickness of about 5 cm in a flume of 4 m long, 15 cm wide and 50 cm high. Five sensors were used to measure the electrolyte conductivity change process at 0.3, 0.6, 0.9, 1.2 and 1.5 m from the solute injector under three flow rates of 3, 6 and 12 L/min and three slope gradients of 4°, 8° and 12°. The peak, mean and leading edge velocities were computed before comparisons were made with those measured by using dye tracer method. The results show that flow velocity was not significantly affected by discharge rate, but notably affected by slope gradient. With the increase in slope, flow velocities increased from 0.031 to 0.070 m/s. The peak velocities were 0.81 to 0.83 times of the leading edge velocities, regardless the effect of the slope and flow rate. The mean velocities were about the same as the peak velocities. The mean velocities were 0.68 to 0.78 times of the leading edge velocities, increasing with distance. The ratio of mean velocity and leading edge velocity can be also used to calculate the flow velocity within gravels measured by dye tracer method. The method should be useful to understand the hydrodynamics of water flow within gravel layers.