A method for measuring erosive flow velocity with simulated rill

•A rill was simulated by sand paper glued with soil particles.•Flow velocity was measured on simulated and actual rills by electrolyte tracer method.•The method was verified by the measured velocity along simulated and real rills.

The water flow velocity along an eroding rill is of interests for understanding rill erosion hydrodynamics. Soil erosion makes the measurement of flow velocity highly variable. In this paper, a new method is suggested to simulate rills so as to make controllable and efficient measurements of erosive velocity of rill flow. A series of comparative flume experiments were conducted to verify the method by measuring the shallow water flow velocity, along both the simulated and real rills, by using a computerized electrolyte tracer method. The experiments involved three flow rates (12, 24 and 48 L/min) and three slope gradients (5°, 10° and 15°). Five sensors were used to trace the solute transport processes at 30, 60, 90, 120 and 150 cm from the location where the salt solute was injected into the water flow. Flow velocities under simulated rill and real conditions were computed by fitting the measured solute transport processes with its analytic solution. The results showed that under different flow rates and slope gradients, velocities along the simulated rill agreed very well with those along the real rill. This demonstrates that the simulated rill well simulates the real rill. This method will help further study of the hydrodynamics in eroding rill.