Understanding rill erosion rate in dry-wet condition

Rill erosion is considered to be the most important process affecting soils created by the concentrated flow of water. In this research to quantify sediment transport and runoff in natural rills, two rill experiments under dry and wet conditions were accomplished in November 2013 in the Golestan Dam. Filed experiments lead to a closer understanding of the dynamics and power of different soil erosion processes in a rill channel. Water is introduced with an intensity of 12 L min−1 into a rill within 10 min. Rill cross sections, slope values, flow velocities and sediment concentrations were measured for each rill at three points every 5, 10 and 16 m from the origin along a rill. The flow velocity within the rill was measured by recording the travel times of the waterfront and of two applied colour tracers .The results showed that the flow velocity in the under wet condition is higher than dry condition. Under dry condition, the highest sediment concentrations are recorded at the initial runoff flow despite lowest flow velocity. The initial high sediment concentration may be attributed to the existence of a thin loose surface layer. Flow velocity increases along the length of the channel towards an increase with flow duration. However suspended sediment concentration measured tend to decline with decreasing the sediment-transport capacity. Temporal variations in the sediment concentrations indicated that changes Sediment concentration at the time of the creation of the nought erosion process with inflow water in the experiments and sediment transport mostly attributed to the bulldozer effect. Also showed that hydrological response and sediment production were significantly different in two rill channels which only ground cover were significantly different