Continuous motion conditions of turbidity current in Xiaolangdi reservoirs, China

Turbidity currents venting is most efficient method for Xiaolangdi reservoir under normal water level when tackling sediment-laden floods to reduce sedimentation. The concept of continuous motion conditions of turbidity current was introduced as the requirements for the main part of turbidity current reach the dam site. Dynamics of turbidity currents in Xiaolangdi reservoir were investigated using the layer-averaged equations of motion. Water-sediment exchange with bed and above have been concealed for simplicity, by which the mechanism that drives continuous motion is subjected to the gravitational force. Two major control parameters, the relative longitudinal bed slope and the relative length of turbidity current, are proposed regarding topography and hydrodynamics. The ratio of the average riverbed longitudinal gradient J from the plunging point to the dam site to the critical gradient J_c of the turbidity current, J/J_c, represents the relative longitudinal bed slope. The ratio of the product of the equilibrium velocity u and duration T of the turbidity current to the radial distance L from the plunging point to dam site, uT/L, represents the relative length of turbidity current. Therefore, a discrimination diagram for continuous motion conditions of turbidity current was determined based on J/J_c and uT/L, successfully differentiated whether turbidity currents can reach the Xiaolangdi dam site.