Effect of Cohesive Sediments in Scour Morphology Downstream of Submerged Sluice Gates

The scouring of cohesive and non-cohesive materials downstream of sluice gates is primarily based on high-velocity flow. The present study considered an experimental hydraulic model of submerged water flow issuing from a sluice gate installed on an apron that leads to the scour hole and dune in a downstream mixture of sand and clay bed. The purpose was to achieve a suitable efficiency of the weight ratio of clay in the sand–clay mixture (c) for the sediment bed. Scour parameters, including maximum scour depth (d_se) and its longitudinal location (x_se), and maximum dune height (h_d) and its location (x_d), were measured and compared for three variations, c = 0.1, 0.2, and 0.3, under five hydraulic conditions. Results revealed that all scour parameters were reduced by adding clay to the sand soil, and the maximum reduction was for d_se with the maximum value of 27.66%. The observed data were analyzed by multiple nonlinear regression analyses for each scour parameter to present new prediction equations for practical uses. The computed statistical parameters of correlation coefficient (R²), root mean square error (RMSE), mean absolute percentage error (MAPE), Nash–Sutcliffe efficiency (NSE), and scatter index (SI) present good accuracy for the predicted equations in the ranges of experimental data.