Model Studies of the Bed Regime of Alluvial Channels as Influenced by Submerged Groins

Experimental studies were conduoted in a straight reach of rectangular channel to determ1ne the dynamic equilibrium depth of scour associated with submerged constrictions or groins. Tests were carried out with various groin geometries in both rigid- and movable-bed models. Velocity traverses were made over the groins and in the constricted region to establish the relationship between the ratio of discharge through the constriction to the total discharge and the relative groin submergence and geometry. Measurements of the eroded bed profile in the constricted region indicated that the equilibrium relative depth of scour was related primarily to the discharge ratio and the constriction ratio. All groin geometries tested demonstrated the capability of providing relatively large scour depths at low stages, and less scour depths at high stages for which a larger portion of the total discharge passed over the groins. Reasonable agreement with predicted relative scour depths was noted for relatively large sediment transport rates.