Features and mechanism of asymmetric double-kidneys scoured geomorphology of pier in tidal estuary

Based on analyzing the natural scour near the axis of the bridge by data of topographical, this paper used a multi-beam echo-sounding system to study local scour around bridge piers. The results showed that the axis of the bridge and the riverbed near main piers presents erosion evolutionary trend. Upstream the pier, there is a serius erosion while sediments deposit at the mid of pier. Downstream the pier, weak erosion is also found. The largest scour depth of the main pier is about 4 m. The local scour shape of the main pier looks like “double kidneys”. The angle of ebb coming current is 10 degree, as well as the scour depth and scope on the south side of the main pier is larger than that on the north.