bridge abutment scour in compound river channels

most previous laboratory studies of local scour at bridge abutments were performed in rectangular channels in which the distributions of flow velocity and bed shear stress were considered uniform in the transverse direction. in reality however, bridge abutments are usually located in the floodplain zone of rivers where velocity and shear stress distributions are directly affected by the lateral momentum transfer. the influence of channel geometry and lateral momentum transfer in compound flow field on scouring phenomenon, however, has not been fully investigated and understood as yet. this paper presents the results of an experimental study performed to investigate the impact of both sediment size and lateral momentum transfer on local scour at abutments terminating in the floodplain of a compound channel. it is shown that, by accounting for lateral momentum transfer at small floodplain/main channel depth ratios (yalh