Impact of Secondary Flow on Bed Form and Sediment Transport in a Meandering Channel for Overbank Flow

Abstract

An investigation of interaction between bed form and secondary flow in a compound meandering channel with straight floodplain banks for overbank was carried out. The mobile bed form in the main channel was measured by photogrammetry and the secondary flow was first visualized with a submergible video camera and then measured using three component laser Doppler anemometer. The results of the bed form and secondary flow during flood indicate that there exists a certain relationship between the bed form and secondary flow. The secondary flow induced by the floodplain flow in the main channel generates another secondary flow cell owing to the bed form change. Those secondary flow cells make sand bars crossing the main channel, particularly, in the cross-over region. Sediment transport rate reduces at an early stage of flooding owing to strong interaction between the floodplain flow and the main channel flow.