Effect of bank stabilization on bend scour in anabranches of braided rivers

Abstract Bank stabilization along migrating river bends leads to deeper outer bend scour, narrower channels and, sometimes, sharper bends. Four mechanisms are identified for these morphological responses: (1) prevention of bank sediment supply, (2) narrowing due to retarded point-bar growth, (3) bend deformation due to local prevention of channel migration and (4) vortices generated by flow impingement. A simplified, axisymmetrical model of water flow, sediment transport, bank erosion and bank advance is used to study the first two mechanisms. Simulations using the model are compared with field data from a bank stabilization project along the Brahmaputra-Jamuna River in Bangladesh. The effects of bank stabilization are reproduced qualitatively but the quantitative results are poor. The model overestimates channel width while underestimating bank migration rate and outer-bend scour.