Abstract:

Apart from the direct effect on the river channel, secondary mountain  disasters induced by Wenchuan big earthquake in 2008 including collapses, landslides, debris flows and barrier lakes have far-reaching influences on river channel morphology in the earthquake region. Based on field data, we analyzed the characteristics of river channel evolution and predicted its development to assist the recovery and reconstruction after the earthquake. In terms of the river pattern, wandering and braided rivers were formed because of severe riverbed uplift, and the channel changed its route owing to extrusion by loose materials from mountain hazards on both sides. Regarding the cross section, high-intensity flood scoured the riverbed and then broadened the river channel; whereas sediment deposition could also narrow the channel. The vertical profile of the river was elevated in general with its structure becoming more stable. River reaches with large rocks and abundant incoming water and sediment will gradually develop to ladder-like structure; while reaches subject to deposition in mid-stream and downstream of the mountain area will exhibit concave profile due to scouring and will develop to linear profile.