Mechanism of flood peak increase along the lower Yellow River and its verification

The paper studies the abnormal phenomenon that a flood peak increased in August.2004 along the lower Yellow River and its hydrodynamic mechanism.It is found that the flood peak increase was mainly due to decrease of channel roughness in the propagation of high-concentrated flood carrying extra fine sediment which was discharged from Xiaolangdi reservoir.The mechanism of this flood is verified by the simulation with a quasi-2-D numerical model,which includes,among others,roughness change due to concentration and sediment size gradation.It is pointed out that the flood peak increase due to roughness reduction may endanger the security of flood control works along the lower Yellow River,so that attention must be pay to this problem.