Simulation to Investigate the Essential Reasons of Typhoon Induced Siltation in Changjiang River Estuary and the Impact to Water Source Area

A well-validated wave model with No. 9912 typhoon is established using Delft-SWAN mode to study the effect of wind wave caused by typhoon on the navigation channel of Changjiang River Estuary. The wave factors including the wave height, wave length, wave period and wave steepness under one typhoon wind scenario---with velocity of 20m/s and direction of NNE35°, obtained from the statistical data, are simulated to show the wave fields under the typhoon wind. The difference between wave orbital velocity near bottom and threshold velocity of the suspended bed sediment in navigation channel and the carrying capacity of suspended sediment in Changjiang River Estuary are calculated to analyze the mechanism of sudden siltation caused by typhoons on the basis of the three basic conditions that of Changjiang River Estuary. The computed results show that in the effort of typhoon, wave height increases sharply and the huge energy induced by broken wave erodes the sediment on the shoals. The sediment carried by wave enters into the navigation channel and causes the sudden siltation in the navigation channel of Changjiang River Estuary.