NUMERICAL SIMULATION OF DEPOSITION IN THE TEMPORARY NAVIGATION CHANNEL OF THE THREE GORGES PROJECT

摘要

Sediment deposition in the temporary navigation channel of the Three Gorges Project was significant, and dredging was carried our each year. Sedimentation in the temporary navigation channel is similar to sedimentation in the permanent navigation channel a few decades later when the sedimentation processes in the reservoir comes to quasi-equilibrium. Study of the sedimentation processes is therefore of practical interests. By applying a depth-integrated 2-D model to the river reach near the dam and a vertical 2-D density flow model to the temporary navigation channel, the sedimentation processes in the channel were simulated and the main factors affecting sedimentation are studied. The sedimentation processes in the channel during 1997-2000 were simulated with the model. The processes and the deposit volume are in good agreement with field data. The simulated deposit volume included the deposit caused by horizontal circulation near the mouth areas and the deposit caused by density flow in the channel. The simulation reveals that most deposition occurs in the flood period when the concentration is relatively high, the deposition caused by horizontal circulation near the mouth areas is less than 20% of the total and the deposit caused by density flow is more than 80% of the total. The simulation also reveals that sedimentation in the channel is almost in linear correlation with the water depth and sediment concentration.