Abstract

The runoff and sediment variation in the upper reaches of the Changjiang River and the scouring and sedimentation in the river channel of the middle mainstream, and the response relation between them, are analyzed and studied in the thesis. Compared with that in the years before 1990, the runoff changes little during the period from 1991 to 2000, while the sediment discharge has decreased sharply, and the average annual sediment discharge at Yichang station has decreased about 100 million tons, by 20%; during the period from 1966 to 1998, the sediment scoured in the low-water channel of the reach from Yichang to Hankou in the middle reaches of the Changjiang River amounts to about 367 million cubic meters, and the scouring in the low-water channel of the reach from Yichang to Chenglingji is dominant, and the undercutting of river bed is obvious. The river bed and swales are silted in the reach from Chenglingji to Hankou, and the sedimentation takes place mainly in high-water shoals.In order to analyze the response relation between runoff and sediment condition and scoring and sedimentation in the river channel, the intensity of the runoff and sediment effect (IRSE): Р=Q²ЧT/S, is put forward to represent the impact of the upstream incoming runoff and sediment on the scouring and sedimentation variation in the river bed.

Keywords: Variation of runoff and sediment transportation, Sediment scouring and silting, Response relation