Integrated River Management - River Dynamics and Integrated River Management - page 758

For the fraction finer than 0.05 mm, S d = 2179 * 0.246 - 514 * 0.65 = 202 million tons
In other words, almost all the sediment coarser than 0.5 mm eroded from the watershed deposits in the
gullies and tributaries of the upper Yangtze River basin; 313 of the 492 million tons of sediment of diameter
in the range of 0.05~0.5 mm and 202 of the 536 million tons of sediment finer than 0.05 mm deposit in
the gullies and the tributaries of the upper Yangtze River basin.
Fig. 11.43 Comparison of the size distributions of sediment deposits in debris flow gullies and tributaries in the upper
Yangtze River basin with those of suspended load at the Yichang and Datong stations. ( S 1—bed load in the Diaoga
River; S 2— S 11 are sediment deposits in gullies and tributaries: S 2—Xiaobaini Ravine; S 3—Dabaini Ravine, S 4—
Tongchangqing Gully; S5—Dade Gully; S6—Xiaohai River; S7—Jiangjia Ravine; S8—Daduo Gully; S9—Xiaojiang
River; S 10—Sunshui River; S 11—Niuri River; S 12—suspended load at Yichang; S 13—suspended load at Datong;
Sm —representative size distribution of eroded sediment from the upper Yangtze River basin)
Figure 11.43 also shows the size distribution of bed load from the Diaoga River, which is an average
of 18 samples weighted with the rate of bed load transportation. The rate of bed load transportation in the
Diaoga River is as high as 100 kg/m.min in flood season, which is much higher than that in the Yangtze
River. Nevertheless, most of the bed load cannot be transported to Yichang but deposits in the gullies and
tributaries in the upper Yangtze River basin.
11.2.3.3 Sediment Transported in the Yangtze River
Figure 11.44 shows the annual runoff and sediment load in the Yangtze River along its course. The
annual runoff increases from upstream to downstream but the annual sediment load increases from the
source to Yichang (the Three Gorges Dam site) reaching its highest amount of 514 million tons/year.
Between Yichang and Luoshan the river flows out of the mountains and enters its alluvial reaches. The
sediment load reduces from Yichang to Hankou (Wuhan) due to deposition.