Integrated River Management - River Dynamics and Integrated River Management - page 762

analysis resulted in the values of k 1 and S c 1 , and S c 2 and k 2 as follows:
6

k 0.4316; S 285 u 10 t

1 c 1

6

u
From Eqs. (11.22-11.24) and using the values of k 1 , S c 1 , k 2 , and S c 2 the following formula is obtained for
the sediment load entering the estuary:

k 0.2905; S 105 10 t

2 c 2

6

u (11.25)
If the sediment load from Yichang and Hanjiang reduce to zero, about 150 million tons of sediment may
be transported into the estuary and all the sediment is eroded from the middle and lower reaches.
Sediment mining has become an increasing sediment demand. In the 1990s, Yibin, Luzhou, and
Chongqing (Wanxian City not included) mined 5.16 million tons of gravel and 10.14 million tons of sand
from the Yangtze River for building material per year (Yi, 2003). It is estimated that the other cities on
the upper Yangtze River including Panzhihua, Wanxian, and Yichang mined roughly the same amount of
sediment from the Yangtze River. The total sediment mining from the upper Yangtze River is around 30
million tons per year. More sediment has been mined from the middle and lower reaches. In the early
1980s the annual mining from the middle and lower Yangtze River was about 40 million tons, this figure
increased to 80 million tons in the late 1990s (Chen, 2004). The Yangtze River Conservation Commission
issued a regulation in 2003 that the total sediment mining from the middle and lower Yangtze River is
limited to 34 million tons per year (Shen et al., 2003). The amount of sediment mining has not really
been reduced. The total capacity of sediment mining is about 6 times of the limit. Illegal mining is active.
The amount of sediment mining from the middle and lower reaches is not less than 80 million tons. At
present the total sediment mining from the upper reaches and the middle and lower reaches is estimated
at 110 million tons per year.
The third sediment demand is for land creation in the Yangtze River estuary. According to the data
from 1951-2002, about 433 million tons of suspended load are transported into the Yangtze River estuary
annually, of which 45 million tons deposit in the reach between Datong and Xuliujing, 28 million tons
deposit in the north branch (north of the Chongming Island), 4 million tons deposit south of the
Chongming Island, 138 million tons deposit in the river mouth and increase the shelf, 180 million tons
are transported into the Qiantang River estuary and deposit there, the rest is transported into the ocean, as
shown in Fig. 11.48 (Wu, 2001).
Figure 11.49 shows the size distributions of sediment deposits (deposit-1 and deposit-2) at the Yangtze
River mouth and the suspended load measured at Datong. The comparison between the size distributions
shows that the percentage of sediment finer than 0.01 mm of the suspended load at the Datong Station is
about 10% higher than those of deposits at the river mouth. In other words, about 10% of the fine
sediment in the suspended load transported to the estuary does not deposit in the river mouth but is
transported away into the ocean by tidal currents. In summary, of the total sediment transported to the
estuary 45% deposits in the Yangtze River mouth for land creation, 45% are transported into the
Qiantang River mouth and deposit there forming a sediment sill, and, only about 10% are transported
into the ocean.
Land creation in the Yangtze River estuary is essential for the development of Shanghai. In the past 50
years the Yangtze River has created 800 km 2 of new land in the river mouth (Jin et al., 1997). The natural
land creation speed has slowed down and does not meet the increasing demand for land. Various
engineering measures have been and will be applied to accelerate land creation. The Shanghai government
has an ambitious plan to create 1,000 km 2 land in the Yangtze River mouth in 20 years by using the
sediment load. It is estimated that 300 million tons of sediment is needed every year for land creation.

S 0.2779 S 0.5684 S 153.8 10 t

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