Geoscience Reference
In-Depth Information
(a)
(b)
800
700
600
500
400
300
200
100
0
1200
sediment from
the river
sediment dammed
in the reservoir
1000
800
600
400
200
0
1967 1970 1973 1976 1979 1982 1985
1945 1955 1965 1975 1985 1995 2005
Calendar year
Calendar Year
Case Fig. 3.1
(a) History of annual sediment discharge at Datong Station, suggesting a decreasing trend since the 1960s.
(b) Accumulative river sediment discharge and amount of sediment dammed in Danjiang Reservoir, middle reach of the
Hanjiang River, one of the major tributaries of Yichange and Datong.
basin subsidence due to the Himalayan orogeny. By contrast, others suggest that a decline
in sediment supply downstream of the dam will be beneficial in that flood levels will be less.
Furthermore, the Danjiangkou Dam, built on a tributary of the Yangtze, is not believed to have
caused downstream incision, and concerns that coastal erosion will occur are countered by
suggestions that mud flats north of the Yangtze will be supplied by tributaries downstream of
the Three Rivers Gorges. The full effects of the Dam Project, and answers to these questions
will not, however, be available for many decades.
Relevant reading
Fuggle, R., Smith, W.T., Hydrsult Canada Inc. & Agrodev Canada Inc. (2000)
Large Dams in Water and
Energy Resource Development in the People's Republic of China (PRC)
. Country review paper prepared as
an input to the World Commission on Dams, Cape Town. http://www.dams.org (accessed 25 June 2004).
Milliman, J.D. & Meade, R.H. (1983) World-wide delivery of river sediment to the oceans.
Journal of Geology
91
, 1-21.
Wang, S., Chen, Z. & Smith, D.G. (2005) Anastomosing river system along the subsiding middle Yangtze River
basin, southern China.
Catena
60
, 147- 63.
Wang, Y. & Zhu, D.K. (1994)
Coastal Geomorphology
. Higher Education Press, Beijing, 244 pp. (In Chinese.)
Yang, S., Zhao, Q. & Belkin, I.M. (2002) Temporal variation in the sediment load of the Yangtze river and the
influences of human activities.
Journal of Hydrology
263
, 56 -71.
showed that engineering of the Rhône River in
France, carried out to control overbank flood-
ing and stabilize the river planform, resulted in
channel narrowing and entrenchment, and in-
creased hazard of low-frequency, high-magnitude
flood events (Fig. 3.17a). Surian & Rinaldi
(2003) carried out a comprehensive review of
the response of Italian rivers to sediment extrac-
tion, dams and channelization, and highlighted
channel incision, generally 3 - 4 m but up to
10 m, and channel narrowing of up to 50%, as
the major effects (Fig. 3.17b). They did, how-
ever, point out that these effects were most
pronounced immediately after the engineering
works were carried out, and that the effects slowed
and became asymptotic. Gaeuman et al. (2005)
demonstrated that the creation of large-scale
diversions and increased water withdrawal for
