5.2 Construction of the TGR
Since the impoundment of the TGR, river channel erosion is serious
downstream of the dam (Fig. 9a, Fig. 9b). From 2002 to 2015, the
scouring volume of the Jingjiang River was 0.71 billion
m3, with an average erosion volume of 0.05 billion
m3/a (Fig. 9a). It is far greater than the average
erosion of 0.0137 billion m3/a from 1972-2002. The
riverbank collapse of the Jingjiang River occurs frequently due to
channel erosion. From 2003 to 2012, there were 654 bank collapses in the
middle and lower reaches of the Yangtze River, with a total length of
495.9 km. After bank failure, the bank will retreat gradually, and the
area of the section will increase (Fig. 9c), which will improve the
channel connectivity.
In the Zhicheng-Shashi reach and Shashi-Jianli reach, the function value
of channel connectivity ranged from 0.9 to 1.0 from 1990-2002; however,
the value gradually increased and was basically greater than 1.0 after
2003, indicating that the construction of the reservoir improved the
downstream channel connectivity (Fig. 8). The channel connectivity does
not change in the Jianli-Luoshan reach since the impoundment of the TGR
because it is located far from the dam.