Figure 6 The variation in sediment load
In the Zhicheng-Shashi reach, the value of the sediment matching index
was approximately 1.0 before 2003. After 2003, the index decreased
significantly to below 1.0 and then decreased to 0.56 in 2015, which
indicated that the river reach was scoured seriously in this period
(Fig. 7a). The variation in the index is consistent with the variation
in river erosion and deposition. In the Shashi-Jianli reach, the average
value of the sediment matching index is 1.0 before 2003, which indicates
that the riverbed elevation is basically stable. However, the index
shows a decreasing trend after 2003, with an average value of 0.5, which
indicates that the channel erosion is severe in this period (Fig. 7b).
In the Jianli-Luoshan reach, unlike in the previous reaches, the values
of the sediment matching index are basically less than 1.0 (Fig. 7c),
mainly because the flow with low sediment concentration flows into the
Yangtze River after the Dongting Lake regulation and storage, causing
the Jianli-Loshan reach to be in the erosion state.