Integrated River Management - River Dynamics and Integrated River Management - page 750

remained unchanged.
Figure 11.37(a) shows the size distributions of bed load before (B1-S and B2-S) and after (B1-R and
B2-R) removal of key stones at two measurement sections, the size distributions of the mix bed sediment
before (Bed material-M) and after (Bed material-R) removal of the key stones and the size distributions
of the cobbles and boulder composing the steps (Bed structure). The mix bed sediment with the bed
structures consisted of various sizes of sediment, including plenty of sand and fine gravel with diameter
smaller than 10 mm, which was the main fraction of bed load. The sediment was stored in the pool sections
and was protected by the steps, which consumed the flow energy and reduced the flow velocity. Figure
11.37(b) shows the size distributions of the bed load on the Xiaobaini Ravine (XB1-S and XB2-S) before
the experiment at two measurement sections, the bed load after destroying the bed structures (XB1-R and
XB2-R) at the two measurement sections, and the bed load on the Hunshui Ravine (HB-S) before the
experiment and after removal of the key stones (HB-R). Similar to the results in the Diaoga River, the
median diameter of bed load increased 2-20 times due to destruction of bed structures. Bed load coarsening
was also caused by the destruction of bed structures.
Fig. 11.37 (a) Size distributions of bed load before (B1-S and B2-S) and after (B1-R and B2-R) removal of key
stones at two measurement sections, the size distributions of the mix bed sediment before (Bed material-M) and after
(Bed material-R) removal of the key stones and the size distributions of the cobbles and boulder composing the steps
(Bed structure) in the Diaoga River; (b) Size distributions of the bed load before (XB1-S and XB2-S) and after (XB1-R
and XB2-R) destroying the bed structures on the Xiaobaini Ravine and Hunshui Ravine (HB-S and HB-R)
Figure 11.38 shows the changes in bed load transportation and S p value after the removal of key stones
of the bed structures on the Diaoga, Xiaobaini and Hunshui rivers. The S p value decreased but the rate of