Integrated River Management - River Dynamics and Integrated River Management - page 752

Between the gorge sections are broad sections with gentle bed gradient. The authors studied the sediment
in the broad sections and found that the sediment consists of gravel and fine sand. The maximum depth
of the sediment is as large as 200-400 m. The gravel, with a diameter mainly from 10 mm to 200 mm, was
not transported into the Grand Canyon but deposited in upstream broad sections. The step-pool systems
in the canyon consumed the flow energy and protected the bed from erosion. Thus, the upstream sections
are stable and a huge amount of gravel bed load is stored there. Figure 11.39(b) shows the Brahmaputra
River in India, which is the downstream reach of the Yalutsangbu below the Grand Canyon. The riverbed
consists mainly of sand rather than gravel, which proves that most of gravel bed load has been not
transported through the canyon to India.
(a)
(b)
Fig. 11.40 (a) Huge step-pool system in the Grand Canyon (near knickpoint 4); (b) Brahmaputra River in India, which
is downstream of the Yalutsangbu River below the Grand Canyon. (See color figure at the end of this topic)
11.2.2.6 Application of the Equaivalency Law
The law of equivalency of bed load motion and bed structures is very useful. For instance bed load was