Answer
The dominant sediment transportation process differs across the three zones of a river system due to varying flow conditions and channel characteristics.
In the upper zone, which is typically the headwaters, the river has a relatively steep gradient, and the flow is fast. In this zone, the dominant sediment transportation process is bedload, where heavier particles such as sand and gravel are transported along the streambed by rolling, sliding, or bouncing.
As the river moves to the middle zone, the gradient becomes more moderate, and the flow velocity decreases. In this zone, both bedload and suspended load play significant roles. Suspended load consists of finer particles, such as silt and clay, that are carried within the water column. As the flow slows down, it can no longer support the finer particles, leading to their deposition in the riverbed or on floodplains.
Finally, in the lower zone, near the mouth of the river, the gradient is very low, and the flow becomes slow and meandering. Here, the dominant sediment transportation process is the suspended load. The river has significant capacity to carry finer sediments, and deposition of these sediments occurs in the delta region or other low-energy areas.
Work Step by Step
Refer to the answer above.
