Question

Essay on landforms created by river​

Answer 1

Answer:

Picture

Changing River Profile

Before looking at specific river landforms it is important to look at how the river channel itself changes downstream. We have already looked at how the river channel in the upper course is shallow and narrow with large bedload that disrupts the efficiency of flow. The bedload is derived mainly from mass movements from the valley sides and eroded rock from the bed and banks of the channel. The valley profile is really just an extension of the channel itself; it follows a symetrical v-shaped form. This narrow valley and river channel is caused by vertical erosion as a result of the high potential energy of the river. As the river stretches downstream both its velocity and discharge increase. Its velocity increases due to more efficient flow and reduced channel roughness. The discharge increases because the catchment area of the drainage basin has increased along with the number of tributaries feeding water into the river. As a result of this increased discharge the river, in its attempt to balance its energy erodes laterally, widening as well as deepening the river channel. At times, the river will exceed the banks and flood across the flatter section of the valley, initially in a youthful phase a floodplain may be eroded out of the valley. Over time a flat extended floodplain devlops either on both sides of the river or dominant on one side. Again in an effort to balance its energy and discharge the river will meander, creating asymetrical river channels; characterised by steep river cliffs on the outside bend of the meander and gentle slip-off slopes on the inside bend of the meander. Unregulated floodplains support permanent and semi-permanent wetlands. Further downstream the floodplain grows in size on both sides of the river as the river channel grows in width and depth. The channel shape becomes once again more symetrical as the channel widens. The meander length and meander belt both increase in size and the erosion of the outside bend slows down

Answer 2

As the river moves through the upper course, it cuts downwards. The gradient here is steep and the river channel is narrow. Vertical erosion in this highland part of the river helps to create steep-sided V-shaped valleys, interlocking spurs, rapids, waterfalls and gorges.

As the river erodes the landscape in the upper course, it winds and bends to avoid areas of hard rock. This creates interlocking spurs, which look a bit like the interlocking parts of a zip.

When a river runs over alternating layers of hard and soft rock, rapids and water