Rivers Essay

A knocking is a term in geomorphology to describe a location of a river or channel where there is a sharp change in channel slope, such as a waterfall or lake. Knockings reflect different conditions and processes on the river often caused by previous erosion due to glaciations or variance in lethality. River terrace- River terrace, bench or step that extends along the side of a valley and represents a former level of the valley floor. A terrace results from any hydrological or climatic shift that causes renewed down cutting.

It generally has a flat top made up of sedimentary deposits and a steep fore edge and it may be the remains of an old floodplain, cut through by the river and left standing above the present floodplain level. Another type of terrace is cut into bedrock and may have a thin veneer of alluvium, or sedimentary deposits. In paired terraces, the terrace features on each side of a valley correspond. Incised meanders- Incised meanders are meanders which are particularly well developed and occur when a rivers base level has fallen giving the river a large amount of vertical erosion power, allowing it to own cut.

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There are two types of incised meanders, entrenched meanders and ingrown meanders. Entrenched meanders are symmetrical and form when the river downcast particularly quickly. Due to the speed which the river downcast, there is little opportunity for lateral erosion to occur giving them their symmetrical shape. Ingrown meanders are asymmetrical. They form when the river downcast at a less rapid pace, giving the river opportunity to erode laterally as well as vertically. Ingrown meanders- Occurs when the incision of the river is less rapid.

The river shifts laterally as well as down to produce a symmetrical cross valley shape. Cavitations- Cavitations is the formation of vapor cavities in a liquid – I. E. Small liquid-free zones (“bubbles” or “voids”) – that are the consequence of forces acting upon the liquid. In the case of the constricted channel and based on the specific (or unique) geometry of the system, the combination of pressure and kinetic energy can create the hydrodynamic cavitations cavern downstream of the local constriction generating high energy cavitations bubbles.