#Entrenched meander definition geography series#

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You can see these being formed in the river model below. Following rejuvenation the river will cut down into its channel and will gradually form a new floodplain. River terraces are old floodplains left perched above the current floodplain. It may become entrenched (symmetrical steep sides on both sides of the river) and form a winding gorge like that of the Grand Canyon. This results in a steep sided meander that is cut into the floodplain. However, when rejuvenation occurs vertical erosion begins to dominate the lateral erosion that usually occurs in a meander (with erosion on the outside bend). They are usually found along the lower course of a river where lateral erosion is greater than vertical. The knick point retreats upstream over time. At this point vertical erosion associated with rejuvenation is at its greatest.

#Entrenched meander definition geography series#

It is usually marked by the presence of a waterfall (or a series of rapids). This is a knick-point.Ī knick point is a sharp break of slope in the smooth, concave long profile of a river. There is usually a height difference at the point of capture and a waterfall is formed. Occasionally, as a river cuts back it can break into an adjacent valley and capture the tributaries of nearby rivers. River capture – over time rivers cut backwards at their source.Fall in sea level caused by isostatic changes – after a period of glaciation the land will start to rise in response to the loss of the weight of the ice.Fall in sea level caused by eustatic changes – during a glacial period, water is stored on land as ice so the sea level changes.If this crosses a river, a waterfall will form and the river will begin eroding vertically at this point. Tectonic changes – Earthquakes can cause uplift along fault lines to create fault scarps several metres high.Rejuvenation can be caused by a number of different factors. Over time the knick point will retreat upstream like a waterfall. So that the river can once again, over time achieve a state of equilibrium by creating a long, smooth profile.

This is used to actively erode the irregularity. The fall in base level means the river now has more energy to available.

If base level falls, a step or ‘kink’ called a knick point is formed in the river’s long profile. The base level is the height or altitude to which the river flows before it either joins another river or reaches the sea. River rejuvenation involves a renewed period of vertical erosion to achieve a new and lower base level. This renewed period is known as rejuvenation. This causes the river to vertically erode its channel to re-establish the its long, smooth concave profile. Typically a river will always try to form a concave shaped profile.įrom time to time something can occur that changes and de-stabilises this equilibrium. Rivers that have this form of profile are in balance with the environment (equilibrium). In terms of transporting water and sediment it is the most efficient profile to have. Over a long time, a river forms a generally smooth profile (see below).