Floodplain and its erosional and depositional landforms. They are often formed during the creation of oxbow lakes.įigure 10. They are characterized by “a crescentic cut in a bluff or valley wall, produced by a meandering stream. They are formed by the remnants of a meandering water channel. When several processes of erosion, transport, deposition and migration of meanders occur, they are formed meander scars (10).The word “oxbow” can also refer to a U-shaped bend in a river or stream, whether or not it is cut off from the main stream. Evolution of a meander and an oxbow lake. They are crescent-shaped and located on the inside of a stream bend, being very similar to, though often smaller than, towheads, or river islands.įigure 9. Point bars are found in abundance in mature or meandering streams. A point bar is a depositional feature made of alluvium that accumulates on the inside bend of streams and rivers below the slip-off slope.Material eroded here is deposited downstream in point bars. Not only are cut banks steep and unstable, they are also the area of a stream where the water is flowing the fastest at a higher pressure and often deeper, making them rather dangerous. Given enough time, the combination of erosion along cut banks and deposition along point bars can lead to the formation of an oxbow lake. Often, particularly during periods of high rainfall and higher-than average water levels, trees and poorly placed buildings can fall into the stream due to mass wasting events. Normally, cut banks are nearly vertical and often expose the roots of nearby plant life. Satellite image showing a meander with a cutbank on the external margin and a point bar in the internal margin of the water stream.
This makes it easier for the river to evolve in its form within time and space as the horseshoes migrate through the erosional plain in a horizontal way rather than a vertical way, as shown below (4):įigure 7. Diagram that shows the relation between the river speed (Y axis), the particle size (X axis) and the total amount of particles eroded, transported and deposited.Īs meandered streams are mostly found in plains, the speed of the flow is not big enough so as to carry big sized particles, which explains why landforms found in this kind of water streams are composed by thin particles. The competence of a stream increases proportionally to the mathematical square of its speed (3).įigure 3. The key lays in the water speed fast water streams have a larger competence that the slower ones, despite the size of the water stream beds.
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