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There are two primary mechanisms of stream bank erosion: fluvial erosion and mass failure. Fluvial erosion is the direct removal of soil particles by flowing water. The rate of fluvial erosion is determined both by the force of the flowing water (e.g. faster flow equals more force) and the resistance of the bank material to erosion (e.g. clay is generally more resistant to erosion than sand).
Erosion and changes in the form of river banks may be measured by inserting metal rods into the bank and marking the position of the bank surface along the rods at different times. [23] Thermal erosion is the result of melting and weakening permafrost due to moving water. [24] It can occur both along rivers and at the coast.
Bank erosion is the wearing away of the banks of a stream or river. This is distinguished from changes on the bed of the watercourse, which is referred to as scour. Erosion and changes in the form of river banks may be measured by inserting metal rods into the bank and marking the position of the bank surface along the rods at different times. [17]
This causes an increase in flooding and watershed erosion which can lead to thinner soils upslope. Streambeds can exhibit a greater amount of scour, often down to bedrock, and banks may be undercut causing bank erosion. This increased bank erosion widens the stream and can lead to an increased sediment load downstream. [10]
A cut bank, also known as a river cliff or river-cut cliff, is the outside bank of a curve in a water channel , which is continually undergoing erosion. [1] Cut banks are found in abundance along mature or meandering streams, they are located opposite the slip-off slope on the inside of the stream meander.
A river bank can be divided into three zones: Toe zone, bank zone, and overbank area. The toe zone is the area which is most susceptible to erosion. [2] Because it is located in between the ordinary water level and the low water level, it is strongly affected by currents and erosional events. [2]
The concave bank is often a cut bank and an area of erosion. The eroded material is swept and rolled across the floor of the stream by the secondary flow and may be deposited on the point bar only a small distance downstream from its original location in the concave bank. The point bar typically has a gently sloping floor with shallow water.
Soil sloughing is also an indicator of active soil movement and frequently requires action to reduce or prevent bank and slope failure. Soil water content is highly related to the mass erosion that leads to soil sloughing or even slopes failure. [ 7 ]