A resultant increase in flow energy is also exhibited. More water is gained by the deepening bend as the river makes its way to the middle course of the river. Usually, the meander formed is characterized by an inner bend which is slower in flow, making water flow to slow down considerably creating a gentle slope of sand and shingle as a result of deposition of the eroded material. The speed of water flow increases and the hydraulic action together with abrasion forces impacted results in increased erosion. Therefore, meanders are formed as a river goes around a bend in which most of the flowing water is pushed towards the outside portion of the water flow. A perfect example could be found in the River Derwent, North Yorkshire which is almost at the point of breaching. This stage of meander formation eventually causes the neck of the meander to be breached by the river creating an ox-bow lake. Just as the surface flow of water hits the outer bank it corkscrews, flows along the river bed then deposits eroded material on the inner bank. The point bar or meander bar is a gently sloping deposit of sand, gravel, and pebbles. Then, a point bar forms on the inner bank. With persistent erosion along the outer bank, a river cliff or bluff is created as a result of hydraulic action and abrasion. As a result of this stage, undercutting often occurs on the outer bank and deposition on the inner bank of the meander. At the opposite side of the channel where the velocity (speed of the flow of water) is lower material is deposited.
In this stage, the river swings towards the bank lateral (sideways) erosion causes undercutting. Ultimately, the river flow starts to swing from side to side. The flowing water weaves around these bars of sediment which in turn creates deeper pathways where most of the water flows called pools and shallow areas where less water flows called riffles. READ: 20+ Thrilling Facts About the Awe-inspiring Beauty of the Victoria Falls Stage 1ĭuring low flow conditions, straight river channels have bars of sediment on their beds. Some associated landforms include: Cut banks, Meander cutoffs, Incised meanders, Oxbow lakes, Scroll bars, and Slip-off slope. Meander geometry or median planform geometry is engaged in the technical description of meanders. The deposition process cuts off the original meander, leaving a horseshoe-like feature known as an oxbow lake. Thus the curvature of the pathway of river water flow increases, and the shape of the meander changes over time. Thus, during low flow conditions, straight river channels develop bars of sediment on their beds which leads to an eventual formation of deeper pathways which ultimately allow more flow of water and consequent formation of a sinusoidal flow of water.Īs a result of the erosion on the outside portion the bend of flowing river water, erosion occurs, coupled with deposition on the inside portion of the sinusoidal curve. Therefore, as water flows from the upper course of a river at very high energy, the impact it has on the landform on which the river is situated elicits erosional, transportation and deposition processes. Usually, the energy accompanying flow water in a river decreases progressively from the upper course of the river to the lowest course of the river. Meander gradients are usually more gentle and they experience lateral (sideways) erosions which widen the channel of the river at the middle and lower courses of a river.
Meanders are typical landforms at the middle and lower courses of a river. The term ‘meander’ is one which refers to a winding curve or bend in a river.
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