![]() Once this occurs an ox-bow lake will form.N. The photograph below shows how close the nexk of the meander is to being breached. The aerial photograph below shows a meander in the River Derwent, North Yorkshire which will soon be breached. Meander formation in supraglacial streams is driven by channel curvature, which enhances heat production and heat transfer to the surrounding ice at bend apexes. 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.Įventually the neck of the meander will be breached by the river creating an ox-bow lake. Meanders are perpetuated through a process called helicoidal flow. This is a gently sloping deposit of sand, gravel and pebbles. The image below shows evidence of undercutting on the outer bank and deposition on the inner bank of the meander.Ĭontinued erosion along the outer bank, as the result of hydraulic action and abrasion, creates a river cliff or bluff. Thus, sinuous curves or bends are formed, known as the meanders, and the course itself is known as the meandering course. When that happens, the river's channel follows the straighter path downhill, leaving behind a crescent-shaped remnant called an oxbow lake. Therefore the river does not get any wider. As long as nothing gets in the way of a river's meandering, its curves will continue to grow curvier and curvier until they loop around and bumble into themselves. On the opposite side of the channel where the velocity (speed of the flow of water) is lower material is deposited. Where the river swings towards the bank lateral (sidewayes) erosion causes undercutting. ![]() Notice how the flow of water weaves around the sediment bars. The map below shows bars of sediment exposed due to the low level of water in the channel. This causes the river flow to swing from side to side. This creates deeper pathways where most of the water flows called pools and shallow areas where less water flows called riffles. Flowing water weavers around these bars of sediment. In low flow conditions straight river channels have bars of sediment on their beds. There are several stages involved in the creation of meanders. The video above shows a meander on the River Derwent, North Yorkshire.Įrosion, transportation and deposition are all processes that create the characteristic features of meanders shown in the images above. Once again we can see deposition on the inside curves of the meander. The river shown in the photograph is swollen due to recent rainfall. Notice the deposition on the inside of the meanders (pale material) and the river cliffs or bluffs (indicated by dark shadows) on the outside of the meanders.Īgain, the image below shows a series of meanders. The image below shows a series of meanders. ![]() This is because vertical erosion is replaced by a sideways form of erosion called LATERAL erosion, plus deposition within the floodplain. They are typical of the middle and lower course of a river. Meanders are typical landforms found in this stage of the river.Ī meander is a winding curve or bend in a river. The river channel has also become deeper. The gradient is more gentle and lateral (sideways) erosion has widened the channel. The middle course of a river has more energy and volume then in the upper course. The force of the water erodes and undercuts the river bank on the outsideof the bend where water flow has most energy due to decreased friction. You are here: home > geotopics > rivers > landforms - middle courseĬase Study - Ganges/Brahmaputra River Basin The formation of meanders is due to both deposition and erosion and meanders gradually migrate downstream.
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