Eventually this is the route the river takes leaving the old meander separate to the river as an Ox-Bow lake. If a river meander becomes increasingly tight over time, leading to a narrow neck, in times of flood the neck is broken through. They are typically found in the middle and lower course of a river. Material that is largest is found on the upstream side of the river. A meander is a winding curve or bend in a river. Where material may be deposited on the inside convex bend of a river. The development of a meander through time is shown below: Sinuosity = actual channel length / straight-line distance. A river is meandering when its sinuosity is above 1.5. In this section of the valley the river erodes laterally. The reasons for the development of meanders remain unclear, but they appear to develop first in times of flood and are related to the occurrence of sandbars. Meanders occur in the middle valley and are the result of erosion AND deposition processes on a river. A pool has more erosion than a riffle, and is caused by turbulence. McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc. River braiding is characterized by channel division around alluvial islands. entrencht man·dr (hydrology) A deepened meander of a river which is carried downward further below the valley surface in which the meander originally formed. It is concluded that the mechanics which may lead to meandering operate in straight channels. ![]() Pools are areas of deeper water and riffles are areas of shallower water. In the data we analysed the meander wavelength, or twice the distance between successive riffles, is from 7 to 12 times the channel width. These features occur due to both erosion and deposition. These are made of fine sediment and occur when a river has a decrease in energy as it enters a lake or the sea. Copyright 2016 by Houghton Mifflin Harcourt Publishing Company. American Heritage Dictionary of the English Language, Fifth Edition. In some countries, artificial levees are put in place to reduce the flood risk.Īt some times of the year, due to snowmelt, rivers may carry a very highload in comparison to their velocity. A stream that has multiple successive meanders and develops in relatively flat areas, such as a floodplain, where sediment consists primarily of fine sands, silts, and muds. ![]() When the amount of water in the river is low deposition takes place, the bed of the river rises and flooding is again likely. If a river floods, material is deposited on the banks, the material that is dropped first is the coarsest, and creates a natural embankment. The edge of a flood plain is quite often clearly marked by a clear slope known as a bluff line. normally in meanders of large rivers, there is active deposition along the convex bank & undercutting along the concave bank. The flood plain can be made wider by the lateral erosion of meanders. A meander forms when moving water in a stream erodes the outer banks and widens its valley and the inner part of the river has less energy and deposits silt. If a river floods, silt is deposited on the land increasing its fertility, and the height of the flood plain increases. If the gradient of the river increases quickly or flows over gently dipping areas of harder rock rapids will result.Īt its most basic level this is land more likely to experience flooding.
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