Edexcel IGCSE Geography Chapter 1 - Pearson Schools

ErosionThere are several different ways in which rivers erode their channels and valleys(Table 1.2).HydraulicactionAbrasionCorrosionWater hits the river bed and banks with such force that material isdislodged and carried away. This is particularly important duringperiods when the river’s discharge is high.The material being carried by a river is rubbed against the the sidesand floor of the channel. This ‘sandpaper’ action widens anddeepens the channel.Minerals in the rocks forming the sides of the river channel aredissolved by the water flowing past them.Table 1.2: The processes of river erosionAttrition is another river process. It involves particles of material being carried bya river becoming rounder and smaller as they constantly collide with each other.This process doesn’t erode river channels and valleys.TransportThis is the movement of material (known as the load) by the river. The load ismade up of material that has been washed or fallen into river. It also made up ofmaterials eroded by the river itself from the sides of the channel. The load can betransported in a number of different ways (Figure 1.11).solutionWhy is attrition not included in Table 1.2?Chapter 1: River environmentslarge bouldersrolled on the bedmaterial dissolved in the watersmall boulders bouncedalong the bedtractionlighter materialcarried along byriver flowsaltationFigure 1.11: Ways in which rivers transport their loadsuspensionExplain why the size of load materialaffects the way it is transported by a river.9