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What changes have occurred in the channel of the river Ely as it flows downstream

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Introduction

What changes have occurred in the channel of the river Ely as it flows downstream This section will highlight the correlation of data and try to explain why certain features of the river channel changing, affects other features of the river. The cross-sectional maps and graph 4 show how the river widens as it deepens. E.g. Site 1 C.S.A is 0.53m square and at site 8 it is 25.2m square Diagram to show the difference in profile at different points of the river. Upper course Lower course The load of the river, and the river itself causes this erosion of the river channel. In the upper course of the river the river is fast flowing, narrow and has a small discharge; also the load is angular with jagged and sharp edges. When the river moves this large material, due by traction and saltation, abrasion occurs as the rocks and stones being transported scour and scrape the riverbed and sides, therefore deepening and widening the river channel. Also the river can react chemically with some of the underlying rock and dissolve it due to the small amount of acid contained within the water, in a process called corrosion. The process of hydraulic action is when the force and weight of the river loosens rock in the bed and banks of the river, so the valley gets wider. ...read more.

Middle

there is less water in contact with friction, so more water can move naturally, which could explain a slight increase with distance from the source (See figure 1.) This could also be explained by reviewing the human interference in the river; one example is at site four (pictured), where a weir has been built to increase the velocity to prevent flooding of the surrounding land. Upper course Lower course Freely moving water Friction with bed Figure 1 And sides This section will highlight the corresponding change in the load size and shape, and explain why these changes occur as the river travels downstream. The pie charts show that as the river travels away from the source, the shape of the rocks and stones changes from being sharp and angular, to a much more rounded shape. Also the compound bar graph shows how the load decreases in size with distance from the source. E.g. At Site 1 there is 6 sub angular rocks and 6 rocks over 10cm, but at Site 8 there is one sub angular rock and 0 rocks over 10cm Diagram to show how load becomes rounder and smaller . This downsizing and rounding of the load occurs due to transportation and erosion processes within the river. As traction carries the larger rocks and boulders along in the upper course, the process of attrition, when rocks are bumping and bashing ...read more.

Conclusion

The joining of tributaries means the discharge will increase and the river valley must become wider. It also means the river will have more power and the efficiency will increase, as will the amount of erosion such as Hydraulic action. More water will be able to move freely, which was a possible explanation for the slight increase in velocity at the lower course of the river, which was unexpected. The area around the river also changes, from being surrounded by steep valleys, to a large plain, and drainage basin where the river floods in certain conditions. The load size unsurprisingly decreased with distance from the source, and they became more rounded, which was caused by such processes as attrition, which benefited with the changes in channel characteristics, as the various transportation processes saw the larger rocks and boulders being slowly transported in the upper course, to the solution carried at the latter survey points. From my investigation, I can see that both the change in channel characteristics and in bed load size and shape are primarily linked with the same key factors mentioned above. I have found out that one change is often the cause of another, as the channel affects the load and various factors such as discharge affect the channel. By recording and explaining all these processes, I think the question has been answered, "What changes have occurred in the channel of the river Ely as it flows downstream?" ...read more.

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