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My aim is to collect data by taking various readings and measurements from the River Conwy to give valid proof of different river processes such as attrition, abrasion and deposition.

Extracts from this document...

Introduction

Introduction Aims & Objectives The River Conwy is a rural river in North Wales. Its source is situated in Snowdonia National park and it flows northerly into an estuary where it meets the Irish Sea. My aim is to collect data by taking various readings and measurements from the River Conwy to give valid proof of different river processes such as attrition, abrasion and deposition. I chose to investigate four factors from source to mouth. My year group and I decided to make five stops so we can note any gradual changes rather than just recording data at two stops. The factors I am studying are: 1. Depth 2. Width 3. Speed of flow 4. Size of sediment We made five different stops along the river which are indicated on the map below. Hypothesis I predict that as I travel nearer to the mouth; the width, depth and speed of flow will increase while the sediment size will decrease. I think this because as a river flows towards its mouth many tributaries join it as they drain the basin and this increasing volume of water is one cause of the river becoming wider and deeper. Also, these tributaries add to the rivers load causing more abrasion to occur. The speed of flow should be slow in the upper course of a river because there are more large boulders and rocks causing obstructions and increasing the surface area in contact with the river therefore producing friction. Whereas downstream, the volume of water increases and there are fewer boulders to slow the flow of water, decreasing the amount of water in contact with the bed and banks. ...read more.

Middle

When the stick passed the other side the timer would stop the stopwatch and using the formula speed = distance/time we were able to calculate the average speed of the stick. This process is shown in fig.10. Unfortunately this did not go according to plan as the tide was coming in and the sticks were being pushed one way by the river and another way by the sea, so they remained in the same place. Below are all of the results. Flow meter Stop number & Name Speed of Flow (m/s) 1. Pont Ar Gonwy 0.98 2. Ysbyti Fan 0.41 3. Betws-y-Coed 1.22 4. Llanwrst 1.01 (outside) 5. Dolgarrog No data Orange Stop Number Speed of flow (m/s) Average (m/s) 1. 0.37 0.448 0.4 0.345 0.351 0.286 0.4 0.37 0.465 0.37 0.345 2. 0.313 0.51 0.2 0.345 0.357 0.372 0.33 0.357 0.435 0.455 0.3 3. 1.25 1.172 1.11 1.37 1.11 1 1 1.37 1.33 0.85 1.33 Size of Sediment To calculate the sediment size we took many readings and calculated the average. In order to measure the sediment we used a calliper ( fig.11.) but this only measured up to 30cm so anything larger than that was measured using a tape measure. When measuring sediment you measure the distance between the two furthest tips using the calliper. In fig.12. Various pieces of sediment are shown. We had to be careful not to measure material next to the river but actual deposited material as rocks next to the river may have come from the ground or a hill close by and this would not count as river sediment. ...read more.

Conclusion

Graph showing the size of sediment in relation to speed of flow. Graph showing the size of sediment in relation to the width. We can see from the opposite graph that there is negative correlation. Therefore I can say that as the width increases the size of sediment decreases. I have also used Spearman's Rank to support my graph and this is calculated below: Stop Number Width (m) Rank Sediment Size (cm) Rank Difference Difference squared 1 8.3 5 11.67 2 3 9 2 12.3 4 12.04 1 3 9 3 25 3 7.76 3 0 0 4 32.5 2 0.437 4 2 4 5 42.5 1 0.1 5 4 16 Spearman's Rank = 1 - (6x?d�) (n�- n) = 1 - (6x38) (5�-5) = 1 - (238) (125-5) = 1 - (238) (120) = 1 - 1.98 = -0.98 On using Spearman's Rank I have shown that it agrees with my graph and that there is negative correlation. -0.98 is very close to -1 and this shows that my results were accurate. These findings surprise me as I did not think they would be related. I saw no clear correlation between speed of flow and size of sediment but this was probably because stop 2 and 3 were extremely wide compared to stop 1 and the depths did not change very much. Therefore at stop s 2 and 3 there is more water in contact with the bed and banks causing friction with water but also the rivers load. The rocks and pebbles carried along by the river abrade the bed and banks and this causes them to break up into smaller stones which get bounced along the river bed until they break up by attrition into fine light material that can be held in suspension. - 1 - ...read more.

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