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To assess whether the modified channel of the river ash is effective in reducing the risk of flooding to local homes.

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GEOGRAPHY COURSEWORK INTRODUCTION Aim: To assess whether the modified channel of the river ash is effective in reducing the risk of flooding to local homes. To achieve this aim I will conduct a number of experiments within both the natural and modified channel to find out if the modified channel is effective in reducing the risk of flooding to local homes. A satellite image of the area studied in which the experiments on the River Ash took place. Both the modified and natural channel can be clearly seen. The location of the River Ash in relation to the UK. A map showing Staines at the source of the River Ash- the River Colne. The area in which the River Ash starts and flows out of the River Colne is very close to the A30 and the George VI Reservoir. A map showing the River Ash in Shepperton near Upper Halliford, Littleton and the Queen Mary Reservoir. A map showing Sunbury at the mouth of the River Ash where the Ash flows into the River Thames Location The River Ash is located in the south east of the UK. Although the river flows through Shepperton- in Surrey- the river is confined within the Spelthorne borough. The river's source is the River Colne in Staines. It flows from Staines in an easterly direction before flowing southeast through Laleham and bypasses Queen Mary's reservoir. It then turns east through Littleton and Shepperton before joining the River Thames in Sunbury. Causes of river flooding There are several factors that increase the risk of flooding in rivers. There are generally four main factors that are: Heavy rainfall is the most frequent cause of flooding. After several days of heavy rainfall the soil that once soaked up the rain becomes saturated so infiltration becomes difficult. This causes a large amount of surface run-off when water simply lies on the surface of the ground. ...read more.


Although we tried to pick as random pebbles as possible my experiment might not be as accurate as it could be because we had to be careful not to pick up dangerous objects. This meant the selection of pebbles was not as random as it could be. Channel Width We measured the width of both the natural and modified channels to find out how much water they could hold. We would expect the modified channel to have a wider channel than the natural channel so it could hold more water. If this was the case it could take more water away from the natural channel and the houses beside it. This would reduce the risk of flooding to the local homes. Method We stretched a 30 m. measuring tape across the channel and measured the distance from the right bank to the left bank. Equipment * 30 m. measuring tape Limitations To make the experiment accurate we had to keep the tape tight and hold it slightly above water level so it was not carried away by the current. This would add length to our results and make them inaccurate. Data Analysis Graph 1 Graph one shows that the natural channel has a larger water width of the modified channel that has a width of two point two metres. This is because the natural channel has been there longer so therefore has had longer to erode laterally. I expected to be able to link this with graph eleven where I expected the float time for the modified channel to be less than the natural. This would have proven that the water in the modified channel was quicker than the natural. This would have proven that the water in the modified channel was moving more quickly than the water in the natural channel so is doing its job properly to take water away from the houses quickly and efficiently. ...read more.


Yet I found this conclusion to be inaccurate and invalid so all my valid conclusions came to the overall idea that the modified channel was effective in reducing the risk of flooding to the local houses and therefore completing my aim. To improve my experiment if I completed it again I could complete the methods more times to obtain more accurate results and form more valid conclusions. This would avoid anomalies and make the anomalies that were collected more predominant and I would be clearer that they were anomalies. I could extend my experiment and completed the methods further downstream to compare my findings at different points in the river and give a good representation of the whole river as opposed to one specific part of the river. It would be interesting to see if my results differed in different parts of the river. I could also complete the experiment in different weather conditions. The weather conditions were incredibly wet with heavy rainfall which may have affected my results in many ways e.g. the amount of water in the river channel would be greater and the speed of flow could have been slowed down. If I tried the experiment in dry weather conditions I would be more likely to achieve more accurate results and therefore valid conclusions. I could also carry out the experiment out in different times of the year to see how the season affects my results. During this project I have gained a deeper understanding of rivers. I learnt about deposition and erosion and how they can affect river channels. I learnt how certain factors can speed up the flow of rivers including the wetted perimeter and grates. I learnt how to carry out a wide range of methods to collect results to help me draw a valid conclusion and I found out how to use new pieces of equipment like the clinometer to perform these investigations. Overall I performed a successful investigation that fulfilled the aim. ...read more.

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