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Introduction

25 Pages Introduction Pages 3-6 Hypotheses (at top of page): Page 3 Maps of Location of River: Page 4 3D map of river: Page 6 Methodology: Pages 6-8 Data Presentation: Page 8-19 Raw Data Table: Pages 8-9 Photos: Pages 10-14 Volume of flow: Proportional Line map: Page 15 Width, Depth, Velocity and Volume of Flow Graphs: Pages 16-17 Vegetation and Height Above Sea Level Graphs/Charts: Page 18 Differences in Height Above Sea Level Graph: Page 19 Data Analysis: Page 19-22 Hypothesis 1: Pages 19-20 Hypothesis 2: Pages 20-21 Hypothesis 3: Pages 21-22 Conclusion: Page 22 Evaluation: Pages 22-25 Final Conclusion: Page 25 Bibliography: Page 25 I formulated my hypotheses based on my current knowledge: * I expect the river to get wider and deeper as it flows downstream because it will be joined by tributaries, and other water e.g. from rainfall, so the volume of water in the river will increase, therefore the width and depth of the river must increase to accommodate this extra water. The extra water will also entail more hydraulic action, so the banks of the river will be eroded more, and more water also means more sediment. This sediment will also erode the banks more; rocks carried by saltation or traction will erode the bed, making the river deeper, and alluvium in suspension will erode the bank. In the upper course of most rivers, due to the bedload, there is usually more vertical erosion than lateral (as the river tries to reach its base level), so the river is deep, but narrow, with steep banks. In the middle and lower course, there is progressively less vertical erosion and more lateral erosion, so the river should get a lot wider and a bit deeper as it flows downstream. Human intervention could change the shape of the river, and indeed the nature of the water itself, and plants and fishes can build up the riverbed with decaying material, or deepen it by foraging for food or growing roots. ...read more.

Middle

However, sites 1 and 9 were a bit murky, and site 3 very much so, suggesting that there was quite a lot of alluvium and silt suspended in the water, which would gradually erode the banks and make the river wider. Of course, I can't see what's in solution in the river, so I don't know how it will affect the river's width and depth It is also evident in most of my data presentation that the river varies a lot between site 1 and 10, and an average is needed to draw conclusions. This could be because the river's chalk bed affects the river's volume because it is porous and allows water to drain through it, and groundwater to rise and fill the river through it, depending on the position of the water table. It is also easily eroded, so the river's depth may be affected by it as well. Furthermore, flowing through an intensely urban area, the Colne is heavily affected by human activity, which may explain some of my outlying results. In addition, the variable weather at the end of august: alternate showers, downpours and sweltering sun, may well have had adverse effects on my data. Looking at the photos, I can see that the river gets wider and deeper as it flows downstream, because some of my narrowest and shallowest sites are 9 and 10, whereas site 1 is very wide and so deep you can't see the bottom. Looking at photos 1, 3 and 9, we can also see that they are murky, as mentioned above, which means there is sediment in suspension in the water which could affect the river's width and depth at that point. However, this sediment is not continuous: the river is clear at most of my other sites, so the lateral erosion is also not constant. Overall, it is obvious that there is a little increase in values from upstream to downstream of the section of river I studied, but a lot of fluctuations too. ...read more.

Conclusion

However, as previously mentioned, this is still just a snapshot in time, and the river conditions could vary greatly across that week/month/year, even if there was no drought or flood that week. All considered, I think I did just about the best investigation I could in the circumstances, but it could have been greatly improved with a lot more time, money and effort if I was a professional or had a professional need. Conclusion: In conclusion, the river seems so follow hypothesis 1, ("as the river flows downstream, it will get wider and deeper"), but not 2 ("as the river flows downstream, the rate of flow will increase") and 3 ("as the river flows downstream, the gradient of the river will get shallower"). It would be interesting to see whether the same results are found on a different river, or if other rivers support my hypotheses. In this investigation, I aimed to prove or disprove three hypotheses drawn from my background knowledge (refer to page 3). I wanted to investigate how the River Colne changes as it flows downstream. I have certainly completed the latter part: I have gained an insight to the Colne's treacherous nature and attained a general idea of how it changes as it flows downstream: it does not follow the theory I have learnt from my lessons, but its width, depth, velocity and volume of flow vary considerably in a very short stretch of river due to several factors. I have completed the first part of my aim too: I proved or disproved all of my hypotheses. In actual fact, I only proved one of them, but I found out that I would need to take readings over a longer time period and a larger sample to be sure of my conclusions, or to draw completely new conclusions and be sure of those. But really, I should study a different river, as the Colne's urban setting and interaction with the Grand Union Canal makes it a bad place to study. ...read more.

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