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How Do River Characteristics Vary Downstream?

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Introduction

How Do River Characteristics Vary Downstream? Introduction On Wednesday 2nd October 2002 a river study was undertaken, investigating how the characteristics of a typical river vary downstream. The river to be studied was the River Lyd; this small river's source is at the junction of the A4136 and the B4234 near Upper Lybrook, Forest of Dean. The Lyd then meanders its way down a small valley towards Lydney, flowing parallel to the now disused Dean Forest Railway. The Lyd then flows into the man-made harbour of Lydney, situated on the Gloucestershire flood plains and then finally confluences with the River Severn, the course of the River Lyd is shown in Fig 1.1. Fig 1.1 The investigation took place on mild day subsequent to a long period of dry weather, this inevitably meaning the water table was fairly low and so decreasing the volume of water within the river, the Forest of Dean is an area of dense woodland. The aim of the study is to prove or disprove the three hypotheses: 1. Discharge will increase further downstream. 2. Cross-Sectional Area will increase further downstream. 3. The larger the wetted perimeter, the greater the discharge. Data Collection The aim of the study was to either prove or disprove the hypotheses concerning the varying characteristics downstream, this was achieved by collecting ...read more.

Middle

i.e. there is virtually no relationship between the two variables and a high probability that the coefficient has occurred by chance. In conclusion, hypothesis two cannot be accepted. i.e. cross sectional area does not increase further downstream. Geographical theories suggest that the hypothesis should be accepted, due to several reasons. Firstly, both the catchment area input (through processes such as surface runoff) and tributary input increases further downstream, the channel is eroded and made larger so to accommodate for the increased volume of water in the channel. The reasons for the results not corresponding with geographical theories, as well as problems and solutions encountered, for scatterplots showing site number against both discharge and cross sectional area, are in the following paragraph. Firstly, the stretch of the river Lyd that the study was carried out did not contain any confluences with tributaries. As mentioned above, the input from tributaries is a main contribution to an increase in discharge downstream, without any tributaries in the data collection zone, the volume of the river or the discharge will not increase. The lack of tributaries affect the cross sectional area as well, as the more water in the channel the larger the cross sectional area will be. ...read more.

Conclusion

Due to the fault in the flowmeter, the second method had to be used to measure the velocity; this method measures the velocity of the surface as the 'ping pong' ball floats in water. However, the flowmeter measures the velocity just below the surface and so the results are not consistent in the respect that the same part of the river was not measured at each site. This affects hypothesis one as discharge is calculated using the velocity of the river. Solution: This problem was unavoidable as it was the fault and the unreliability of the equipment. Problem: The title of the investigation is fairly general and extensive in respect to the areas in which the study has to cover, although only three hypotheses were chosen there several other hypothesis options available. Solution: Create another title such as: 'Investigate changes in river channel morphology' Problem: This investigation demonstrates the changes of river characteristics in only one way, this being hypothesis three - the larger the wetted perimeter, the greater the discharge. Solution: Investigate different hypotheses such as, 'the greater the hydraulic radius, the greater the discharge.' On this basis, it is difficult to suggest that this study has achieved the aim of its title i.e. 'How do river characteristics vary downstream?' However, this may be due to the inappropriate methods of data collection, explained in the first problem. ...read more.

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