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# How do river characteristics vary downstream?

Extracts from this document...

Introduction

How do river characteristics vary downstream? To investigate how river characteristics vary downstream, a study took place over 1-3rd October '03, on the River Lyd, concentrating on the stretch that flows through Parkend in the Forest Of Dean. The aim of the exercise was to look mainly at both the Velocity and Cross Sectional Area, comparing and studying the data, but also Hydraulic radius, wetted perimeter and the physical geographical features of the river, looking for any significant differences as the river flowed downstream. Above: [fig.1] Map showing River Lyd & investigation sites To begin the investigation, it was decided that information from 12 sites would to be recorded and these sites were to be set 100m apart and each site would cover a distance of 10m. Equipment used included: * 3 range poles - steepness of riverbed and depth * Stop watch - timing pooh stick * Clinometer - Angle of slope of the riverbed * Pooh stick / Orange - calculating velocity * Tape measure - cross sectional area Method 1. Insert the range poles across the riverbed at equal distances (left, centre and right), measure the depth at each and calculate an average. ...read more.

Middle

The graph [fig.2] also shows very little correlation with some huge anomalies at depths of 20.3 upstream and 2.7 downstream, where opposites to these results would be expected. The main reason for this random data would be the fact that rain hadn't fallen in the area for months before hand, which wouldn't reflect fairly the true flow & depth of the river. Usually in October a lot of rainfall would be expected & the river should be in peak flow. Also the section of the River Lyd investigated [fig.1] was only in the middle course & therefore wouldn't follow the general geographical theory. Reasons for the anomalies may have been a large area of deposition or a pool created from fast flowing water. Hypothesis 2 'The velocity of the river will increase as width of the river increases'. Spearman's rank correlation coefficient: Velocity rank width rank D D 0.71 3 250 8= 5 25 0.95 1 330 6 5 25 0.66 4 295 7 3 9 0.24 10 200 11 1 1 0.22 11 230 10 -1 1 0.54 7 180 12 5 25 0.10 12 350 5 -7 49 0.94 2 420 3 1 1 0.65 5 550 2 -3 9 0.38 9 400 4 -5 25 0.41 8 250 8= 0 0 0.55 6 650 1 -5 25 Total: 195 1. ...read more.

Conclusion

Another major problem was the fact that there had been little to no rain in the area for months before hand, owing to the extremely hot summer, which meant the flow was smaller & the results may not have reflected the real data. Changes Given the chance to repeat this experiment, certain aspects of the investigation would need to be altered or changed. Choosing a larger river would be a main point, as this could give more typical, expected results. It would also have to be done in a season when the rain would have more effect on the river or in two seasons, summer & winter to compare the two, and see if this has effect on the velocity / hydraulic radius. More sites should be included and cover a larger stretch [nearer / further from the source] as this would produce a wider set of results and knowledge in which to accept or reject the hypothesis. Conclusion This study was designed to investigate how characteristics of the River Lyd changed downstream. The three hypotheses tested were rejected & therefore this section of river does not fit the studied models and geographical theories. ...read more.

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