1. IntroductionHypothesisWe know every river starts its journey from its source. In the upper course of the river, the channel is at a high above its base level i.e. its mouth. Thus the gradient is high. Due to the height, it has a lot of potential energy. So it uses this energy to reach its base level. So the process mainly at work is vertical erosion. Further it has got a lot of interlocking spurs. There is less lateral erosion taking place. So the bed load is composed of bigger rock particles with irregular size. When it reaches the middle course, the river is quite near to its base level.
So it uses its surplus energy to erode sideways. Hence the processes like abrasion, attrition, hydraulic action smoothens the rough edges making the shape circular. The lateral erosion and transportation may give rise to features like meanders and oxbow lakes. When it reaches the lower course, it is almost near to its base level. So it doesn’t have sufficient energy to erode or transport bed load. So the main process at work is deposition leading to features like floodplain and deltas. Expected outcomes
River pang is one of the tributaries of the River Thames. Since the river doesn’t flow into a sea it should have a confluence not a mouth. So it doesn’t have a delta in its lower course.it has a confluence at village of Pangbourne in Berkshire. Also as it’s just a tributary, the features like interlocking spurs, waterfall, meanders, oxbow lakes, deltas and floodplain is less likely to be seen. However basic features about gradient, bed load size, velocity will have changes as we move down the stream. The gradient should decrease. Also the bed load size should decrease due to continued (vertical + lateral) erosion. The velocity should increase as well. Location
It is located in the West Berkshire. It runs for approx. 23 kms from its source at Compton to its confluence with Thames in the village of Pangbourne. The source is not stationary it differs as per rainfall patterns. At first, as shown in the map above, it flows south from Compton through the villages of Hampstead Norris and Frilsham before turning east to flow through the village of Bucklebury, Stanford Dingley and Bradfield.
To the east of Bradfield, the Pang is joined by River Bourne and turns to North to flow through the village of Tidmarsh and Pangbourne. Eventually it enters the Thames between Whitchurch Lock and Whitchurch Bridge. It flows to Thames at Pangbourne on the border of AONB. Site 1- Compton
Site 3-BuckleburySite 4-Moor copseSite 5-TidmarshSite 6-Pangbourne
2. MethodDescription of fieldwork techniquesWe went to river Pang on 24th June Friday. The aim was to study the hydrological characteristics and how it changed downstream. Many measurements were taken with channel at different sampling points. We measured the following things: * Wetted perimeter
It is the region of river bed that is in contact with the water. We used a tape measure and took it along the channel by moving along with it. * Channel depthFor this we first put the ranging poles and then measured it with tape. * GradientFor this we required the ranging poles and the clinometer. After adjusting the ranging poles in a straight line we used the clinometer to find the gradient. * Velocity
* Bed load sizeFor this we picked up random of 10 stones from different parts of each site and took an average of them. Also we analysed the shapes of the bed load.
Problems encounteredThe data we had for wetted perimeter was a crude one. This was because the tape needed to be stretched along the river bed under water which was quite difficult. However the data for bed load was quite accurate as we repeated the expt. and took the average.
3. Data presentation and analysis
From the graph, the river slowly increased its velocity and the width as it travelled downstream. When the river reaches the middle course it is quite near to the base level. So it uses the surplus energy to erode the sides. Hence meanders are seen as in moor copse. So due to lateral erosion the channel increases its width. In the middle course the size of load becomes smaller due to repeated abrasion and attrition. Hence the friction decreases which increases the flow per second of the river. However there was an exception in the last site in pang Bourne.
The width of the river was smaller because of channelization. Pang Bourne is a residential area. So levees are put up in the sides as a flood protection technique. There were changing features seen along the channel. The river at Compton was very narrow. However there were no interlocking spurs or v shaped valley which is to be seen in the source.
This area had got a bit of agriculture done and few houses. It was surrounded by hills though. Human intervention was not seen because of the absence of road infrastructure. When we went to buckle bury the place was a residential area. It has a parish church as well. In some places the farmers had installed artificial bank called levees so as to protect the crops from being flooded. Meanders began to show up a bit in moor copse which is a part of SSSI. It became dominant in Tidmarsh. However no oxbow lakes could be seen. In it we could see the river cliff and slip off slope.
The area was however covered with trees and was protected from human intervention as it is a part of SSSI. When we reached pang Bourne we saw a confluence instead of a mouth in the river Thames. The velocity of river pang met with the Thames and hence created a deep place in the river. Also as it was only a small section of the river investigated within Berkshire we didn’t see any deltas. Overall judging we could see some of the important features of the river in the trip.
4. Evaluation and conclusionSuccess of the investigation and comment in the hypothesis Our main intension of visiting River Pang was to see the changing features along a river channel. We were supposed to see features like waterfall, gorge, interlocking spurs, v-shaped valley in the upper course. In contrast to this we just figured out the source and saw the velocity, gradient, and the bed load. Despite this the data we received were quite reliable. So I think our experiment did go quite well.
Similarly we were to see meanders and oxbow lakes in middle course. In this we did see the meanders in moor copse. We also found changes in the velocity, and wetted perimeter. This confirmed our theoretical knowledge. In the similar pattern we were expecting to see delta, levees and floodplain in the lower course. We did see levees in Pang Bourne as a flood protection technique as the velocity of river increases downstream. We also found changes in the measurement of velocity. So our experiment was reliable. Limitations
However there was a bit of problem in the measurement of gradient as the result came out to be 0 every time. This result was definitely anomalous. This may probably be either due to problem in the instrument or due to wrong way of measurement. Also in site 6 we could only take reading of velocity once instead of thrice due to lack of time. So we should have managed the time in the beginning or divided the time instead. Extensions
As an extension I think we should have chosen to do our experiment in the main river instead of its tributary. As we had our experiments done in a tributary we actually missed important features of the river as explained in the above paragraphs. Also as said earlier we had to manage our time as well.