Course Work Example: The Chess River

2021-07-08 04:43:52
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George Washington University
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Course work
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The River Chess is known as a chalk stream due to the facts that its source is ground water held in the chalk of the Chiltern Hills. The River rises from north of Chesham in the Chiltern Hills and flows via Buckinghamshire as well as Hertfordshire and at long last joins River Colne in Rickmansworth. The River gets it water from springs that form after the water table reaches ground level. The water is rich in mineral and emerges from the ground at a temperature of 100C ("River Chess Association - The River Chess," 2017). The chalk streams have a unique character and provide a safe environment for wildlife to thrive making it a great place to visit to experience the nature. For instance, water voles are one of the United Kingdoms endangered species are found in this river- also in the urban areas of Chesham. The data for the research was taken from two different sites Chesmam moor and Sarratt Moor

 

Figure 1: showing the map of Chess River

The Chess catchment occupies an area of 105 sq.km and the average rainfall at the catchment is about 768 mm per annum (Harrison, 2017). The river flows via upper and middle chalk outcrops that in some sections are overlain with glacial gravel and clay-with-flints deposits. Small sections of reed beds occur to the northern part of the river at Chorleywood. The river is mainly a clear and fast flowing river that flows over gravel beds. The major settlements are Chorleywood, Chesham, and Rickmansworth. The river is approximately 17.9 km in length, has a 60 m fall, and it is normally chalked stream. It has one tributary which is Chalk Stream with a length of 1.7 km ("River Chess Association - The River Chess," 2017). The Old River Chess was the initial course of the Chess prior the construction of lakes at Latimer Park. The purpose of this paper is to analysis reasons why discharge increases downstream at the Chess River. Also the paper will prove that width increases downstream. Also, the paper looks at some evidence that the gradient will increase as one move from the source to mouth.

According to Bradshaw Model, the Chess River can be represented by the diagram shown below:

Figure 2 showing how discharge of the river

In the diagram, when the river is at the upper course is on the right and when it descends to its lower course. First, river discharge is when it reaches its utmost peak of capacity of water. Bradshaw Model asserts that a river discharges it water to lower course. The river discharges its water due to increase in water capacity as a result of surface runoff, or rainfall ("Changing Channel characteristics," 2017). Second, the occupied channel width is the distance covered by water from one end of the other. During the rainy season, the width is longer while during a dry season, the width is shorter. The river gets wider at the lower course as the water increases downwards from various sources. Third, channel depth is defined as the height from the surface of the water to the bed of the river. The depth decreases down the river as some water increases from tributaries. Fourth, average velocity is defined as the speed of the river as it flows down the course. Bradshaw Model asserts that speed of a stream increases slowly downstream. Three main factors influence the velocity of the river:

Gradient influence the flow of the river as the steeper gradient increases the velocity of water flows.

Shape of channel also affects the velocity of the river

Channel roughness affected the velocity in that the rougher the channel, the slower the water flows. When there is a big boulder in the river, the water moves around it slowing the flow, and in case the channel is smooth the river will flow a bit faster. Also, velocity is different between asymmetric and symmetric channels, as illustrated in the diagram below:

Figure 3 showing uniform channel velocity

Figure 4 showing asymmetric channel velocity

Load quantity is affected by the amount of charge that the water contains. An increase in speed and discharge capacity as the depth of the rivers increase may contain high speed and more energy to carry the heavy load down the river. According to Bradshaw theory, the amount of load increases down the river due to the rise in depth and velocity of the river. On the issues of load particles- the size of the particles will decrease downstream due to various types of attrition and corrosion ("Changing Channel characteristics," 2017). Corrosion is when the load carried by the river is rubbed against the banks leading to wear as result of sandpaper effect. Attrition refers to when stones carried by the river hit one another resulting to smaller rounded pebbles. Ultimately, the stones are decreased to a small size such as those of silt particles.

The stream order is calculated from source to mouth, to get an indication of shape and size of the river channel. This is calculated as follows:

Stream order 1: streams have no tributaries supplying them with water- the river begins at original spring up in the source

Stream order 2: streams occur where two stream order one rivers come together at a confluence

Stream order 3: streams occur where two stream order two rivers join at a confluence- and the stream order goes on like this.

A cross sectional area shows the meters squared- the area of the river that can be taken a slice through from bank to bank to prevent water flow. It is calculated in 2 ways- multiplying the average depth with the width to get an approximate measurement. When accurate depth measurement is known, the cross section can be plotted on paper using appropriate scale to assist in calculating a more accurate cross sectional area. The cross sectional area increases downstream as water enters into the river from the major tributary rivers. A wetted perimeter refers to the measure of the amount of water that comes into contact with the banks and bed of a river (Firas, 2017). This also increases down the river as water increases due to the tributaries flowing into the river. Hydraulic radius refers to the measure of the efficiency of the channel in transporting sediment and water. According to Bradshaw model, this measure should increase as the stream increases in size. The power also increases hence the channel bed should be less turbulent/rough due to erosion effects. Hydraulic Radius is computed by dividing CSA by wetted perimeter, and this can be represented by the diagram below:

Figure 5 showing how to measure hydraulic radius

Channel bed roughness is measured using Mannings Roughness coefficient.

Part B

We conducted our field study during the summer season, and the trip took us three days from 15th- 18th July. Most of my colleagues could not outstand the night cold and the danger of the wild animals hence we only collected our data during day time. We took the data from 2 different sites along the Chess River. The sites were Chesmam moor and Sarratt Moor. A measuring tape was used to measure the width of the river because it is portable and easy to use. We were a group of ten people, but it took two folks to measure as the measuring tape was being placed at the edges of the bank and its reading taken (Firas, 2017). The other group members were jotting down the readings in meters. After measuring the width, we started measuring depth using a ridged meter ruler. According to Bradshaw model, we predicted that the depth would increase down the stream as the river gets deeper from the source. As a way of preventing the water from building up, we used the narrow edge of the ruler and stood adjacent to the ruler to avoid affecting the results.

Site name Distance from source (km)

1.Queens Head 10

2.Meades Water Gardens 13

3.Blackwell Farm 16

4. Latimer Bridge 19

5. Scotsbridge 22

Figure 6 showing the sites where measurements were taken

We measured of the wetted using measuring tape by spreading it along the width of river Chess, and we left it lacking. One of our group members then walked along the measuring tape and told us the reading of the tape to be recorded. We ensured that the readings were not altered by working upstream from left to the right bank. We used an impeller and a hydro prop to measure the velocity of river Chess. We placed the impeller onto the hydro prop and ensured that it did not touch the bed which would affect our results. As a group of two people was busy placing the impeller on the river, two others were ready to start a stopwatch immediately after the impeller was placed on water. The rest of the group took the reading the time taken for the impeller to get to a two third of the depth.

Figure 7 when measuring the velocity of Chess River

The type of data that was used is primary as we had to collect it directly from the field by measuring as required. Quantitative research is used because it usually tests the hypothesis and this means that it would help in proving that discharge increases downstream. Structured data collection was used where we collected data at an interval of 3 km a long Chess River. The data is collected at a specific point to avoid the result being influenced by researchers. We visited the site and obtained the relevant data from River Chess. The reason why we chose River Chess is that it is one of the major rivers in the United Kingdom. It is a home of wildlife that attracts tourist earning the substantial country amount of revenue.

Data collected The hypothesis that will be used to prove or disapprove Equipment used How the data was collected and strength

The river width increases as the distance increases downstream Three people

Tape measure Two to three people were needed to come up data for the measurement,

Two individual stood on the two sides of the river with the third individual participating in the process of recording the figures. The last person managed the process of data recording by making sure that wrong data was prevented The data was primarily obtained as a firsthand data by making sure that the right tape measure was used

Additionally, the tape measure was very simple to use

Additionally, the one who was recording data did it straight away to avoid recording of wrong data.

Hardly, no chance of human error since the whole process was straight forward.

Since we used the same tape at every site which meant was fair test

Part C

Site 1

Distance from source Width Average velocity Average depth Cross-sectional area Discharge

10km 120 cm 1.5m/s 1.82 cm 172 cm2 245m3/s

At site1 the velocity is low due to factors such as small depth and colossal vegetation. The current water discharge of 245m3/s increases downstream the water flows faster outside the meander and a bit slower along the inside of the meander.

Site 3

Distance from source Width Average velocity Average depth Cross-sectional area Discharge

16km 405 cm 2m/s 212cm 256cm2 305m3/s

The above velocity supports the hypothesis that velocity increases downstream because the width has increased significantly while the discharge has increased by about 100m3/s. The massive increase in width is the major reason for the increase in water discharge.

Site 4

Distance from source Width Average velocity Average depth Cross-sectional area Discharge

19km 350cm 1.2m/s 18.62cm 5012cm2 5028m3/s

At this point, the average velocity is high at midstream because there is less friction resulting from riverbanks. The water is not obstructed meaning it will move faster.

Conclusion

As reported by Bradshaw style, the river load tends to increase the downstream as a result of the velocity and depth of the river. On the hand, the loads particles also play a major role since the size of the particle existing in the river tend to decrease the downstream movement gradually. The reason is resulted by the different nature of attrition and corro...

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