The River Skirfare Essay Sample

The River Skirfare Pages
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Hypothesis 1;

‘Bedload will decrease in its size and angularity downstream’.

By this, I mean that the material being carried, eroded and transported by the river will be smaller and more rounded downstream, than the material upstream.

Hypothesis 2;

‘The efficiency of the river will increase as you look further downstream.’

This is where the river’s ability to carry and transport material is greater downstream, but not upstream. Hence, we can say that upstream, has a poorer efficiency, than that downstream.

Hypothesis 3;

‘The velocity of the river will increase further downstream.’

This would mean that the further down the river you travel the greater the surface speed of the river. Gradient will also be of great use as there will be an inverse relationship between the two variables, velocity and gradient. The further downstream, gradient will start to decrease. In other words the land around the river will be much more level downstream, but steeper upstream.

SECTION 2

Introduction;

This investigation sets out to prove or disprove three hypotheses. The hypotheses have been developed around the study of a river and hence, set out to focus on the processes and changes in the river downstream. To understand any possible changes or processes in as much detail as possible I have chosen three hypotheses that I think will help me achieve this best. These are stated above, but more concisely are, as follows;

* ‘Bedload will decrease in its size and angularity downstream’.

* ‘The efficiency of the river will increase as you look further downstream.’

* ‘The velocity of the river will increase further downstream.’

These I feel will give me the best possible understanding and evidence of the processes that are carried out in a river landform.

This investigation has taken place on two points on the River Skirfare. The River Skirfare is located in the Littondale region in the Yorkshire Dales National Park. The two locations which will be sampled for a range of data will be Arncliffe (Downstream) and Halton Gill (upstream). These can be seen in the area Littondale on Fig.2.1, and individually in Fig.2.2 and Fig.2.3 on the next page;

From this map of Littondale we can see the locations of both Halton Gill and Arncliffe. It also shows me many other factors that will affect the hypotheses. One of these factors is the relief of Littondale. If the relief is steep from Halton Gill to Arncliffe then this will have a profound effect on the velocity of the river, hence will be extremely useful when analysing the velocity as required by the third hypothesis. And as velocity has an interlinked relationship with capacity, the maximum amount of material that can be transported by a river at a given time, and competence, the river’s ability to carry a particle of a given size as bedload, then this means that it will also help in analysing the second hypothesis.

Fig.2.2. (above) gives a detailed diagram of Halton Gill. This is the upper course of the stream. Here we can see that the area is extremely steep north of the river, and shows a valley in which the river runs through.

Fig.2.3. (below) shows a diagram of the area surrounding Arncliffe. This area is built up a lot more, and is much flatter around the river. We can also see the increase in size of the river. This will have a significant impact on the capacity of the river, and the amount of friction that is occurring. It might also be able to give some sort of signal as to what type of transportation is taking place, whether it is saltation or traction.

What will be very prominent in this investigation is the links between the hypotheses. This has been mentioned before in scant detail, but will certainly prove to be very important, not only due to the frequency of the links but of the significance in understanding the river processes that are occurring in the River Skirfare. The links will be seen between the three hypotheses. The third hypothesis, ‘The velocity of the river will increase further downstream.’ provides the links between the hypotheses. For example, an increase in velocity downstream ensures that there is more erosion taking place downstream where the speed of the river becomes faster. This is because there is more energy in the river when there is a higher velocity. More energy means that processes such as attrition and abrasion can occur more regularly therefore, there is more erosion occurring. This would link into the first hypothesis, ‘Bedload will decrease in its size and angularity downstream’ as the more erosion that takes place will mean that there will be smaller and more rounded material where erosional features like attrition take place. And as erosion would increase downstream, due to the rise increase in velocity, bedload would decrease in size and angularity downstream. This is just one example of the links that will be found.

To understand this investigation in thorough detail it is important to understand both the erosional and transportation processes that occur within a river. These can be seen in diagrams on the next page. First though, is important to understand the wider fluvial processes within a river. These are, as already mentioned erosion and transportation, but also, not mentioned is deposition. These fluvial processes are all linked into one another, especially through factors like velocity and efficiency. Such factors are the basis of my investigation. All these processes will occur within a river. Erosion is the amount of erosion that occurs at one point in the river. Transportation is how much material the river is carrying or is capable of carrying. Deposition (sometimes referred to as sedimentation) refers to the amount material in the river that is deposited at any point. Along the river these will occur in varying quantities. The most accurate analysis of this relationship can be seen in the ‘Hjulstrm Curve’. It shows the relationship between the three processes, velocity and size of particles that lie in the river.

TRACTION Transportation Processes. SALTATION

SUSPENSION SOLUTION

ATTRITION Erosional Processes. HYDRAULIC ACTION

CORROSION/SOLUTION ABRASION

SECTION 3

Methodology;

To display the methods used to gain data for this investigation more clearly I will separate the three hypotheses and discuss the methods used to gain the data for each. What is important to mention is that on all of the hypotheses linear sampling was used for efficiency in time, but also to attain accurate results easier.

* ‘Bedload will decrease in its size and angularity downstream’.

Data Collected/ Method Used

Where?

When?

Why Was It Collected?

Strengths Of Method

Weaknesses And Improvements

Stone Chart- Measures Angularity of bedload.

26th March 2003

Two sections of river. One upstream (Halton Gill), the other downstream (Arncliffe), During the day, 11:00- 14:00

To collect data that will show the angularity of the material on the riverbed at two sections at the river. Any difference in angularity will help determining the hypothesis’ accuracy.

* Simple method of data extraction

* Not time consuming

* Easy to record

* Only takes a line of the riverbed- perhaps should take a cross-section.

Ruler measuring material- gives an accurate size of the material at the two locations, upstream and downstream.

26th March 2003

Two sections of river. One upstream, the other downstream, During the day, 11:00- 14:00

Taken at the same time as the angularity measurements.

Collected because it adds greatly to the data needed to prove or disprove the hypothesis. Will show the differences (if any) in the size of material at both upstream and downstream.

* Taken at the same time as that of the angularity measurements

* Gives a cross-section of material size upstream and downstream

* Inaccurate, only gives the longest length of the material. – Perhaps the surface area would be more accurate in determining its size.

As we can see from the table above the data that can be collected for the first hypothesis is rather limited and certainly not very technical to attain. This though, is perhaps the beauty of it, they are very simple methods of data collection, and hence, are very unlikely to go wrong. For example, the stone chart. A stone chart is made consisting of diagrams of stones, all with varying angularity, from very angular to very rounded. Once at the river Skirfare the aim is to take a cross-section of material at Halton Gill and Arncliffe. With this material we compare it to that on the chart and make a judgement to which angularity diagram it is most like. The stone chart can be seen on the next page. The measuring of the material is just as simple, if not more so. A ruler and recording equipment is all that is needed. Material is measured then the results are recorded. The cross-sections of material at Halton Gill and Arncliffe are simply taken and measured. Once this has been done an average is then worked out at each location and then it becomes much easier to compare the material sizes between Halton Gill and Arncliffe.

The reasons for this set of data being collected over any other are that most importantly it provides an accurate method of testing the hypothesis. It provides the most obvious and most accurate comparison of the material size and angularity between Halton Gill and Arncliffe. Because it is easy to collect and reliable is another reason as to why this data is being collected. These are major advantages, especially when there is only a set amount of time to collect data. The only possible criticisms with these methods is that firstly, to measure size of material a possible better way to measure it is by taking the surface area. This would be much more accurate, but more time consuming and unpractical when there is a limited amount of time to collect data. The other quarrel is that to get a better impression of the size of material at each location perhaps rather than a cross-section (i.e. a line in the riverbed) perhaps a square area would be more accurate.

* ‘The efficiency of the river will increase as you look further downstream.’

Data Collected/ Method Used

Where?

When?

Why Was It Collected?

Strengths Of Method

Weaknesses And Improvements

Cross-sectional Area.

26th March 2003

Two sections of river. One upstream (Halton Gill), the other downstream (Arncliffe), During the day, 11:00- 14:00

Will help give an impression of the capacity of the river.

Leads to extraction of information such as; those below. Also enables me to calculate discharge.

Only one method of retaining the data. This can be very time consuming.

Wetted Perimeter.

26th March 2003

Two sections of river. One upstream (Halton Gill), the other downstream (Arncliffe), During the day, 11:00- 14:00

Will show how much the river is affected by the forces of friction against the banks and bed.

Enables me to work out the hydraulic radius. Calculates the amount of friction on the river.

Taken from the cross-sectional area. So the same weaknesses apply. See above.

Hydraulic Radius.

26th March 2003

Two sections of river. One upstream (Halton Gill), the other downstream (Arncliffe), During the day, 11:00- 14:00

Will measure directly how efficient the river is. It is a measure of efficiently. Will help directly with the hypothesis.

It is a direct measure of efficiency. Will give the most accurate figure on efficiency.

Little weaknesses. Is just simply secondary data, and a calculation. Little weakness in mathematics!

Chemical Test.

26th March 2003

Two sections of river. One upstream (Halton Gill), the other downstream (Arncliffe), During the day, 11:00- 14:00

Shows how much material is in a sample of river water.

Shows directly the amount of material in the river water.

Only a small sample. Of little importance.

We can see that from the table above that the second hypothesis requires a great deal more data. But not only this, it also requires more understanding of the processes as we shall see later on, and also more understanding of data collecting. The cross-sectional area data is provided by placing a measuring tape from one end of the river bank to the other across the river. Then every 50cm from bank to bank the measurement between bank-full level and the riverbed is taken. This from one side of the river to the other enables us to plot a graph which in turn gives the cross-section of the river. This is a rather simple method, but yet time consuming, needing only two meter rulers and a long measuring tape with somebody recording the results from the bank. It is also integral to this hypothesis as much of the other data needed comes from this primary research.

The wetted perimeter can be taken from the plotted cross-sectional graph data; hence, it is secondary data. It is done by looking at the graph and measuring the amount of river bank and bed that is being subjected to the river. This can be done by following the line with a piece of string. It shows the amount of friction that the river is being subjected to. This is because the river bank and bed cause friction between them and the river water. This method is very solid and reliable as there are few factors that can go wrong. Also, another method that is reliable but more importantly very integral to this hypothesis is the hydraulic radius. This is a mathematical equation that gives a calculation of the efficiency of the river. It is the following equation;

Cross-sectional Area A Hydraulic

Wetted perimeter P Radius

This gives a direct measure of the efficiency of the river at both locations. Therefore it is of great importance. Especially as it has few weaknesses or things that could be improved upon, as shown by the table.

The last piece of data is the chemical testing. This is primary evidence for the investigation. Despite this though, it does not necessarily hold a great deal of importance. All that was needed is a conical flask and some tablets that measure the amount of material in suspension or solution in the river water. River water is collected in the flask and then the tablets are added. To show that material is being suspended or held in solution in the river tablets are added until the river water in the flask changes in colour. Depending on how many are added, this shows how much CaCO3 is in the river water. CaCO3 is calcium carbonate, also known as chalk. This then gives an impression of the material being transported by the river. This though, is not that beneficial. This is because it does not show any other material in the river other than CaCO3. Plus it is just a small sample that is taken at each location. It is not adequate enough to conduct an investigation on.

* ‘The velocity of the river will increase further downstream.’

Data Collected/ Method Used

Where?

When?

Why Was It Collected?

Strengths Of Method

Weaknesses And Improvements

Flow Vane.

26th March 2003

Two sections of river. One upstream (Halton Gill), the other downstream (Arncliffe), During the day, 11:00- 14:00

Gives the most accurate data on the velocity of the river.

Will hopefully support the dog biscuits data.

Electronic equipment. Designed to measure the velocity of the river

Could be done all across the river rather than just one location. This would give a better average velocity of the river.

‘Dog Biscuits’.

(Distance / time =Speed.)

26th March 2003

Two sections of river. One upstream (Halton Gill), the other downstream (Arncliffe), During the day, 11:00- 14:00

To collect data on the velocity of the river.

This is the main data for the velocity of the river Skirfare.

Easiest method of measuring velocity of the river. Lots of results are available at both locations.

Do not travel in a straight line.

Can get caught up in the bank, hence, can be time consuming.

Despite this being a rather simple hypothesis to test, there are two methods that can be used to collect the necessary data that are rather time consuming. The first method the flow vane is taken using electronic equipment. This means that reliable and accurate measure of the velocity of the river can be taken. Although time was restricted and so was the access to the flow vane. Therefore, when it was used only one point in each location could be taken.

This meant that it was unable to get a good set of average results. Still, those that were taken were accurate and will be able to support the, ‘Dog Biscuit’ data. This was a very simple method of data collection. Dog biscuits were thrown into the river and timed over a particular distance. The, ‘Time, Distance, Speed’, Equation could then be used to work out the velocity of the river. This would be measured in meters per second. This could be done numerous times and so lots of results would give a strong average. The only problem is that the dog biscuits can sometimes get caught up in the banks of the river of overlaying rocks in the river. Lots of results would make up for this fault though.

These two methods complement each other and will provide very useful data for analysis in trying to contend with the hypothesis.

SECTION 4

Data Presentation;

In this section I shall display all the data that was collected from the fieldwork at the locations Halton Gill and Arncliffe. The data that will be shown is that that is described in the methodology in the previous section. As seen in the methodology data has been collected that will help test all three of my hypotheses. The next section is where the data will be analysed; this is what will help in testing the hypotheses.

Again, for purposes of presentation quality the data will be split based on which hypothesis they refer to.

* ‘Bedload will decrease in its size and angularity downstream’.

Firstly I shall display the data concerning the size and shape of the material at each location on the river Skirfare in tables as it was taken at the locations.

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