Geography investigation - The River Skirfare located in the Littondale region in the Yorkshire Dales National Park.

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Geography Module; River Studies

SECTION 1

Hypotheses;

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 ‘Hjulström 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’.

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.

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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 ...

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