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

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.

This is a preview of the whole essay

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.’

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.’

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.

Tables of Results

These tables show the primary data that was taken from the locations Halton Gill and Arncliffe at the river Skirfare. It obvious to see that the larger material lies at Halton Gill, the location upstream on the river Skirfare. This is seen from the averages; Halton Gill’s long axis is 116.625mm, and its short 53.75mm. When compared to Arncliffe further downstream; its long axis being 73.75mm and its short 50mm. However this will be seen more clearly from the following graphs, taken from the table.

Presentation of Data

By looking at the averages of both size and shape of material at Halton Gill and Arncliffe this would be simple method and will be a good place to start in determining the hypothesis; ‘Bedload will decrease in its size and angularity downstream’.

This first graph simply shows the average size of material at both locations on the river Skirfare. It shows that the materials in both axes are larger in Halton Gill, which is upstream on the river. Although, while there is a very large gap in the long axis between the locations, the gap between the short axis is very little. Indeed, it is only a gap of 3.75mm. The cause of this perhaps is the anomaly in the results at Arncliffe, where there is a very large result, 120mm, amongst other results that go no higher than 70mm. This will be further discussed in the next section though.

The previous two graphs show the size of the material at each location in a lot more detail. They show the exact size of each stone that was recorded along the profile of the river Skirfare both upstream and downstream. To explain this more clearly; if we look at the material in the river at Arncliffe for example, in particular the material 600m away from the bank. The material used for the reading of the long axis is the same used for that of the short axis. This means that the same stone is used to collect both the short and long axis at each position in the river. These graphs also show the average size. This is all that is required really but the extra detail gives me an extra insight and may help in explaining any anomalies further on.

Now there is the other side of this hypothesis-the shape of the material in the river Skirfare will become more rounded downstream. This data cannot possibly have been collected in raw data such as numerical figures. Instead, it was as mentioned collected purely on the basis of observation and then constructing an opinion on the materials angularity. This makes it a little more difficult to display, especially as the results are either; angular, sub-angular, sub-rounded, rounded or well rounded. This can be seen in the stone chart shown earlier in this investigation. To get a round this problem I have assigned each measurement of angularity with a number, from 1 to 5. The most angular (‘Angular’ on the stone chart) being assigned to the number 1. The least angular (‘Well-Rounded’ on the stone chart) being assigned to the number 5. This can be seen in the table below more clearly;

From this it is possible to work out an average in the angularity of the material at the locations Halton Gill and Arncliffe. This can be seen in the following tables and graphs;

These tables show the result of the method of assigning numbers to the angularity scales. These can now be put into graphs. I have chosen to represent the data into ‘Radar’ graphs. This is because they make the data easy to read.

We can see from the data that the angularity of the material at Halton Gill is much more angular than that at Arncliffe. This would mean that the material at Arncliffe is more rounded. The fact that the material at Halton Gill only twice goes above two on the ‘Angularity Scale’ against the material at Arncliffe reaching as low as two only twice shows this clearly. What also adds’ to the evidence are the averages on the graphs. Arncliffe has an average of 3 which is more rounded than Halton Gill’s average of 2. This though, is less convincing than the previous statement.

The evidence displayed rounds up all the data available to draw an analysis as to how it helps prove this hypothesis. This will be done in the next section. A summary of this data though is that the material is larger and more angular at Halton Gill than that at Arncliffe.

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

The data needed to make a conclusion was taken at the two locations. This is then taken and shown in such a way that it will help bring a valid conclusion to this hypothesis. The tables containing this primary data can be seen below.

Tables of Results

These previous two tables show the most important information for this hypothesis. This data is that of the cross profile of both Arncliffe and Halton Gill riverbeds on the River Skirfare. From the methodology we can see that much of the information to analyse this hypothesis comes from this primary data. What they actually show is a cross-section of the riverbeds of the River Skirfare at Arncliffe and Halton Gill. At every 50cm the measurement between bankfull and the riverbed was taken. When the data is recorded and then plotted on a line graph it shows a profile of the riverbed and all its dimensions. These results have been plotted by hand and can be found attached to this investigation entitled, ‘Cross-section Of The River Skirfare At Halton Gill.’, ‘Cross-section Of The River Skirfare At Arncliffe.’, And, ‘Cross-section Of The River Skirfare At Halton Gill And Arncliffe’. The first two to be mentioned are individual graphs of the two locations. The last to be mentioned sees both locations being plotted on the same graph. This is so that it is easier to come across any similarities or differences.

As mentioned earlier from the cross sectional data it is possible to extract additional data to help determine each locations efficiency. One such form of data is the wetted perimeter. This is extremely useful because then we can measure the forces of friction upon the river. It is all the water in the river that touches the riverbanks and bed. Then from this the hydraulic radius can be calculated. This is a mathematical ratio, and gives a direct measure of efficiency. This has been mentioned before in more detail in the methodology.

The above graph shows the cross-sections of the River Skirfare at Arncliffe and Halton Gill.

This section is very much inter-linked into one another due to the equation that gives us the hydraulic radius. This is the wetted perimeter and the cross-sectional area. For the purpose of this investigation it is best that the cross-sectional area and the hydraulic radius are based on quite adequate averages of the data that has been collected. This is because it not within these capabilities to base it on detailed data. The wetted perimeter though will be done very accurately using the hand drawn graphs and measuring the lines. The results from this can be seen below. This will hopefully give an insight in to the efficiency of the river at both locations being studied.

Wetted Perimeter

Halton Gill

Total line graph length= 26cm.

Scale; 1cm: 125cm

Total riverbank and bed length= 26cm x 125cm

=3250cm.

This value takes into account the part of the banks that were not covered by the river. The river was at a level of 54cm below bankfull at the day of the investigation. Hence these can be taken away from this figure

Right side of the bank that was not submerged; (5cm x 125cm) 625cm

Left side of the bank that was not submerged; (4cm x 125cm) 500cm

Total; 1025cm

Wetted Perimeter;

Total riverbank and bed length – Riverbank not submerged

3250cm – 1025cm= 2495cm

Arncliffe

Total line graph length= 58cm.

Scale; 1cm: 125cm

Total Riverbank and bed length= 58cm x 125cm

=7250cm.

Like the Halton Gill calculations this does not take into account the part of the banks that were not covered by the river. The river at this location was 84cm below bankfull on the day of this investigation. I shall calculate the length of the area uncovered to determine the wetted perimeter;

Right side of the bank that was not submerged; (7cm x 125cm) 875cm

Left side of the bank that was not submerged; (8cm x 125cm) 1000cm

Total; 1825cm

Wetted Perimeter;

Total riverbank and bed length – Riverbank not submerged

7250cm – 1825cm=5425cm

The wetted perimeter for both locations can now be displayed in a table and stacked graph, as follows;

This data shows how much friction is placed upon the river at the different locations. It will be of great use in determining the rivers efficiency at the relative locations.

The next part of the data is the hydraulic radius. It is one of the most effective methods in evaluating this hypothesis. This is because it gives a direct measure of the efficiency of a river. As shown before, it is a simple equation using the cross-sectional area and the wetted perimeter at any one point in the river, as follows;

For the benefit of this investigation the wetted perimeter attained earlier will not be used. Instead a new method will be used to attain an average wetted perimeter and an average cross-sectional area. This will provide a more reliable result in concern to the hydraulic radius. It will also provide a more rounded number making an analysis of this section much more credible.

To attain the new average wetted perimeter and cross-sectional area, the average depth below the river level will be attained. This will give the new wetted perimeter from which the cross-sectional area can be worked out.

Halton Gill;

The following table is taken from the attached appendix graphs, entitled, ‘Distance between River Skirfare Surface to Riverbed at Halton Gill’. (Graph 2. b)

This enables the following diagram to be drawn of the River Skirfare at Halton Gill;

Using the diagram the wetted perimeter and the cross-sectional area can now be worked out, hence so too can the hydraulic radius.

Wetted Perimeter; 21cm+ 21cm+ 750cm= 792cm

Cross-sectional Area; 21cm x 750cm= 15,750

Hydraulic Radius; 15,750cm =20

792cm

Arncliffe;

The table below is taken from the graph, ‘Distance between River Skirfare Surface to Riverbed at Arncliffe’. (Graph 1. b)

This table can produce the diagram of the River Skirfare at Arncliffe. This can be seen below;

Wetted Perimeter; 2000cm+ 53cm+ 53cm= 2106cm

Cross-Sectional Area; 2000cm x 53cm= 106,000cm

Hydraulic Radius; 106,000cm = 50

2106cm

Now that the calculations have been made concerning the hydraulic radius they can be placed in a graph to show the difference between the two.

The hydraulic radius is essentially a measure of how well a river overcomes the forces of friction placed upon it, and therefore, how efficient it is. The above graph shows that the hydraulic radius at Arncliffe is more than twice the amount than at Halton Gill. This would certainly show that the river is more efficient downstream at Arncliffe, with a massive hydraulic radius value of 50. The Halton Gill value is also quite high (20), but it is still far behind Arncliffe.

There will be many contributing factors to this result and they can be found in the next section of this investigation under analysis. This result is of great importance as it is the integral part of this particular hypothesis, in understanding the efficiency both up and downstream of a river.

The last method of testing that was suggested in the hypothesis was the chemical testing between the two rivers to show a chemical analysis of the efficiency of a river upstream and downstream. As mentioned in the methodology this method fails to hold a great deal of importance, and indeed, in terms of results; integrity. On location at the river Skirfare this method of data collection did not produce significant enough results to be able to include in this investigation. This method failed to produce any comprehensive results that could be used either to prove or disprove this hypothesis concerning efficiency. Hence, no results for the ‘Chemical Test’ will appear in this investigation.

Despite this miss-hap though, the rest of the data would show that there is a very strong census of support for the hypothesis in the data shown. Though the wetted perimeter and cross-sectional area are not much use in determining the direct efficiency of a point along a river, the hydraulic radius provides an overwhelming amount of support in this particular hypothesis. This will be of great use in the following section.

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

This section when compared to the previous two is a little less intensive in the amount of data and the effort put into it. This does not however, make it any less significant. As all the hypotheses link in together then the data for this hypothesis is just as important as any of the other two hypotheses.

Dog Biscuits;

Table of Results

These two tables show the results for the dog biscuits test that was carried out on the River Skirfare to determine the velocity of the respective locations. For these results to be truly valuable they need to be converted in to the ‘velocity’ of the river. This is opposed to just how many seconds that it took a dog biscuit to travel 10meters downstream. To do this the common equation is used to measure the speed of the river. This is;

Using this, the above results for the dog biscuit test can now be converted into velocity of meters per second. This will be done by taking the distance travelled for each dog biscuit (which is 10 meters for all.) and dividing that by the amount of seconds it took. This will only be done for the averages.

This table gives a rather clear indication of the results. However, to be thorough, these results can be seen on the next page in a graph.

The above graph gives a strong impression that Arncliffe has the greatest overall velocity. This is true for all the locations in the river (except ‘Middle’) and the average velocity also. The Middle reading shows that Halton Gill has the larger velocity though. This is most likely an anomaly, especially as the other locations would seem to support the theory that Arncliffe has a greater velocity than Halton Gill does. The reason for this anomaly is most likely the varying speed of channels in the river. This is especially true of Halton Gill where because of the low height of the river material surfaces and this causes the change in the natural speed in the river.

This graph is ample evidence to support the concerning hypothesis that, ‘Velocity of the river will increase further down stream.’ It clearly shows that there is a greater velocity at a downstream location, Arncliffe, rather than an upstream location, Halton Gill.

Unfortunately the results for the ‘Flow vane’ method were not successful and therefore cannot be displayed. There was not sufficient time to complete this method of data collection as much of the time was taken up with the longer methods of data extraction. It was deemed less important that the dog biscuit method and hence this is what this investigation relies on. It is unfortunate because the two methods complimented each other. However this is not to say that the dog biscuits method is not sufficient alone, as it does provide very significant data.

SECTION 5

Data Analysis;

Now that the data for the three hypotheses has been displayed some judgements on them can start to be made. This is what this section aims to provide. The three hypotheses can be split up so that comments can be made on their accuracy and suggestions can be made as to the processes involved in creating these results. These can then be brought together for the next section to provide an overall conclusion to the investigation as a whole.

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

There are two parts to this hypothesis. Firstly there is the size of material and secondly, there is the angularity of the material. These are best dealt with when split separately. This is so that more clarity can be provided in understanding the influences that affected the size and angularity of material at the river Skirfare at the two locations.

As in the previous section, the size of material will be the first to be dealt with. This hypothesis is very strongly supported by the data that was collected. This is seen especially in the graph titled; ‘Average Material Size at Halton Gill and Arncliffe’. As the title suggests this is simply a graph showing the average sizes of the material at the respective locations. There is an overwhelmingly convincing figure in this graph between the long axis of the locations. Arncliffe is the greater size with a very comprehensive difference of 42.875mm. The short axis does not provide such convincing evidence, but still supports the hypothesis with a difference of 3.75mm in Arncliffe’s favour.

The reason for such a small difference in the short axis can be identified when looking at anomalies in the results. At 600m across the river at Arncliffe a result was taken that was particularly in accordance with the others. It can be seen on the graph, ‘Size and Distribution of Material in the River Skirfare at Arncliffe’ on page 13. Here it can be seen that the result at 600m is far larger than those surrounding it. The material for this location in the river is twice as large in both axes than any of the other material recorded in the River Skirfare at Arncliffe. This is what causes the short axis value to be higher than perhaps it would be had more results been taken.

Measuring angularity used a very different method from measuring the size of material. The stone charts were a good simple way to describe how smooth or rough the material was. The results as shown in the previous section show that angularity in material tends to decrease downstream. Results showed that Halton Gill’s results were mostly ‘Angular’ or ‘Sub- Angular’, whereas Arncliffe’s tended to be mostly ‘Rounded’ and ‘Sub- Rounded’. This synopsis led to the averages using figures that related to the angularity chart. This can be seen on the table on page 13. The averages came out as Arncliffe being ‘Sub- Rounded’ and Halton Gill being between ‘Angular’ and, ‘Sub- Angular’. This is firm support of the hypothesis stated that angularity decreases downstream. In which it has with Halton Gill (upstream) having a greater angularity than Arncliffe (downstream).

It is now possible to say that the hypothesis, ‘Bedload will decrease in size and angularity downstream.’ Is true. This is taken from all the evidence that has been presented in the previous section and the final analysis that has been carried out above. Both size and angularity readings were smaller and more rounded at Arncliffe than at Halton Gill. Finding that this is true, it is important to look at the processes involved in producing these effects.

Assuming that the third hypothesis, ‘Velocity will increase downstream.’ Is true then this will help in explaining the processes that occur in the river that causes the material to decrease in size and angularity downstream. When there is a greater velocity in a river this means that there is also a greater amount of energy in the river to carry out the processes that shape the river, its channel and all the material within it. Using this theory that energy is greater downstream then this would suggest that there is more energy for the river to carry out such processes as erosion at Arncliffe rather than Halton Gill.

Hence, the process of erosion occurs more frequently at Arncliffe than at Halton Gill. This goes a long way in explaining how the material at Arncliffe is smaller and more rounded than at Halton Gill. Upstream there is a smaller river with a smaller discharge and width. Because of this there is not a great deal of energy in the river; there is not enough discharge or mass within the river to build up a great deal of energy. This lack of energy means that various processes cannot occur very frequently, this is not to say that they do not occur at all though.

Such processes are, in the case of this hypothesis, erosional processes. An overview of these processes can be seen on page 5. It is these that change the actual size and shape of the material in the river- the bedload. Firstly Processes such as abrasion and hydraulic action are involved which create larger sized material by colliding against material in the riverbed and banks, and by material being forced apart by the force of the water movements. It is these two that create the larger more angular sized material and hence occur more frequently upstream. Following these processes are attrition and corrosion. These occur more frequently downstream where there is greater energy. It is this processes that round off the material making it less angular. Attrition, as shown in the diagram is the collision of material within the river. Corrosion is the chemical reactions that occur between the river water and the material- this erodes the material down.

The importance of the amount of energy must not be under-estimated in referring to this hypothesis. More will be made of this later but, the essence of this principle is that more erosional processes take place downstream where there is a greater amount of energy for them to occur, and less occur upstream where there is not as greater amount of energy. Linked with this hypothesis is the third and last hypothesis concerning velocity. All three will be brought together in the conclusion which follows this section.

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

The data for this section was by far the largest with a vast collection. There was the Cross-sectional Area, Wetted Perimeter and the Hydraulic radius. Within this hypothesis there is a great deal of processes. These will be dealt with as they come up through looking at the various data in no particular order.

Defining efficiency is the best starting point to understanding the following explanation of results and processes involved in them. A rivers efficiency is simply how good it is at overcoming the forces of friction that are placed upon it. Hence, the processes to be concerned with in this section while analysing results are the processes or factors that will affect friction on the river.

The cross profile of a river shows much about how well the river can overcome the forces of friction. There are various cross profiles attached to this investigation. However one of these can be seen on page