Study the downstream changes of Loughton Brook.

Channel Storage                        Water in rivers and lakes.                        

Condensation                        The process in which gas is turned to liquid.                                                         In this case water vapour turns to water.

Evaporation                                The process in which water is heated by the                                                      sun and absorbed. The water changes to                                                 water vapour.

Ground Water storage                Stored water in underground, permeable                                                 rocks.

Groundwater flow                        this occurs when percolated water moves                                                 below the water table to a river

Precipitation                                Precipitation is rain hail sleet and snow

Short-term Storage                        This occurs after interception on plant leaves                                         and flowers

Soil Moisture storage                This is when water is stored in the soil and                                                 used by plants

Surface Run-off                        Water flows over ground to lakes and rivers

Through Flow                        This is when infiltrated water moves through                                         a river

Transpiration                        The process in which plants lose water

Stream Orders

        It is possible to classify streams within a drainage basin. We can do this by identifying their succession through their importance. A stream originally has a stream order of one until another tributary joins it. When two streams of the same stream order join the stream order will increase to two. Stream ordering shows us the different stages of the streams development. Fig.  shows the stream ordering of Loughton Brook's drainage basin.

Long Profile

        A river's cross profile comprises of three stages the upper, middle and lower stages. The upper stage characteristically contains narrow, steep banks and a steep river bed. Erosion is the main action taking place here. In the middle stage the river has a large discharge and a slightly gentler gradient. The main action is still erosion but this time it is more lateral erosion taking place than the vertical erosion of the upper stage. The lower stage has the greatest discharge and velocity and its main action is deposition (This is all shown in Fig.  ).

        In the upper stage interlocking spurs, waterfalls and rapids are the only features found. The middle stage has meanders and ox-bow lakes. In the lower stage we find flood plains, levees and deltas.

The River Channel

        The river channel consists of the river bed and the banks. A number of processes occur in a river channel which can explain the various landforms seen downstream.

Erosion in the River channel

        Rivers erode in four main ways, called erosion processes;

1. Corrasion: This process is also known as abrasion. When large pieces of bedload material wear away the riverbed and banks.

2. Attrition: When rocks being transported are eroded it is known as Attrition. The sediment knocks against the bed or each other and breaks apart becoming smaller and rounded.

3. Hydraulic action:        This is when the force of the water wears away and weakens rocks.

4. Solution: This process is also known as corrosion. It occurs when limestone and chalk dissolve in water.

                        

Transportation in the River channel

        Transportation is the movement of eroded material. Another word for eroded material is sediment. There are four types of transportation;

1. Suspension:         is when fine silt and clay material is mixed and carried in the water itself.

2. Saltation: is when small grain-sized particles are bounced along the ground.

3. Traction: is when small boulders and large rocks are rolled along the river bed.

4. Solution: is when sediment is dissolved into the water itself.

Deposition in the River channel

        Deposition is the process in which river sediment drops its load. This happens when the velocity of the river is lower than normal and when a rivers load is greatly increased. There are four stages of deposition. Firstly large material carried by the river is deposited in the higher reaches. Secondly, Gravel, sand and silt carried in a suspension with the water are then deposited in lower reaches. Fine particles of clay and silt are then carried until they are dropped in estuaries and deltas. Lastly, Dissolved load is not deposited and stays with the water even after it rejoins the sea.

Hypothesis

        Based on my survey and common knowledge, I have listed some hypothesises that may prove to be either right or wrong. I will investigate to find out whether these suppositions are true or not during the course of my coursework.

• As the stream order increases channel depth will increase.

        This is because more as more streams join the river, the volume of         water increases, which enables more vertical erosion.

• As stream order increases wetted perimeter will increase.

        The wetted perimeter would evidently increase due to the large         influx of water resulting in a large overflow.

• As stream order increases discharge will increase.

        Due to the growing amount of water the discharge would be greater         as the water also increases in speed.

• As stream order increases pebble sizes will decrease and their shape will be more rounded.

        More water would mean that the water levels will rise and put more         pressure on the load i.e. the pebbles. With more water pressure the         

        pebbles tend to be more eroded and smoother which results in them         being smaller and more rounded.

• As stream order increases cross-sectional area increases.

        If the water depth and water width increases then surely the cross-        sectional         area will increase too because the cross-sectional area is the water width multiplied by the water depth.

• As the stream order increases the channel width will increase

        More (lateral) erosion will mean that the channel width will         decrease.

• As the stream order increases gradient will decrease.

        The gradient decreases as the river leaves the upper stage and         lessens upon reaching the middle and lower stages.

        To obtain the results needed for our coursework, my Geography class split up into different groups so that we could all cover all nine sites of Loughton Brook. My group collected data from sites 2, 6 and 9. These sites were the basis for my hypothesis and are known as my primary data. However, Instead of using the data from Site 6 I used data from Site 3 just so that I have a source of secondary data. No more data was collected as I felt that the three sites that I had chosen were sufficient enough to cover my research without the complication of more data from other sites. To acquire results for my survey I needed certain equipment which was provided for by the Epping Forest Field Studies Centre.

Equipment Needed

        To carry out my survey and find out the downstream changes of Loughton Brook, I needed certain equipment in order to take the necessary measurements. The equipment is;

1. A clipboard, pencil and recording sheets,
2. Cork,
3. Gun clinometers,
4. Plastic bucket
5. Ranging poles
6. Ruler
7. Tape measure
8. Timekeeping device

Clipboard, pencil and recording sheets

        A clipboard was required to write on, as the area was very wet and muddy during our visit. Pencils were needed to write our various measurements and results with, and recording sheets were supplied by the Epping Forest Field Studies Centre to write them on it. There were two types of recording sheets. One was a river recording sheet on which information on each site was to be written down. There was also a space to draw a sketch of the river site on this sheet. The second was a measurement recording sheet to record load size and shape side on one side and all other river measurements on the other. The load size and shape side also comprises of the Powers Roundness Index.

Cork

        A cork was required to measure the float time so that we can find out the surface velocity of the river site.

Gun Clinometers

        Gun Clinometers were used to measure the gradient.

Plastic Bucket

        A plastic bucket was needed to carry all of the equipment and pebbles that needed measuring (excluding the ranging poles).

Ranging Poles

        Two ranging poles were required. They were white in colour. The ranging poles were used for the gradient, the height of the banks and the water width among other measurements.

Ruler

        A one-meter ruler was required to measure the load size of the pebbles, the height of the banks, the water depths / widths and the wetted perimeters.

Timekeeping Device

        A watch was used as a timekeeping device during my survey because there were not enough stopwatches to go around.

Fig.  shows all the equipment we used.

Measurements Needed

        To carry out my survey and find out the downstream changes of Loughton Brook, I needed certain measurements from the stream sites that I was studying. The measurements required were;

        

1. Bank to water width
2. Channel Width
3. Cross-sectional Area
4. Float Time
5. Gradient
6. Height of the banks
7. Load shape
8. Load size
9. Water Depth
10. Water Width
11. Wetted Perimeter

Bank to water width

        The bank to water width is measured by inserting a ranging pole in the water and another ranging pole flat on the bank to form a right angle. This ensures that the poles are straight. The second pole is then measured from the bank till the water by a tape measure / 1m ruler. Two ranging poles and a tape measure / 1m ruler are required.

Channel Width

        The Channel width is measured by adding the water width and the bank to water widths on each side of the bank. A 1m ruler was required.

 

Cross-sectional Area

        The cross-sectional area is useful in calculating discharge. It is obtained by multiplying the water depth with the water width. The cross-sectional area is measures in m².

Float Time

        The float time is calculated to help measure the average time needed for discharge. It is measured by dropping a cork in the water and timing it to see how fast it travels in one meter. A cork, timekeeping device and 1m ruler are required.

Gradient

        The gradient is important because it tells how much vertical corrasion has taken place. Therefore the gradient shows us how the land slopes (usually steep during higher stages and gentle during lower stages). To obtain the gradient, two poles are put into the river bed parallel to each other. A gun clinometer is then held on to the mark of the first pole and pointed in the same spot on the other pole, marking a right angle. The gradient is then measured in degrees. Two ranging poles and a gun clinometer are required.

Height of the Banks

        The height of the bank is measured from the water till the bank. A ranging pole goes in the water and the second ranging pole forms a right angle from the bank to the water by lying flat on the bank of the river to ensure that the poles are straight. The ranging pole is taken out of the water and the wet part is measured with the measuring tape or 1m ruler. Two ranging poles and a tape measure / 1m ruler are required.

Load Shape

        The load that I used for observing the shape was pebbles. From each site ten pebbles were collected and were estimated according to their angularity or roundness as well as their sphericity (according to the Powers Roundness Index).

Load Size

        The load that I used to determine the size of the load was pebbles. From each site I collected ten pebbles and measured them with a tape measure. All measurements were in cm. A tape measure required.

Water Depth

        The water depth is measured by ranging poles. Three measurements are taken at each site, the left, middle, and right hand sides. The measurement is added and then divided by three for the average water depth at each site. A ranging pole and a tape measure are required.

Water Width

        Water width was necessary for obtaining the channel width. A tape measure is used to measure the water from one side to the other starting at the place where the bank to water point ends.

Wetted Perimeter

        The wetted perimeter is the distance that the water is in contact with. It is measured with a tape measure and its measurements are in cm. A tape measure is required.

        To record our results we were given river measurement recording sheets. These had spaces to record various types of data and also had the Powers Roundness Index to measure the sphericity and roundness of the river load i.e. pebbles. This section illustrates the various results I have acquired in the survey. My results are displayed in the form of graphs, charts, diagrams and other means of graphical representation.

Bank to water widths

Cross-sectional Area

Discharge

Float Time

Gradient

Height of banks

Surface Velocity

Water Depths

Water Width

Wetted Perimeter

Pebble Shape

Pebble roundness

Pebble Sphericity

Pebble Size

        Since the pebble sizes are continuous data, I will represent them in the form of histograms by putting all the long axis data into class intervals of 1cm.

        

        

        In this section I will analyse the data collected on the characteristics of the river and compare it to my original hypothesis. I will also establish links between the data. My results show that most of my predictions were correct according to my hypothesis. There are some inaccuracies which may have been due to incorrect measurement or other exceptions.

        My hypothesis stated that the water width and channel width would increase as the stream order increased. At Site 2 the rivers water width was 0.82m, whereas at Site 3 and Site 9 it was 0.98m and 1.85m respectively. At Site 2 the rivers channel width was 1.7m, whereas at Site 3 and Site 9 it was 2.15m and 3.07m respectively. Since the stream order increased as the river progressed (and so the Site number increased) more water was present due to the various tributaries joining the river. More water meant that the river had to expand either vertically or horizontally through the influence of hydraulic action. . The river has more energy due to the large amount of water and so erodes the river. During the later stages of a river there is more horizontal or lateral erosion rather than vertical erosion. Corrasion will also occur and will widen the channel. I conclude this by saying that my hypothesis of the water width and channel width increasing was proven within the basis of my results.

        I also included water depth in one of my hypotheses by saying that it would increase as the stream order increases. This was based upon the fact that as the stream order increased the volume of water increased. The large volume of water would erode the riverbed and riverbanks through vertical and lateral erosion. This proves that there is a link between water depth and vertical corrasion because increased water depth shows the presence of vertical corrasion. My results showed didn’t display this correctly. In Site 2 and 3 the rivers depth was 0.24m, and in Site 9m it went down to 0.19m. This could have been due to human error by someone taking down incorrect measurements.

        One of my hypotheses was that the surface velocity would increase as the stream order increases. I think this will happen because river discharge usually increases downstream due to the drainage basin becoming bigger, and therefore the volume of water reaching the channel via tributaries, surface flow, through flow, and groundwater flow increasing.  I think that the velocity will increase downstream due to the decrease in number of pebbles and rocks.  As the pebbles decrease in number and size, friction also decreases allowing a faster discharge. My hypothesis about the surface velocity increasing as the stream order increased was proven correct within my results. Surface velocity is linked to the gradient because as the gradient decreases the gravitational potential energy lessens. As a result water in the river doesn’t flow down as quick.

        In my hypotheses I said that the wetted perimeter would increase as the stream order increased. This is obvious because the amount of water increases as we go downstream and more water would mean contact with the surface area around the river banks. I have come up with results which support my hypothesis. At Site 2 the reading for my wetted perimeter was 0.98 and at Site 3 and Site 9 it was 1.39 and 1.78 respectively.

        The cross-sectional area increased as the stream order increased because of the increasing erosion from the growing amount of water as the river progressed. Vertical and lateral erosion increased due to the river depth and water width respectively. Site 2  had a cross sectional area of 0.2m² which went on to 0.24m² in Site 3 and finally 0.35m² at Site 9. My hypothesis was proved correct by my results as the cross-sectional area increased as we went down the river.

        In one of my hypotheses I predicted that the gradient would decrease as the river went downstream. This is because there is more lateral erosion along the early stages of the river, whereas as the river progresses the erosion changes primarily to vertical erosion. The lateral erosion makes the riverbed steeper during the earlier stages of the river and so the gradient is seen as decreasing. At Site 2 the gradient was 0.21° in my results, and at Site 3 and Site 9 was 0.2° and 0.05° respectively.

        My final hypothesis was that the pebble size and shape would decrease and become more rounded as the stream order increased. At the source of the river, the pebbles were very angular and larger but downstream they were much smoother and smaller.  This is because the river smoothes the pebbles and wears them away as it transports them downstream before depositing them.  Transportation occurs through traction, saltation, suspension and solution.  The longer that they have been transported, the smoother they are as they have spent the maximum time in the water being rounded. As the velocity of a river increases, so too does the load it can carry and the rate at which it can erode.  A river may erode by one of four processes: Attrition, hydraulic action, corrasion and corrosion. My hypothesis was proved correct as the river load became smaller and more rounded as the river went downstream (as the stream order increased).

        This section details the proficiency and flaws of my coursework as well as the limitations that I had. My assessment is based upon my opinion of everything that I did perhaps slightly inaccurately, and my results.

        The sites chosen in our survey were chosen for us by the Field Studies Centre itself by dividing us into two or three groups. I chose two sites from my group and one site from a different group. The two sites from my group that I had decided to keep were the first and last sites of the river (Sites 1 and 9). The site that I chose from another group was Site 3. I chose it because the data taken was easily accessible as it was given to me by a friend. All sites were crammed into 800-900m of river because below that point flood management schemes occurred. Since I only measured a few sites of this river I might not have gotten a clear indication of Loughton Brook’s downstream changes. However, had I measured the entire rivers length I would have had more accurateness in my survey. This is true as it is a basic fact in statistics that the larger your data/sample the more accurate your results are likely to be.

        The equipment that we used in our survey was fairly accurate as there was no great deficiency in equipment except in one case. When the tape measure was being used for other purposes, the pebble size had to be measured by the 1m ruler and estimated.

        A different problem that we had was that we had gone to Epping Forest in a very wet season. It had rained the day before so water levels were higher than normal. The ground around it was muddy too so we may have had a problem measuring the wetted perimeter. The surface velocity had certainly increased due to the higher discharge and therefore more river energy. Since our group didn’t particularly want to get wet, they tried to estimate the water width by taking the tape measure out of the water and reading it rather than try reading it underwater. Therefore their hands may have slipped and they may have recorded the wrong information.

        In reality I had no control of the data given to me by the other group. Therefore they could have made the same mistakes as my group and possible more. All sites (of which I have included in my results) took the survey on the same day. Our calculations were all correct as all of us had the basic competency required.

        My results showed that as Loughton Brook goes downstream;

• The bank to water width increases
• The channel width increases
• The cross-sectional area increases
• The float time decreases
• The gradient decreases
• The height of the banks increases
• The load shape becomes more well-rounded
• The load shape becomes more spherical
• The load becomes smaller
• The water depth decreases
• The water width increases
• The wetted perimeter increases

        All of my results agree with my original hypothesise listed in my introduction except for the water depth. The water depth in my results decreases. The water depth stays the same at Sites 2 and 3 (0.24m) and decreases to 0.19m. I expected it to increase because the large volume of water would erode the riverbed and riverbanks through vertical erosion. In my opinion the measurement could have been incorrect due to human error (by someone taking down incorrect measurements etcetera).

        We could have improved our investigation by ensuring that we came on a different day so that we could have conducted our survey under normal conditions. We could also have improved our results by obtaining another tape measure to measure the pebble accurately. Overall, I consider that the results collected on the survey were higher than satisfactory. The results produced seem to agree with my statement.

GCSE Geography Revision Guide

        Published by: CGP

Key Geography for GCSE: Book 1

David Waugh

Understanding GCSE Geography

Ann Bowen & John Pallister

Published by: Heinemann

Epping Forest Field Studies Centre