These are the five sites that we collected data from and proved our hypothesis at.
Hypothesis
- As the depth of the river increases from source to mouth, the sediment size will decrease.
I came to the decision to test this hypothesis, as it is fairly complex yet obvious. The sediment size will decrease as attrition from boulders makes the size smaller. Also corrasion from rocks rubbing on the riverbed will cause the bed to become deeper as the river flows from source to mouth.
- The width of the river will increase towards the mouth of the river.
This is because of lateral erosion taking place. As meanders of turns in the river become more frequent, the erosion takes place on the outside of the turn making the river wider.
- As the velocity increases, the gradient will decrease.
This is because as the velocity increases, so does the hydraulic radius. The gradient will decrease because, as in all rivers, it begins at a high peak at finished at sea level, so the river level out towards the mouth to stay at sea level and not fall below.
Methodology
METHODOLOGY
The following data needed to be collected to prove our hypothesis River width, Gradient, Wetted perimeter, Depth, Sediment size and Velocity.
At each point we carried out the same method to find each group of data.
River Width The river width is simply the width of the river. We decided to find the width of the river so we could test the hypothesis of: the width of the river will increase towards the mouth of the river. To find the width, two ranging poles were placed either side of the river where the water came into contact with the bank. With a measuring tape tied to each pole, we could measure the distance from one side to the other. On each pole we marked out where the tape would be tied to so that it gave us a level reading at the same point, thus making the reading fair. We then read the distance between each pole, giving us the width of the river at that point. This was used at every site. We encountered some problems such as the poles falling over when we were pulling the tape tight so that it gave us an inaccurate read, but we easily overcame this by making members of the group hold the poles so they stood at 90 degrees.
Gradient The gradient is the angle that the river flows at. We decided to find the gradient so that we could link the hypothesis of: As the velocity increases, the gradient will decrease. To find the gradient, two ranging poles were once again used. These, this time, were placed in the middle of the river running parallel to the river and its banks, standing one meter apart. The marks that were used to find the width of the river, which are the same height on both the poles, were used. Placing it next to the mark on one pole, we used the clinometer by aiming it at the mark on the other pole. This gave us a reading of the gradient. To ensure that the reading was accurate and fair at each site, we made the same person from the group take the reading from each site using the same techniques, also, another person checked the reading the person had given at each site and if the reading proved incorrect, we would take the average from the two results. However the clinometer did require the personnel carrying out the reading to use their own personal judgment, which might have been faulty. We did come to a few problems while performing the test, as the river had a very stony bed. What we did to overcome this was to remove the first layer of large boulders so that the ranging poles could stand in the smaller shingle underneath. This technique was used for both poles at all sites to keep the test as fair as we could.
Wetted Perimeter The wetted perimeter is the area of riverbed that water comes into contact with. Finding this data would show us how the size of the river increases from source to mouth, giving us secondary data as well as the width and the depth. In order to find the wetted perimeter, the measuring tape was placed at one-river banks where it came into contact with the water. Then, the tape was placed across the river and members of the group stood on the tape so that it came into contact with the bed at as many different points as possible. This was all under the water, so when the tape reached the other bank and the water came into contact with it, the measurement was recorded at this point. Although this seems fairly complicated, it was easy to carry out, and we achieved a fairly accurate result. The only way, in which the reading was unfair, is that the tape was not in contact with the entire riverbed, most of it where feet had been holding it down was in contact, but not all of it. This could of lead to results being slightly different than they should have been at each site.
River Depth The river depth is how deep the river is. I found this so that I could test the hypothesis: As the depth of the river increases from source to mouth, the sediment size will decrease. To find the depth of the river, we divided the width of the river into 7. This is so we could find the depth at each point and find an average. The depth was measured by a meter rule being placed at the first point across the river, against the riverbed. Where the water met the ruler the measurement was taken and recorded. To make sure that the reading was accurate, two people from the group viewed the reading and agreed on the measurement. The rule was twisted so that it ran parallel with the river; making it more streamlined which made the measurement easy to take. The people taking the reading were downstream from the rule so they did not interrupt the flow of water. The bottom of the meter rule, marked 0, was placed at the riverbed. Once again boulders became an inconvenience towards the top of the river, because they were larger, so we moved them out of the way and placed the rule against the shingle below. We repeated this for the seven points across the river and at the four other sites. The depth was taken to 1 decimal place.
Sediment Size This is the size of the deposits in the river such as boulders and rocks. Finding the sediment sizes allows me to continue with the hypothesis that: As the depth of the river increases from source to mouth, the sediment size will decrease. To find the results, the river was split into the same 7 points as when finding the depth. From each of these points we took 3 rocks from the riverbed. We measured the longest side and then threw them over the bank so that we would not be able to pick that rock up again by mistake. The person picking up the rocks, tended to pick up the bigger rocks as they could only feel the rocks that were coming out of the water, not see them. The chances were that they would pick up the bigger rocks because they covered more of the riverbed. The same person did all of the picking up of the rocks, as different people may have had a tendency to pick up larger or smaller rocks. Once they had picked them out of the water, they passed them to another person who measured the longest edge and then discarded of the rock.
Velocity The velocity is the speed that the river is flowing at. I chose to find out these readings so that I could test the hypothesis: As the velocity increases, the gradient will decrease. Once again the 7 splits in the river were used. At each point a device called a flow meter was used. A flow meter is an instrument, like a fan, that turns when under pressure from the flow of water. This device was placed a point and the number on the dial was observed and recorded. The person stood downstream from the device, facing it upstream to catch the full flow of the water. Once in position the button was pressed and the reading begun. After 1 minutes of timing from another member of the group, the button was pressed to stop the dial. This new reading on the dial was then recorded. To find the counts per minute, the number on the dial after the 1-minute of recording was taken and the number on the dial before the recording was taken from it. This process was then repeated at each of the 7 points across the river and then at each site. The test was performed well and we came into no difficulties. However in some places we did not get a true reading as some large rocks that we could not move obstructed the flow meter. This gave us some unusual results.
Data Presentation
Data Presentation
Hypothesis 1
As the depth of the river increases from source to mouth, the sediment size will decrease. To prove these results, I need to show the depth of the river at the sites and also the sediment size at the different sites. Depth
Sediment Size
I chose these types of graphs as it displays the data simply. The graphs show the sediment sizes and the depths.
This graph shows the depth plotted against the sediment size. It is easy to make a comparison with them both plotted on a graph.
Hypothesis 2 The width of the river will increase towards the mouth of the river.
Hypothesis 3. As the velocity increases, the gradient will decrease.
This graph shows the width of the river at different sites. It is plotted in this way as it helps to see a cross sectioned view of the river.
Hypothesis 3 As the velocity increases, the gradient will decrease
These graphs show the gradient and the velocity.
Analysis and conclusion
Analysis
- As the depth of the river increases from source to mouth, the sediment size will decrease.
This hypothesis turned out to be, according to my results, mostly incorrect. For the depth of the river data, sites 2,4 and 5 proved to be anomalies. The other results showed that the hypothesis were correct, that the depth of the river increased from source to mouth and the sediment size decreased from source to mouth. Judging from my graph, the results showed a little bit of change in the direction that would prove my hypothesis to be correct, however the anomalies made it more difficult to show. Site 2 and 4 turned out to be shallower than site 1 which should not of been the case, along with site 5. It should have got deeper as the river goes from its source to its mouth otherwise water would not flow out to the sea but stay in the hills. The only reasons that could justify the anomalies in the data could be that we measure the river at only 5 sites. Because we only measured the river at 5 sites, it did not show us the true landscape of the river. The only way to overcome this factor is to test the entire river, which is impossible. We may of merely just chosen the wrong points in the river to test, maybe a few feet either way of the sites could of given us the data that we were looking for. Another reason for these results could be that we measured wrong at the three sites. Which may or may not of been true, but is a possibility. Also another problem could have been that the river was too small and did not have enough water in it and energy to cause corrasion against the riverbed from rocks to take place, as the river did not flow fast enough to move the rock. However, the sediment size did decrease from the source to the mouth, except for sites 3 and 4. These may have been for the same reasons as above, or that the river was too small for attrition from large boulders to take place. There was a negative correlation from site 1 to 5, whereas it should have had a positive correlation.
- The width of the river will increase towards the mouth of the river.
From my graph, I cannot prove my hypothesis to be correct. All of the results seem to be anomalies. The graph had a negative correlation whereas it should have had a positive correlation. All of the results were anomalies and formed hardly any trend. This may have been that we did not go to the correct points at either side of the river, or that we chose narrow or wide parts at them specific points in the river. Where we measured to the edge of the bank, maybe we should have measured to the point where the water comes into contact with the bank. Also, we may have not been measuring straight across the river and had the tape at an angle, this would of given us extra distance that may of affected our results. From looking at secondary sources, the width of the river should definitely of got bigger as we reached the mouth.
- As the velocity increases, the gradient will decrease.
This was not conducted very well in accordance to our results or the river didn’t give us the results we were looking for. From my graph, I can see that the velocity started to increase overall from site 1 to site 2. However this pattern did not continue as site 3 turned out to have the lowest velocity of all 5 sites. Site 4 was fairly high and then site 5 became very low. The strange results may have been because the sites were not equally spaced out or that the area in which the equipment was used was deep or shallow. The gradient was slightly more successful, with sites 1,3 and 5 following a pattern and with sites 2 and 4 becoming anomalies. I put these down to the fact that we did not go deep enough into the riverbed; instead we stayed towards the surface of a layer of shingle. We should have maybe gone deeper. Or maybe it was down to the person who was taking the readings, as on the equipment they used, there were several marks from where to record the data from. Maybe this was the case.
