Goyt Valley Physical Fieldwork GCSE — Transcript

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1. 0:00The second paper 3 revision video will
2. 0:02go through our physical field work that
3. 0:04we did in the upper go valley. Watch the
4. 0:06first video too as it goes into more
5. 0:08detail about our human fieldwork in
6. 0:10Newington.
7. 0:12So for our physical we studied the goit
8. 0:14river and one of its tributaries called
9. 0:16deepcluff in its upper course between
10. 0:19mlesfield and buckton. You need to know
11. 0:22what we did and why we did it. That's
12. 0:24your justification. and also to evaluate
13. 0:27what we did to say whether the results
14. 0:28were accurate. You need to know what we
15. 0:31investigated the methods how we
16. 0:33presented and analyzed the data. So
17. 0:35firstly you need to remember the title
18. 0:37how does a river change as it flows
19. 0:39downstream.
20. 0:42The river goit flows north from its
21. 0:44source near goits moss through a couple
22. 0:45of reservoirs why bridge marple and
23. 0:48eventually joins the mury in Stockport.
24. 0:50Again, we need to justify the location
25. 0:53to give reasons why this is a good
26. 0:55location to study how a river changes
27. 0:57downstream. Firstly, it's accessible by
28. 1:00a footpath from a car park. Secondly,
29. 1:03there are some tributaries, so the
30. 1:04volume of water in the river will
31. 1:06increase over a small area. And thirdly,
32. 1:09the river here is in the upper course, a
33. 1:10narrow, steep-sided valley, so it's
34. 1:12likely to be shallow enough to wade in
35. 1:15and take measurements safely.
36. 1:17We need to know what the risks were and
37. 1:19how we minimized them. The valley sides
38. 1:22were steep, so we stuck to the paths.
39. 1:24The river was deep in places, so we only
40. 1:26went in when it was shallow enough so we
41. 1:28didn't fall in. The rocks were slippery,
42. 1:30so we wore footwear with a good grip.
43. 1:33And the grass was dry and could catch
44. 1:35fire, as it had done a couple of weeks
45. 1:36previously, so we did not like matches
46. 1:39or and were careful not to leave glass
47. 1:41around.
48. 1:43We broke our main title down into three
49. 1:45sub questions. Firstly, does the
50. 1:47velocity of the river change as you go
51. 1:49downstream? Velocity is the speed of
52. 1:51water going down per second. Secondly,
53. 1:54does the discharge of the river increase
54. 1:56downstream? Discharge is the amount of
55. 1:58water passing a point per second. And
56. 2:00thirdly, does the shape of the bed load
57. 2:03change as you go downstream.
58. 2:06So now we need to think about how we
59. 2:08chose where to collect our data. In
60. 2:10other words, to justify our sampling
61. 2:11strategy. We could have chosen to
62. 2:14collect our data at random sites. If we
63. 2:16had done that, we might have chosen some
64. 2:18sites too close together to show a
65. 2:20difference uh that we were trying to
66. 2:21prove in our title. Ideally, we would
67. 2:24have collected our data systematically
68. 2:26along the 50 km stretch of the river go
69. 2:29um at regular intervals, but this would
70. 2:31have taken a lot of time and the river
71. 2:33may have been too deep lower down to
72. 2:35measure it safely.
73. 2:38So, we decided to use a stratified
74. 2:41sampling strategy and to collect data at
75. 2:43three sites that look different to each
76. 2:45other. The first one being Deepcluff, a
77. 2:47small tributary with a small catchment.
78. 2:50Site two being on the river goit just
79. 2:52before it's joined by Deepcluff, that's
80. 2:54a larger catchment. And site three being
81. 2:56after the confluence of the two rivers,
82. 2:58which has a larger catchment area. This
83. 3:00meant we would be able to see uh
84. 3:02differences in discharge and velocity.
85. 3:04And we also use secondary data collected
86. 3:06at different points further up and
87. 3:08further downstream on the go to give
88. 3:10more data.
89. 3:12We need to be able to describe, justify,
90. 3:14and evaluate our methods to link what we
91. 3:16did to the questions we were trying to
92. 3:18answer and understand what might have
93. 3:20influenced the accuracy of the results.
94. 3:22The first thing we did was to measure
95. 3:24velocity so we could see if it increased
96. 3:26downstream. At each site, we put a
97. 3:28hydrop into the water at three points
98. 3:30across the width and time how long it
99. 3:32took for the impeller to spin along to
100. 3:34the end of the rod. The impella thread
101. 3:37was 3.2805
102. 3:39meters. So we could then calculate the
103. 3:40velocity and we calculated the a average
104. 3:43velocity for each site. This was primary
105. 3:46stratified data data we collected
106. 3:48ourselves at three selected sites. So
107. 3:51now we need to evaluate if this method
108. 3:53produced reliable results. Well, the
109. 3:55water was too low in places at the sides
110. 3:57to turn the impeller as there had been
111. 3:59little rain. So this made the river look
112. 4:01slower than it was. So to overcome this,
113. 4:04we tried measuring surface velocity by
114. 4:06timing how long it took for a dog
115. 4:08biscuit to float downstream. 10 m.
116. 4:10Generally, the biscuit floated on low
117. 4:12water, so was a better method, but
118. 4:14sometimes it got stuck by boulders.
119. 4:17We also used secondary data when we got
120. 4:19back to school, taken at sites higher up
121. 4:21than ours and extending another 20 km
122. 4:24downstream. This let us see if the
123. 4:26velocity changed over a wider area than
124. 4:28we were able to measure in a day. So,
125. 4:30their data was probably more accurate
126. 4:32than ours as it covered more sites and
127. 4:33wouldn't have been as affected by
128. 4:35anomalies as ours might have been.
129. 4:37However, it wasn't directly comparable
130. 4:39to ours as it was taken at a wetter time
131. 4:41of year when the discharge and the
132. 4:43velocity would have been greater. The
133. 4:45second questions we were trying to ask
134. 4:47is whether discharge increased as you
135. 4:49went downstream. Discharge is the amount
136. 4:51of water passing a point each second.
137. 4:53And we can measure that by measuring the
138. 4:55cross-sectional area in meters cubed and
139. 4:57then multiplying that by the velocity in
140. 4:59meters/s to give the amount of water
141. 5:02flowing past measured in cubic meters or
142. 5:04So each side we site we measured
143. 5:07the width using a tape measure and we
144. 5:08used a ruler to measure the depth at
145. 5:10five points across the width to give an
146. 5:12average depth. So did it produce
147. 5:14reliable results? Well, we chose
148. 5:17sections we could stand in and avoid the
149. 5:19deepest parts and boulders. So the
150. 5:21cross-section didn't always represent
151. 5:22the whole area.
152. 5:27Finally, to see if the bed load got
153. 5:28smaller as the river flows downstream,
154. 5:30we categorize the shape of stones using
155. 5:32a P angularity table. We selected stones
156. 5:36randomly by putting a ruler in the water
157. 5:38every meter in a 10- m stretch and
158. 5:40taking one stone out. It was difficult
159. 5:42to measure larger boulders, however, so
160. 5:44we did end up selecting the smaller
161. 5:46stones to measure. So stones may have
162. 5:48actually looked a little bit more
163. 5:49rounded than they were in reality.
164. 5:52So let's turn our attention now to how
165. 5:53we presented our data. And again, we
166. 5:55need to be able to justify and evaluate
167. 5:57our presentation methods. We used our
168. 6:00secondary data of velocity over the nine
169. 6:02sites on the river going downhill and we
170. 6:05plotted these two variables on a
171. 6:06scatterraph. Scatterraphs are brilliant
172. 6:09at showing if there is a relationship or
173. 6:12correlation between two variables. In
174. 6:14this case, distance and velocity. So it
175. 6:17lets us answer our question about
176. 6:18whether velocity increases downstream.
177. 6:21And then we can draw a line of best fit
178. 6:23which goes near or through as many lines
179. 6:25as possible. and it shows how strong
180. 6:27this relationship is and shows up any
181. 6:29anomalies. So if those po points are
182. 6:31very close to the line, there is a
183. 6:33strong relationship and if they're quite
184. 6:34a long way from the line, the
185. 6:36relationship is weaker. And of course,
186. 6:38we can see if it is a positive or
187. 6:40negative relationship.
188. 6:42So we need to evaluate this data
189. 6:44presentation method. You can see it's
190. 6:46very visual. It's clear to see a
191. 6:48positive correlation as distance
192. 6:50increased, velocity increased, and it's
193. 6:52clear to see that this relationship was
194. 6:53particularly strong higher up the
195. 6:55valley. It's also clear to see an
196. 6:57anomaly at 16 km at Marple Weir because
197. 7:00the weir blocked the river and caused
198. 7:02the water to back up and slow down the
199. 7:04flow.
200. 7:06We calculated the discharge by
201. 7:08multiplying the cross-sectional area by
202. 7:10the velocity. And then we presented this
203. 7:12by coloring in one square on a grid of
204. 7:14100 squares for each cubic meter of
205. 7:17water. We then put the grids next to
206. 7:19each other on a map to geollocate it.
207. 7:22This presentation method made it easy to
208. 7:24visually compare sites. And by putting
209. 7:26it on a map, we could see spatial
210. 7:28change, how the amount of water
211. 7:29increased as you move down the valley,
212. 7:31which is what we were trying to prove.
213. 7:34Finally, we presented our results of
214. 7:36pebble angularity using a stack bar
215. 7:38graph for each site. This again helped
216. 7:40us see changes very visually as you can
217. 7:42compare changes in color categories
218. 7:44across the three bars plotted side by
219. 7:46side. You can see the angular pebbles
220. 7:49shown in orange decreased and rounded
221. 7:51pebbles shown in gray increased. Uh pie
222. 7:53charts would have also had a similar
223. 7:55impact.
224. 7:57So what did we find? Does the river go
225. 8:00change as it flows downstream? Yes. The
226. 8:02discharge increases because the river
227. 8:04has more water in it. uh relatively less
228. 8:06of that water is being slowed by contact
229. 8:08with the river channel and therefore its
230. 8:10velocity gets faster too and because it
231. 8:14flows faster stones bash against each
232. 8:16other and are eroded by attrition to
233. 8:18become rounder. So yes the go does
234. 8:20change as it goes downstream.
235. 8:24So finally we need to evaluate how
236. 8:26accurate our results were. Um and what
237. 8:29did we do to make sure that our results
238. 8:31were reliable?
239. 8:33Firstly, we used an average of five five
240. 8:35measurements across the river to reduce
241. 8:37any inaccuracies. And we also stood
242. 8:39downstream of the impella so we didn't
243. 8:41impede the flow. So why might our
244. 8:44results not have been completely
245. 8:45accurate? Well, we selected sal sh sh sh
246. 8:48sh sh sh sh sh sh sh sh sh sh sh sh sh
247. 8:48sh sh sh sh sh sh sh sh sh sh sh sh sh
248. 8:48sh sh sh sh sh sh sh sh sh sh shallower
249. 8:48spots so we could stand in them and
250. 8:50these might have made the velocity
251. 8:51reading seem slower than if we' used
252. 8:53deeper sites and also the weather had
253. 8:55been fairly dry um just before we went
254. 8:57so that in some places the impella
255. 8:59hardly turned even though the water was
256. 9:01actually flowing.
257. 9:02However, using secondary data taken at a
258. 9:04wetter time of year enabled us to reach
259. 9:06a more accurate conclusion. When
260. 9:09measuring angularity, as we've already
261. 9:10said, we tended not to measure the
262. 9:12boulders as they were too large.
263. 9:13angularity may have seemed um smoother.
264. 9:16Uh what could we have done differently
265. 9:18to make our results more reliable? Well,
266. 9:20we could have used the dog uh biscuit
267. 9:22method alone to measure surface velocity
268. 9:25as you could do this in shallower water
269. 9:27and we could have um added our data
270. 9:30together across the whole year group to
271. 9:32reduce the effect of um anomalies and
272. 9:35have a bigger data set.
273. 9:37And very finally, here are a few exam
274. 9:40questions. So, make sure you can answer
275. 9:42all of them.