A group of students was investigating the characteristics of local streams and rivers. They decided to do fieldwork at three sites which are shown on Fig. 8 (Insert). The two hypotheses used by the students were: Hypothesis 1: Width, depth and wetted perimeter of the river channel increase downstream. Hypothesis 2: There is a relationship between the size and the roundness of pebbles on the river bed. (a) Before beginning their fieldwork the students received advice from their teacher. [Figure 8]

1. (a)(i)Suggest three pieces of advice their teacher gave them to keep them safe whilst carrying out fieldwork.[3]
2. (a)(ii)Give two reasons why their teacher suggested they might do a pilot study.[2]
3. (b)To investigate Hypothesis 1, the students made two measurements at each site. They measured the width of the river channel and the depth of the river at points across the channel. Suggest what equipment they would use to measure the width of the channel and the depth of the river and how they would make the measurements. Width of channel Depth of river[4]
4. (c)(i)The results of their measurements are shown in Table 3, below. Table 3 Channel measurements Width of Depth of river at distances across the channel (m) Wetted Site channel 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 perimeter (m) (m) A 1.3 0.15 0.1 1.4 B 2.3 0.14 0.18 0.33 0.2 2.5 C 6.5 0.2 0.26 0.29 0.3 0.33 0.38 0.47 0.48 0.51 0.36 0.35 0.26 Use the results in Table 3 to complete Fig. 9 below by: • completing the cross-section of the channel at Site B; • shading in the river channel at Site B. [Figure 9][3]
5. (c)(ii)The wetted perimeter (the part of the channel cross-section which the river touches) is labelled on Fig. 9 at Site C. Measure the length of the wetted perimeter at this site. ........................................................... metres[2]
6. (c)(iii)How and why will the speed of river flow be affected by contact with the river channel?[2]
7. (c)(iv)The students made the conclusion that Hypothesis 1: Width, depth and wetted perimeter of the river channel increase downstream was correct. How would you use their results to support this conclusion?[2]
8. (d)(i)Next the students made some measurements to investigate Hypothesis 2: There is a relationship between the size and the roundness of pebbles on the river bed. At each site (A, B and C) a student selected 10 pebbles at random from the bed of the river. He then measured the size and roundness of the pebbles using the equipment shown in Fig. 10 (Insert). Suggest how he made the two measurements. pebble size roundness of pebble. [Figure 10][2]
9. (d)(ii)The results of the student's work are shown in Table 4 below. Table 4 Site A B C Average (mean) pebble size (cm) 12 9 7.5 Average roundness score 2 3.5 4 Plot the average pebble size and roundness score for Site B on Fig. 11 below. [Figure 11][2]
10. (d)(iii)What conclusion would the students make about Hypothesis 2: There is a relationship between the size and the roundness of pebbles on the river bed?[2]
11. (d)(iv)Suggest why pebble size and roundness change downstream.[2]
12. (e)Suggest four ways that the students could have improved their data collection methods to make their results for both hypotheses more reliable.[4]

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