Students who lived near a desert area in Saudi Arabia, were investigating the effects of river processes in a valley called a wadi. Although there was no river flowing in the valley when the students were doing their fieldwork, they could see some evidence of the work of the river when it had flowed through the valley. The students investigated the following hypotheses: Hypothesis 1: The gradient of the valley floor decreases downstream. Hypothesis 2: The river's bedload becomes smaller and more rounded downstream.

1. (a)To investigate these hypotheses the students worked at three sites along the valley, one in the upper, one in the middle and one in the lower course.
2. (a)(i)To test Hypothesis 1 they measured the slope of the valley floor as shown in Fig. 9 (Insert). Describe how they measured the slope.[3]
3. (a)(ii)Calculate the average (mean) angle of slope in the middle course of the valley. Put your answer into Table 1. [Table 1.0][1]
4. (a)(iii)Why did the students make four measurements at each site?[1]
5. (a)(iv)What conclusion would the students make about Hypothesis 1: The gradient of the valley floor decreases downstream? Support your answer with evidence from Table 1.[2]
6. (b)To investigate Hypothesis 2: The river's bedload becomes smaller and more rounded downstream the students measured the bedload in the wadi at each of the three sites. Using a random sampling method they picked 20 rocks. They then measured the size and weight of each rock and estimated its roundness. The equipment which the students used to measure the bedload is shown in Fig. 10 (Insert). Describe how the students made each measurement. Size Weight Roundness[4]
7. (c)The students' results from the middle course site are shown in Table 2 below. [Table 2.0]
8. (c)(i)Plot the size of rock samples 6 and 9 in the middle course site on Fig. 11 below. [Figure 11.0][2]
9. (c)(ii)Use the results in Table 2 to complete the histogram for the middle course site in Fig. 12 below. [Figure 12.0][3]
10. (c)(iii)Look again at the roundness score chart in Fig. 10 (Insert). To plot the classification of roundness on pie graphs, the students produced Table 3 below. [Table 3.0] Use the data in Table 3 to complete the middle course site pie graph in Fig. 13 below. [Figure 13.0][2]
11. (c)(iv)Do the results of the students' fieldwork support Hypothesis 2: The river's bedload becomes smaller and more rounded downstream? Support your conclusions with evidence from Figs 11, 12 and 13.[4]
12. (c)(v)Give two reasons why the river's bedload changes downstream. 1 2[2]
13. (d)Exfoliation is one weathering process which affects rocks in a dry river bed in a desert. Describe this process.[3]
14. (e)Suggest three ways that the students could have improved their data collection methods used to investigate the two hypotheses. 1 2 3[3]

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