O-LevelGeographyThe natural environment2217/22 · May/June 2018 · Q830 Marks

Students at a school in England did fieldwork on a local river. They wanted to investigate how the river changed downstream.

(a)Before splitting up into separate groups the whole class of students did a pilot study at one site. Identify two advantages of doing a pilot study from the table below. Tick (✔) your choices. look at different features along the river draw a map of the course of the river learn how to work safely in the river practise fieldwork techniques get to know other students before they begin fieldwork Tick (✔)[2]
(b)Two groups of students worked separately to investigate the following hypotheses: Hypothesis 1: The river gradient becomes steeper downstream. Hypothesis 2: The size of pebbles on the river bed becomes smaller downstream.
(b)(i)To investigate Hypothesis 1 the students measured the gradient of the river bed over 10m at five fieldwork sites. Describe a method to do this. Refer to the equipment they would use in your answer.[5]
(b)(ii)One group of students (group A) made one measurement at each site and the other group (group B) made four measurements. Explain why the results of group B should be more reliable.[2]
(c)The results of the measurements made by group B at each site are shown in Table 8.1 below. Table 8.1 Measurements of angle of gradient made by group B Angle of gradient (°) measured over 10m Site Measurement 1 Measurement 2 Measurement 3 Measurement 4 Average angle (°) 1 upstream 11 14 7 5 9 2 6 7 9 7 7 3 3 6 5 2 4 4 10 3 8 6 7 5 downstream 4 11 5 4 6 Note - average figures given to the nearest whole number
(c)(i)At which site (1 to 5) is the largest variation in measurements? Site[1]
(c)(ii)Fig. 8.1 below shows a method chosen by one student to present the results in Table 8.1. Use this method to show the average gradient at site 3.[1]
(c)(iii)What conclusion would the students make about Hypothesis 1: The river gradient becomes steeper downstream? Support your answer with data from Fig. 8.1 and Table 8.1.[3]
(d)To investigate Hypothesis 2: The size of pebbles on the river bed becomes smaller downstream, the students in group A selected 10 pebbles at random from the bed of the river at each site.
(d)(i)Suggest two weaknesses of selecting pebbles at random.[2]
(d)(ii)The students in group B collected their sample of 10 pebbles at equal distances across the river bed. Which one of the following describes this method of sampling? Tick (✔) your answer. average balanced biased stratified systematic Tick (✔)[1]
(d)(iii)Using a ruler the students then measured the length of the pebbles. The measurements of the pebbles collected by group B at site 2 are shown in Table 8.2 (Insert). Plot on Fig. 8.2 below the length of pebble number 3 and the average length of the pebbles at site 2.[2]
(d)(iv)The students decided that Hypothesis 2: The size of pebbles on the river bed becomes smaller downstream, was partly true. Use evidence from Fig. 8.2 to explain why they reached this conclusion.[3]
(d)(v)Explain why pebbles generally become smaller downstream. Refer to processes of erosion.[3]
(e)Whilst the two groups of students worked on Hypotheses 1 and 2, other students investigated how other characteristics of the river changed downstream.
(e)(i)Suggest a suitable hypothesis to investigate. Do not choose gradient or pebble size.[1]
(e)(ii)Describe a method to investigate your hypothesis at the five fieldwork sites.[4]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (May/June 2018). The mark or mark type is shown in brackets.

[1] 8(a) learn how to work safely in the river
[1] 8(a) practise fieldwork techniques
[1] 8(b)(i) Measure 10 m distance along river / downstream / upstream.
[1] 8(b)(i) Put two survey poles on / in river bed / put poles in middle of bed. Poles must be vertical.
[1] 8(b)(i) Students hold ranging poles at either end of measured distance. Agree height on ranging pole / at or near top of poles. Lines up identified position.
[1] 8(b)(i) Use clinometer from agreed height on 1 pole to same height on other pole. Read off / measure / find the angle / degrees (NOT slope / gradient).
[1] 8(b)(i) Repeat several times and calculate average. (Max 5, includes 1 mark for naming equipment if used correctly e.g. clinometer, ranging pole / poles / survey poles, tape measure. Credit appropriate labelled sketch if given.)
[1] 8(b)(ii) Remove the effect of any anomaly.
[1] 8(b)(ii) Gives an average result.
[1] 8(b)(ii) One result may be inaccurately measured / eliminates error.
[1] 8(c)(i) Site 1.
[1] 8(c)(ii) Straight line plot from 4 (above 0) to 0 (on 10) for site 3. Line must go from 4 to 10 for credit.
[1] 8(c)(iii) Hypothesis is FALSE / NOT TRUE – 1 mark reserve.
[1] 8(c)(iii) Evidence: Overall gradient is less steep or less at Site 5 than at Site 1 / downstream OR Site 1 is steepest (NOT refs to any 2 sites).
[1] 8(c)(iii) Evidence: At Site 5 gradient is 6° but at Site 1 it is 9° (1 RESERVED Data).
[1] 8(c)(iii) Hypothesis is PARTLY FALSE / PARTLY TRUE – 1 mark reserved.
[1] 8(c)(iii) Evidence: Gradient is less steep downstream for first 3 sites BUT last 2 sites steeper than Site 3 / overall gradient less but anomaly at Site 3.
[1] 8(c)(iii) Evidence: e.g. Site 1 9° falls to 4° at Site 3 BUT increases to 7° at Site 4 / 6° at Site 5. (1 RESERVED Data).
[1] 8(d)(i) Rocks selected may not be typical / representative of the rocks at that site / anomaly.
[1] 8(d)(i) All rocks may have been taken from same area of river bed / not across channel / taken from same place.
[1] 8(d)(i) Not a fair / reliable sample / students choose rock / bias.
[1] 8(d)(ii) Systematic.
[1] 8(d)(iii) Plotting length of pebble: 13.4 plot above Site 2.
[1] 8(d)(iii) Plotting average length: horizontal line at 7.2 above Site 2.
[1] 8(d)(iv) NOTE: Decision is given as PARTLY TRUE; do not credit any decision by the candidate.
[1] 8(d)(iv) Evidence: Overall decrease in size / average size from site 1 to site 5.
[1] 8(d)(iv) Evidence: Main anomaly to trend is site 3 which contains largest average size.
[1] 8(d)(iv) Evidence: 1 mark MAX. for paired average data from any two numbered sites e.g. Site 1 9.4 cm decreases in size to 6.8 cm at Site 5; Anomaly at Site 3 which at 10.6 cm largest / larger than Site 1 at 9.4 cm.
[1] 8(d)(v) Attrition OR pebbles crash into each other.
[1] 8(d)(v) Abrasion / corrasion OR hitting river bed / bank reduces size.
[1] 8(d)(v) Corrosion / solution OR water dissolves rocks.
[1] 8(d)(v) Smaller pebbles moved further downstream as lighter to transport.
[1] 8(d)(v) Smaller pebbles found downstream because longer in water.
[1] 8(e)(i) Hypotheses must be written as a statement or question and relate to characteristics of the river. (NOTE: pebble size or gradient = 0 in (i) and (ii)). Appropriate examples: River velocity increases downstream; Does river velocity vary across the channel?; Channel width increases downstream; Does channel depth increase downstream.
[1] 8(e)(ii) Method to measure channel width: One student / pole on each bank / side of river. Place measuring tape across channel / from one bank to the other.
[1] 8(e)(ii) Method to measure channel width: Keep tape taut / stretched. Poles must be directly across / at 90 degrees to banks.
[1] 8(e)(ii) Method to measure channel width: Repeat at different sites and calculate average width. Record measurement at each site.
[1] 8(e)(ii) Method to measure velocity using floats: Put poles / sticks 10 metres or fixed distance along river. Use tape measure to measure distance.
[1] 8(e)(ii) Method to measure velocity using floats: Put float / orange in river at start of distance. Start stopwatch / timer when float released at start point.
[1] 8(e)(ii) Method to measure velocity using floats: Measure time taken for float to travel between poles. Stop stopwatch / timer when float passes end point.
[1] 8(e)(ii) Method to measure velocity using floats: Repeat at different points and calculate average speed. Record results from each site.
[1] 8(e)(ii) Method to measure velocity using flowmeter: Put meter / propeller / flowmeter below surface of water / into water. Propeller must face upstream.
[1] 8(e)(ii) Method to measure velocity using flowmeter: No obstacles in front of propeller. Read / look at digital reading / display to see speed.
[1] 8(e)(ii) Method to measure velocity using flowmeter: Take several / repeat readings and calculate average speed. Repeat at different points and calculate average speed. Record results from each site.