Some students wanted to investigate the flow of a river on a meander. Before they began their fieldwork their teacher spoke to them about safety when planning their fieldwork. The students decided to investigate two hypotheses about the speed of flow (velocity) of the water in the river: Hypothesis 1: Velocity on the surface varies across a river meander. Hypothesis 2: Velocity is greater on the surface and decreases as the depth of the channel increases.

Mark scheme

Marking points from the official mark scheme (May/June 2010). The mark or mark type is shown in brackets.

1. [3 @ 1 = 3] (a) Don't do fieldwork/check conditions if river is in flood/deep/fast-flowing Wear strong shoes/wellingtons to protect feet Don't do fieldwork alone – at least two preferably three people/group Wear waterproofs to keep warm/protective clothing/light clothes which will dry Keep a look out for dangerous animals Don't do fieldwork if river is badly polluted/don't drink water/Veil's disease Tell someone where you are going/take a mobile phone for emergency Complete in daylight/before it gets dark May be slippery rocks/bank NOT don't run around/push each other in/swim in river
2. [3] (b) (i) Measure section along river Time floats over measured section Repeat timing exercise at points 1, 2 and 3 across river Calculate surface velocity: distance time
3. [3] (b) (ii) Rest rule/ruler on river bed - NOT ‘in river' Ensure rule is upright/vertical Take reading of water surface on rule/measure part of stick which is wet May suggest string & weigh & tape measure Lower string to river bed Mark / observe water level on string Measure wet section NOT repetition of measuring across river No credit for equipment – must describe its use
4. [2] (b) (iii) Velocity is greater near the outer bank of the meander/sample point 3 Velocity decreases towards the inner bank/sample point 1 Alternative to above ideas: velocity varies at different points/there are variations in velocity across river/velocity increases from sample point 1 to point 3 – NOT wording of hypothesis Velocity is greater where river is deeper/least where river is shallow Credit 1 mark (not reserve) for two comparative figures from 18, 41, 72 or difference between them No hypothesis mark
5. [3 @ 1 = 3] (c) Only measuring surface velocity Measurements could be affected by external influences such as floats get stuck on vegetation strong wind may interfere with movement of float Route taken by floats is unpredictable Floats all move into main current of river, so not really testing velocity across a meander Too few sampling points Only taking one measurement at each sampling point/need to do more Random positioning of sample points/not equal distances apart NOT human error weaknesses such as inaccurate timing/distance measurement
6. [3] (d) (i) Put flow meter on the bed of river/into river Must be held vertically Stand downstream or to the side of the flowmeter Propeller must be facing upstream Propeller spins/moves Record digital reading/display shows velocity Take several readings and calculate average NOT take measurements at different points in river
7. [2] (d) (ii) Completion of 20cm per second isoline Minus 1 mark for each error
8. [1] (d) (iii) Shading on diagram the area where velocity is greater than 40cm per second
9. [4] (d) (iv) Agree/partly agree with hypothesis – reserve mark Supporting data – two current measurements: e.g. 40-37-19 cm per second But where current is strongest there is exception/hypothesis doesn't apply everywhere across meander Here the greatest velocity is at about 1/3 of depth/just under water surface Supporting data – two current measurements: e.g. 60-68-70 cm per second Then velocity does decrease below 1/3 of depth Allow two marks for comparative figures (not reserve)
10. [2] (d) (v) Surface velocity is affected by friction with atmosphere Velocity near bed/banks of channel reduced by friction with channel Greatest velocity is where current is strongest/river is deeper/has most energy NOT 'velocity is greater on outside'
11. [4] (e) Similarities: Greater velocity slightly beneath surface/at surface Greater velocity where river is deeper Velocity reduces near bed/banks Differences: Velocity faster in middle of channel on a straight section Velocity decreases more evenly towards bed/banks on straight section 1 mark reserve for similarity/difference