Get That Grade

This was a trick question. At 630768 the height was just less that 40 m above sea level. (You can tell by reading the contour just next to the river.)
At 750750 the river is still just below 40m, judging by the contours. However, there is also a spot height at 742760 which suggests the river is just below 36m.

2	Just over 12 km. You can work this out by counting the kilometre squares.

3	3 Gentle; Flat.

(i) From 685779 to 675768 the land runs across a plateau. It slopes very gently down from a height of 91 metres to a contour line at 90 metres.
(ii) Then, to 672767 it slopes steeply down, from 90 to 40 metres in a distance of less than 0.5 km.
(iii) Here it becomes almost flat, as it crosses the river's floodplain.
(iv) From 668767 it slopes quite steeply upwards, to a height of 95 metres at 653750.

It is on a floodplain. The land does not slope down to the river. There may even be banks alongside the river (levées) to stop it flooding. These will make drainage even more difficult. Evidence of the poor drainage can be seen in 6677, where a little tributary stream flows alongside the main river. It probably cannot join the main river because of the levées.

6	You could describe one of the meanders, or the steep slopes on the edge of the floodplain, caused by undercutting. If you have a very good knowledge of this topic you may even describe one of the 'eyots' (little islands in the river like those at 670764 or 680749).

Here you must use your knowledge rather than your map-reading skill. The main point of this question is that you should know when a river deposits material and when it erodes. You may well have written about the cross-section of the river here; about the strength of the current concentrated on the outside of the bend and the gentler current on the inside of the bend.

9	It soaks into the surface. It probably infiltrates through the soil into the rocks below.

10	Permeable — because there is no surface drainage. (It is actually chalk — see 7178 for further evidence.)

11	V-shaped contours pointing back up towards the high land show that there is a valley.

(a) It is much steeper than the Thames.
(b) It is a narrower with no floodplain. It is also more steep sided — clearly a V-shaped cross section.
(c) The steep gradient and V-shaped cross-section both suggest it was a youthful tributary of the more mature Thames. You may just be able to see the interlocking spurs coming in from the valley sides.