Hydrology and fluvial geomorphology 1.Photograph A shows a meander. Letters X, Y and Z show three positions within the river channel. (a) Using Photograph A, state the position where:

(i) erosion is dominant; X [1] (ii) deposition is dominant: Z [1]

(b) With the aid of a diagram, explain why the line of fastest velocity (thalweg) is not always found in the middle of the channel. [3]

Usually the fastest velocity in a river is found on the outerbank of the river where erosion is the most prominent.

MS:

Diagrams of either a cross section or plan with a velocity profile would be useful here. A valid approach would be through the discussion of the thalweg, especially around a meander. The cross section velocity profile could be used to explain how the friction from the river bed means the line of fastest velocity is not always central. A diagram of plan or cross section with explanation would be sufficient to access all 3 marks. Maximum of 2 marks if no diagram.

(c) Explain how the transport of material within a river channel varies with velocity and discharge. [5]

The transport of material varies with size. In general, the larger the material size the more energy is needed to transport therefore the higher velocity needed. This is not true for clay and slits as because they bond together meaning it is harder to break the particles and transport them.

MS:

Three key changes could be noted. The size of the sediment being transported would increase with velocity i.e the competence of the river would increase. The method of transportation may change, with larger sediment being transported by saltation or suspension. The amount of sediment being transported would also increase with velocity and discharge i.e capacity. Higher quality answers could also mention the Hjulstrom graph.

Atmosphere and weather 2 Fig. 1 shows some components which may change as a result of global warming.

(a) Using Fig. 1: (i) state two components which would be expected to increase during global warming; [2]

Sea surface temperature and air temperature in the lowest few km

MS: Any two of: Air temperature in the lowest few km / temperature over land / Marine air temperature / sea surface temperature / ocean heat content / water vapour / sea level.

(ii) state two components which would be expected to decrease during global warming. [2]

sea level and water vapor