AO1 (6 marks)

Marking instructions
Markers must apply the descriptors in line with the general marking guidance and the qualities outlined in the levels-based mark scheme below.
Indicative content guidance
The indicative content below is not prescriptive and candidates are not required to include all of it. Other relevant material not suggested below must also be credited.
Relevant points may include:

Storm hydrographs shape depends on physical features of drainage basins (size, shape, drainage density, rock type, soil, relief and vegetation)
The key shapes of the hydrograph are the steepness of the rising limb, the nature of the peak discharge as well as the characteristic of the falling limb.
The size of the drainage basin will affect the shape of a storm hydrograph as smaller drainage basins will mean that overland flow will more quickly reach the river and so create a steeper rising limb and a shorter lag time.
The shape of drainage basin will affect the shape of a storm hydrograph as more rounded drainage basins will mean that overland flow will more quickly reach the river and so create a steeper rising limb and a shorter lag
time.
The drainage density of the drainage basin will affect the shape of a storm hydrograph as drainage basins with a high drainage density will mean that overland flow will more quickly reach the river and so create a steeper rising limb and a shorter lag time.
The rock type of the drainage basin will affect the shape of a storm hydrograph as drainage basins with impermeable rocks such as granite will mean that overland flow will more quickly reach the river and so create a steeper rising limb and a shorter lag time.
The soil type of the drainage basin will affect the shape of a storm hydrograph as drainage basins with soils with a low infiltration rate such as clay soils will mean that overland flow will more quickly reach the river and so create a steeper rising limb and a shorter lag time.
The topography of the drainage basin will affect the shape of a storm hydrograph as drainage basins with steep slopes will mean that overland flow will more quickly reach the river and so create a steeper rising limb and a shorter lag time.
The vegetation type and amount of the drainage basin will affect the shape of a storm hydrograph as drainage basins with sparse vegetation will mean that overland flow will more quickly reach the river and so create a steeper rising limb and a shorter lag time.
The levels of antecedent soil moisture will affect the shape of the storm hydrograph as saturated soils will mean that overland flow will more quickly reach the river and so create a steeper rising limb and a shorter lag time.

Accept other explanations of how the physical features of drainage basins affects the shape of storm hydrographs

Hydrological Cycle (Edexcel A Level Geography)

Topic Questions