a. Differences could include:
b. Answers should refer to the reasons for the rapid response in the urban area due to lack of interception, impermeable surfaces (roads, roofs, paving), thereby reducing infiltration, and the presence of artificial and rapid drainage channels (drains, sewers, flood channels), explaining the rapid rising limb, high peak discharge and rapid falling limb on account of overland flow/runoff.
The slower and lower response in the forested area could be explained by higher interception, the retention of water by litter, absorption by root systems, high soil and bedrock permeability.
Award [1 mark] for each valid reason suggested and award additional marks for depth of explanation (of the operation of factors and associated processes).
- higher peak discharge in the urban area
- shorter lag time in the urban area
- steeper rising limb in the urban area
- the longer peak discharge in the forested area
- there may be other features e.g. differences in base flow, urban hydrograph has two peaks.
b. Answers should refer to the reasons for the rapid response in the urban area due to lack of interception, impermeable surfaces (roads, roofs, paving), thereby reducing infiltration, and the presence of artificial and rapid drainage channels (drains, sewers, flood channels), explaining the rapid rising limb, high peak discharge and rapid falling limb on account of overland flow/runoff.
The slower and lower response in the forested area could be explained by higher interception, the retention of water by litter, absorption by root systems, high soil and bedrock permeability.
Award [1 mark] for each valid reason suggested and award additional marks for depth of explanation (of the operation of factors and associated processes).