River, floods and management - questions

Question 1

Describe how water reaches a river channel in a drainage basin. 4 marks

Answer 1

• Overland flow/surface runoff where water is running over the land surface into the channel (1).
• Throughflow where water has infiltrated into the soil (1) flows parallel to the surface and into streams (1) above water table/unsaturated zone.
• Direct precipitation/channel catch over the river channel (1).

Question 2

Explain likely effects of the forest on river discharge. 5 marks

Answer 2

• Vegetation = slow down the rate at which the water reaches the river
• Increasing the lag-time and reducing peak.
• Leaves - intercept the rainfall en route to the ground. This delays the progress of the water.
• Some will reach the ground as stemflow and drip, whilst some may never reach the ground and the river due to evaporation.
• Deciduous forest - effectiveness of interception will vary, being less apparent during the winter when the leaves have been lost.
• The trees will also use some of the water to maintain growth and slow the speed at which water gets to the river and so the amount via overland flow and throughflow is much less.
• Leaf litter soaking up water before infiltration.