SURFACE RUN OFF:
water which
flows QUICKLY
across the
surface
Human factors affecting surface run off
Deforestation
Cutting down trees means there are no
leaves to INTERCEPT rainfall. Rain
reaches the ground very quickly and the
soil can become saturated. The water
cannot INFILTRATE the soil so surface
run off rates INCREASE.
High levels of surface run off mean
water is finding its way to the river
very quickly. This means the river is
much more likely to flood.
Urbanisation
Urban areas are
covered in concrete
and tarmac. This
stops rainfall
INFILTRATING into the
underlying soil. This
INCREASES surface
run off rates.
High levels of surface run off mean
water is finding its way to the river
very quickly. This means the river is
much more likely to flood.
Farming
Ploughing fields removes vegetation
preventing INTERCEPTION. Ploughing the
land can create channels which funnel water
downhill. Both of these things increase
surface run off rates
High levels of surface run off mean
water is finding its way to the river
very quickly. This means the river is
much more likely to flood.
Physical (natural) factors affecting surface run off
Geology
NON POROUS rock does not have any gaps in it. This means it cannot store
water. When it rains, the soil above it becomes saturated very quickly
because the water cannot PERCOLATE into the underlying rock. This
increases surface run off rates.
High levels of surface run off mean
water is finding its way to the river
very quickly. This means the river is
much more likely to flood.
Prolonged or heavy rainfall can prevent
rainwater infiltrating into the soil (either
because it is saturated or because the
rain is falling faster then it can infiltrate).
This increases surface run off rates.
High levels of surface run off mean
water is finding its way to the river
very quickly. This means the river is
much more likely to flood.
THROUGH FLOW: water
which flows SLOWLY
through the soil
GROUNDWATER FLOW:
water which flows
very SLOWLY through
the underlying rock
Water stores
surface water e.g. rivers, lakes
and reservoirs
Weather. During periods of prolonged or
heavy rainfall, stores of water in the
drainage basin will increase.
soil
Weather. During periods of prolonged or
heavy rainfall, stores of water in the
drainage basin will increase.
rocks
Geology
Porous rocks have gaps (pores) where water
can be stored. Limestone is a porous rock.
Non porous
rocks have no
spaces so they
cannot store
water
Weather. During periods of prolonged or
heavy rainfall, stores of water in the
drainage basin will increase.