Hydrograph data to plot
Thinking through Geog
2. Rivers flood due to a number of physical
and human causes.
3. Flooding appears to be an increasingly
• To know the terms:
Flooding, hydrograph, rising limb, falling
limb, lag time, drainage basin
• To be able to explain the factors that
• To know the frequency and location of
flood events in the UK over the past 20
• Surface storage
• Soil moisture
• Surface run off
• Through flow
• Groundwater flow
• Water table
Factors affecting discharge
•Amount and type of rainfall • Soil
•Temperature • Land Use
•Previous weather conditions
Most floods occur because of the
Amount and type of rain
• Prolonged rain – long and continuous periods of
rainfall lead to saturated ground
• With drizzle, there is time for water to infiltrate
soil and underlying rock
• Heavy rain which causes large amounts of run-off
in a short period of time
• High temperatures lead to greater evaporation
and transpiration rates so river levels decrease
• Snow melt – in spring a sudden increase in Textbook
temperature which melts snow and ice. - In winter page 109
the water cannot seep into frozen ground
• Previous weather conditions
• Rock type
• Rock type determines how much water
infiltrates and how much stays on the surface.
• Relief affects the rate at which water runs
off the land surface and into rivers. Steep
slopes give faster run off due to gravity
• Gentle slopes allow time for infiltration
Human activities can make the
flood risk worse …
• Building on a floodplain.
Tarmac and concrete are
impermeable which means
that more water runs off
the surface and faster.
• Deforestation reduces
interception by the trees
and so more rainwater
reaches the surface
quicker increasing rates
of surface run off
• Textbook page 110 task 3
• You are to produce a double page spread around the
title ‘ The reasons river discharge fluctuates’
• In the central box give the meaning of ‘river discharge’
• Place the factors around the central title
• Add information to each factor to explain how discharge
• Illustrate each factor with diagrams, sketches or photos.
• Your finished work should be informative, accurate,
interesting, colourful and original
Which are physical and which are
Plenary human factors?
What factors increase
The risk of flooding?
Building in the
* Very wet soil
* Many tributaries * Impermeable
* Cutting * Hard dry soil rock
Card sort activity
Cut out the two hydrographs – one for a
‘flashy’ river and a gentle graph
Now cut out the individual cards and place
them under the appropriate hydrograph.
A particular slide catching your eye?
Clipping is a handy way to collect important slides you want to go back to later.