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Slide 2

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The Hydrological Cycle
Storage Flows and Processes Outputs
· Interception (often · Infiltration · Evaporation
vegetation or · Stem flow (running · Transpiration
buildings) down a stem or tree) · Evapotranspiration
· Percolation · River discharge
· Vegetation (all the (seeping through
water contained in soil to the water
plants) table)
· Interflow (flowing
· Surface (puddles downhill through
etc) permeable rock
above the water
· Groundwater table)
(stored in the rocks · Surface run-off
or soil)…read more

Slide 3

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The Storm Hydrograph
Peak discharge ­ this is the highest point on
the graph and is when the river discharge is at
its greatest.
Lag time ­ the delay between peak rainfall and
peak discharge (it takes time for the rainwater
to flow into the river!).
Rising limb ­ the part of the graph up to peak
Falling limb ­ the part after the peak
discharge.…read more

Slide 4

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What influences the discharge?
Drainage basin characteristics - the larger ­ the more
precipitation it can catch ­ so a higher peak discharge
Rock type ­ impermeable rock does not store water, so there
is little infiltration ­ so a higher peak discharge
Soil type ­ clay soils have low infiltration - so a higher peak
Vegetation ­ more vegetation ­ more water is lost through
evaporation + transpiration ­ so a lower peak discharge
Precipitation ­ Intense storms increase peak discharge and
can then cause severe floods e.g. Boscastle floods
Temperature ­ hot/dry and cold/freezing conditions results
in hard ground. This reduces infiltration ­ so a higher peak
discharge…read more

Slide 5

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River Erosion
Hydraulic action ­ pressure of water breaks
rock particles away from beds and banks
Abrasion ­ rocks scrape and rub against
Attrition ­ (doesn't erode bed) rocks smash
into each other and become smaller, rounder
Cavitation ­ air bubbles in water implode
causing shockwaves that breaks rock off the
Corrosion ­ the dissolving of rock by chemical…read more

Slide 6

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River Transportation
Solution ­ substances that can dissolve are
carried along in the water (e.g. Limestone)
Suspension ­ very fine material (e.g. Silt and
Clay) is whipped up by turbulence and carried
Saltation ­ larger particles (e.g. Pebbles and
Gravel) bounce along the river bed from the
force of water
Traction ­ very large particles (e.g. Boulders)
are pushed along the river bed by the force of
water…read more


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