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Physical Geography _ Theme A

Components of the drainage basin cycle
Infiltration: when water soaks into the upper layers of the soil.
Ground water flow: when the water stored in the rock below the surface travels
laterally (sideward) through the rocks towards the river or sea.
Percolation: the deep downward…

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Tributary: a stream which flows into a larger river.
Water shed: the boundary between drainage basins, it is often a ridge of high land.
Mouth: the end of a river where it meets the sea, oceans or lake.

















Erosion

Hydraulic action
Sheer force of running water erodes the river bed…

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Transportation

Solution
Soluble materials dissolve in the water and are carried in solution.
Suspension
The smallest load, like fine sand and clay, is held up continually within the river
water.
Saltation
The bouncing of medium sized load along the river bed.
Traction
The rolling of large rocks along the river…

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This happens when the river has less energy/ velosity is reduced.



For example

River enters sea or lake
When flood water flows onto *flood plain
inside of a *meander/ shallow areas along river
When the river has a sudden increase in its load e.g landslide
When the river *discharge (amount…

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The Lower Course ­ close to mouth

The bed load is small and rounded
River channel is wide and deep
High river discharge
High energy/ river velocity
Low friction from the bed load and river bed and banks










1. width and depth increase

(width x depth = cross sectional area)…

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size decreases / roundness increases
upper course river has low discharge + energy + large and angular boulders as
river does not have enough energy to move these.
lower course river has small rounded particles they may have been transported
by river + during transportation they have hit into each…

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Eventually the overhang of harder rock will collapse and the waterfall retreats
upstream.
Downstream of the waterfall is a gorge ( a valley with steep vertical sides)
































Meanders

A feature of the middle course and lower course

The cross section of the meander is asymmetrical. Due to the differences in…

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A point bar/ slip off slope (area of sand and small pebbles) is found to the inside
of the meander.
Energy losses by friction is higher where there is less water, this is to the inside
of the meander.
A river cliff or steep bank is found to the outside…

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Erosion takes place ­ hydraulic action and corrosion ­ at the outer bend.
Erosion cuts the bank of the interlocking spur.
Inner bend has slower/ less water deposition takes place.
Overtime the meander migrates laterally (sideward) and downstream.
Inner bend deposition ( point bar) continues forming.
Outer bend ­ interlocking…

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