RIVERS REVISION

FLOOD MANAGEMENT

There are 2 types of flood management:

SOFT ENGINEERING - using natural solutions to reduce flooding

- Much cheaper and less visually instrusive

- Not as effective

HARD ENGINEERING - building a permanent physical structure to reduce flooding

- Very effective at reducing flooding

- Very expensive and not visually attractive

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Soft Engineering

AFFORESTATION

Planting trees to increase interception

CONTROLLED FLOODING

Allowing flooding on low value land

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Hard Engineering

DAMS

Large barrier built to regulate the flow of a river

FLOOD CONTROL CHANNELS

Diversion channels which can be used to channel the overflow

FLOOD BARRIERS

Walls built alongside the river to reduce the risk of flooding

LEVEES

Embankments built next to a river to increase the channel capacity

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Definitions

INTERCEPTION - trees and plants stop rain reaching the ground

INFILTRATION - movement of water into the soil

PERCOLATION - movement of water from the soil into the rock

SURFACE RUN-OFF - water running over the ground without soaking in

TRANSPIRATION - water loss from vegetation

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DRAINAGE BASINS

DRAINAGE BASIN - is the area of land which is drained by a river and its tributaries

WATERSHED - is the line which divides one drainage basin from the next

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RIVER PROCESSES - Types of Erosion

SOLUTION - chemicals carried in the water dissolve rocks

HYDRAULIC ACTION - water forces air into cracks causing them to become bigger

ABRASION (CORROSION) - materials rubbing along the river bed and banks

ATTRITION - rocks colliding and breaking into parts

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Types of Transportation

SALTATION - small pebbles bouncing along the river bed 

TRACTION - large rocks rolling along the river bed

SOLUTION - material is dissolved in the water

SUSPENSION - small material floating in the water

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RIVER LANDFORMS - Waterfalls

They are created where hard rock overlies soft rock.

(http://www.bbc.co.uk/staticarchive/e992064ed45631c8ce8a26a9ef6d9e85cacd1279.png)

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Oxbow Lake

MEANDERS are bends in a river and overtime can become an OXBOW LAKE.

(http://a.files.bbci.co.uk/bam/live/content/zgpxn39/large)

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Levees

They form along the edge of the river channel where material is deposited during flooding.

(http://web.mst.edu/~rogersda/levees/press&siever13.13.png)

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HYDROLOGICAL CYCLE

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