GSCE Geography Rivers

8/6/2019 GSCE Geography Rivers

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In the upper course therivers cross section is narrowand in a deep V shape,because erosion is mainly downwards as it is fastflowing because the gradientis high. The material carriedhere is large.

In the middle and lowercourse, the river becomes

wider and the river is slowermoving as the gradient isless. This means thaterosion is mainly lateralthan downwards. The rockscarried are smaller due toattrition and the fact thatthe river is slow and unableto move large rocks. More

deposition occurs here.



Interlocking spurs: when the river winds around hard rock, it forms cliffs thatinterlock

When the water flows

over hardrock then

soft rock, it

will erodethe soft rock

faster by hydraulicpower andCorrasion,forming a waterfall.

The waterfall

willeventually

undercutthe softerrock and theoverhang of

the hardrock will

eventually collapse.

When the water hits

the plungepool, someof it retreatsupstream,forming a

gorge.



Here, the gradient becomes lesssteep and erosion is more lateralthan downwards, so the rivertransports more material. It doesthis in four ways:

Traction: large boulders run alongthe river bed

Saltation: smaller pebbles arebounced along the river bed.

Suspension: the finer sand and siltlike material is carried in the water

Solution: minerals like limestoneare dissolve in the water and are

carried along.



A meander is a bend in ariver.

The water is deeper and

flows faster on the outsidebend of the river.

The force of the watererodes the outside bend

forming a river cliff.

The water is shallower andflows more slowly on the

inside of the bend.

Sand and gravel that theriver no longer has the

energy to carry isdeposited on the inside of

the bend forming a slip off slope.



H ydraulic power and Corrasionerode the OUTSIDE bends of a

meander, as the water flows fasterthere.

Deposition occurs on the SLIP OFFSLOPES, because the river flowsslower here.

This makes the neck of the meandernarrower and narrower until eventually it is broken through, normally when theriver is in flood as it has extra energy.

The river then flows along the straightpath as it is quicker. The meander is

sealed off by deposition to form an ox-bow lake.



Definition: leveesare natural

embankments of silt along the banksof the river. Thereare many naturalones on the banksof the Mississippi.

When the river floodsit pours over the banks

and onto thefloodplain. The water isslowed by friction and

the larger coarser

material is depositedfirst but the finer

material travels furtheraway.

During dry weatherthe speed falls,

causing deposition.

The channelbecomes full of silt, which makes the

bed rise.

A fter many floodsthe river banks havelevees and the river

bed maybe raisedup so much that theriver rises above the

floodplain.



A delta is a flat area of sand and silt builtout into the sea. It is found at the mouthof the river.The area around a delta is gradually filled in

with sediment and becomes dry land.

Deposition forces the river to split up into several

distributaries (a smaller river leaving a larger one).

This deposited sediment builds up over years,creating a delta.

A s the river reaches the sea the sea acts as a break and the riverslows down, dropping its sediment. The salt from the sea alsomakes the salt and sand particles stick together.

The river needs to be carrying a large load and the seaneeds to be sheltered without strong winds and

currents.



The river tees is mainly used for

Forest fruits round trees:

Farming (mainly sheep farming)

Forestry Reservoirs. Tourism

Large towns

with:

Shops Offices Farmland IndustriesFlood

defences



R un off: TR un off: The water that runs down hills into rivers.he water that runs down hills into rivers.Impermeable rocks:Impermeable rocks: Rocks that do not allow water to pass throughRocks that do not allow water to pass through

The causes of riverflooding:

Heavy rain overlong periods

Heavy snowfallsthat melt

Impermeable rocksmake the water run

off quicker

Rivers that have littleplant or tree cover

around are more likely to flood, because thesecan absorb some of the

rain.

Urban areas causeflooding, the concreteand tarmac cause therainwater to run off quicker into rivers.



Wh y doesBangladesh

flood?

Deforestationmeans less

absorption of water

Heavy rainfalldue to monsoon

climate

Snow melts on theHimalayas, flowing

down to the rivers.

Cyclones (violentstorms)

frequently hit

Describe theeffects of a flood

in an LEDC.

Bangladesh 1998

1 million people were lefthomeless.

240 villages wereflooded.

Over 1000 people were killed.

Supplies of foodand water ran low

Diseases spread

1 billion dollars

worth of damagedone

How did it manage a flood disaster?

�Distribute food

�Provide fresh water and sanitation supplies

�The aid agencies provided boats to rescuepeople

Bangladeshsuffers fromflooding nearly every year, butthe floodwaterbring with themfertile silt, whichdoes make thearea good forfarming.



Theeffects of a flood inan MEDC

TheMississippi river in

1993

28 peopledied

36,000peoplemade

homelessR oads and

railwaysunder water

Electricity lines

collapsed

Farmlandflooded

10 billiondollars

needed to

repairdamage.

The Mississippi river. (DA RTS)

D- dams andreservoirs

were built on

the tributary rivers

reducing thequantity of

waterreaching themain river

A -afforestation

to absorbmore water

R- reroutingthe river,

shorteningthe river andallowing the

water totravel away

quicker

T-tallerlevees

S-spillways-overflowchannels



The building of levees or

embankments

Huge damsbuilt

Storage basinsto take in waterdiverted fromthe main river

A fforestation

Floodforecasting and

warningschemes

Improved floodshelters

Less technologies tofight floods in

LEDCs

No early warningsystems

Less medical andrescue services

They need the goodfarmland to growcrops to survive

Cannot afford tomove

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