CASE STUDIES V- UNIT 1 - QUESTION 1

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THE MISSISSIPPI FLOODS - 1993

Causes : 1) Snow melt in spring 2) Heavy rain in April 1993 = saturated 3) Thunderstorms in June/July = rapid surface run off 

Reducing Flood Risk :

1)Dams+ Reservoirs - Hold back water - MISSOURI = 6 DAMS + 105 RESERVOIRS 

2)Strengthen Levees - higher + strengthened 

3) Cut off Meanders - Straighten + shorten course + water drain away quicker 

4) Afforestation - trees intercept rainfall +delay effects of flooding 

5) Dredging - deepen river bed= hold water + prevent flooding

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THE RIVER DERWENT- MARCH 1999- IN BRITISH ISLES

WORST FLOOD IN 70 YEARS 

Physical Causes -

Heavy rainfall over North York moors 250mm in 12 days

Ground in Derwent basin = already saturated 

Human causes - 

Peat removed from North York Moors 

Houses built on floodplain = high surface run off  = Urbanisation

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RIVER MANAGEMENT SCHEME OUTSIDE UK - MISSISSIPPI

13 million dollars damage 

Hard engineering solutions - 

raised banks / levees - 15 m along 3000km 

over 100 dams built 

meanders cut 

river straightened- 1750km 

Soft engineering - 

Afforestation - The tennessee valley 

SUSTAINABLE ? 

NEED MANAGEMENT 

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COASTAL MANAGEMENT IN BRITISH ISLES - NEWCASTLE CO

GROYNES: 

1980S - trapped snad being moved by longshore drift 

decayed 20 years 

expensive

GABIONS:

Mouth of river Shimna in 2006 

Sustainable = protected prominade 

Unsustainable = need replaced + expensive 

Sea Wall - 

2002 - curved face =absorbs + deflects energy - 4m cost - Unsustainable

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