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Droughts

CAUSES

  • changes in atmospheric circulation when it doesnt rain much 
  • changes in atmospheric prssure can make annual rains fail (e.g monsoon)
  • high pressure weather systems block depressions (weather systems that cause rain)

PRIMARY IMPACTS

  • vegetation dies (crops)
  • people and animals die dehydration
  • aquatic animals die due to dried up rivers and lakes
  • soil drys out and is easily eroded by wind

SECONDARY IMPACTS

  • animals+humans die starvation due to food shortage
  • conflicts over water supplies, so people mov away
  • farms close cauing unemployment
  • winds pick up dry soil causing dust storms
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Droughts 2

HUMAN ACTIVITIES INCREASE IMPACTS

  • overgrazing reduces vegetation so increases soil erosion caused by the drought
  • excessive irrigation (water artificialy pumped from rivers, lakes to farmland to increase crop production), it depletes water in rivers so theres less water

REDUCING THE IMPACTS

  • farming techniques, drought resistant crops, drip irrigation (delivers small volumes of water directly to crops roots) nore efficient
  • conserve water by reducuing amount used in homes
  • install water butts to collect rainwater use water garden
  • emergency aid with food and water
  • prediction, moniter rainfall, once predicted things can be done e.g hosepipe ban

SUSTAINABILITY

  • effective and environmentally friendly, but building wells depletes groundwater less in future
  • building resovoirs reduce thers water downstream, some more cost effective
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Coastal Erosion

TYPES

  • hydraulic action- waves crash against rock and compress air in tiny crack creating pressure on rock, crack repeatedly widened until breaks off
  • abrasion-eroded particles in water scrape and rub against rock, removing small pieces
  • attrition- eroded particle sin water rub against eachother, break into smaller fragments
  • corrosion- weak carbonic acid in seawater dissolves rok=cks like chalk and limestone

CLIFF RETREAT

  • erosion occurs at part of cliff due to waves
  • wave cute notch appears with unstable rock above
  • unstable rocks falls down and the materials cleared away by waves
  • new wave cut notch forms
  • cliff retreates and a wave cut platform forms

CLIFF MASS MOVEMENT

  • slides- material moves in straight line  slumps- material moves with rotation
  • rockfalls- material shifts vertically
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Coastal Management Strategies (hard)

SEA WALL- concrete wall reflects waves to sea. Barrier to prevent flooding, protects coast.

creates strong backwash erodes wall, very expensive build maintain

RIP RAP- boulders piled up. absorb wave eneergy, reduce erosion and flooding

can be moved by strong waves so need to be replaced

GROYNES-wood/stone fences right angkes to coast. widen beaches,protect flooding+ erosion

starve beaches further down coast as stops LSD, narrow beaches bad protecting coast

REVETMENTS- slanted structure made concrete at foot cliffs. absorb wave energy, stop erosion

expensive, create strong backwash erodes under barrier

GABIONS-rock-filled cages, at foot of cliffs. absorb wave-energy, reduce erosion.       ugly

BREAKWATERS-concrete blocks deposited sea bed of coast. force waves break offshore reduce erosive power.    expensive, can get damaged in storms

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Coastal Management Strategies (soft)

BEACH REPLENISHMENT- sand and shingle from elsewhere added to the beach

creates wider beaches which slow waves, protection form flooding and erosion

can kill organisms on sea bed e.g sponges and corals, very exoensive, has to be repeated

MANAGED RETREAT- removing an existing defence and allowing the land behind it to flood

wil become marshland creating new habitats, flooding+erosion reduced behind marshland, cheap

may disagree what land is allowed to flood e.g flood farms ruins farmers livelihood

SUSTAINABILITY

  • reduce flooding today wihtout using up non-renewable resources or damagin environment
  • hard engineering usualy less sust than soft engineering strategies, cost more money buid and maintain and damage environment more
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Squatter Settlements

WHAT ARE THEY- badly built illegal settlements found in and around the city 

LOCATION

  • edge of city- more space and availability of land, easy access to city centre
  • derelict land- unsuitable for permanant development, sheltered, access to water

WHY THEY ARE A PROBLEM

  • bad reputaion/ view of the city,          high crime rates
  • crowding means diseases spread easily and quickly
  • no waste disposal so it contaminates the river        residents dont pay taxes

IMPROVING THEM

  • self-help schemes, governemnt gives supplies to build your own home
  • site and service schemes, pay a low rent for site and money is used to pay for basiv sevices in the area
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Flood Management (hard)

DAMS- wall built across river, upper course      RESOVOIR- artificial lake formed behind dam

releases water slowly reducing flood risk, use as drinking water and produce hydroelectric power

very expensive to build, can flood existing settelements, eroded material deposited early not along natural corse making farm land downstream less fertile

CHANNEL STRAIGHTENING- meanders cut out by building artificial straight channel

water moves out of area more quickly, reducing flood risk

flooding may occur dwnstream instead as its carried there faster

MAN-MADE LEVEES- embankments along both sides river

river channel can hold more water, cheap, reduces risk

if they break, causes catastrophic flooding

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Flood Management (soft)

FLOOD WARNINGS- warned through tv, radio, newspapers or internet

impacts reduced, time to pu tpossessions upstairs. sandbags into place, evacuate

doesnt stop it from happening, may not hear/ have access to warning (especially LEDC)

PREPARATION- buildings modified to reduce damage floood could cause, people make plans

impact reduced, buildings less damaged, people know wat to do

doesnt guarantee security, give false sense of scurity, expensive modifiy homes and buildings

FLOOD PLAIN ZONING- restrictions prevent building on part of flood plain that will be affected

risk reduced, impermeable surfaces not created, impact reduced, no road/ house to be damaged

expansion of urban area limited if no other building sites, no help areas already built on

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