Case Studies Flashcards
(60 cards)
Bangladesh 1998 Flood — human causes
- Corruption - less money for flood defences
- Lack of international investment in flood defences - not seen as useful
- River diversion - reduces silt downstream, preventing protective floodplain from forming
- International debt - Bangladeshi government repaying loans instead of social schemes
- Deforestation in Himalayas - reduces interception and evapotranspiration, increases runoff and soil erosion, reducing channel capacity
- Overseas pressure - to invest in economy and exports
- Urbanisation - high population density and growing cities (impermeable surfaces) puts more people at risk
- Sinking of 120,000 fresh water wells in 1980s - lowered water table, caused land to subside at 1 inch per year
Bangladesh 1998 flood — physical causes
- Tropical storms – cyclones bringing heavy rains, strong winds and tidal surges
- Rivers silting up – reduces channel capacity. Increased by deforestation in Nepal.
- Snowmelt in the Himalayas (June–September) – produces melt water which enters the Ganges and Brahmaputra
- Low-lying floodplain – 80% of Bangladesh is floodplain, 50% of the country is less than 5 m above sea level. Ganges and Brahmaputra converge to form a huge delta
- Tidal surges – river water is prevented from escaping into the Bay of Bengal
- Monsoon rains – climate is one of the wettest in the world
Bangladesh 1998 flood — effects
- Two thirds of the country was covered in floodwater. Dhaka was 2 m underwater
- Some areas were underwater for over two months
- 1040 people were killed either by drowning or by disease that followed the flood e.g. cholera and typhoid
- Water contaminated by waste and dead bodies/carcasses, spreading disease. Diarrhoea and dysentery
- 24 million made homeless
- 130 million cattle killed
- 668,000 hectares of cash crops destroyed, affecting 2.5 million farmers
- Almost all the country’s rice was wiped out
- Export industry production fell by 20%, 400 clothing factories had to close
- Dhaka sewage system collapsed, drinking water contaminated
- 6,500 bridges and 11,000 km of road damaged
Bangladesh 1998 flood — measures to reduce flooding
Short term
• 350,000 tonnes of cereal bought and distributed by government
• Key supplies provided by countries and relief organisations. UN appealed for $74 million.
• UK donated £21 million
Long term
• Afforestation in foothills of Himalayas
• Debris cleared, repairs made to sewer systems and houses
• Development of flood warning system
• Dredging of silt around major cities to increase channel capacity
Bangladesh 1998 flood — benefits
- Provides fertile alluvium
- Regular flooding essential for high yield of paddy rice
- Reduces need for irrigation
- Transport of people and supplies, even during flood
- Flat land is easy to build on
- Source of water for drinking and cooking. Fish is a staple food
- Flood events help bring money to improve flood defences
- High population density leaves people with no choice but to live on the delta
Holderness Coast — opportunities
• Industry (Easington Gas Terminal supplies 25% of UK gas) • Farming (fertile boulder clay) • Spurn Spit ○ 6km of Heritage coastline ○ Over 200 bird species ○ Recreation, tourism ○ Jobs — Humber Pilot Station • Tourism ○ Seaside towns e.g. Bridlington, Hornsea ○ £450 million per year ○ 8.5 million day trips per year
Holderness Coast — causes of erosion
Geology
• Glacial Till (boulder clay) deposited in Ice Age
• Easily attacked by weathering and erosion
• Prone to slumping and mass movement
Weathering
• Rain saturating cliffs
• Biological
• Salt weathering
• Freeze thaw
Processes
• Hydraulic action: strong NE fetch, destructive waves
• Corrasion by chalk fragments from Flamborough Head
• Attrition: high level of suspended load (chalk, clay)
Longshore drift
• N to S
• Groynes starve areas further south
Human
• Groynes
• Climate change: storms, rising sea levels
Holderness Coast — impacts
Services • B1242 at risk before Mappleton defences • Sands Lane, Barnston drops into the sea • Gas/water pipes damaged by collapsed houses Families • Stress • Financial loss • Houses — loss of value, insurance, forced to move • Barnston Caravan Park — 10 pitches lost a year • Humber Pilot Station — job losses Farming • Sue Earle farm, Cowden ○ Cattle fall off cliff ○ £250,000 farmhouse lost ○ £3,500 demolition cost ○ Lost grazing land ○ Mappleton defences increased erosion from 3ft to 30ft per year Seaside towns • 29 towns/villages lost • Valuable tourist resorts at risk Wildlife • Spurn Spit (salt marsh, sand dunes): 200 bird species • Cliff habitats Industry • Easington Gas Terminal ○ only 12 m from sea ○ 25% UK gas ○ 1 km rock revetment
Holderness Coast — Management
• Example: Mappleton (hard)
○ Rock groynes
§ Trap sand
§ Wide beach slows cliff erosion
§ More durable than wood
§ Ugly
§ Expensive (£1500+/m²)
§ Limited lifespan
○ Rip-rap
§ Relatively cheap (£1000/m)
§ Protects other defences from scour
• Example: Withernsea (hard)
○ 2.3 km, £6.3 million
○ Sea wall
§ Expensive (£7000/m2)
§ Lifespan 50-100 years
○ Groynes
○ Rip-rap
§ Protects wall
○ Offshore breakwater reef
• Example: Mappleton (soft engineering)
§ Cliff regrading, marram grass
• Example: Great Cowden (managed retreat)
○ Compensation to farmers
○ Material protects other areas e.g. Tunstall
○ Cheaper
○ More sustainable
○ Creates habitats
• Example: Spurn Spit (do nothing)
○ 1900s groynes abandoned in 1961
§ Cheaper
§ Nature
§ Threat to heritage coastline
§ Risk to Humber Pilot Station, safety
§ Risk to jobs
○ Loss of land, cows ○ Loss of income
Great Barrier Reef — benefits
- Increased marine biodiversity (> 1 million species of plant and animal found in reefs)
- Income from tourism
- ¼ of world’s fish comes from reefs (1 sq. km produces 15 tonnes of fish annually)
- Half of medical research is linked to marine organisms. Coral reef organisms are used in cancer and HIV treatment.
- Coastal barriers: reduce power of waves, storms, hurricanes, typhoons, tsunamis. This reduces erosion, flooding and property loss, saving $billions per year.
- A$5 billion per year from tourism
Great Barrier Reef — threats
• Pollution from agriculture and industry
○ Waste contains nutrients
○ Other plants begin to out-compete the coral
○ Coral is starved of oxygen, eutrophication occurs
• Dredging close-by (for construction)
○ Makes waters cloudy
○ Starves coral of sunlight, impairing growth, eventually killing the coral
• Tourists
○ Step on live coral
○ Bump into reefs
○ Drop cigarette butts into waters
○ Anchors
Great Barrier Reef — protection
• ⅓ of reef is off-limits to fishermen
○ Prevents overfishing, balances food chain
• Ban on cyanide fishing
○ Captures fish alive
○ Harmful to coral
• Government reducing farmers’ use of nitrogen based fertiliser
○ Would runoff into the sea, increasing eutrophication
• Policies on cruise ships and anchorages
○ Limit traffic
○ Provide permanent anchorage
○ Impose speed limits
• Eco-Tourism certification
○ Incentivises companies
Amazon deforestation —reasons
• Population pressure
• International debt
• National policies
• Demand for resources from MEDCs and TNCs
○ Timber
○ Minerals
○ Hydro-electric power led to clearing to create lakes
• Government subsidies for cattle ranching and cash crops
• Fuelwood collection — charcoal
• Farming
○ Slash and burn
○ Subsistence
○ Commercial cattle ranching, plantations
• New roads (e.g. Trans-Amazonian Highway)
• Development
○ E.g. Carajas (world’s largest iron ore mine)
• Tourism
• Scientific purposes
Amazon deforestation — impacts
• Selective hardwood logging also damages other trees
• Destruction of canopy damages soil
○ No roots to bind soil
○ Soil is compacted
○ Soil erosion
○ Landslides
○ Silting up of rivers
• Breaks nutrient cycle
○ Nutrients leached from soil by heavy rain
○ Causes farmers to make new plots
• Environmental scarring
• Global climate
○ One third of O2 comes from tropical rainforests
• Local drought due to reduced evapotranspiration
• Water quality
○ Toxic metals from mining polluting rivers e.g. Al, Hg
○ Also kills fish
• Destruction of wildlife habitats
• Plant species (cosmetics, medicines)
• Amerindians
• Malaria
Cassiterite washing leaves pools of water, breeding grounds for mosquitoes
Amazon deforestation — management
• Land reform in surrounding areas
• Sympathetic farming e.g. Rubber tapping
• Harvesting forest fruits
• Educating locals
• Harvesting medicinal plants e.g. Copaiba (cosmetic), Jaborandi (glaucoma), Emetine (cancer)
• Ecotourism (jobs: tour guides, maids)
• Establishing National Parks e.g. Jau NP, 1986
• Establishing ecological reserves
• Sustainable logging
○ Selective cutting (circumference, number/hectare)
○ Limit size of machinery & entry tracks
○ Heli logging
○ Integrated cutting (several species for different uses collected at once)
○ FSC
Sahel —natural causes for desertification
- Average temperature has risen over last century
- Following rainfall, up to 90% evaporates
- Droughts e.g. 1968–1973 drought
- Global warming will cause droughts to become more severe
Sahel — human causes (population pressure)
• Increased demand for food
• Population doubling every 20 years
• 3% population increase per year, while food production only increases by 2% per year. This leads to over-cultivation, overgrazing and over-irrigation
• Over-cultivation: reduces soil fertility, damages structure, makes it crumbly, likely to be blown away
• Over-grazing: sustainable carrying capacity being exceeded
○ Animals forced to eat roots, killing vegetation
• Over-irrigation: wastes valuable, leads to salinisation as water evaporates
○ Creates impermeable, infertile salty crust
○ Poor salt quality, kills vegetation
• Tourism taking up land, 4x4 vehicle tracks compact soil
• Border closures cause nomads to stay in one place, leading to overgrazing
War causing migration to refugee camps e.g. 30,000 migrated to Sudan during Ethiopia vs Eritrea
Sahel — human causes (firewood)
- High demand: deforestation
- Limited energy sources in Sahel leads to reliance on wood
- Deforestation makes ground vulnerable to wind, causing soil erosion
- Some farmers change to fuelwood collectors
Sahel —impacts of desertification
• Erosion of top soil
○ Reduced productive area — Niger 2,500 sq km lost per year
• Decreased productive land
○ Niger producing 1/20th of the food they could 40 years ago
○ Causing famine and death
• Forced migration
○ Creates problems: refugee camps, food shortages, humanitarian aid, spread of disease due to high density in camps, strain on host country
○ E.g. 2 million from Mali to Burkina
• Violence due to scarcity of land
○ E.g. Sudan: Black African farmers vs. Arabic herders
• Animal migrations
○ E.g. Rodents move south, destroying crops, bringing new diseases
Sahel —management strategies
• Fences, tree lines: retain soil
• Water harvesting using diguettes allows water to soak in
○ Burkina: 50% increase
• Drip-irrigation: reduces waste, prevents salinisation
• Solar ovens reduce need for firewood
• Tree planting programme
○ 1 million trees being planted in Ethiopia’s rift valley
○ Senegal ‘green wall’ project: 15 km tree belt
Kobe Earthquake — cause
Pacific and Philippine sea plates subduct under Eurasian plate due to higher density
Plates became stuck, allowing pressure to build until plates finally slid past each other
Kobe earthquake — primary effects
200,000 buildings collapsed 1 km of Hanshin Expressway collapsed 120/150 Kobe port quays destroyed Bullet trains derailed ~4,000 people killed Electricity, water, gas supplies destroyed
Kobe earthquake — secondary effects
Broken gas pipes and cables started fires, burning ~7,500 wooden buildings
Blocked roads delayed emergency services
Broken water supplies delayed firefighting
230,000 left homeless
Broken phone lines reduced communication
Kobe earthquake — long-term effects and management
July 95: water, gas, electricity, phone lines fully functioning
Port back to 80% within 1 year
Kobe lost place as #1 Japanese trade centre
1999: 134,000 homes built to stricter regulations
Buildings build further apart, on more stable land
More earthquake prediction instruments
Major transport routes reinforced
Many moved from the area permanently (jobs or safety)
Jobs created in construction
