physical geography f763 earth hazards

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  • Created by: charlie
  • Created on: 12-02-15 21:01

Earth hazards course

Earthquake Activity 

  • Primary: ground movement, liquefaction, roads, bridges and buildings collapse 
  • Secondary: firestorms, landslides, tsunami, disease, homelessness, aftershocks 
  • Tohoku + Haiti 

Volcanic activity 

  • Primary: lava flows, pyroclastic flows, ash, tephra, volcanic gases
  • Secondary: lahars, landslides, tsunami
  • Pinatubo + Mt St Helens + Sakurajima 

Mass Movement (and slope failure)

  • Venezuela + Aberfan + Holbeck Hall 

River Flooding 

  • Boscastle + Bangladesh 
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earthquake causes

PHYSICAL 

  • earthquake characteristics (energy, location of focus, depth of focus, epicenter, duration)
  • site characteristics (coastal? relief? loose sediments)
  • temporal considerations (time of year, seasons, day of week, time of day)

HUMAN 

  • built environment (age, material, density, infrastructure) 
  • population characteristics (wealth, education, density) 
  • risk management (monitoring, hazard mapping, education, building reg, emergency services) 
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impact of an earthquake - Tohoku MEDC

PHYSICAL 

  • earthquake characteristics (9.0 richter scale, 32km depth of focus, epicentre 72km away from land, lasted 6 mins, 671 5.0 aftershocks)
  • site characteristics (dropped coastline 0.6m, 10m tsunami wave, landslides, amplification, liquefaction)
  • temporal considerations (11th March 2011, friday, 2.46pmm, lasted 6 minutes ) 

HUMAN 

  • built environment (130,500 buildings, 4000 roads, 29 railways, 78 bridges down/unsafe)
  • population characteristics (ageing, good education, high density, poorer part of Japan, 10,000 dead, 20,000 missing)
  • risk management (60s of warning, 58% headed for higher ground, texts, transport shut down)

IMPACTS

  • economic - (130,500 buildings destroyed, 4000 roads damaged, $150Bn ...)
  • social - (3,000 reported missing + presumed dead, 16,000 dead...)
  • environmental (dropped coastline, extensive tsnami defences ruined, Fukushima leak into environment)
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Tohoku MEDC management

PREDICT -

  • S-WAVES took 90 s to reach Tokyo 

PREPARE -

  • japanese self defence force mobilised 

PROTECT -

  • 3 principles (SAFE, SUSTAINABLE, COMPASIONATE),
  • building resilience 
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impact of an earthquake - Haiti LEDC

PHYSICAL 

  • earthquake characteristics (epicentre 25km from Port-au-Prince, focus 13km down, magnitude 7.0, 
  • site characteristics (loose sediments - amplification, coastal, 
  • temporal considerations (12th Jan 2010,  tuesday 4.53pm 

HUMAN 

  • built environment (high density, pop. growth)
  • population characteristics (rapid growth
  • risk management (negligible, poor reg., very poor)

IMPACT 

  • economic (port destroyed - tough for aid /$8bn/ 'pancake effect' / 180,000 homes damaged. 15% GDP loss from 2010)
  • social (20,000 deaths, 1 million homeless, cholera, poor water supply) 
  • environmental (oil + poisonous chem. leaked from unstable buildings, debris, water pollution
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impact of an earthquake - Bam LEDC

PHYSICAL 

  • earthquake characteristics (magnitude 6.3, 60 aftershocks in 6 days, 
  • site characteristics (landslides, rockfalls, 
  • temporal considerations (26th Dec 2003, friday, 5:26 am) 

HUMAN 

  • built environment (mud-brick, lack of earthquake proofing, 85% buildings destroyed
  • population characteristics (very dense, quick growth, 25,000 killed, 100,000 homeless
  • risk management (little reg., 
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human response to earthquake - Bam LEDC

  • search + rescue in 2 hrs 
  • 12,000 airlifted to hosp.
  • 92,000 tents donated 
  • 400,000 ready-to-eat meals 

PROTECT 

  • city rebuilt with technology in mind to make more earthquake resistant in future 

total cost: US$1.5Bn 

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Earthquake human responses (3P's)

PREDICT 

  • signs (radon gas, initial shocks, water tables drop, animal behaviour)
  • P-waves detected --> SMS text sent --> transport stopped ---> S-waves arrive

PREPARE 

  • education (starting early, continued process, know what to do in emergency) 
  • survival kits (torch, radio, water, blanket, food, knife, mask, gloves...)

PROTECT (constucuton saftey features) -LIFE SAFE 

  • wide base (less liquefaction) + deeper foundations 
  • counter weights (reduces movement, stresses, fratures)
  • core elevators (hardened core, evacuation quick) 
  • cross bracing (limit lateral movement)
  • window shutters (stop glass smashing)
  • avoid 5-20 storeys (causes resinence if no rubber pads - waves travel up + down)
  • fire training / building ID number 
  • floating foundations (waves not passed up) 
  • sprinklers + laminated glass 
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Volcano impacts, responses - Mt St Helens

background - US 

  • 18th May 1980, 08.32am / VEI 5 / 57 dead 
  • wildlife habitats destroyed (deer, elk, bears...) /  $1.1 bn cost 

Impact (P+S)

  • S - landslide (triggered by 5.1 earthquake, 2.8km of deposits, 110-240km/hr)
  • P - pyroclastic flows (0.2km deposits, 80-130km/hr, 700d.c temp)
  • S - lahars (snow melt + rain mobilised, 15-80km/hr, reduced channel capactiy) 

prepare 

  • red zone + blue zone (some parts should have bee red)

predict (today)

  • seismic monitoring (earthquakes) + deformation (ground surface movement, GPS, Tiltmeters)
  • image analysis (photographs aerial + ground based) + volcanic gas (relates to depth + type of magma)
  • thermal imaging (nature of volcani hazard)+ rock analysis (petrological monitoring) 
  • hydrology (topographic change DEM, sediment erosion, deposition, lake elevation, lahars) 
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Volcano impacts, responses - Mt Pinatubo

background - Philippines 

  • 15th june 1991 VEI 6
  • 800+ dead 
  • $250m 

impacts (P+S)

  • P - 2.5km caldera replaced crater 260m lower, killed 50% farm animals 
  • P - 5km debris, ash sent 35km into air 
  • S - lahars for years (rain soaked ash 
  • S - 650,000 lost jobs, 50,000 lost homes 
  • S - 1d.c temp rise, 

response 

prepare 

  • USGS 8km exclusion zone saved 5000 lives 
  • saved $250m of property 
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volcanic hazards causes

EFFUSIVE (lava flow dominated) vs EXPLOSIVE (pyroclastic flow dominated) 

PRIMARY 

  • lava flows (doesn't kill, slow, damages briges, farmland)
  • pyroclastic flows 27% (causes death, fast, carpets area with material)
  • ash + tephra (trapped in aircraft engines) 
  • volcanic gases (CO2 poisons population living close)

SECONDARY 

  • lahars 17%  (causes death, 30km/hr, ash on landscape mobilised by rain, silts rivers)
  • landslides 17% (causes death, material thrown onto steep lanscape)
  • tsunami (weight on volcanic cone + magma chambe collapse)
  • disease 30% 
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Landslides causes

PHYSICAL CAUSES 

  • period of torrential rainfall saturates soil on slope 
  • soi composition + rock type 
  • triggers - hurricanes, earthquakes, volcanoes 
  • marine erosion / slope gradient 

HUMAN CASUES 

  • removal of vegetation (less binding strength)
  • LEDC's urban living on slopes (deforestation)
  • undercutting of slopes (excavation) increases instability (transport systems)
  • population pressures / global warming / building weight 

MANAGEMENT

  • national policy - informing a naional strategy on coastal zone management 
  • local policies - monitoring / coastal defences / ground stability 
  • network + groups - CLIFFS (climate impact forecasing for slopes) / university links for info 
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Vargas, Venezuela mudslides

BACKGROUND

  • 14-19 Dec, 1999
  • 8000 individual homes damaged 
  • 30,000 dead / $1.79 Bn economic losses / bodies swept to sea 

CAUSES 

human 

  • poor communication and education 
  • population pressures built on foot of mountain scares (300,000 in 1km) / poverty 

physical 

  • steep topography (crest of Sierra de Avila 2,700m in 10km of coast) 
  • air rises + cools 6.7d.c every 1000m 
  • little area to build on (exception of alluvial fans - areas of deposition by rivers) 
  • storm season usually May-October however cold front interacted with pacfic ocean 
  • 6-7am 16th Dec measured 72mm (orographic / relief rainfall) 
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Aberfan Landslide

BACKGROUND

  • 21st Oct 1966 
  • 147 dead (116 from Pantglas Junior school) 

HUMAN 

  • built at foot of spoil heap no. 7

PHYSICAL 

  • built on a spring (mobilised material)
  • sandstone (200mm/hr) clay inderlying (2mm/hr)+ coal seams 
  • heavy rain in Oct 
  • very steep slop 

MANAGEMENT (NOT USED) 

  • vegetation (anchors + reduces moisture) 
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Vargas, Venezuela mudslides management 3P's

PREDICT 

  • warnings from cracks in walls 
  • stairs begin to pull away 

PREPARE

  • temporary walls built 
  • canals 
  • supports 

PROTECT 

  • slope sabilisation (geometric - alter slope profile through terracing)
  • slope stabilisation (hydrogeological - water content reduction + drains / trenches) 
  • slope stabilisation (mechanical - reinforcemen gabions / shotcrete / netting / pins)
  • slope stabilisation (natural - afforestation as roots bind + reduce water content) 
  • EDUCATION 
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flooding causes

PHYSICAL 

  • excessive precipitation levels (antecedent conditions high water table / snow delayed response)
  • intense precipitation (larger surface runoff as slow infiltration rates)
  • snow melt (surface runoff if ground underneath still frozen) 
  • climatic hazards (hurricanes / cyclones)

basin charateristics :-

  • soil geology (sand 200mm/hr clay 5mm/hr)
  • gradient (flashy response) / vegetation (interception storage increases time)
  • basin shape + size (cone acts as funnel)

HUMAN 

  • deforestation (removal of inerception storage + roots)
  • urbanisation (impermeable surfaces restrict interception storage + infiltration) 
  • river management (bridge shape + levees - aggredation / silting)
  • climate change (air temp rises - grater air vapour held - inc. potential - more frequent storms)
  • poorly maintained defences 
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flooding LEDC Bangladesh CAUSES

Background 

  • 1998 megaflood
  • brahmapura, ganges, meghna 
  • 150Million people (50Million below poverty line)
  • 25% country floods in monsoon season 

PHYSICAL 

  • 70% land below 12m 
  • 1000mm per day 
  • ice retreat in Himalayas 30m in 30 years 
  • vast basin - rivers drain an area 12x size of the country - more volume of water 

HUMAN 

  • 282% population increase between 1961-2011
  • deforestation - high demand for wood 
  • top soil removal - more ploughed land
  • urbanisation - growing cities 
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flooding LEDC Bangladesh IMPACTS

ECONOMIC 

  • less as its an LEDC ($1Bn)
  • 2m tonnes of rice lost / 500,000 drowned livestock 

SOCIAL 

  • covered 57% of country killing 1300 people 
  • destroyed 7 million homes 
  • diseases spread - cholera + diarrhoea 

ENVIRONMENTAL 

  • habitats drowned 

MANAGEMENT 

  • very slow as lack of insurance 
  • slow aid as lack of bridges + roads (washed away) 
  • LEDC very little money for recovery 
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flooding MEDC Boscastle CAUSES

BACKGROUND 

  • 16th August 2004 
  • daytime 
  • flash flood 

PHYSICAL 

  • antecedent conditions (5 inches in few hrs / 2m river level rise / 'brown willy' effect 420m above sea level / SW winds meet anticlockwise area of low pressure causing tropical storm) 
  • basin charateristics (steep valley cone shape, thin soils, impermeable shale (clay), confluence of Jordan and Valency, little tree coverage)  

HUMAN 

  • little control system (poorly managed culverts)
  • poor bridge construction 
  • residens + authorties not prepared - rarely happens 
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flooding MEDC Boscastle IMPACTS

ECONOMIC 

  • destroed 100 homes and businesses / 75 cars and 5 caravans detroyed / swept out to sea
  • 6 weeks of tourist season lost (witchcraft museum)

SOCIAL 

  • no fatalities / injuries (small population of 740 people)

ENVIRONMENTAL 

  • vegetation and debris left upstream 

MANAGEMENT 

  • insurance meant that houses were quick to recover 
  • bridge replaced and made more efficient (larger hydraulic radius)
  • channel dredging / culverts upgraded + repaired / carpark replaced with permeable surface 
  • EA burnt vegeation and removed debris to stop floating downstream 
  • lack of education / training fore reconstruction - so focussed on clearing up not protection 
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flooding management MEDC LA

PHYSICAL CAUSES

  • 3000 km2, soft + easily eroded rocks 
  • 60 miles of high urbanisation - deforestation - little interception + fast run off 
  • steep slopes - thin soils - poor vegetation (CHAPARRAL)
  • gulleying of rocks forming hills - smaller cpaacity 

HUMAN CASUES 

  • tall buildings act as mountains :  inc. rainfall by 20% + inc. lightning strikes (friction) 
  • agredation leads to depostion from mountans high up 

DEFENCES 

  • widespan bridges - straemlined support stands 
  • Rivers semi circular shape - high HYDRAULIC RADIUS 
  • concrete smoothed - reduce friction + inc. river speed 
  • DEBRIS DAM --> FLOOD CONTROL BASIN/DAM (san gabriel) --> SPREADING GROUND --> IMPROVED CHANNEL 

1915-LA flood control authority took sediment from sea-reduces beach building-causes erosion

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