physical geography f763 earth hazards
- 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
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)
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)
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
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
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.,
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
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
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)
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
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%
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
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)
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)
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
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
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
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
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
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
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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