physical geography f763 earth hazards

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 

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) 

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)

PREDICT -

• S-WAVES took 90 s to reach Tokyo 

PREPARE -

• japanese self defence force mobilised 

PROTECT -

• 3 principles (SAFE, SUSTAINABLE, COMPASIONATE),
• building resilience 

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

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., 

• 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 

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 

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) 

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 

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% 

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 

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) 

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) 

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 

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 

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 

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 

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 

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 

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