Multiple Hazards

Multiple Hazards: Philippines – “A Disaster prone country.”

• Location and geography:• Asia, SE of China, N of Indonesia• 7100 islands• Rainforest climate – equatorial• Lower middle income – LEDC, NIC? GNP pc - $686, UK -

$11700• Rapidly growing population – BR 30/1000, UK 13/1000• Rapid industrialisation – although agriculture still 23%

GDP• Population pressure leads to environmental degradation

due to soil erosion and deforestation

Causes of multiple hazard environment:

• “In Asia, only India experiences more hazards…”• “Settlement, land use and social and economic

vulnerability increase hazard potential.”

• A) Climatic Hazards:• 1) Typhoons (tropical cyclones)• 5-10 degrees latitude – ideal, sea temperatures in S.

China Sea• Associated risk to coastal settlements from high winds

and storm surges, e.g. East Coast Luzon• Damage to forestry, crops and bamboo housing – “A

serious barrier to economic development.”• Risk raised by coastal development and removal of

Mangrove Swamps• Season: June to November, on average 4-9 destructive

per year – ave. 529 deaths and $68 million damage


• 2) Floods:• Coastal floods associated with typhoons• Inland, heavy rain from typhoons is hazardous• Total average annual precipitation of 2083mm• Manila – Capital on Luzon – especially vulnerable• Steep relief of mountainous areas – Flash Flooding –

rapid runoff – West Luzon• Lowland areas – floodplains – used for agriculture and

developed urban settlements – population density is high – in major urban areas (Manila) drainage is poor and especially shanty towns on peripheries are vulnerable

• Flood season also due to Monsoon Climate

• 3) Drought• 1980s and 1990s serious four year droughts• Bush fires and agricultural production are key issues


• 4) Fire:• January to June – Fire season – forest cover increases

risk• Dry season high temperatures – often associated with

high winds to fan fires and encourage spread.• 1998 – Worst year on record – wildfires spread in more

than 80 locations across islands – El Nino phenomenon• Climate change and associated increase in

temperatures raises risk• Not all natural causes, but some linked to lightning

strikes during intense tropical summer thunderstorms


• B) Tectonic Hazards:• 1) Earthquakes:• Philippines located in 2 subduction zones: Philippine

(continental) Plate is caught astride two destructive margins

• Eurasian Plate (South China Sea Plate) advancing 3cm/year• Pacific Plate rapid advance – 7cm/year• Through centre of island group runs active geological fault

– Philippines Fault• (Diagram!)• High risk of earthquakes due to rapid movement speeds• 1589-1983 – sixty nine destructive quakes• 1990: 7.7 quake – epicentre Rizal City Luzon – 1666 dead,

3500 injured, £300 million damage, 2 million population affected

• Causes liquefaction and landslides, also activated dormant volcanoes – Taal and Pinatubo – eruptions 1991


• 2) Tsunamis:• At risk from local and global scale events• Local caused by earthquakes along Philippines fault – 10

mins response• Global from locations such as Western USA – 16 hours

or Japan 3 hours• Mindano and southern islands especially vulnerable• 1994: offshore quake from Mindano – 6m waves,

damage to 4okm stretch of Coastline, 78 deaths, destruction of coastal settlements and fish faming developments and coastal roads and infrastructure


• 3) Volcanoes:• Volcanic activity associated with subduction zones from

the Pacific and Eurasian plates• Risk increased due to earthquake activity from

Philippines fault• Hazard raised due to settlement of volcanic locations –

population pressure and associated volcanic soils• E.g. 1991 Pinatubo – see later• 200 in total, 17 active• Associated hazards – pyroclastic flows, ash falls, lava

flows, lahars• Tropical storms and Monsoon season will later act upon

loose volcanic materials and create devastating landslides

• Alters profiles and regimes of local rivers – floods of lowland and urban areas


• C) Geomorphic Hazards:• 1) Landslides:• Slope stability low in volcanic ranges anyway, steep

relief e.g. W. Luzon Range• Downslope forces and sheer stress increases due to:• Earthquake and volcanic activity, Typhoon winds,

Lubrication from monsoon and typhoon rainfall• 1990 Earthquake – 100,000 landslides in Caraballo

Mountains• Types: debris flows, mudslides, some rock slides• Soil and material destabilised by mass deforestation

and cultivation of steep slopes due to population pressure

One hazard event illustrates best: Pinatubo 1991

Drought prior to eruption weakens economy

1990 earthquake reactivates Pinatubo

1991 Eruption Lava Flows andAsh Falls

Pyroclastic FlowsLahars

Tropical Storm Honing andMonsoon season

River Flooding 1991-93

Philippines: Hazard Management:

• Low incidence of hazard recording and mapping• Lack of high tech equipment due to cost• Management organisations exist: PAGASA – organises

prevention and protection planning, Dept of welfare helps victims, PHIVOLCS – volcanic and seismic event forecasting and warnings

• Low risk perception – low media access – publicity is the key focus of preparedness strategies

• Use of low cost disaster resistant pre-fab housing• Moves towards urban planning and land use regulation• Self-help protection government funds community

trainers to further knowledge• Hard engineering of rivers used (Increases risk?) –

levees• Coastal revetments to protect from storm surges• International aid is a requirement – 2 million after 1990

earthquake – UK and US and UN key donors

Multiple Hazard Case Study: Western USA

• 1) Location: “The Most hazardous area in any MEDC.”• Pacific coastline• Major cities – Los Angeles, San Francisco, San Diego• Coastal plain and to East mountain ranges: Cascades

(N), Coast Ranges, Sierra Nevada (S)• States: California, Oregon, Washington

• Sketch map!

• 2) Plate Boundaries:• Pacific and N. American Plate – a conservative margin

with transform fault – San Andreas fault• In NW destructive margin Juan de Fuca and N. American

plates – subduction zone – Cascade volcano range


• 3) Climate:• Mild winters and hot dry summers• Intense winter rainstorms – both orographic and

convectional rainfall – December and January worst weather months

• Storms and rainfall set to increase in future – sea temps raised by climate change – a “semi-rainless climate.”

• High levels of evaporation and huge water consumption – in total only 12cm runoff/year

• High winds have drying effect – Santa Ana wind – very high windspeeds

• Set up by intense heating and therefore pressure differences


• 4) Types of Hazards:• A) Volcanic activity:• Cascade Range due to plate boundaries is active with

key peaks Mt. Rainier and Mt. St. Helens• Key eruption St. Helens, May 1980:

- Rising magma blocked by hardened volcanic plug- Creates bulging cryptodome on N Flank- Force 5 earthquake – huge landslide- Lateral blast from cryptodome and massive blast waves of

gas, steam and dust – nuree ardent- Further eruptions, massive landslide/avalanches- Flood surge in Toutle River- Secondary effects from river floods- 25km blast zone, 61 deaths, environmental and economic

devastation


• B) Earthquakes:• Associated with destructive margins in Washington and

Oregon – volcanic activity and subduction – medium scale

• Stronger activity along San Andreas fault, plus whole network of Faults across S. California

• Dense population of Urban LA and San Francisco increase risks

• 1906 – Huge SF earthquake, 1994 – 6.7 – “moderate”• Area is “overdue a large event” – past 200 years is a lull

during which urban LA has grown directly over historical epicentres of major events

• 1994 Earthquake: 60 plus dead, half billion dollars damage, destruction of freeway system and thousands of high rise buildings


• C) Tsunamis:• Due to submarine earthquakes and eruptions in mid-

Pacific huge fetch• Put much of west coast and especially LA at risk also

Malibu beach locations• Local events linked to San Andreas fault network gives

potentially no warning time• 1964 – 119 died along west coast – California and

Oregon – event linked to Alaskan earthquake to North• During 20th century there have been 300 recorded

events of various magnitudes, $500 million damage to property alone


• Climatic Hazards:• A) Flooding:• Coastal floods linked to storm surges every year from

winter storms – Long Beach recently devastated – whole of Californian coast is suffering coastal subsidence to increase risk, plus desirability of coastal property

• Flash floods – encouraged by steep relief of inland ranges e.g. Sierra Nevada and Coastal Range. LA experiences flash floods and associated debris flows every year – 1995 worst on record

• 1995 – heavier snowfalls due to climate change and El Nino – led to minor avalanches and huge surges in spring months due to meltwater. Set to continue.

• 1995 – 8 deaths – LA to San Francisco highway washed away, 38 counties designated emergency areas.


• B) Drought• 2003 Drying Santa Ana wind• Overuse of water in naturally dry climate• Driest year since 1932 – dried vegetation and

flammable conditions for bushfires• Runoff below 12cm average

• C) Fires:• 2003 – drought for two years, accelerated by high winds• Dead vegetation as fuel source – also bark beetle

epidemic kills trees to spread fire• Sagebrush fuel supply flourishes in these conditions –

predicted to spread more as a result of climate change• 15 deaths, ½ million hectares burned, almost 1000

homes


• Geomorphic Hazards:• A) Avalanches• Low risk until recently – snow bound peaks of sierra Nevada

and cascade range were too distant to create risk avalanches were low frequency and magnitude

• Global warming increases risk, vibrations of earthquakes can set off

• B) Landslides• Earthquake induced along all of West Coast• Hillsides above LA surround it like a bowl – destabilised by

winter rainstorms and adds lubrication• Geology – loosely consolidated sands and gravels and

impermeable clays around Santa Monica• 2003 – Campsite disasters outside LA. Series of landslides kills

16. Wildfires had removed vegetation. Worst downpour for 20years

• Severs key local roads and prevents search for survivors – federal aid and disaster classification


• Hazard Management:• Contrast to LEDC of Philippines• Here is not awareness but fatalism and misperception that

increases risk – up to 70% of residents in some areas have no hazard insurance. Now California is making this insurance compulsory – state funded

• Regular drills for earthquakes in schools and workplaces• Awareness spread through net sites and publicity –

encourages each home to have an emergency plan includes: storing food and medical supplies

• Each city has plan – “Integrated Hazard Management” e.g. Santa Clarita district of LA

• Technology used to assess risk, map, predict monitor key locations and research to identify high risk zones. Used to inform planning and development decisions

• Uses hazard proof or reinforced buildings – earthquake adjustable!

• Infrastructure – roads and railways use engineering techniques to aid prevention of landslides and flood damage

Multiple Hazard Case Study:

• Why do we find locations which experience multiple hazards?

• 1) Co-incidental links – explained by location of area/country

• 2) Causal links – secondary and tertiary hazards caused by other hazards

• 3) Human activity – increases risk from specific hazard or increases frequency and magnitude of that hazard – can also increase perception of that hazard

• Multiple Hazard environments are a combination of these three factors.

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Multiple Hazards