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Introduction to Natural Hazards• What is a “Geohazard”? – Earth processes (involving the lithosphere, hydrosphere & atmosphere) that, upon interaction with human activity, cause loss of life and property Hazardous geo- human process condition process or result – It is important to understand the human element • without it, there would be no hazard • because of it, the science of geohazards becomes more important every year – mitigation: reduction/prevention
Why is the human element so critical?• The Earth’s population is increasing • more people living in hazard-prone areas • populations are becoming hyper-concentrated • consumption of resources • examples: – today there are 6 billion people on Earth ( ~ 50% live in cities) – by 2025, there will be ~8 billion people (~ 66% in cities) – of these cities, 40% are coastal » prone to severe storm and tsunami damage – and a large majority lie in areas subject to other geohazards (for example volcanoes and earthquakes)
•CANNOT stop the geologic processes •CANNOT stop the population growth/expansion•Therefore, we must try to reduce (mitigate)the hazards through: •scientific study •population education •changes in engineering/building practices •management plans and hazard response scenarios
Types of Natural Hazards• Volcanoes, floods, earthquakes, tornadoes, tsunamis, etc. – can act adversely on human processes – can occur: • without warning (e.g. earthquakes) • with warnings (precursors) (e.g. satellite monitoring of cyclone tracks, or the presence of ground deformation at a volcano before an eruption)
• To help mitigate the hazard we need to know:• Frequency vs. Magnitude – F: how often a given event occurs in a certain region – M: how powerful (amount of energy released) an event is • for example, high M hazards happen with low F, but are much more destructive• Scope – S: area affected by a given hazard • local: landslides, floods, earthquakes, fire … • regional: tsunamis, volcanoes, larger earthquakes, cyclones … • global: large volcanoes, global warming, meteorite impacts …
Practical Exercise 1.Impact of Environmental Disasters
What is an Earthquake?• Ground movement caused by the sudden release of seismic energy due to tectonic forces. The focus of an earthquake is the actual location of the energy released inside the Earth’s crust. The epicentre is the point on the Earth’s surface directly above the focus.
Why do earthquakes occur?• Seismic energy is usually caused by the brittle failure (fracturing) of rocks under stress. Figure showing the distribution of earthquakes around the globe• This commonly occurs due to movement along tectonic plate boundaries
Earthquake MagnitudeMagnitude Earthquake Effects Approx. number each year < 2.5 Usually not felt, but recorded 900,000 2.5-5.4 Often felt, only minor damage 30,000 5.5-6.0 Slight damage to buildings and 500 other structures 6.1-6.9 May cause a lot of damage in very 100 populated areas 7.0-7.9 Major earthquake. Serious 20 damage. > 8.0 Great earthquake. Can be totally 1 every 5-10 years destructive near the epicentre.
San Francisco - Great Earthquake• Magnitude 7.7 - 8.3
Earthquake Hazards• These are important hazards to understand: – the natural hazard that on average kills the highest number of people per year (> 1 million during the past century) – commonly strikes without warning – no time for evacuation – not a predictable trend to earthquake numbers, magnitude or location • 1000s of large earthquakes every year • ~ 20 are > M7.0 and these account for 90% of the energy released and 80% of all the fatalities
How do we mitigate thehazard from earthquakes? • Reinforce buildings • Education • Disaster plan
Earthquakes and Tsunami’s• An earthquake under the ocean has the potential to form a tsunami.• The earthquake must vertically displace overlying water (extensional or compressional faults - not transform) Extension Compression Transform
2004 South AsianBoxing Day event• Biggest earthquake in 40 years!• Magnitude 9.2• 150 km off the west of Northern Sumatra• Generated a disastrous tsunami in 12 countries
Second largest recorded earthquake • The earthquake occurred at a convergent tectonic plate boundary (subduction zone) • An estimated 1,600 km (994 miles) of faultline slipped about 15 m (50 ft)! • The earthquake released 20 x 1017 Joules of energy – Equivalent to: • 475,000,000 kg of TNT • 23,000 Hiroshima atomic bombs!
Tsunami Animations of the Boxing Day tsunami showing how the tsunami radiated from the entireAbove: Countries most effected by length of thethe tsunami 1,600 km (994 miles) rupture.
A villagenear thecoast ofSumatralays in ruinafter thetsunami.
How do we mitigate the hazard from tsunamis?• Monitoring – process is very technology- intensive • high costs for many poorer countries – often no technology available to monitor local tsunamis • for example, • Papua New Guinea has no monitoring stations – reliant on the Pacific Tsunami Warning Center • tsunami in 1998 was not detected
How do we mitigate the hazard from tsunamis?• Building restrictions in hazard prone areas – In Hawaii, Hilo harbor and downtown was destroyed by the tsunamis of 1946 and 1960 – The town is now rebuilt on higher ground and the devastated area is a park
How do we mitigate the hazard from tsunamis?• Seawall construction – cause early wave breaking – prevent wave run up into urban areas
How do we mitigate the hazard from tsunamis?• Education – warning systems – evacuation plans – general understanding of the hazards involved Punishment Natural event From God 35% 45% Bomb 20% Population reaction: Papua New Guinea (1998)
Tropical Cyclones• Background: – Can be deadly! • For example, in 1991 a large cyclone in Bangladesh killed >138,000 people in just two days!
Tropical Cyclones • Most widespread destructive weather hazard – For example: Hurricane Floyd (1999) • only a moderate level hurricane • caused US$5.6 billion in damage in the Bahamas and North Carolina (USA) and 57 fatalities (Left) Three different cyclones spinning over the western Pacific Ocean on August 7, 2006.
How do cyclones form?The above figure shows how cyclones form. The green arrows showwhere warm air is rising. The red arrows indicate where cool air is sinking.
What damage is produced?• Storm Surge – water that is pushed toward the shore by the force of the cyclone winds.
What damage is produced?• Wind – responsible for the loss of power and utilities – wind damage affects larger areas than surge – flying debris – tree loss
What damage is produced?• Flying debris – debris propelled at high speeds
How do we mitigate the hazard from a cyclone?• Monitoring – early warning systems• Infrastructure – cyclone walls – communal shelters• Education and planning
Natural Hazards Summary Graph showing the number of deaths per year due to natural hazard events
Damage HAZARD PotentialAwareness- Effect on Elements Society Quicker Recovery Elements at Risk Action Plans Huge Losses/ Communities Damages More Resilient Reduced More Stable Society Losses
Damage HAZARD Potential Elements at RiskNatural Features Societal ElementsRiver/Stream Banks People & Live-stockLow-lying Areas Huts & Semi-permanent HousesSea & Sea-coast Weak BuildingsSlopes of hills Agri. & Horticultural crops Livelihood tools / Equipment Unsecured personal assets Public Infrastructure
CYCLONEDamagePotential Poorer than Society before Elements at Risk Disruption of Normal life & Huge Losses/ Development Damages Suffers
Types of disastersMajor natural disasters: Minor natural disasters: • Cold wave • Flood • Thunderstorms • Cyclone • Heat waves • Drought • Mud slides • Earthquake • StormMajor manmade disaster: Minor manmade disaster: 1. Setting of fires • Road / train accidents, riots 2. Epidemic • Food poisoning 3. Deforestation • Industrial disaster/ crisis4. Pollution due to prawn • Environmental pollution cultivation 5. Chemical pollution. 6. Wars
Scale of DisasterIs Dependent on :• Lead Time Available.• Intensity of Hazard.• Duration.• Spatial Extent.• Density of Population & Assets.• Time of Occurrence.• Vulnerabilities existing in the Elements at Risk.• Hazard X Vulnerability = Disaster
ELEMENTS AT RISK• People• Livestock• Rural Housing Stock• Houses Vulnerable• Crops, Trees,Telephone, Electric poles• Boats, Looms, Working Implements• Personal Property• Electricity, Water and Food Supplies• Infrastructure Support
AIMS OF DISASTER MANAGEMENT• Reduce (Avoid, if possible) the potential losses from hazards.• Assure prompt and appropriate assistance to victims when necessary.• Achieve rapid and durable recovery.
PRE-DISASTER DURING DISASTER POST- DISASTER DISASTER MANAGEMENT CYCLE
Stages of Disaster Cyclone BEFORE DURING AFTER Jan - Apr MAY June- OctWell BeforeWeeks-Months Just Before Actual Time - Hours Period Rescue Relief Rehabilitation Reconstruction
Role Players in Disasters• People : Individuals, House -Holds, Volunteers• Gram Panchayat : Sarpanch, Panchayati Secretary, Panchayati Members• Village Elders : Caste/Community/Religious Leaders, Teachers, Doctors, Engineers, Retired Army & Police Personnel• Govt. Deptl. Officers : Agriculture, Medical, Engineers (Housing, Roads & Buildings, Irrigation) Revenue Department, Public Health, Police etc. NGOs
DEFINITIONS OF “VULNERABILITY”• “The extent to which a community, structure, service or geographic area is likely to be damaged or disrupted by the impact of particular disaster hazard…”• “Vulnerability is the propensity of things to be damaged by a hazard”.
DISASTER PREPAREDNESS• Disaster preparedness aims at minimizing the adverse effects of a hazard -• Through effective precautionary actions• Ensure timely, appropriate and efficient organisation and delivery of emergency response following the impact of a disaster.
PREPAREDNESS• Vulnerability Analysis and Mapping to include Resources.• Assess strengthening requirements and execute.• Funding for preparedness must be arranged.• Peoples’ cooperation through Political leaders, elders, Volunteers and NGOs• Create lead time by interpreting Warnings• Plan to include movement of resources with time frame.• Aim to reduce the destructive potential of cyclones, timely & appropriate relief to victims and quick & durable recovery
Disaster Preparedness Framework COMPONENTS OF PREPAREDNESSVulnerability Planning InstitutionalAssessment FrameworkInformation Resource Warning System Base Systems Response Public RehearsalsMechanisms Education and Training
Disaster Response Activities• Warning• Evacuation/Mitigation• Search and Rescue• Assessment• Emergency Relief• Logistics and Supply• Communication and information Management• Survivor Response and coping• Security• EOC & coordination• Expedite rehabilitation and reconstruction.
Floods and Water HazardsElements at Risk Main Mitigation• Everything in the Strategies. flood plain. • Land use control• Earthen or soluble • Engineering of structures strictures• Buried services • Elevation of structures and utilities • Flood control structures• Food stores • Reforestation projects• Crops and (watershed livestock management)
Strong Winds Main MitigationElements at Risk Strategies.• Lightweight structures.• Elevated utilities • Structural (Power and engineering communication lines) measures.• Fishing boats and • Planting of other maritime industries. windbreaks.