Natural Hazards and Disasters

• Natural hazard is a natural process and event that threatens human life and property
• Geologic, hydrometeorological, and coastal hazards can be categorized as natural hazards
• Disaster is a hazardous event over a limited time in a defined area
• Criteria for a natural disaster include 10+ people killed, 100+ people affected, state of emergency declaration, or international assistance request
• Catastrophe refers to a massive disaster requiring significant money and a long recovery time

Important Concepts

• Geologic cycle describes the complex interactions between tectonic, rock, hydrologic, and biogeochemical cycles
• Tectonic cycle involves the creation, movement, and destruction of tectonic plates
• It is responsible for the production and distribution of rock and mineral resources and hazards like volcanoes and earthquakes
• Rocks cycle is the largest geologic sub-cycle, and is linked to others
• It depicts the changing transition through geologic times of igneous, sedimentary, and metamorphic rocks
• Hydrologic cycle is the movement of water from oceans to the atmosphere and back
• Biogeochemical cycle involves the transfer or cycling of chemical elements through the atmosphere, lithosphere, hydrosphere, and biosphere
• Carbon is exhaled by animals as CO2, enters the atmosphere, and is taken up by plants

Geologic Hazards

• A geological hazard is a natural geologic event endangering human lives and threatening property
• Earthquakes, landslides, and volcanic eruptions are geologic hazards

Earthquakes

• Around one million earthquakes are felt each year, but few are noticed or major
• An earthquake occurs as the Earth's surface trembles when energy is released from strain in rock layers
• Earthquakes can be associated with volcanic eruptions or plate tectonics

Basic Earthquake Features

• Epicenter is the place on the Earth's surface above where the ruptured rocks broke up to produce an earthquake
• Focus is the point of initial breaking or rupturing within the Earth
• Hypocenter is directly below the focus

Earthquake Measurement

• Earthquakes are measured and compared by intensity, magnitude, and moment magnitude
• Intensity describes the effects of ground motion on people and structures
• Magnitude measures the amount of energy released
• Moment magnitude indicates the earthquake size based on the area that ruptured along a fault plane, movement slippage, and rock rigidity near the quake's focus
• Moment magnitude is used by most news reporters
• Ritcher Scale was developed by seismologist Charles Ritcher, used by some news reporters still

Effects/Linkages of Earthquakes

• Shaking and ground rupture are immediate effects of a catastrophic earthquake involving ground shaking with surface rupture and displacement
• Liquefaction during earthquakes causes intense shaking that can turn near-surface water-saturated sand from solid to liquid
• Regional changes in land elevation includes vertical deformation like uplift and subsidence, causing damage in coastal areas and along streams, and changing groundwater table

Landslides

• Landslides are natural hazards closely linked to earthquakes because they are one of the most common triggers, particularly in hilly or mountainous areas
• Earthquake-triggered landslides can be destructive and cause great loss of life
• Fires can start as shaking ground and surface displacements break electrical power and natural gas lines.
• Fires after earthquakes are more dangerous because broken firefighting equipment, blocked streets, and broken water mains
• Disease can be a hazard as earthquakes cause loss of sanitation/housing, contaminated water supplies, disruption of public health services, and disturb the natural environment

Landslides Defined

• A landslide is downslope movement of rock, debris, earth, or soil
• A slope is a slant or incline on a land surface
• Landslide forces rely on earth material, topography/slope angle, climate, vegetation, water and time

Factors of Landslides

• Earth material relates to mineral composition, cementation, and weaknesses like layering in sedimentary/metamorphic rock or geographic fault lines
• Topography and slope angle refers to the height of a hill or mountain above land, with steeper slopes increasing the driving force
• Climate involves weather over years/decades, influencing timing/amount of water that erodes a slope and affects vegetation
• Vegetation cushions the impact of falling rain to prevent erosion, but also adds weight
• Water in slopes leads to saturated soil slips/debris flows, deep infiltration over months/years, and water erosion, all decreasing stability
• Time causes weathering of rocks, reducing their strength through water contact

Man-Made Landslide Factors

• Intense deforestation, soil erosion, construction in prone areas, roads/communication lines in mountains, weak foundations, buried pipelines, and a lack of understanding landslide hazards are man-made factors of vulnerability

Landslide Effects/Linkages

• Landslides can cause people/property to get hit or buried in falling debris
• Homes, roads, and utilities on hills can be damaged
• Flooding can occur upstream as landslides block rivers, spreading disease from disturbed fungal spores
• Landslides are caused by earthquakes, volcanoes, storms, and fires
• Landslides may be responsible for flooding if they form an earthen dam across a river or cause tsunamis/flooding when water is displaced

Volcanic Eruptions

• Volcanic eruptions are dramatic and violent agents of change
• They are significant geologic hazards due to widespread and long-lasting effects
• Volcanic activity is related to plate tectonics, with most volcanoes near plate boundaries
• This activity rises from spreading and sinking lithospheric plates that interact with earth materials, producing magma

Volcanic Terminology

• Magma is molten rock under the Earth's crust
• Lava is molten rock erupted by a volcano
• Vent is the opening of a volcano where lava and volcanic material extrude

The Ring of Fire

• The Ring of Fire is an area in the Pacific Ocean basin with a high number of earthquakes and volcanic eruptions
• It is a 40,000 km horseshoe shape associated with oceanic trenches, volcanic arcs, belts, and plate movements

Volcano Classification

• Active volcanoes are currently erupting or showing unrest
• Dormant volcanoes are not active but could become active again
• Extinct volcanoes are considered unlikely to erupt again

Eruptions

• An eruption occurs when magma, gases, or steam break through vents in the Earth's surface
• Mild eruptions discharge steam/gases or expel lava quietly
• Strong eruptions involve violent explosions that send clouds of gas-laden debris into the atmosphere or sideways from a collapsed volcano portion

Earthquake Mitigation

• Earthquake hazard reduction programs may come from government officials or the National Disaster Risk Reduction Management Council
• The goals are to understand earthquake source, determine earthquake essentials, predict earthquake effects, apply research, strategically locate critical facilities, and use structural protection/education
• These programs also aim to increase insurance/relief measures and prepare people

Earthquake Preparations

• Before: Home safety checks can increase survivability, including chimney/foundation checks and securing large objects like water heaters
• During: Teach "drop, cover, and hold on" which means to drop to the ground, take cover under sturdy furniture, and hold on until shaking stops
• After: Take deep breaths, look around, leave building carefully, avoid moving during shaking, turn off gas lines, and move to an open area/away from fallen power lines/trees

Landslide Mitigation

• Identify areas likely to experience landslides
• Educate and warn people of impending landslides
• Design slopes/engineering structures for prevention
• Control landslides after they've started
• Avoid development on sites where landslides are occurring or likely to occur
• Evacuate and relocate people when necessary

Volcanic Eruption Mitigation

• Forecasting is done by the Philippine Institute of Volcanology and Seismology
• Education and Evacuation provides information on how people perceive a volcanic hazard
• People live near volcanoes for various reasons, including being born there, fertile land, optimism, or economic limitations

Geohazard Mapping/Assessment

• Geohazard Mapping and Assessment Program of the Department of Environment and Natural Resources (DENR), implemented by Mines and Geosciences Bureau (MGB)
• Aims to identify geologic hazard-susceptible areas and lessen the impact
• It has determined landslide and flood prone areas
• The developed map is accessible on the Mines and Geosciences Bureau's website

Definition of Hydrometeorological Hazards

• Hydrometeorological hazard is an atmospheric, hydrological, or oceanographic process that endangers human lives and threatens property
• Cyclones, monsoons, flooding, and tornadoes are hydrometeorological hazards

Cyclones Defined

• Cyclones are coined from the Greek word meaning "coil of snake"
• An area or center of low atmospheric pressure with rotating winds
• Tropical cyclones form over warm tropical/subtropical ocean water between 5° and 20° latitude
• Extratropical cyclones develop over land/water in temperate regions between 30° and 70° latitude
• Cyclone intensity is indicated by wind speeds and lowest atmospheric pressure

Cyclone Terminology

• Hurricanes are strong tropical cyclones in the Atlantic and Pacific Oceans, named after a Caribbean word for the god of winds/destruction
• Typhoons are strong tropical cyclones in the Pacific Ocean west of the International Dateline, named after a Chinese word for "scary wind"
• A tropical cyclone is a large thunderstorm complex rotating around an area of low pressure over warm tropical/subtropical water
• Low-intensity cyclones are tropical depressions/storms
• High-intensity cyclones are hurricanes/typhoons

Requirements to be Hurricane/Typhoon

• To be classified as a hurricane/typhoon, a tropical cyclone must have sustained winds of at least 119 km/hr
• Hurricanes/typhoons need tremendous heat to develop and only form where the sea surface temp is at least 26°C

Stages of Hurricanes/Typhoons

• Tropical Disturbance: A large area of unsettled weather, generally 200-600 km diameter, with a mass of thunderstorms that persists for over 24 hrs, may lead to tropical depression
• Tropical Depression: Tropical disturbance becomes a tropical depression as winds increase and spiral, forming a low pressure center
• Tropical Storm: Depression becomes a tropical storm, winds reaching more than 63km/hr and the storm is given a name, and Hurricane/Typhoon forms if conditions worsen

Features of a Hurricane/Typhoon

• Rainbands are clouds that spiral around the hurricane/typhoon
• Eyewall is the innermost band of clouds with the most intense winds

Effects of Cyclones

• Effects of cyclones include flooding, thunderstorms, tornadoes, storm surge, heavy rains, and high winds

Monsoons Defined

• A monsoon is climate marked by seasonal shifts in prevailing winds between winter and summer, found in tropical Asia, Australia, Africa, and the Indian Ocean
• Monsoon rainfall is important to agriculture for over half the world's population
• Research is being conducted to increase understanding of monsoon predictability, maximizing its benefits, and reducing extreme event impacts

Types of Monsoon Winds

• Northeast Monsoon occurs from November to February, causing cold temperatures and rain over the eastern coast of the Philippines
• Southwest Monsoon occurs from July to September, responsible for rainfall during the wet season
• Trade winds generally come from the east and are prevalent when NE monsoons are weak

Flooding

• Flooding is a natural process of a river's overbank flow
• River flooding is related to the amount/distribution of precipitation in the drainage basin, rate of soaking into the earth, and how quickly surface runoff reaches the river

Terms Related to Flooding

• River refers to a natural stream of water that flows in a channel with defined banks
• Stream refers to any body of water that flows in a channel
• Drainage basin refers to the region drained by a single stream or river
• Runoff is water from rain/snow flowing over the ground into streams

Types of Floods

• Flash floods result from intense rainfall over a small area in a short duration
• Downstream floods cover a wide area and are usually produced by storms of long duration that saturate the soil and produce increased runoff

Effects of Flooding

• Primary effects are injury, loss of life, and damage to farms, homes, railroads, bridges, roads, and communication systems caused by swift currents, debris, and sediment
• Secondary effects result from the disruption and malfunction of services, causing short term pollution of rivers, hunger, disease, and displacement

Tornadoes

• Tornadoes are small-diameter column of violently rotating air developed within a convective cloud and in contact with the ground
• These atmospheric vortices generate the strongest winds with measured extreme events above 500 km/hr
• Tornadoes are a result of instability within air masses and wind systems
• Wind speeds and destructiveness are measured through the Enhanced Fujita Scale of tornado intensity
• Waterspouts are tornadoes that form overwater

Mitigation/Adaptation for Hydrometeorological Hazards

• Accurately forecast storms, issue advisories, adhere to building codes, have organized evacuation procedures, hazard preparedness, education, and insurance programs are all strategies to employ

Flood Response

• The Geohazard Mapping and Assessment Program informs discussion on landslides, mitigation, and adaptation
• Construction of physical barriers such as concrete flood walls can occur
• Channelization is defined as straightening, deepening, widening, clearing, and lining existing streams
• Relocating people from floodplains/flood prone areas, education, and preparing for a flood are all examples of responses

Flood Preparation

• Check with your local flood control agency to see if your property is at risk from flooding
• Make up a flood kit, including a flashlight, blankets, raingear, battery powered radio, first-aid kit, rubber gloves, and key to personal documents.
• Talk about possible flooding with your family and housemates, considering writing a flood plan, and store notes to your flood kit

Flood Response Actions

• Be prepared to evacuate, observe water levels, and stay tuned to a radio and television news and weather reports
• Move people, pets, and valuables upstairs or to a higher ground
• Do as much as possible in daylight
• Keep warm and dry

Coastal Processes

• Coastal landforms are created by a wide variety of coastal processes with two major processes: erosion and accretion
• Erosion is the group of processes where debris or rock material is loosened and dissolved by destructive waves, causes property damage, and requires adjustments
• Accretion refers to the gradual increase in the area of land as a result of sedimentation

Coastal Hazards

• Waves are generated by offshore winds, sometimes thousands of kilometers from where the waves reach the shoreline
• Rogue waves are gigantic and extremely dangerous waves, larger than similar waves in the sets around them
• Rogue waves can strike the shore and somewhere in the open ocean and may reach 100 ft

Sea Level Change

• Sea level change results from a number of processes, some operate locally and others affect regional or world wide ocean effects
• Eustatic sea level, also know as global sea level, is controlled by processes that affect the overall volume of water in the ocean and the shape of the ocean basins
• Relative sea level is the position of the sea at the shore influenced by the movement of the land and the movement of the water

Storm Surge

• Storm surge is the local rise of sea level resulting from water pushed toward the shore by winds swirling around a storm
• The causes are stress exerted by wind on the water surface and low atmospheric pressure in the storm that pulls the sea surface
• A storm surge is a continual increase in sea level as a storm approaches landfall

Saltwater Intrusion

• Saltwater intrusion is the induced flow of saltwater into freshwater aquifers caused by groundwater over-pumping

Saltwater Intrusion Terms

• Groundwater is the water beneath the surface of the ground, consisting largely of surface water that has seeped down
• Aquifer is any geological formation containing or conducting ground water, especially one that supplies the water for wells, springs, etc

Saltwater Impacts

• Saltwater intrusion happens when groundwater levels in aquifers are depleted faster than they can recharge
• The encroaching seawater will encounter an area known as the zone of dispersion, where the freshwater and saltwater mix, contaminating freshwater supplies
• The limited potable drinking water supply in areas affected by saltwater intrusion and water with salinity detrimental to growing agriculture are effects of saltwater intrusion

Coastal Hazard Mitigation/Adaptation

• Evacuation plans and shelters where policy makers have understanding of storm surges and adequate willingness to anticipate future storm surges needed
• Relocating people from coastal erosion and storm surge prone areas can occur through initiatives by government or residents
• Education could include distribution of pamphlets and videos, workshops/trainings, and internet information
• Prevention and control of saltwater intrusion by reducing pumping or using time-share pumping from wells, relocating wells, or redesigning the well field