Managing Natural

hazards
ENVIRONMENTAL MANAGEMENT
CHAPTER 6. KULSOOM
 Structure of the Earth
• The structure of the earth is divided into four major
components:
 the crust
 the mantle
 the outer core
 the inner core.
 Each layer has a unique chemical composition, physical
state, and can impact life on Earth's surface.
 https://www.youtube.com/watch?v=9bm1qTDfLo0
 https://www.youtube.com/watch?v=UZ1SdtH2Kkw
Two types of crust

OCEANIC CRUST(SIMA) CONTINENTAL CRUST (SIAL)

• Mainly made of rock called basalt • Mainly made of rock granite
• Tinner average depth 6 km • Thicker average depth 35 km and
• Younger 100 km in mountains

• Sink and is continually being • Older

renewed and destroyed • Cannot sink and is neither destroyed
nor renewed
 Lithosphere and Asthenosphere
• The lithosphere is the brittle crust
and uppermost mantle – it is solid –
planets uppermost layer
• The asthenosphere is solid upper
mantle material that is so hot that it
behaves plastically and can flow.
The lithosphere rides on the
asthenosphere.
 What are natural hazards?
• A natural hazard is a natural phenomenon that might have a negative effect on
humans and other animals, or the environment.
• A natural hazard is a naturally occurring event that will have a negative impact on
people
• Natural disaster when a natural hazard causes damage and the people affected are
unable to cope
• They are natural events
5 Natural hazards
•Earthquake – most unpredictable (geological hazard)
•Volcanoes - (geological hazard)
•Cyclones - (Climatic hazard)

• Flood - (Climatic hazard)

• Drought - (climatic hazard)
 Plate boundaries
• The thin crust of Earth is not a continuous layer
• It is divided into 7 major tectonic plates and eight minor( smaller) tectonic plates
• Lithosphere is made up of crust and upper mantle
• The Tectonic plates is a piece of lithosphere that moves slowly on the
asthenosphere.
• Example of smaller plates – Nazca and Phillippine plates
• Most geologic activities, including volcanoes, earthquakes, and mountain
building(fold mountains), take place at plate boundaries.
Types of plate boundaries:

• Plate boundaries are the where two or more plates meet.

• ~Constructive or divergent -two plates are moving apart from each other.
• ~Destructive or convergent - two plates are moving towards each other.
• ~Conservative - two plates move against each other

https://www.youtube.com/watch?v=Z1b3yNgIfKw
https://www.youtube.com/watch?v=FbbwaAIMvvs
 Constructive or divergent

• Move apart from each other

• New magma from mantle rises to the surface to fill the gap
between the plates because of convection currents

• Convection currents transfer heat from place to place example

– heat from the core causes convection currents in the magma
these cause plates to move

• Magma turns to lava, solidifies when contact is made with cold

ocean water and forms basalt

• This whole process is called sea- floor spreading or ridge push.

• Rift valleys are formed along fault lines

• Small earthquakes are triggered

 Destructive or convergent

• Two plates move towards each other

• One plate, usually oceanic plate sinks below the
other – oceanic plate or continental plate
• It is destroyed in the subduction zone
• An ocean trench is formed where the oceanic plate is
subducted – trenches are deepest part of the ocean
• Sediments on the sea bed between two plates are
compressed and folded up to form mountain
• Friction from plate movement in the subduction zone
creates earthquakes - makes the rock melt – and
produces magma – cause volcanoes
Convection Currents
 Conservative
• Two plates move against each other
• May be moving in the same direction
but at different speeds
• Friction caused by rock rubbing
against rock forms earthquakes
Guess?
 How are fold mountains formed?
• Formation of Fold Mountains
• Fold mountains form along destructive plate boundaries.
• They form when two plates with landmasses on them move towards each other.
• The plates push layers of accumulated sediment in the sea into folds between them.
• This becomes a fold mountain range.
• Most fold mountains continue to grow as the plates constantly move.
• Examples: the Himalayas (Asia), Rockies (USA), Andes (South America), Alps (Europe)
• https://www.youtube.com/watch?v=r9Uu-Gp2ztg
Earthquake
 Earthquakes
• An earthquake is the shaking of the surface of the Earth resulting from a
sudden release of energy in the Earth’s lithosphere that creates seismic waves.
• Earthquakes occur along every type of plate boundary
• Nine out of ten strong earthquakes(above 6.0) occur at destructive boundaries
• Focus – the point of origin of the shock underground
• Epicenter – The point on the earth's surface vertically above the focus of an
earthquake.
• Fault line - is a break or fracture in the ground that occurs when the Earth's
tectonic plates move or shift and are areas where earthquakes are likely to
occur.
• Shock waves move out from the center and affect surrounding areas,
decreasing in strength as the distance from the epicenter increases
• The 1960 Valdivia earthquake on 22 May 1960 is the most powerful earthquake
ever recorded. 9.4 to 9.6 on Ritcher scale
 Terms
•Seismograph - Sensitive
instrument on which the waves
caused by earthquake shocks are
recorded
•Richter scale measures the
strength of an earthquake
 Earthquakes – Impact
• Impact on people is entirely negative
• Primary effect of an earthquakes
• Pillars supporting bridges and roads can collapse.
• People are killed in their homes, places of work and vehicles. – great killers and cause
human suffering
• Many more are injured or trapped .
• Landslides, Tsunami, Disease
• The secondary effect of earthquakes are those that happen in hours minutes and days after
the earthquake
• broken gas pipes can cause explosions
• sparks from damaged electricity cables can cause fire.
Earthquake effect
• Tsunamis – Giant sea waves caused by earthquakes on the sea floor.
Dangerous for people living in low-lying costal areas
• Landslides – Mass movements of soil and rocks on steep slopes which can
destroy villages – earthquake shock triggers that flow downslope
• Disease- epidemics-typhoid and cholera spread easily when bursts pipes lead to fresh
water supplies being contaminated by sewage
Important factors that affect the amount of
destruction and number of casualties
• Number of people living close to the epicenter
• Quality of building construction
• How well prepared people and emergency services are
Earthquake management

Good earthquake management saves lives

1. Building that can resist earthquake
2. Educate people
3. Teams of emergency workers should also be trained in advance
4. The authorities need to have emergency supplies of clean water, food , and medicines
in store

5. Use land use zoning - Make sure that factories are not located next to houses –- as oil
tanks can explode and chemicals can catch fire so houses need to be in a different zone
than factories
 Earthquakes and buildings
• How to make building earthquake resistant?
• Make foundation piles of alternating layers of steel and rubber
• Shape building like a pyramid
• Damping and bracing systems to help absorb shocks
• Foundations sunk deep into bedrocks
• Computer controlled weights on the roof to reduce shaking
• Disadvantages of making building earthquake resistant
• The building are too expensive to built
 Earthquakes
Prediction Preparation and protection

• Instruments such as seismometer can • Earthquake proof buildings – Older

monitor tremors. building can be retrofitted

• Epicenters and the frequency of past • Smart meters that cut off gas supplies to
events can be mapped to see if a pattern prevent fire
is developing
• Land-use planning important services
• Measurement of local magnetic field such as schools and hospitals are built in
low risk areas
• A hazard zone map can be drawn based
on geological information and ground
stability
 Earthquakes – Impact and management (Recap)

Impacts Management
People are killed in their homes, place of Constructing earthquake-resistant
work and vehicles. buildings.

Pillars supporting bridges can collapse. Ensuring factories are not located next to
houses.
Tsunamis, landslides and diseases. Educating people about what to do in an
earthquake.
Volcanoes
 Volcanoes
• A volcano is an opening in the Earth's crust that
allows molten rock, gases, and debris to escape to
the surface.
• A volcanic eruption occurs when magma rises to
earth's surface lava pours out of a crater and with
time builds up a cone-shaped mountain
• Happens at both constructive and destructive plate
boundaries
• The eruption of Tambora in Indonesia in 1815 killed
the most people. It was a huge eruption that sent ash
into the stratosphere that then spread around the
world.
World distribution of volcanoes – Pg 172
Positive impact / Advantages of Volcanoes
• Volcanic soils are some of the worlds most fertile – they are rich in minerals of
many different types, well drained and easy to work – the lava from the volcano
has weathered over hundreds of thousands of years
• Create Geothermal power using steam from the hot ground to drive turbines and
generate electricity
• Tourism
• Minerals near the crater – e.g sulphur
• Heating for homes and offices
 The negative impacts of volcanoes on people

 Rocks, volcanic bombs, and ash may rain down on top of people living on the volcano’s
slope .
 Lava flows can be so fast that people do not have time to move out of their path.
 Poisonous gases and fumes may drift overpopulated areas before people realize what is
happening.
 Heat may melt snow on mountain tops, which sets off mud flows that sweep houses and
people away
Note – for question on impact of volcano – look at both positive and negative impact . If
no positive only negative – state this in the answer
Note – usually volcanic activity is often on the top of the mountain where there is no one living
But if volcano keeps on erupting for weeks, months or years, then destruction is over a wider
area and can cause destruction to houses, crops, animals, trees
 Management of Volcanoes
1. Employ scientists to monitor to volcano from a ground station Example –mount Etna
is Italy
2. New technology - Satellites can be used to monitor heat changes – useful in remote
areas and developing countries without ground station
3. Train and educate local people in emergency procedures
4. Have an exclusion zone created by government to keep people out of the area
warning before signs of eruption
 Temperature increases in and around the crater
 Increased amounts of steam and gases seen coming from the crater
 small earthquake shocks felt in surrounding areas
 Volcanoes
Prediction Preparation and protection

• Seismometer can monitor tremors caused • Study past eruptions of a volcano and
by rising magma. create a volcano hazard map

• Satellites using heat-seeking cameras can • Plans such as lava diversion channels,
measure increasing ground temperature lava barriers, spraying lava with water and
halting lava advance by dropping
• Tiltmeters and global positioning systems concrete slabs into the flow
monitor changes in volcano shape
• Building reinforcements for example
• Emissions of steam and gas(sulfur sloping roofs to protect against ashfall
dioxide) can be monitored
 Impact and management of Volcanoes(Recap)
Impacts management

Fast-moving lava can kill people Employ scientist to monitor the volcano.

Poisonous gases and falling ash can make Satellites can be used to monitor heat
it hard for them to breathe. changes.

Heat may melt snow on mountain tops Educate local people in emergency
which setts of mud flows that sweep houses procedures.
and people away.
Tropical
Cyclones
Tropical Cyclone
 Cyclones
• Tropical cyclones are storms which from in the deep (over 60 metres), warm(at least
270C) tropical oceans and cause very strong winds and heavy rain.
• A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure
center, a closed low-level atmospheric circulation, strong winds, and a spiral
arrangement of thunderstorms that produce heavy rain or squalls (sudden violent gust
of wind or localized storm)
• Worst effects of cyclone are felt in coastal areas – Cyclones lose their power once
they start to cross land because cyclones feed off warm sea surface
• Most predictable of natural hazards
 How are cyclones formed?
• Cyclone is formed when the sea water is at its hottest – must be at least 27°C and the
warm ocean water must be at least 60 m deep
• Air above the sea surface is heated and the warm moist air start to rise due to increased
evaporation
• As it does, a deep center of low pressure develops which sucks up more air from the
surface
• Wind speed around the center of the cyclone increases to 150 -200 kph in a huge circular
swirl of cloud up to 600 km across
• Torrential(continuous) rain falls from the clouds except in the eye in the center where
weather is calm and dry
• Cyclones feed off warm sea surface and so lose their power source once they start to cross
land
• Occurs at latitude 5° and 20° north and south
Hurricanes, Cyclones and Typhoons
• are all basically the same thing, but are given different names depending on
where they appear.
• Hurricanes are tropical storms that form over the North Atlantic Ocean and
Northeast Pacific.
• Cyclones are formed over the South Pacific and Indian Ocean.
• Typhoons are formed over the Northwest Pacific Ocean
• https://www.youtube.com/watch?v=FxF8fPdtGao
Category of Cyclone

• Using Saffir-
Simpson hurricane
wind scale
 The negative impacts of cyclones
1. Tropical cyclones are responsible for immediate loss of life and great amount of damage
2. Torrential rains can cause flooding
3. Public utilities are badly disrupted – electricity, telephone, fresh water
4. The farming economy can be ruins – fields are under water and farm animals are dead
5. After the storm dies down, people are in state of shock from death of family and friends
and from economic losses ( damage to homes, possessions and businesses)

6. Can have serious health consequences like cholera and typhoid epidemics due to
disruption of water supplies, waste disposal and sewage – Mosquitos multiply rapidly
leading to an increased risk of malaria
Management of cyclones ( reducing negative impact of cyclone)

 Warning can be given in sufficient time for property to be boarded up (Boarding

up is the process of installing boards on the windows and doors of a property to
protect it from storm damage) and for people to leave the area
 People are educated in advance about the emergency procedures to adopt
after a weather office warning
 Police, fire, and ambulance services can practise emergency drills
 Hurricanes are notoriously unpredictable, suddenly changing courses and
becoming stronger but using weather satellites can help warn people
Strategy in developing country
• Most countries at risk from tropical cyclones are developing countries
• If the cyclone hits a populated area , loss of life can be huge .
• There is also less chance of preparation in advance and detailed warning about
is arrival
• Strategy is to build cyclone shelters containing emergency food and water close
to villages in areas with a high cyclone risk
 Tropical cyclones
Prediction Preparation and protection

• Tracked using • Cyclone shelters

satellites
• Building on stilts so not flooded by storm surge

• Embankments built along coast

• Preserve mangrove swamps to absorb the energy of storm surges

Tropical Cyclones
Impacts Management

Heavy rain, strong wind, large storm Warnings can be given in sufficient time
surges near landfall, and tornadoes. for people to be evacuated.

Flooding. Police, fire and ambulance practice

emergency drills.

Fields are under water and livestock are People are educated.
dead.
Floods
Flood (Climatic Hazard)
• A flood is an overflow of water that submerges land that is usually dry.
• Flooding is when the discharge of a river exceeds the capacity of the river’s
channel
• Flat land next to the river is known as flood plain because it’s the first area to be
flooded
• Floods are classified as human causes and physical causes
 Human causes of flooding
• Deforestation – Cutting down trees reduces the rate that water enters soil and allows
rainfall to directly fall on the ground
• Urbanisation – Concrete does not allow water to pass through and leads to more
overland flow. Storm drain speeds up the movement of water to the nearest river
• Cultivation/Agriculture – Overgrazing and using heavy farm machinery makes soil
not allow water to pass through
• Climate change – Global warming may lead to a rise is sea-level as well as more
rainfall and storms in certain parts of the world
 Physical Causes of floods

• Weather - Rivers breaking their banks after heavy rainfall (Torrential downpour) much more than
usual
• Prolonged period of rain
• Combination of prolonged rain and torrential downpour
• Rapid snow melt
• There is an increase in surface run-off that rivers and streams cannot cope with all the water
flowing into them
• Tsunamis
• Storm surge - A storm surge is a rise in sea level that occurs during tropical cyclones,
typhoons or hurricanes
 Physical Causes of floods
• Land Relief – Steeper gradients/slope can lead to faster overland flow
• Previous year rainfall – very wet and saturated soil
• Soil and rock type – Soil and rocks that does not allow water to pass through
Such as clay or granite leads to greater overland flow
• Saturated soil – When soil is saturated with water, all the pores are filled with water so
cannot hold more water – water will flow
• Compacted soil – Heavily compacted soil contains few large pores, less pore volume
and a greater density reducing water discharge and water passing through
 Negative impact of flooding
• Immediate Short term effect
• People can do little – main aim is survival
• When water level begins to go down people can get and seek emergency help
and aid which will help decrease human suffering and damage to the local
economy
• Long term effect
• Money is needed for recovery
• Rich country and rich people can recover faster
• Poor countries rely on international aid
 Good side of river flooding
• Every time a river floods, it leaves behind silt
• Silt is a fine grained deposit, light and easy to work and rich in minerals – so excellent
soil for farming
• Many people can be fed from farming on fertile plains
• Examples – flooding in Bangladesh leads to great fertility of the Ganges Delta
 Impact of flood and long term recovery
management – Pg 184
Immediate Short-term Long term recovery includes
• Loss of human life • People in need of medical • Repair and build new houses
treatment for injuries
• Houses destroyed • Replace bridges, roads and
• Homeless people railway lines
• Offices, factories and work
places flooded out • People suffer from water – • Restore essential public
related disease services like water and sewage
• Livestock carried away
• Shortage of safe drinking water • Reclaim farm land
• Crops ruined
• Food shortages • Buy new seeds and animals
• Road and rail bridges washed
away • Problems of moving between
places
• Communications disrupted
 Storm hydrograph
• Discharge – amount of water flowing in the river – is
constantly monitored
• When water levels are rising, flood warnings are issued
• Storm hydrograph shows river discharge after a storm
• Lag time is the difference between the peak of the
rainstorm and the peak of the discharge
• The shorter the lag time the steeper the rising line the
greater the risk of flooding – need to issue flood
warning - urgent action needed- people should move
to flood shelters on higher ground
 Management of flood
• Big rivers are managed rivers - by building large dams
• Water can be held in dams in times of high rainfall and surface run-off
• Banks along the sides of rivers can be increased in size and strength –
Hard engineering technique – can be effective but expensive to built and
maintain
• Stop deforestation on valley and plant new trees
• Flood warnings can be issued. Graphs called storm hydrographs are
issued to show river discharges after a storm
 Flood
Prediction Preparation and protection

• Monitor the amount of rainfall and • Hard engineering projects like levees, flood
the change in river discharge barriers, flood control channels and dams

• Knowledge about the • Soft engineering project such as afforestation,

characteristics of the drainage controlled flooding and storage basins
basin (A drainage basin is
any area of land where precipitation • Straightening, widening and deepening the river
collects and drains off into a common channel by dredging and clearing vegetation
outlet, such as into a river, bay, or
other body of water) and type of • Land – use planning to use higher land for
storm is valuable for determining settlements, restrict development on floodplains
the possible severity of the
flooding • Use sandbags and pipes
 Impact and management of floods
Impacts Management

Damage to property. Reduce deforestation.

Destruction of crops. Build large dams

Loss of livestock.
Drought
 Drought
• A drought is a period of dry weather longer or worse than normally expected – lack of
rain or less rain than normal over a period of time
• Droughts can lead to a deficit in water supply with insufficient water to support plants,
animals and people
• A drought can last for months or years, or may be declared after as few as 15 days.
• Drought happens most in the tropics – where there is wet season and dry season
• Droughts occur anywhere but in particular in Africa
• Droughts are responsible for more deaths than any other natural hazards.
 Physical causes of drought
• Change in regular weather pattern and evaporation exceeds precipitation reasons
for this are below-
• Air in high pressure system sinks and rain clouds do not form. If the sinking air
covers a larger area than normal droughts can occur
• Changes in atmospheric circulation patterns changing storm tracks and wind
patterns. Example – Inter Tropical Convergence Zone(ITCZ) in Sahel region of
Africa – the moist rising air at the ITCZ does not move north to reach the Sahel
• ITCZ is a low pressure belt that lies around the equator where the north- east and south-
east trade winds meet , it receives high precipitation because of intense heating from the
sun.
 Physical causes of drought
• Climate change – leader to warmer worldwide temperatures will decrease rainfall in some parts of the
world leading to more drought
• El Nino Southern Oscillation can cause droughts in areas where climate is normally wet – El Nino caused
by warming of ocean surface water in the Pacific ocean off the coast of Peru – cause droughts in
Australia
• La Nina – is the counterpart to El Nino – surface water in the Pacific Ocean along South American
decreases in temperature - Cooler water contribute to drier conditions in parts of North and South
America
• El Nino lasts less than a year – La Nina lasts for 1 – 3 years

• https://www.youtube.com/watch?v=wVlfyhs64IY
• https://www.youtube.com/watch?v=tyPq86yM_Ic
Human causes of drought
• Agricultural practices make land more vulnerable to drought
• Farmers depend on irrigation techniques for water
• Overcultivation and overgrazing leads to soil compaction – soil is less able to hold
water
• As soil becomes drier it can lead to erosion and slowly desertification

• Deforestation – lack of trees decreases soil infiltration (maximum rate that water
enters soil) and increases soil erosion
• Building a dam can cause drought downstream of the dam reducing flow of water
 Impact of drought
• In drought, because surface water becomes intermittent- natural vegetation like grasses, bushes
wither and turn brown and die out – increasing risk of wildfires – leading to smoke and poor air quality
• In rural areas, where people depend on farming – lack of water causes problems like crops may die,
yield is reduced, livestock may die due to shortage of grazing
• In rural areas, farmers income decreases – leading to lack of food and malnutrition, famine and death
– the very young, sick and elderly die first and malnutrition reduces the ability to resist disease
• Efforts to grow crops and keep animals during drought increases the risk of soil erosion and
desertification resulting in permanent environmental damage
• As water level falls in reservoirs, people depend on underground water leading to overuse of
groundwater leading to dry wells and no water
Impact of drought
• If food aid does not arrive quickly – migration out of the area is the only option
• Most people are in temporary refuge camps
• When rains return, the majority move back to their own villages and farms
 Management of droughts
• Providing food aid(international) to the malnourished and underfed – increases the chance
of survival – temporary solution
• Long term is to help people with guidance on how to increase food production in the
villages
• Government can help by increasing water ability
• Water Aid charities help with providing water
• Other solutions include
• Rainwater harvesting – collecting more of the rain falling in wet season for use in dry periods
• Tree planting to prevent soil erosion and run off
• Water conservation and storage – example building small stone or earth dams
• Organic compost pits to improve soil fertility and its water holding capacity
 Droughts
Prediction Preparation and protection

• Monitoring precipitation and • Increase water supplies by dams and reservoir, ponds,
temperature wells, pumps and use of aquifers, water transfer by
pipeline and desalination

• Water conservation such as using storage tanks, spray

irrigation, planting drought-tolerant crops, reducing
deforestation and increasing water cycle

• Agricultural improvements such as planting shelterbelts to

reduce wind and evaporation, building low banks across a
slope to encourage water to seep through and fencing to
control overgrazing

• Government stockpiling supplies of water, food and

medicine
 Impact and management of droughts

Impacts Management

Yields are greatly reduced. Rainwater harvesting.

Lack of food leads to malnutrition, famine Tree planting.

and death.

Livestock may die. Growing drought-resistance plants.

Impact of natural hazards
• Impact can be short term and long term
• Some impacts are the same for all natural hazards like – injuries, loss of
livelihood, destruction of property and infrastructure
• Impact is greater on communities who are poorer because of the lack of finance
to rebuild, lack of insurance , lack of technology and expertise to deal with the
event.
Impacts
of
natural
hazards
 Strategies to manage the impact of natural
hazards
• Focus on the three P’s – Prediction, Prevention or protection
• Dealing with natural hazard before, during and after the event
• Short term strategies include
• warnings (message, TV, radio)
• Providing food, water supplies, temporary shelter

• Long term strategies

• Training emergency services
• Providing education
• Awareness so people stockpile essential items
Managing natural hazards
• Improvements in technology makes it possible to predict and protect against
natural hazard
• However, it is expensive and aid is required in the rebuilding process
 Information
• Natural disasters are very much part of the natural cycles. But accelerated changes
in demographic and economic trends disturb the balance between the ecosystem
and leading to increased frequency and the negative impact of disaster. As the 21st
century approaches, we face a challenging mix of demographic, ecological and
technological condition which make population more vulnerable to the impact of
natural calamities. However, the number of natural disasters are not more than they
were in the past, but what has increased is the magnitude of the effect of each
disaster. The important and related factor is the population-pressure in almost all
the countries, for people to live on and use marginal land which by its very nature
may put inhabitants and property at great risk.