Disaster management

1. CERTIFICATEPROGRAMME
IN
DISASTER MANAGEMENT
(CDM)
ACADEMIC COUNSELLOR
Col. (Prof.) Rajive Kohli, Ph.D.
kohli9r@gmail.com 1
CDM-0l
Foundation Course in Disaster Management
BLOCK – 2
TYPOLOGY OF DISASTERS – I
IGNOU-eVidyaBharati

2. Block - 2 Typology of Disasters – I
Unit 5 Earthquake
Unit 6 Flood and Drainage
Unit 7 Cyclone
Unit 8 Drought and Famine

3. Unit 5 Earthquake
5.1 Introduction
5.2 General Characteristics
5.3 Pre-cursors : Instrumental and Non-Instrumental
5.4 Vulnerability
5.5 Impact and Effects
5.6 Nature of Damage

4. Unit 5 Earthquake
5.1 Introduction
1. One of the most frightening and destructive phenomena of nature is a severe earthquake and its
terrible aftereffects.
2. Earthquake is a tremor caused by a violent movement of a part of the earth's crust.
3. An earthquake is a sudden movement of the Earth, caused by the abrupt release of strain that has
accumulated over a long time.
4. Tremor or quivering of the earth with a few severe shocks on earth takes place in an earthquake.
5. For hundreds of millions of years, the forces of plate tectonics have shaped the Earth as the huge
plates that form the Earth's surface slowly move over, under, and past each other.
6. Sometimes the movement is gradual. At other times, the plates are locked together, unable to release
the accumulating energy. When the accumulated energy grows strong enough, the plates break free.
7. If the earthquake occurs in a populated area, it may cause many deaths and injuries and extensive
property damage.
8. It may occur owing to volcanic eruptions or sudden dislocation in the rock structure.
9. Any sudden shaking of the ground caused by the passage of seismic waves through Earth's rocks.
10.Seismic waves are produced when some form of energy stored in Earth's crust is suddenly released,
usually when masses of rock straining against one another suddenly fracture and “slip.”

5. Over 80 per cent of large earthquakes occur around the edges of the Pacific
Ocean, an area known as the 'Ring of Fire'; this where the Pacific plate is
being subducted beneath the surrounding plates. The Ring of Fire is the most
seismically and volcanically active zone in the world.

6. Unit 5 Earthquake
5.2 General Characteristics
1. Characteristics of an earthquake:
• its location, magnitude, fault orientation, and direction of slip
• important for understanding tectonic processes at global and regional scales.
2. Three main parts to an earthquake:
• the focus, or origin of the event;
• the seismic waves; and
• the fault along which the earthquake occurs.
3. Epicenter is the projection to the surface, perpendicular to the hypocenter that reflects the intensity of
an earthquake, a product of the liberation of tensions in the failure or weakness area in the Earth's crust.
4. Two types of earthquakes:
• Tectonic earthquakes are produced by sudden movement along faults and plate boundaries.
• Volcanic Earthquakes induced by rising lava or magma beneath active volcanoes.

7. A fault is a fracture or zone of fractures between two
blocks of rock. Faults allow the blocks to move relative to
each other. This movement may occur rapidly, in the form
of an earthquake - or may occur slowly, in the form of
creep.

8. There are three major kinds of seismic waves: P, S, and surface waves.
P and S waves together are sometimes called body waves because they can travel through the body
of the earth, and are not trapped near the surface.
P wave is a sound wave traveling through rock.

9. Earthquake magnitude scales
Earthquake size, as measured by the Richter Scale is a well known, but not well understood,
concept. The idea of a logarithmic earthquake magnitude scale was first developed by Charles
Richter in the 1930's for measuring the size of earthquakes occurring in southern California using
relatively high-frequency data from nearby seismograph stations. This magnitude scale was
referred to as ML, with the L standing for local. This is what was to eventually become known as
the Richter magnitude.
As more seismograph stations were installed around the world, it became apparent that the
method developed by Richter was strictly valid only for certain frequency and distance ranges. In
order to take advantage of the growing number of globally distributed seismograph stations, new
magnitude scales that are an extension of Richter's original idea were developed. These
include body wave magnitude (Mb) and surface wave magnitude (Ms). Each is valid for a particular
frequency range and type of seismic signal. In its range of validity, each is equivalent to the Richter
magnitude.
Because of the limitations of all three magnitude scales (ML, Mb, and Ms), a new more uniformly
applicable extension of the magnitude scale, known as moment magnitude, or Mw, was developed.
In particular, for very large earthquakes, moment magnitude gives the most reliable estimate of
earthquake size.
Moment is a physical quantity proportional to the slip on the fault multiplied by the area of the fault
surface that slips; it is related to the total energy released in the earthquake. The moment can be
estimated from seismograms (and also from geodetic measurements). The moment is then
converted into a number similar to other earthquake magnitudes by a standard formula. The result
is called the moment magnitude. The moment magnitude provides an estimate of earthquake size

10. Magnitude scales, like the moment magnitude, measure the size of the earthquake at its
source. An earthquake has one magnitude. The magnitude does not depend on where the
measurement is made. Often, several slightly different magnitudes are reported for an
earthquake. This happens because the relation between the seismic measurements and the
magnitude is complex and different procedures will often give slightly different magnitudes for
the same earthquake.
Intensity scales, like the Modified Mercalli Scale and the Rossi-Forel scale, measure the
amount of shaking at a particular location. An earthquake causes many different intensities of
shaking in the area of the epicenter where it occurs. So the intensity of an earthquake will vary
depending on where you are. Sometimes earthquakes are referred to by the maximum
intensity they produce.
In the United States, we use the Modified Mercalli (MMI) Scale. The Mercalli Scale is based
on observable earthquake damage. From a scientific standpoint, the magnitude scale is
based on seismic records while the Mercalli is based on observable data which can be
subjective. Thus, the magnitude scale is considered scientifically more objective and therefore
more accurate. For example a level I-V on the Mercalli scale would represent a small amount
of observable damage. At this level doors would rattle, dishes break and weak or poor plaster
would crack. As the level rises toward the larger numbers, the amount of damage increases
considerably. Intensity X (10) is the highest value on the MMI.

11. Unit 5 Earthquake
5.3 Pre-cursors : Instrumental and Non-Instrumental
Earthquake scale
Charles F. Richter developed the original earthquake scale in 1935. Over time, technology has improved and
today researchers use the moment magnitude scale to quantify the size of an event.
There aren’t any limits on how small or large magnitude values are on the scale, but most graphics usually
show ranges from 0 to 10.
Earthquakes with a magnitude of less than 2.0 can’t be felt but are the most common.
Earthquake damage doesn’t happen until a magnitude of 4.0 or greater is reached.

12. Unit 5 Earthquake
5.4 Vulnerability

13. Unit 5 Earthquake
5.5 Impact and Effects
The destructive effects of earthquakes are from landslides, tsunamis, fires, and fault rupture. The violent
shaking of the ground produces the greatest property losses and personal injuries.
The primary effects of earthquakes are ground shaking, ground rupture, landslides, tsunamis, and
liquefaction. Fires are probably the single most important secondary effect of earthquakes.

14. Unit 5 Earthquake
5.6 Nature of Damage

15. Earthquakes affect humans by:
1) Loss of Lives
2) Social impacts
3) Injuries
4) Mental effect/Psychological effect
5) Economic Impacts
6) Environmental effects

16. We cannot prevent natural earthquakes from occurring but we can significantly mitigate their effects
by identifying hazards, building safer structures, and providing education on earthquake
safety.
By preparing for natural earthquakes we can also reduce the risk from human induced earthquakes.

17. Unit 6 Flood and Drainage
6.1 Introduction
6.2 Causal phenomena and characteristics
6.3 Vulnerability
6.4 Predictability, forecasting and warning
6.5 Preparedness
6.6 Mitigation with special reference to flood plain zoning
6.7 Adverse effects

18. Causes of Floods
Flooding conditions may occur due to:
• River in spate
• Snowmelt
• Storm surges
• Short intense storm causing flash floods
18

19. Flooding in rivers in mainly caused by:
• Inadequate capacity within the banks of the rivers to contain high
flows.
• River bank erosion and silting of riverbeds.
• Landslides leading to obstruction of flow and change in the river
course.
• Synchronization of flood in the main tributary rivers.
• Flow retardation due to tidal and backwater effects.
• Poor natural drainage.
• Cyclone and heavy rainfall.
19

20. Flood Mitigation Measures
Structural
• Dams and Reservoirs
• Embankments, flood
walls, sea wall, levees
• Natural detention basin
• Channel improvement
• Drainage improvement
• Diversion of floodwaters
Non- structural
Modifying the susceptibility :
• Flood plain management
• Flood proofing including disaster
preparedness, and response planning
• Flood forecasting and Warning
Modifying the flood loss burden
through:
• Disaster Relief
• Flood fighting including Public Health
Setting up of flood forecasting and
warning
20

21. • Floods occur everywhere – tropics, plains,
deserts.
• Everyone in their lifetime pass near a
flood.
• Past provides the best forecast.
• Largest known flood in any area is likely to
be exceeded
21

22. Unit 7 Cyclone
7.1 Introduction
7.2 Characteristics
7.3 Forecasting and Warning Systems
7.4 Preparedness
7.5 Risk Reduction Measures
7.6 Effects

23. What is a cyclone?
1. A cyclone is a system of wind that moves rapidly inward with a low-pressure
area in the middle.
2. In meteorology, it refers to the large mass of air that surrounds a strong
atmospheric center.
3. The internal winds moving over an area of ​​low pressure allow us to view the
storm in a spiral shape.
4. The large-scale (synoptic scale) polar vortex and extra-tropical cyclones are the
largest low-pressure systems.
5. The synchronous scale also includes tropical cyclones such as tropical cyclones
and subtropical cyclones.
23

24. 1. Tropical cyclones form only near the equator, in warm ocean waters.
2. A cyclone is formed when warm, moist air near the ocean’s surface rises upward.
3. When air rises away from the ocean’s surface, it generates a low-pressure zone
beneath it.
4. It causes air from higher-pressure places to travel towards the low-pressure
area, warming the air and causing it to climb above.
24

25. Where do tropical cyclones occur?

26. Sea Surface Temperature
TC’s form over warm water
Equator

27. Locations of Tropical Cyclone Formation
TC’s form near but not on the equator

28. Typical Tropical Cyclone Tracks
Note that “hurricane”, “typhoon”, and “cyclone” are local names for the same thing

29. Nickname for a tropical cyclone, which is
an intense tropical low pressure system with
maximum sustained winds of 74 mph or higher.
Known as typhoon in eastern North Pacific and
cyclone in Indian Ocean and South Pacific.

30. More Definitions

31. Hurricane Katrina--seen from space
How does
this look
from an
airplane
flying in the
eye of the
storm?
Note the
slope of
the eyewall

32. Sketch of Mature Hurricane Structure
Vertical cross section along AB in previous slide
A B
Note that
the storm
is a high
aloft and a
low at low
levels
Note the
slope of
the eyewall

33. Top of a Tropical Cyclone
Upper-level cloud, wind, & pressure
eye

34. Satellite photo of the top of a tropical cyclone
High
clouds
swirling
outward

35. Wind
Heavy Rain/Floods
Tornadoes
Types of Hurricane Damage
Storm surge

36. Category 4 Damage: Galveston 1900

37. Storm surge
Types of Hurricane Damage

38. Storm surge
Types of Hurricane Damage

39. Important factors that make a hurricane develop
Warm ocean--hurricanes get their energy from
the ocean
Humid atmosphere--need high humidity to get
clouds to develop
Weak “wind shear” --if wind is stronger at
upper levels than lower levels, storm top
separates from lower part of storm

40. Cyclone Monitoring & Mitigation Project
To cover 13 cyclone prone States and UTs [cost Rs.1050
crores in collaboration with World Bank.]
Strengthening of cyclone tracking and monitoring and early
warning system.
Storm surge modelling.
Preparation of disaster management plans at different
levels.
Conservation and regeneration of mangrove forest & coastal
shelter belt plantation.
Construction of saline embankments and cyclone shelters.
(Approved by Government)
40

41. 24-hforecastland-fallpositionerror:28km
24-hforecastlandfalltimeerror:2hr(delay)
Track Prediction of TC:
MAHASEN (11-
16 May, 2013)
Source: www
.mosdac.gov
.in/ cyclone

43. Unit 8 Drought and Famine
8.1 Introduction
8.2 Distinction Between Drought and Famine
8.3 characteristics of Droughts
8.4 Predictability, Forecasting and Warning
8.5 Vulnerability
8.6 Mitigation
8.7 Typical Effects

44. 1. Drought is a situation created generally insufficient levels of rain resulting in water
shortage that affect the economic and physical well being of a community.
2. Drought or scarcity of water to satisfy the normal needs of agriculture, livestock or
human population is generally associated with semi-arid or desert climates.
3. Drought can also occur in areas that normally enjoy adequate rainfall and moisture
levels.
4. A drought is defined as drier than normal conditions.
5. This means that a drought is "a moisture deficit relative to the average water
availability at a given location and season".
6. Drought can limit the growing season and create conditions that encourage insect
and disease infestation in certain crops.
7. Low crop yields can result in rising food prices and shortages, potentially leading to
malnutrition.
8. Drought can also affect the health of livestock.
9. A drought can last for days, months or years.
Droughts
Unit 2 Understanding Disasters: Causes and Effects

45. 1) Briefly describe the distinction between drought and famine.
1. Drought results in shortfall in agricultural production and hence may
causefood shortages.
2. Due to the reduced purchasing power of the poorer sections of the
society and if timely help is not available from the community or
governments, the situation can lead to famines.
3. Drought causes crop failure, but mismanagement of the drought
mitigation can cause famines.

46. Types of Drought
1. Meteorological Drought. When dry weather patterns dominate an area.
2. Socioeconomic Drought. When the supply and demand of various
commodities is affected by drought.
3. Hydrological Drought. When low water supply becomes evident in the
water system.
4. Agricultural Drought. When crops become affected by drought.
5. Socioeconomic Drought. When the supply and demand of various
commodities is affected by drought.
6. Ecological Drought. When natural ecosystems are affected by drought.

47. Q. Discuss the characteristic features of a drought.
1. It builds over a period of time with increased scarcity of water generally due to
insufficient or erratic monsoon rains.
2. It is a creeping phenomenon.
3. Drought can be localized covering a district or a group of districts, or be
widespread cover-up a state or a group of states.
4. Area affected by a drought usually takes an elliptic shape instead of a circular
coverage.

48. 1. As drought is very much linked with the performance of the monsoon, the
predictability of droughts is also limited to the monsoon.
2. But monsoon, by its inherent nature is highly variable in time and space
which means that rainfall is neither predictable nor evenly distributed.
3. For good agriculture, well distributed and evenly spaced spells of monsoon
rain are required. But in actual circumstances, it is rarely so.
4. The encouraging feature is that even if there is a delay of few days and the
monsoon never fails the entire country.
5. a The seasonal forecast of monsoon rainfall helps in the predictability of
droughts.
Q. Discuss briefly the predictability of droughts in India.

49. 1. Monsoon rains are deficient.
2. Non-irrigated agricultural lands.
3. Source of water for irrigation dries lip.
4. Low moisture retention in soil.
5. Deficiency of moisture at critical stage of crop growth.
6. Farmers can't adapt to drought or do not get alternatives seed.
Lack of alternate sources of income for those rendered jobless due to drought.
Q. List the situation that create can aggravate droughts.

50. 1. Construction of check dams to store water.
2. Watershed management and water rationing.
3. Cattle management and proper selection of crop for drought affected
areas.
4. Leveling, soil conservation techniques.
5. Reducing deforestation and firewood cutting in the affected area.
6. Education and training of the people.
Q. Briefly discuss the mitigation strategies or actions that can lessen
the drought impacts.

51. 1. The effects of drought can be divided into primary and secondary.
2. primary effects of drought mainly results in loss of crops, livestock and other
animals, water for drinking and hygienic use, loss of hydroelectric power generation
and loss of industrial production.
3. Secondary effects of drought follow and result from primary effects.
4. More prominent secondary effects are: poor health, disease and loss of livelihood.
5. In such circumstances, people begin to migrate in search of better grazing lands for
their cattle herds or to the cities to seek alternate source of income.
6. If the dwindling supplies of food are not replaced, famine can occur, further
accelerating the migration, which could lead to social conflict.
Q. Drought impacts can be highly varied and widespread and are
potentially one of the most destructive hazards. Discuss.