Disaster Assessment

8/8/2019 Disaster Assessment

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Disaster Assessment


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Types of natural disasters

Landslides Earthquakes

Tsunami

Cyclones Floods

Snow avalanche

Case studies for disaster

assessment using Geospatial

techniques

Use of Remote Sensing & GIS

software for disaster assessment.


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The natural disasters have become fast recurring

phenomena all over the world causing huge loss of

human lives and crumbling impact on the economy of

a country.

Natural disasters are inevitable and Indian subcontinent

is prone to all type of natural disaster, e.g., earthquake,

flood, drought, cyclone, Tsunami, landslides,

avalanche, forest fires, etc.

The natural disasters can not be prevented fully but

their impact can be minimized with sound disaster

management strategy aided by the latest technologicaladvancements in the field of Geoinformatics.


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The disaster management is a multi-

disciplinary endeavour, requiring many typesof data with spatial and temporal attributes

that should be available to district

administrators in the right format for

decision-making.

Geographic Information System (GIS) is apowerful tool which can be used to create

integrated geo-database, visualize scenarios,

develop advanced spatial models and

effective solutions, prepare disaster zonationmaps, and the management plans.


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Landslides


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Landslides occur when stability of slope changes from a stable to

an unstable condition.A change in the stability of a slope can be due to :

Natural causes :

Ground water pressure

Loss of vegetative structure and soil nutrients

(after forest fire)

Erosion of a slope by rivers or ocean waves

Slope saturation by snowmelt or heavy rains Earthquakes

Volcanic eruptions

Human causes : Deforestation,

Cultivation and construction,

Vibrations from machinery or traffic


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Global zones of landslide risk


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Landslide classification

1. Debris flow

Slope material that becomes saturated with water

develop into a slurry of rock and mud that pick uptrees, houses and cars, thus blocking bridges and

tributaries causing flooding along its path.

2. Earth flow

Downslope, viscous flows of saturated, fine-

grained materials, moving at speeds from 0.17 to

20 km/h.


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3. Debris avalancheChaotic movement of rocks soil and debris

mixed with water or ice (or both). Here the

movement is much more rapid.

4. Movement

Debris slides begin with large blocks that break

apart as they move towards the toe. This

process is much slower than that of a debris

avalanche.


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5. Sturzstrom

Mobile, flowing very far over a low angle, flat, or even slightly uphillterrain.

6. Causing tsunamis

Landslides that occur undersea, or have impact into water, can generate

tsunamis.

7. Deep-seated landslide

Landslides in which the sliding surface is

mostly deeply located below the maximumrooting depth of trees (depth > 10 m)

8. Shallow landslideLandslide in which the sliding surface is

located within the soil mantle or weathered

bedrock (depth < 1 m)


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The analysis is mainly done for

Identify factors related to landslides,

Estimate relative contribution each factor,

Establish a relation between factors and landslides,

Predict the landslide hazard of future

The factors used for landslide hazard analysis are

Geomorphology

Geology

Land use/land cover

Hydrogeology

Landslide hazard analysis and mapping provides useful information for

catastrophic loss reduction and for development of guidelines forsustainable land use planning.


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Since many factors are considered for landslide

hazard mapping, GIS is an appropriate toolbecause it has functions of collection, storage,

manipulation, display, and analysis of large

amounts of spatially referenced data which canbe handled fast and effectively.

Remote sensing techniques are also highly

useful, before and after satellite imagery are

used to gather landslide characteristics,

distribution and classification to reveal how thelandscape changed after an event, what may

have triggered the landslide, and process of

regeneration and recovery.


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Using satellite imagery in combination with GIS and on-

the-ground studies, it is possible to generate extremely

detailed maps of past events and likely future landslides.

Such maps have the potential to save lives, property, and

money.


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Landslides is one of the major natural catastrophes of the NilgirisDistrict, which account for a considerable loss of life and damage to

communication routes, human settlements, agricultural and

forestland.

The problem of landslides becomes more aggravated, especially during

the rainy season.

CASE STUDY

Data used :

A watershed has been taken for landslide hazard

zonation (LHZ)

mapping is done using 10-meter contour intervalSurvey Of India toposheets

6-meter spatial resolution IRS LISS-III + PAN

is used to give broad and qualitative ideas for

landslide risk Management.


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Further needs :

For effective zonation and management, Contourinterval of 2 meters is necessary and spatial

resolution of 1 meter is needed.

Though optical resolution data is increasing day-by-day (Quick bird, Cartosat, etc.), getting vertical

resolution is still challenging in passive remote

sensing.

Interferometric techniques can be effectively

employed to improve the existing Digital Elevation

Model to monitor minor changes in terrain.

The RISAT mission of government of India,

RADARSAT of Canada, ENVISAT of ESA

(European Space Agency) will provide necessaryspatial data for such analysis.


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Methodology


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The study has demonstrated the application of

various remote sensing techniques in order to obtain

the model for the effective mitigation.

We can classify the hazard zones into very low, low,

moderate, high and very high.

This highly depends on the slope of the place. In this

paper, we have analyzed the usage of the

conventional methods such as photogrammetryalong with the modern techniques of remote sensing

using satellite images.

We also discussed the use of advanced technology,which has been planned to be used in the future such

as space borne SAR and high-resolution optical data.


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Earthquakes


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There are around 500,000 earthquakes each year.

About 100,000 of these can actually be felt as Minor earthquakesoccuring nearly all around the world in places like California, Alaska,

Guatemala, Chile, Peru, Indonesia, Iran, Pakistan, Portugal, Turkey, New

Zealand, Greece, Italy, and Japan.

Larger earthquakes occur less frequently.

e.g. In a particular time period roughly ten times as

many earthquakes larger than magnitude 4 occur

than earthquakes larger than magnitude 5.


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An earthquake is the result of a sudden release of energy in the

Earth's crust that creates seismic waves. by rupture of geologicalfaults, volcanic activity, landslides, mine blasts, and nuclear tests.

The frequency, type and size of earthquakes experienced over a

period of time is referred as seismicity or seismic activity of an

area .

When a large earthquake occurs at seabed it

causes tsunami.

The earthquakes can also trigger landslides and

volcanic activity.


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An earthquake's point of initial rupture is called its focus or hypocenter.

The point at ground level directly above hypocenter is called epicenter.

Earthquakes are measured with a seismometer

Records of a seismometer are known as a seismograph.

The magnitude of an earthquake is reported withmagnitude 3 : imperceptible lower earthquakes and

magnitude 7 : causing serious damage over large areas.

Intensity of shaking is measured on the modifiedMercalli scale.


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Shaking and ground rupture

Severe damage to buildings and other structures.

Landslides and avalanches

Slope instability leading to landslides.

Fires

Damaging electrical power or gas lines.

Soil liquefaction

Saturated granular material like sand temporarilyloses its strength and transforms from a solid toliquid because of shaking.

Tsunami & Floods

Long-wavelength, long-period sea waves produced

by the sudden movement of sea water. Overflow oflarge amount of water reaches land causing flood.

Human impacts

Earthquakes may lead to disease, lack of basic

necessities causing loss of life.

Impacts ofearthquakes


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Allahabad has now got the status of Metro-city

with a population of over 10 lakhs.

The volume of information needed for naturaldisasters far exceeds the capacity to deal with

them manually and thus there is a need for a GIS

based Decision Support System (DSS).

A GIS based DSS for disaster management can be

developed consisting of three modules

1. integrated geo-database module;

2. module consisting of disaster management

models;

3. user-interface module.

CASE STUDY


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The various stages involved in the preparation of GIS

based DSS for disaster management for Allahabad

include

development of an integrated geo-database

consisting of various thematic maps,

demographic data, socio-economic data

infrastructural facilities at village level under GIS

environment.

The information required for decision making during any disaster is

diverse, spatial and temporal in nature.

Remote sensing technology can be advantageously used for detailed near

real-time monitoring, damage assessment and long-term relief

management.


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The various thematic maps include

road network map,

water supply network map,Fire control office map, urban sprawl map,

drainage map and

land use map

The various utilities like

education facilities,

medical facilities, electricity, etc.

and other information from Census 2001available for the district have been

represented spatially using GIS.

A menu driven Graphical User Interface (GUI) has

also been developed so that the GIS based DSS for

disaster management can be used by administrators

who may not have in-depth knowledge of working inGIS.


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By navigating through GUI, planners with basic

knowledge of computers can work on this systemand this is expected to increase the acceptability

of the present system among planners and

decision-makers.

The ArcGIS software and Erdas Imagine

software have been used for carrying out the

work in the present study.

The GIS based DSS for disaster management

proposed for Allahabad district may be adopted

for further implementation by districtadministrators.


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Tsunami


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A tsunami is a series of water waves caused

by the displacement of a large volume of abody of water, usually an ocean, but can occur

in large lakes.

Due to the immense volumes of water and

energy involved, tsunamis can devastate

coastal regions.

Earthquakes, volcanic eruptions and other

underwater explosions, landslides and other

mass movements, meteorite ocean impacts and

other disturbances above or below water can

generate a tsunami.


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Tsunami in the deep ocean has a wavelength ofabout 200 km traveling at about 800 km/h

Due to long wavelength the wave oscillation at anygiven point takes 20 or 30 min to complete a cycleand has an amplitude of only about 1 m.

This makes tsunamis difficult to detect over deepwater.

Ships rarely notice the passage of tsunami wave.

As the tsunami approaches the coast and the watersbecome shallow, wave shoaling compresses the

wave and its velocity slows below 80 km/h.

Its wavelength diminishes to less than 20 km and itsamplitude grows enormously, producing a distinctly

visible wave.


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Since the wave still has a long wavelength, thetsunami may take minutes to reach full height.

When the tsunami's wave peak reaches the shore,the resulting temporary rise in sea level is termed'run up'.

Run up is measured in metres above a reference sealevel.

A large tsunami may feature multiple wavesarriving over a period of hours, with significanttime between the wave crests.

About 80% of tsunamis occur in the Pacific Ocean,but are possible wherever there are large bodies ofwater, including lakes. They are caused byearthquakes, landslides, volcanic explosions, andbolides.


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CASE STUDY

The Nicobar Islands was one of the several islandswhich were severally damaged by the Great

Tsunami on 26 December 2004.

The origin of tsunami was series on underseaearthquakes, the largest being measured 9.3 M.

The direct consequence of Great Earthquake, that

ruptured the sea floor up to 100 km in places, was

displacement of a huge volume of water that

translated into tsunami of colossal proportion.

The great tsunami event caused the devastation and

a loss of life in south and south East Asia including

the Andaman and Nicobar Islands.


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Materials Used:

Software :

ArcView,

ERDAS IMAGINE etc.

Data :

Survey of India (SOI) topographic Maps,

Satellite imageries- IRS-IC LISS III (24 Feb. 1999),

IRS-P6 (16 Feb. 2005 & 01 Feb. 2005),

GPS-Garmin etrex & Garmin vista,

High precision Oregon scientific Altimeter


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Methodology:

The digital analysis of the P6 digital satellite data wasdone by using the image processing software.

Image enhancement techniques with brightness

contrast and break points is used in delineatinginundation of tsunami water on islands by acquiring

actual reflectance values from satellite data.

The coastal mapping was made by on screendigitization

The wave height, run up elevation, coastal erosion

delineation and impact of damages was made by using

the DEM/DTM.

The field data of the various locations that were

collected with the help of handheld GPS to verify the

tsunami wave height as well as the distance from sea.


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The tsunami wave height are measured based on

the satellite imageries and the DEM generatedusing SOI contour and 1m SRTM data with a

vertical resolution of +/-1m.

Inundation distances in the island were so large thatthey were most easily measured from satellite

images, where sediment deposited by the waves

and vegetation killed by the saltwater are clearly

visible

The flow direction of the tsunami water was from

all sides of the island

The pre and post tsunami images have been studied

for the observation of subsidence.


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In order to assess the damages the pre and post

tsunami satellite data are critically analysed in the

GIS domain.

For this a base map is generated from the SOI

topographic map of the region.

Based on this map the coastal area of the two

scenes (pre and post) have been classified and

vectorised using the ERDAS vector and ArcView

software.Overlay analysis of these classified vector data is

performed to find out the changes in the coastal

corridor of the Island and ultimate the assessment

of the damages is done form this analysis.

The application of High resolution Remote Sensing

data and GIS techniques are used to assess thetsunami hazards in the Car Nicobar Island.


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THANK YOU

sources : www.wikipedia.comcase studies from :www.gisdevelopment.com

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Disaster Assessment