ce 488 – coastal disasters · 1. coastal earthquakes 2. under sea volcanic eruptions 3. under sea...

Tsunami, Cyclone – Module 3 01-04-2019

Compiled by Shimi Lawrence, SCTCE 1

CE 488 – Coastal disasters -Cyclones , Tsunami

01-04-2019 23:45:55 1

The Coast

• Over 50% of the Earth’s people live within 50miles of a coast!

• Typically susceptible to flooding

• Impact of flooding• property damage

• loss of life

• saltwater intrusion

01-04-2019 23:45:56 2



• TSUNAMI – “Harbour wave”

• Tsunami – are large waves that are generated when the

sea floor is deformed by seismic activity

• Tsunami wave caused by

1. Coastal earthquakes

2. Under sea volcanic eruptions

3. Under sea landslides (submarine slides)

• Tsunami is not a single wave, It is series of waves.

• Travel at a speed of more than 800 km/hr.

INTRODUCTION

01-04-2019 23:45:56 3

TSUNAMIS:

Physical Interactions Encompass

The Lithosphere, Core, Mantle, Asthenosphere, Hydrosphere, and Biosphere

01-04-2019 23:45:56 4



THE POTENTIAL DISASTER AGENTS OF A TSUNAMI

01-04-2019 23:45:56 5

Tsunami – A series of large waves generated by suddendisplacement of seawater (caused by Earthquake, volcaniceruption or submarine landslide); capable of propagation overlarge distances and causing a destructive surge on reachingland. Observed mainly in Pacific.

What is a Tsunami

• A series of waves with wavelength of a few km and period 10min to 2 hrs, that results from the displacement caused by largeearthquakes (vertical movements) volcanic eruptions, or bysubmarine slides .

• Speed can be 800kmph.

• Open sea, height can be upto 1m (often not felt)

• Near coast, it reaches a height upto 30m and weigh millions oftons.

• The energy released during the 2004 Tsunami is said to be 4.75lakh kilo tones.• 23000 times the energy released by the atomic bomb that destroyed

Hiroshima.

• Propagates in a radial direction from the source01-04-2019 23:45:56 6



01-04-2019 23:45:56 7

Ocean wave and Tsunami

01-04-2019 23:45:56 8



TSUNAMI HAZARDS (POTENTIAL DISASTER AGENTS)

• High-velocity, long-period water waves

• Wave runup

• Flooding

• Wave retreat

• Shoreline erosion

01-04-2019 23:45:56 9

HIGH VELOCITY IMPACT OF

INCOMING WAVES

TSUNAMIS

INLAND DISTANCE OF WAVE

RUNUP

VERTICAL HEIGHT OF WAVE

RUNUP

INADEQUATE RESISTANCE OF

BUILDINGS

FLOODING

NO WARNING, OR

INADEQUATE WARNING

PROXIMITY TO SOURCE OF

TSUNAMI

CAUSES OF

DAMAGE/DISASTER

CASE HISTORIES

01-04-2019 23:45:56 11



Some Tsunami

01-04-2019 23:45:56 12

Location Date Magnitude Damage/Loss

Central part of Western Sumatra

10th Feb 1797 8 > 300 death

South Western Sumatra 24th Nov 1833 8.8 – 9.2 Flooded all the southern part of West Sumatra

Central Sumatra & Nias 5th Jan 1843 7.2 Many

Western Coast of Sumatra

16th Feb 1861 8.2 Several thousands

Krakatau 27th Aug 1883 Volcano caused > 36000

Aceh and Nias Island (Indian Ocean Tsunami)

26th Dec 2004 9 – 9.3 > 270,000 (Indonesia, India, Srilanka, Thailand, Maldives, Bangladesh)

Tsunami in IndiaDate Cause Impact

August 1883

• Explosion of theKrakatoa Volcano inIndonesia

• East Coast of India• 2 m tsunamis recorded at

Chennai

26 Jun 1941

• 8.1 EQ in AndamanArchipelago

• East coast of India wasaffected , but no estimates ofheight of tsunami available

27 Nov 1945

• 8.5 EQ at a distance ofabout 100 km South ofKarachi

• West coast of India fromNorth to Karwar affected

• 12m Tsunami felt at Kandla

26 Dec 2004

• 9 – 9.3 EQ Indian Ocean Tsunami

• 4 km water depth , 713 kmph.• In 10m water depth , the

velocity reduced to 36kmph01-04-2019 23:45:56 13



01-04-2019 23:45:56 16

01-04-2019 23:45:56 17



Countries affected

1. Indonesia

2. Thailand

3. Srilanka

4. India

5. Myanmar

6. Malaysia

7. Bangladesh

8. Somalia

States affected in India

1. Andaman and nicobar

2. TamilNadu

3. Pondicherry

4. Kerala

5. Andhra Pradesh

01-04-2019 23:45:56 18

Impact of Tsunami as a whole- In India

Particulars TamilNadu Pondicherry Kerala Andhra

Pradesh

Length of coast affected 1000 Km 25 km 250 km 985

Incursion of water into

land

2 km to 3.5

km

300m to 3 km 1-2 km 500m to

2km

Average height of waves 7 m to 10 m 10 m 3m to 5

m

5m

Population affected 6.91 lakhs 43,000 24.7

lakhs

2.11lakhs

Dwelling units affected 1,12748 10,061 11,832 1,557

Animal lost 5,477 506 520 195

Cropped area hit 2,589 ha 792 ha 810 ha 790 ha

Source: Ministry of Home Affairs01-04-2019 23:45:56 19



01-04-2019 23:45:56 20

Tsunami Impact

01-04-2019 23:45:56 23



01-04-2019 23:45:56 24

TSUNAMI WAVE RUN UP

01-04-2019 23:45:56 25



01-04-2019 23:45:56 27

Coastal Preparation

• Inundation simulation

• Coastal zoning

• Structural adjustments

• Insurance

• Barriers to flooding

01-04-2019 23:45:56 29



Preparedness - Tsunami

• Know about the Tsunami evacuation plan, (if you are new at aparticular Tsunami prone locality)

• Plan Tsunami evacuation route, if familiar with the locality, to a highground or an elevate place.

• Radio for updating (battery operated)

• Disaster Supplies kit (emergency medicines, food items that wouldlast long like biscuits, packed items, water)

01-04-2019 23:45:56 31

How to get protected from Tsunami

Precautions Details

Avoid constructions(buildings) within severalhundred feet from thecoastline.

Damage from Tsunami and strong winds,cyclones are more here

Elevate coastal homes Can help in reducing the damage toproperty from most tsunami waves

Flood preparedness /precautions

Floods happen.

Post Tsunami • Get advise of an Engineer to divertTsunami waters, from our property

• Tsunami walls

Tsunami walls / sea walls The purpose of a sea wall is to protectareas of human habitation, conservationand leisure activities from the action oftides, waves, or tsunamis.

01-04-2019 23:45:56 32



Tetrapods

01-04-2019 23:45:56 33

01-04-2019 23:45:56 34



Tsunami Response

• Identify areas at risk•Warning system•earthquake monitoring• tsunami detection

•Warning signs•earthquake• trough arrival

01-04-2019 23:45:56 35

TSUNAMI WARNING SYSTEM

In 1965- International Tsunami Information

Centre (ITIC).

• Under water earth quakes are monitored by sensors on

the floor of the sea

• The sensors pass on information to floating buoys on the

surface whenever they detect any change in sea pressure

• Information is then relayed to satellite which pass it on to

the earth stations.

• Inform well in advance 3 to 14 hours.

01-04-2019 23:45:56 36



Tsunami Warning

01-04-2019 23:45:56 37

Tsunami Warning

01-04-2019 23:45:56 38



Warnings(Reference: FEMA)

• Tsunami waves are not coastal waves

• An unusual lowering of ocean water, exposing the sea floor• “drawing back of water” is a precursor of strong water surge

• Beaches, lagoons, bays, estuaries , river mouths are thedangerous places that can be affected.

• Large tsunami waves can reach a height of 20-50 ft along thecoast or higher.

• Cannot predict how many surges or what time will elapsebetween waves.• Can return after 8 hrs also.

• Japan, California, Indonesia examples.

01-04-2019 23:45:56 39

Protect ourselves during EQMove to a high ground or inland as soon as you can and Stay there until informed to return.

Tsunami

01-04-2019 23:45:56 41

➢ Occurrence of the tsunami-generating earthquake can be recorded onseismographs and communicated via satellites to the warning center, wherecomputer-based models calculate tsunami heights and travel times.

➢ This could be verified by a series of wave rider buoys and accordinglytsunami warning can be issued.

➢ Such warning systems exist in Pacific countries including the U.S. and Canadasince 1964

Warning system:



Cyclones (Cyclones, hurricanes, Typhoons)

01-04-2019 23:45:56 45

India

• Coastline : 7516 km

• 5700 km prone to various degrees of cyclones

• Vulnerable to cyclone related disasters, loss of lives, livelihoodopportunities, damage to public, and private property and severedamage to infrastructure and resultant consequences.

• 13 coastal states and Union Territories• 84 coastal districts

• Tamilnadu, Andhra Pradesh, Orissa, West Bengal & UT-Pondicherry (EASTCOAST), Gujarat (west Coast) – vulnerable to cyclones.

• 1/3rd population affected

01-04-2019 23:45:56 46



Cyclone (tropical storm)

• A weather system consisting of an area of low pressure, inwhich winds circulate at speeds exceeding 61kmph –Tropical storm.

• Winds rotate around the low pressure centre in an anti-clockwise direction in the Northern Hemisphere and in aclockwise direction in the Southern Hemisphere.

• Storm Surge – is an abnormal rise in the level of water alonga shore, primarily as a result of the high winds and lowpressures generated with tropical cyclones; generallyaffects only coastal areas but may intrude some distanceinland.

01-04-2019 23:45:56 49

Coriolis effect

• When the earth rotates, the area around the equator rotates fasterthan at the poles.

• So if something thrown from North pole, it gets deviated from thelatitude and take a diverged path to reach the equator (biggestlongitude).

• This is because the equator moved much than the polar longitudes.

• It would get deflected while reaching destination (somewhere inequator region)

01-04-2019 23:45:56 51



• Decision Support System (DSS) - Generation of Hazard maps in respectof habitation of different infrastructure, housing and crop damagesbased on the cyclone wind distribution of storm surge and heavyrainfall along the cyclone track starting from its coastal landfall.

• Depression (low pressure area) – region where the barometricpressure is lower relative to that in the surrounding regions at thesame level and wind speed in circulation between 17 – 27 knot (31- 49kmph).

• Eye of the cyclone – Centre of a cyclone. It’s the point where the windrotates in a counter – clockwise direction . In the centre of the eye,wind is calm or slight and rainfall and cloudiness is nil or mild.

• Gale – Wind speed between 34 – 40 knots

• 1 knot – 1 nautical mile per hr – 1.852 kmph

• Landfall – a point on the land where cyclone just crosses the coast

• Lead time – Period of a particular hazard between its announcementand arrival

• Mangroves – plants / trees growing on sheltered shores , estuaries,bays, creeks, and barrier islands.01-04-2019 23:45:56 52

• Non structural measures – non engineered measures toreduce or avoid possible impacts of hazards such aseducation, training, capacity development, publicawareness, early warning, hazard vulnerability analysis,communication.

• Structural measures – Any physical construction to reduceor avoid possible impacts of hazards, which includeengineering measures and construction of hazard –resistant and protective structures and infrastructure.

• Risk Mapping – Identifying high-risk areas by correlating ahazard to the terrain and to the probability of occurrence.Risk maps are presented which shows the type and degreeof hazard represented by a natural phenomenon at a givengeographic location.

• Zonation – It is the subdivision of a geographical entity(country , region, etc) into homogenous sectors, withrespect to certain criteria ( for example, intensity of hazard,degree of risk, same overall protection against a givenhazard)

01-04-2019 23:45:56 53



Hurricanes

01-04-2019 23:45:57 54

Structural Measures for cyclone risk mitigation

i. Structural safety of lifeline infrastructure in coastal areas

ii. Establishing a robust system of locating multi-purpose cycloneshelters and cattle mounds

iii. Ensuring cyclone resistant design standards are incorporated in rural-urban housing schemes in coastal areas

iv. Building all weather road links to all coastal habitations and cycloneshelters/cattle mounds

v. Maintaining the full designed carrying capacity of main drains andcanals along with feeder primary/secondary/tertiary channels,creating additional flood flow canals in frequently inundated areas.

vi. Construction of saline embankments to prevent ingress of salinewater associated with cyclonic storm surge.

vii. Encouraging public private partnership with corporate/ trusts.

01-04-2019 23:45:57 56



Management of Coastal zones – Effective cyclone risk reduction (MoEF, State remote sensing agencies, Ground water

development Board, Coastal area development,and Irrigation)

1. Mapping and delineation of coastal wetland, patches of mangroves,shelter belts, identification of potential zones for expanding bio shieldspread based on remote sensing tools.

2. Regulating infrastructure and development activities in coastal zones

3. Monitoring water quality

4. Developing Integrated Coastal Zone Management (ICZM)

5. Evolving eco-system restoration plans for degraded ecological zone

6. Developing delta water management and fresh water recharge

7. Coastal bio-shield spread, preservation and restoration/ regenerationplans

8. Implementing coastal flood zoning, flood plain development, regulatoryplans

9. Ground water development and augmentation of freshwaterrequirement in coastal urban centres

10. Development of aquaculture parks in the identified potential zones.01-04-2019 23:45:57 57

• Indian coastline (~7500 km)

• vulnerable to hazards

normal➔ wind, waves,

tides, currents,

sediment movement

extreme ➔ cyclones,

storm surges, (~6 / yr)

tsunami, (1, 2/century)

oil spills,…

01-04-2019 23:45:57 59

▪ Impact depends on: -Density of population, (25 % ➔ within 50 km)-Design of structures and quality of construction, -Environment (presence of mangrove forests,..)



Cyclones & Storm surges

• tropical cyclone➔ a rotating wind

(low pressure disturbance

generally with heavy rainfall)

• As cyclone approaches coastal area,

strong on-shore winds create➔ water current circulation,

together with lowering of pressures

➔ rise of several meters in sea level

(Storm surge)

➔ flooding large areas of the coast

01-04-2019 23:45:57 60

Tropical Cyclones Hurricanes Tornado Cyclone Typhoon

Weather Phenomenon

Sustained winds of 111 mph (96 knots) or more

Violently spiralling funnelcloud extend frombottom of thethunderstorm to theground.



Winds (Strong rotating winds)

< 322 kph > 483 kph

Names (based on place of occurrence)

Atlantic & Northeast Pacific

Much less land mass South Pacific & Indian Ocean

North west Pacific

Place of occurrence Over tropical or subtropical waters, and has closed, low – level circulation. (Speed more than 74 miles per hr)

Location Over the ocean Over the land

Size (observed) 160 – 1600 km wide

4km wide (largest), usually 0.8km wide

Life cycles Days to weeks Spontaneous and short-lived. Sec to minutes

Require hot, humid air near the ground with a cool air mass above. Strong wind velocity at higher altitudes (wind shear)

01-04-2019 23:45:57 62



WIND AND WATER

PENETRATE BUILDING

ENVELOPE

SEVERE

WINDSTORMS

UPLIFT OF ROOF SYSTEM

FLYING DEBRIS PENETRATES

WINDOWS

STORM SURGE AND HEAVY

PRECIPITATION

IRREGULARITIES IN

ELEVATION AND PLAN

POOR WORKMANSHIP

FAILURE OF NON-

STRUCTURAL ELEMENTS

CAUSES OF

DAMAGE/DISASTER

CASE HISTORIES

01-04-2019 23:45:57 65

Hurricane Impact

• High winds

• Heavy rain

• Storm surge

01-04-2019 23:45:57 67



Lessons learned about disaster resilience

All cyclones

Early warning is essential forevacuation

preparation of the last line ofdefense, which are essentialfor disaster resilience

Timely emergency response isessential for disaster resilience

01-04-2019 23:45:55 71

Coastal Erosion- by breaking waves and

associated currents

01-04-2019 23:45:57 73

Oil Spillscaused by accidents involving tankers, barges, pipelines, storage facilities

can harm marine life, which in turn can harm human beings through food



Sea Dykes (barriers, embankments, dams, sea walls)

➔Protect low-lying areas against flooding

➔Mound of sand and clay – sloping towards sea to reduce wave run up

➔Slope surface armored with grass, asphalt, stones, or concrete slabs

Structural measures for hazards reduction

Shore protection manual, 1984, Coastal Engineering Manual, 200301-04-2019 23:45:57 74

Sea walls

Vertical faced (concrete or stone filled)

Problem -- toe erosion(use with groins)

Sloping faced (armored with concrete slabsor armor units)

Parallel to shoreline

01-04-2019 23:45:57 75



Revetments -- protection from erosion

Bulkheads -- basically for slope stability

01-04-2019 23:45:57 76

Groins

- Fixed or adjustable

- High or low height

- Permeable or impermeable

Updrift ➔ accretionDowndrift ➔ erosion

➔ saw-tooth shoreline

Walls Perpendicular to shoreline; rubble mound or sheet piles

Storm surge barriers ➔ A series of movable gates (sliding or rotating)

that prevent water intrusion in low lying areas- open – normally; but closed – in storm surges

01-04-2019 23:45:57 77



Non-structural measures

--Building sand dunes and growing vegetation around them

--Artificial beach nourishment – removal of sand from one place andand transportation to some other placeupstream where erosion feared

--Providing bio-shields

01-04-2019 23:45:57 78

Bio-shields

01-04-2019 23:45:57 79

• Mangroves

• Coral reefs

• Sea grass

• Sea weeds

• Animal habitats

• Marine parks

• Marine sanctuaries

http://mbgnet.mobot.org/salt/coral/reef1large.jpg



Mangroves

• Located in inter-tidal regions, can grow in salinewater and in sheltered places like creeks andestuaries

•Act as buffer against storm surges arrest erosion,trap sediments, harbor fish

•But certain species are sensitive to excessivesedimentation, stagnation, oil spills

01-04-2019 23:45:57 80

(Source: www.deh.gov.au/.../ protect/images/mangroves.jpg)

Gujarat and Orissa cyclones, presence of mangrove buffers ➔ less destruction

Coral Reefs -natural barriers against erosion and storm surge

• corals ➔ slow growing colonies of animals

- growth rate = 1, 10 cm / yr.

- occur in shallow tropical areas

- sea water should be clean, clear and warm - provide habitat for a large variety of

animals and plants

01-04-2019 23:45:57 81

(Source:mbgnet.m

obot.org/salt/

coral/faq.htm)

http://mbgnet.mobot.org/salt/coral/reef1large.jpg

http://mbgnet.mobot.org/salt/coral/polyplarge.jpg

http://mbgnet.mobot.org/salt/coral/fish1large.jpg



Necessary to quantify the protection the bio-shields provideand determine limits beyond which they are not so effective.

01-04-2019 23:45:57 82

Destruction - outbreak of reef-destroying animals, storms,depletion of essential symbiotants chemical

pollution, mechanical damage, nutrient or sediment loading

Oil spill control

•Mechanical Containment• Booms and barriers >

• Skimmers• Sorbents (oil collecting

sponges)

•Chemical and Biological dispersants

-- disintegrate oil

-- Used in conjunction with mechanical means

01-04-2019 23:45:57 83



Cyclone & TornadoCyclone Tornado

An atmospheric system of rapidly circulatingair massed about a low-pressure center,usually accompanied by stormy oftendestructive weather. Storms that begin in theSouthern Pacific

A rotating column of air ranging in width froma few yards to more than a mile and whirling atdestructively high speeds, usually accompaniedby a funnel-shaped downward extension of acumulonimbus cloud. Winds 40-300+ mph

Clockwise in the southern hemisphere andcounterclockwise in the northern hemisphere.

Clockwise in the southern hemisphere andcounterclockwise in the northern hemisphere.

Commonly quite strong. The scale formeasuring cyclones is called the BeaufortScale and Saffir-Simpson scale and may vary indifferent countries. Winds may approach300kph and cause widespead damage.

The scale used for rating the strength oftornadoes is called the Fujita (F), EnhancedFujita (EF), and TORRO (T) Scale.

Southern Pacific Ocean, Indian Ocean.Cyclones in the northwest Pacific that reach(exceed) 74 mph are "typhoons".

Tornados have been spotted in all continentsexcept Antarctica.

10-14 per year (frequency) The US records about 1200 tornadoes/yr.Tornadoes occur commonly in spring and thefall season and are less common in winters.

Occur in warm areas Places where cold and warm fronts converge.Can be just almost anywhere.

Forms of precipitation – RAIN Forms of precipitation – RAIN, SLEET, HAIL01-04-2019 23:45:57 86

Lessons learned about disaster resilience

ALL CYCLONESRecovery and reconstruction is about knowing what to do differently when

starting over again.

01-04-2019 23:45:57 89



Vulnerability Modelling - Wind hazards

• Mathematical tools that allow impact metrices to be estimated based on hazard metrices.

• 5 major types of vulnerability models.1. Past loss data – based2. Past lost data – based enhanced with expert judgment3. Heuristic4. Component-based5. Simulation based

1,2 – past lost data – insurance claims information and the impact metric a repair or replacement cost.(assuming the vulnerability still exists for the same type of event in future also)

2 – considers expert opinion on the event and further enhancement in technology and practices for the study.

Recent researches use complex statistical analysis or data mining approaches to draw greater causal information from the damage/ loss data.

01-04-2019 23:45:57 90

Heuristic models (potential damage model) & Component Based model

Heuristic Models

• Based on expert judgement

• Used when no empirical damage information is available or for developing more complex simulations or component based model.

• Requires much engineering knowledge for success of this model.

Component Based Model

• Considers individual components of a system and aggregate these up to overall damage.

• Laboratory testing and Engineering judgment required.

• Best in assessing efficacy of component level mitigation measures or changes to building practice.

01-04-2019 23:45:57 91



Simulation Based Model

• Simulates time-dependent hazard loading, load transfer and resultantdamage to a structure in a probabilistic manner, with progressiveelemental failure and load path updating

• Monte-carlo type simulation – multiple realisations of the hazard andresponse are simulated.

• These are aggregated to develop mean vulnerability relationships,together with uncertainty bounds.

• Secondary damage causing mechanisms such as debris impact, wateringress during tropical cyclones.

• Validation using loss data or damage survey information.

• Provides greatest level of understanding when it comes to damagecausation, which provides great explanatory and comparativecapabilities when issues such as mitigation efficacy, is the prime pointof interest. (from safety and financial point of view)

01-04-2019 23:45:57 92

Vulnerability of Building Structures - Winds

Components Aftermath

Wind External fabric of building, failure of individual components ( windows, roof sheeting), resulting in secondary damages (water ingress), Taking away building materials and damaging structures by impact, damage to household items.

Debris impact, household damage, personal effect (vacating premises)

01-04-2019 23:45:57 93



Flood vulnerability studies - Cyclone

• When cyclone moves close to coastline, they generate a surge ofwater that can inundate low lying areas.

• Fast moving flood waters – have wave actions.

• Slow rising riverine flooding –

• Flood water comes in contact with building and causing degradationor failure of electronics.

• Flood waters, in hydrodynamic loading, damage occurs to buildings.

01-04-2019 23:45:57 94

Flood characteristics that can cause damage to buildings

• Inundation depth

• Flow velocity

• Duration of inundation

• Rate of inundation

• Contaminant loading

• Size and amount of debris,

• Time of inundation (night/day)

• Frequency of inundation

01-04-2019 23:45:57 95



Floods in roads & transportation and relief

• For immediate emergency response and post-disaster recoveryefforts.

• Adverse events – damage of roads, inundation, overtopping ofbridges, by erosion and by scouring, falling of trees, downing ofpower lines. – no traffic lights/ signals.

• Roads inundation - period, nature of water flow, underlyingfoundations

• GIS Based study

01-04-2019 23:45:57 96

Water Supply

• Required for drinking, and daily requirements

• Cooling of power stations for power production.

• Unless, underground scouring or damage to pipelines, vulnerability is less.

01-04-2019 23:45:57 97



Telecommunication

• Radio, telephones, internet, cellular services, & Banking andcommerce.

• Electricity required for cooling the telecommunication equipments.

• Overhead power lines, Transmission towers, telephone lines,antennae, satellite dish are vulnerable to high wind events anddebris impact.

• Floods damage junction boxes, and underground cables, (erosion andscour)

• Vulnerability studies w.r.t telecommunication networks due to floodsis less.

01-04-2019 23:45:57 98

CE 488 – Coastal disasters -Cyclones , Tsunami

01-04-2019 23:45:57 99

ce 488 – coastal disasters · 1. coastal earthquakes 2. under sea volcanic eruptions 3. under sea...

Documents