Dr. S.S.L.Hettiarachchi

Dr. S.P.Samarawickrama

University of Moratuwa

________________________Dr.N.Wijeratne

University of Ruhuna

Dr. Juan Carlos Villaran

UNU, Bonn

Dr.Hong Kie Thio

URS, USA

____________________________

Acknowledgements-

USAID/IOTWS Project

NSF, Sri Lanka

PARI, Japan

WAPMERR, Geneva

Geo Science, Australia

University of Arizona

UNU, Bonn

Tsunami Risk Assessment for Coastal Cities of Sri Lanka

Case Study for the Port City of Galle

Galle Bay and Headland comprising the Dutch Fort

Port of Galle

City Center

City of Galle

Moratuwa

Kalutara

Ahungalla

Hikkaduwa

Galle

UnawatunaMatara

Yala

Kirinda

8.4

8.8

3.5

4.5

09.45 hrs09.20 hrs

2 nd Wave

1 st Wave1 st Wave09.20 hrs2 nd Wave09.40 hrs

09.20 hrs09.10 hrs 1 st Wave

2 nd Wave

06 30 00 N

06 00 00 N

82 00 00 E81 30 00 E81 00 00 E80 30 00 E80 00 00 E79 30 00 E

Payagala

Hambantota

09.30 hrs09.45 hrs 2 nd Wave

1 st Wave

3 rd Wave12.20 hrs

2 nd Wave

1 st Wave

3 rd Wave

09.30 hrs09.45 hrs12.20 hrs

6.910.310.2

6.0

Tangalle

4.1 3.7

7.0 4.5

GalleDistrict

Approach towards Risk Assessment

Multi Hazard Coastal Risk Assessment Framework

…. towards Disaster Risk Reduction

Risk= Hazard x Exposure x Vulnerability x Deficiencies in Preparedness

Early Warning and Countermeasures against tsunamis and Mitigation Options

Multi Hazard approach considers all coastal hazards, each having a frequency of occurrence and potential impact (intensity /spatial distribution)

Risk = Hazard x Vulnerability x Deficiencies in Preparedness

The separation between Vulnerability and Deficiencies in Preparedness is done to highlight the existing vulnerabilities and those deficiencies which could enhance the loss of life during disaster.-Awareness

-Early Warning

-Response

-Evacuation / Safe Places

-Evacuation Structures/ Tsunami Resilient Infrastructure

Next Destructive Tsunami ?Next Destructive Tsunami ?

Indian Ocean Tsunami 26th December 2004

Tsunami 17th July 2006

Tsunami 12th Sept 2007

Tsunami 28th March 2005

Early Warning and Countermeasures against tsunamis

Promote successful evacuation from tsunamis

Mitigate tsunamis (Mitigation Options)

• Early Warning System (Local and Regional)

• Public Warning System• Hazard, Vulnerability and Risk Maps• Set Back • Evacuation Routes & Structures

•Physical Interventions (Artificial Methods, Natural Methods and Hybrid Methods)

•Design Guidelines for exposed infrastructure

Promote successful evacuation from tsunamis

Early Warning and Countermeasures against tsunamis

Mitigate tsunamis (Mitigation Options)

• Early Warning System (Local and Regional)

• Public Warning System• Hazard, Vulnerability and Risk Maps• Set Back • Evacuation Routes & Structures

•Physical Interventions (Artificial Methods, Natural Methods and Hybrid Methods)

•Design Guidelines for exposed infrastructure

Risk Assessment- Hazard, Vulnerability and Capacity

Assessment of the Tsunami Hazard and Exposure 1

(1) Tsunami Hazard Source

(2) Tsunami Hazard Impact on land

Exposure

Source

Exposure

Hazard impact on land

Disaster- Hazard impact on land

Hazard event within the broader hazard source

Exposure

Vulnerability

Tsunami Hazard Source Tsunami Hazard Impact on land

Geological and Seismic Studies of the hazard sources

Hydraulic, Geological and other investigations of the impact of the tsunami hazard on land

2.1.

Probabilistic Tsunami Hazard Modelling (PTHM)

Deterministic Tsunami Hazard Modelling

3. 4.

1 Study of the Hazard Source

Geological and Seismic Studies

•Previous events (their location, magnitude and sequence)

•Seismic Gaps

•Potential tsunami sources

•Identification of ‘Credible Scenarios’

2 Study of the impact of the hazard on land

Impact Profile for a given tsunami

Field observations of known events

Measurements from instruments

0

10

20

30

40

50

60

70

80

12/26/04 0:00 12/26/04 6:00 12/26/04 12:00 12/26/04 18:00 12/27/04 0:00

Time

Satellite Images

Paleotsunami Research

Field investigations and application of special techniques on PaleotsunamiResearch

Exposure of the island

Exposure to theTsunami Hazard on land at a given location

Enhanced Exposure to the Tsunami Hazard on land at a given location

3 Probabilistic Tsunami Hazard Modelling (PTHM)

Based on the principle of Probabilistic Seismic Hazard Modelling (PSHM)

Tsunami hazard Source Sensitivity

Allows identification of particular source areas of high vulnerability for a siteWave heights for a 475 year

recurrence time

after Hong Kie Thio

4 Deterministic Tsunami Hazard ModellingDeepwater Modelling, Near-shore and Inundation

Modelling

(1) To study overall exposure of the island

(2) Simulate tsunamis which have taken place and where possible, compare with field measurements on height, inundation and run up.

(3) Simulate potential tsunamis based on ‘Credible Scenarios’ obtained from Geological and Seismic studies of the hazard.

Mathematical Modelling comprise two types of modelling for the different phases of tsunami wave propagation

Regional Models (deep water)

-Generation

-Deep waterPropagation

-Interaction with the Continental Shelf

-NearshoreTransformation

-Shoreline Entry

-Inland Dissipation

Overall

Exposure

Tsunami

Hazard

Impact on

land

Local Models (nearshoreand inundation)

Hazard Model Vulnerability Model

Hazard Data& Parameters

Elements at Risk & Vulnerability

EventOccurrence

EventPropagation

PhysicalImpact

Social & Economic

Impact

EventScenario

TotalRisk

Evaluate all possible (probable) event scenarios

Begin Risk Analysis

Risk Model Flow ChartRisk Model Flow Chart

HazardHazard

ExposureExposure

VulnerabilityVulnerability

after John Schneider

Deep Water Modelling

4.0

0.0-1.0

3.02.01.0

For a ‘given credible scenario’ Deep water Modelling will provide

•Wave heights at the boundary

•Useful information for the development of an Advanced Tsunami Warning System

Information of Overall Exposure

Mathematical Simulation of tsunamis

F1F1 = 300 km

Mathematical Simulation of the IOT

F2

F2 = 570 km

Mathematical Simulation of the IOT

F3

F3 = 330 km

Mathematical Simulation of the IOT

F1 = 330 km

F2 = 570 km

F3 = 300 km

F3

F2

F1

M=9.2

(3.32 N, 95.85 E)

Indian Ocean Tsunami 26th Dec 2006Mathematical Simulation of the IOT by WAPMERR

M=9.2

(3.32 N, 95.85 E)

M=8.7Tsunami 28th March 2005

(2.07 N, 97.01 E)

M=8.4Tsunami 12th September 2007

(4.52 N, 101.37E)

Enhanced Exposure to theTsunami Hazard on land at a given location

Submarine Geological features

Impact of Submarine Geological features, Coastal Processes and Local Geometry on Tsunami Wave Amplification Regional

Location

Location with respect to the Continental Shelf

Shoreline Geometry

Reflection of waves

The influence of Wave Reflection from Maldive Islands

Enhanced Exposure-Characteristics influenced by the shape and geometry

Energy concentration at headlands and in bays

Increase in Height/Speed and formation of Eddies

Concentration of wave energy

depth contoursInc

oming

wav

e ray

s

Historic Dutch Fort

West East

Enhanced exposure of the City of Galle

Bay – increase of speed & height and circulation

Headland – concentration of energy and spreading around the headland

Galle Bay and Headland

41

212

1

2112 )/()/(/ hhbbHH =

Nearshore and Inundation Modelling

Modelling of Tsunami Hazard on land for Assessment of Hazard/Risk

For a ‘given credible scenario’ Inundation Modelling will provide

1. Inundation Height

2. Distribution of Inundation level

3. Velocity of the propagating wave

4. Currents

5. Intrusion length

6. Run-up (where applicable)

7. Flood volume (if possible)

Nearshore and Inundation Modelling

Key Parameters

Inundation Height

Distribution of Inundation level

Velocity of the propagating wave

Currents

Intrusion length

Run-up (where applicable)

Flood volume (if possible)

Modelling of ‘different credible scenarios’ will provide a Data Base of the Key Parameters relating to inundation which could be stored in a GIS to obtain a clear understanding of Hazard and Risk

Development of Critical Scenario

Security of People and Infrastructure

Inundation Depth :>50 cm Human killed (Velocity is strong )

:>1.0 m Partial damage House

:>2-3 m Total damage and

:>5.0 m Damage Building

Hazard Maps of Inundation Contoursbased on Inundation Modelling of different scenarios

(a) Scenario A

(b) Scenario B

(d) Scenario D(c) Scenario C

Anuga Model (GeoScience-Australia)

Hazard Map of Inundation Contours based on field measurements of IOT

after Dr.N.Wijeratne

Dynamic Hazard Map of Inundation of IOT for Galle- PARI, Japan based on Deterministic Tsunami Hazard Modelling

M

For Scenario Mathematical Modellingof nearshore propagation and inundation from tsunamis the requirements are

-Availability of a reliable model representative of the phenomena

-Quality Data

Seabed topography

Land topography

Collaboration with

(1) PARI, Japan

(2) Geo-Science, Australia

(3) Model of Prof. Imamura

(4) ICG/IOTWS

Lidar Surveys of the Coastal Zone carried out with Italian Assistance

Colombo

Kalutara

GalleHambantota

Pottuvil

BatticaloaPuttalam

Lidar Surveys of the Coastal Zone carried out with Italian Assistance

HyperDEMHyperDEM””The precise 3The precise 3--D model D model of the coastal areas of of the coastal areas of Sri LankaSri Lanka

Airborne Airborne acquisition(Stage 1)

Airborne Airborne acquisition(Stage 2)

SatelliteSatelliteacquisitions(Stage 2)

Detail Topographical Data

Detailed Topographical Data (LiDAR Surveys)Detailed Topographical Data (LiDAR Surveys)Full 3Full 3--D reconstruction of the urban area of Galle. In foreview, the DuD reconstruction of the urban area of Galle. In foreview, the Dutch Forttch Fort

2 Vulnerability

Structural, Economic, Human, Social, Cultural and Psychological

Vulnerability represents the proneness of society and its full structure to be affected by the hazard.

Vulnerability is a dynamic in character, it is modified by people, organizations, governments, social processes, economic trends, natural events, etc.

Vulnerability depends on the type of hazard, and it can be conceived as having various degrees or levels depending on the magnitude of the external event.

after Juan Carlos Villagran

The Sector Approach

NationalState or

ProvinceDistrict or Municipal

Local or Community

Single unit or house

Human being

Housin

gBas

ic Lif

elines

Health

Educati

on

Infra

struc

ture

Commerc

eInd

ustry

Finan

ce

Telec

ommunicatio

nsPhysical

FunctionalEconomic

Human condition / Gender

Geographical Level Dimension

Dimension of Sectors

Dimen

sion of

Components

Agricu

lture

Energ

y

Vulner

abilit

y of a

parti

cular

healt

h fac

ility o

r cen

ter

The vulnerability of the particular health facility is to be determing via the assessment of physical, functional, economic (if private), human condition / gender; administrative, and environmental components.

Administrative Environmental

NationalState or

ProvinceDistrict or Municipal

Local or Community

Single unit or house

Human being

Housin

gBas

ic Lif

elines

Health

Educati

on

Infra

struc

ture

Commerc

eInd

ustry

Finan

ce

Telec

ommunicatio

nsPhysical

FunctionalEconomic

Human condition / Gender

Geographical Level Dimension

Dimension of Sectors

Dimen

sion of

Components

Agricu

lture

Energ

y

Vulner

abilit

y of a

parti

cular

healt

h fac

ility o

r cen

ter

The vulnerability of the particular health facility is to be determing via the assessment of physical, functional, economic (if private), human condition / gender; administrative, and environmental components.

Administrative Environmental

after Juan Carlos Villagran

Capacity, Resilience and Preparedness3

-Awareness-Early Warning-Response-Evacuation / Safe Places-Evacuation Structures -Tsunami Resilient Infrastructure

28th March 2005-Successful evacuation

Assessment of the Degree of Public Awareness on tsunamis

1200 interviews: 600 School Children & 600 General Public

A, 13%

B, 15%

C, 2%

D, 2%

E, 6%F, 42%

G, 15%H, 5%

How can an approaching tsunami be identified?

A - Information obtained from an early warning system

B - By local mass media (TV/radio etc.)C - International media (BBC/CNN)D - Awareness by Police E - Information from general publicF - Abnormal receding of seaG - Abnormal changes in animal/bird

behaviorH - Advancement of a huge wave

towards coastline

Did you receive an early warning of the tsunami on 28 March 2005?

Yes49%

No29%

Not relevant 22%

TV 40%

Radio 13%Police/Forces

21%

Telephone 7%

Word of Mouth 19%

If ‘Yes’, how?

Improving Coastal Community ResilienceBased on Methodology developed by the USAID/IOTWS Project

Governance

Socio-economy and Livelihoods

Coastal Resources Management

Land Use Management and Structures

Risk Knowledge

Warning and Evacuation

Emergency Response

Disaster Recovery

0123

GovernanceSocio-economy and

Livelihoods

Coastal ResourceManagement

Land Use Managementand Structures

Risk Knowledge

Warning & Evacuation

Emergency Response

Disaster Recovery

Middle Level Managers

0123

GovernanceSocio-economy and

Livelihoods

Coastal ResourceManagement

Land Use Managementand Structures

Risk Knowledge

Warning & Evacuation

Emergency Response

Disaster Recovery

Villagers

Design Guidelines for Tsunami Resilient Infrastructure

Development of Design Guidelines should be based on Damage Assessment should cover analysis of infrastructure (in the context of wave environment) which were

(1)-destroyed (2)- damaged (3)- least affected (survived)

Fig 3.0 :Unawatuna to Dodanduwa

Mahamodara

Fully Damaged

Not Damaged

Partially DamagedDPN

NNPD

NN

DDDDDD

DDDD D

DDDDDD

DDDD

PP

PD

P

PPD

DDP

NNN

NN

NPPD

PPD

NN

SCALE

0 1 2 km

Dadalla

Gintota

Wellaboda

Galle

Unawatuna

Railway

Water Body

Road

Pattern of damages to houses (Unawatuna to south of Hikkaduwa)

City of Galle

Damage to the City Center.

Damaged houses behind Gall bay.

Damaged bridge.

Damaged houses behind Gall bay.

Inundation and Damage in Galle

Design Guidelines for Tsunami Resilient Infrastructure

a) Rehabilitation of damaged structuresb) Strengthening existing structuresc) New construction

(1) Overall Design Guidelines(2) Detailed Design Guidelines

(a) (b)(c)

Overall Design Guidelines providing advice on location, layout, orientation, structural configuration, geo-technical considerations and other considerations relating to good design practice.

Detailed Design Guidelines leading to hydraulic and structural loads, geo-technical issues and detailed design information

Building a Tsunami Resilient Community

Map for Tsunami Hazard based on IOT

Inundation Contours after Dr.N.Wijeratne

Map for Safe Locationsafter Dr.N.Wijeratne

Safe Locations Safe areas and safe buildings

Map for Safe Locationsafter Dr.N.Wijeratne

Safe Locations Safe areas and safe buildings

Map for Evacuation Routes and Places(should be well sign posted)

Preparation of Tsunami Evacuation Plans with the participation of community

Tsunami Education Programme

Typical Tsunami Education Materials