Sam.S.L HETTIARACHCHI, Saman.P SAMARAWICKRAMA, Nimal WIJERATNE University of Moratuwa, Sri Lanka, Democratic Socialist Republic of

1. Tsunami Risk Management
Case Study for the Port City of Galle
Sam Hettiarachchi
University of Moratuwa
and Chair of Risk Assessment Working Group UNESCO/IOC/IOTWS
Nimal Wijeratne
University of Ruhuna
Saman Samarawickrama
University of Moratuwa
With the assistance of
Phil Cummins, GeoScience, Australia
Juan Carlo Villagran, UN-SPIDER, Vienna
PARI, Japan

2. Documents from Working Group on Risk Assessment of IOTWS
Guideline on Tsunami Risk Assessment
and Mitigation for the Indian Ocean
Knowing your Tsunami Risk and what to
do about it
UNESCO/IOC Manual and Guideline 52
June 2009
A Probabilistic Tsunami Hazard Assessment
of the Indian Ocean Nations
Implemented by Geo Science Australia as an
activity of Working Group 3
September 2009

3. Approach to Risk Assessment and Mitigation
in the coastal zone

4. Approach towards Risk Assessment and Mitigation
Multi Hazard Coastal Risk Assessment Framework
Risk = f (Hazard , Vulnerability )
Risk = f (Hazard , Vulnerability , Capacity)
Risk= f (Hazard , Vulnerability , Deficiencies in Preparedness)

5. Case Study on Risk Assessment- Port City of Galle
Presentation of the selected components of the study
1. Tsunami Impact on the City of Galle
2. Assessment of the Tsunami Hazard and Exposure
3. Assessment of Vulnerability
4. Capacity, Resilience and Preparedness
5. Initial Risk Analysis
6. Information and Maps for the benefit of the community
7. Mitigation

6. 1 Tsunami Impact on the City of Galle in the Southern Province
N Batticaloa
Chilaw
2.3 07 30 00 N
2.0 SCALE
2.7 NOTE : ALL INUNDATION HEIGHTS IN METERS
2.0
10.00 hrs
1 st Wave
13.00 hrs Negombo 2.7
2 nd Wave
3.0
Tsunmai Heights 07 00 00 N
Mattakuliya
Colombo 11.3
Moratuwa
Galle 8.4
10.2 10.3 6.9
09.30 hrs 1 st Wave Kalutara District 06 30 00 N
09.45 hrs 2 nd Wave 8.8
12.20 hrs 3 rd Wave Payagala
4.5 7.0
4.5 6.0 Yala
Ahungalla
09.10 hrs 1 st Wave
3.5 Kirinda 09.20 hrs 2 nd Wave
Hikkaduwa
4.1 3.7
09.30 hrs 1 st Wave Hambantota
 
 
 
Galle
09.45 hrs 2 nd Wave Tangalle 06 00 00 N
12.20 hrs 3 rd Wave Unawatuna
09.20 hrs 1 st Wave Matara
09.45 hrs 2 nd Wave 09.20 hrs 1 st Wave
09.40 hrs 2 nd Wave
79 30 00 E 80 00 00 E 80 30 00 E 81 00 00 E 81 30 00 E 82 00 00 E
Assessment tsunami wave heights and inundation
from field studies

7. Disaster Statistics in the Galle City administrative area due to the
Indian Ocean Tsunami
497 residents were killed
89 residents disappeared
There is no record on the visitor casualty figures
996 residents were injured
1588 houses were damaged
1272 buildings other than the housing units were damaged
8114 residents were affected
(Source: Dept. of Census, Sri Lanka)

8. 2 Hazard Analysis
Source
Exposure
Tsunami Hazard Source
Exposure
Tsunami Hazard Impact on land
Hazard impact on land

9. Tsunami Tsunami
Hazard Exposure Hazard Impact
Source on Land
Impact Profile for the tsunami
MEASUREMENTS MODELLING TOOLS
FROM INSTRUMENTS
Deterministic
FIELD STUDIES and
Probabilistic
IMAGE ANALYSIS
Science of Tsunamis

10. Hazard Analysis Impact Profile for the tsunami
80
70
60
Velocity Magnitude
50
40
(cm/s)
30
20
10
0
2/26/04 0:00 12/26/04 6:0012/26/04 12:0012/26/04 18:0012/27/04 0:00
Time
Measurements Field studies Satellite Images
from instruments of IOT
Modelling Tools
Deterministic Tsunami Probabilistic Tsunami Hazard
Hazard Modelling Modelling (PTHM)

11. Tsunami Science
Enhanced exposure of the City of Galle
Energy concentration at
headlands and in bays
Bay – increase of speed & height and circulation
Historic
Dutch Fort
West East
Headland – concentration of energy and 1 1
2 4
spreading around the headland H 2 / H1 (b1 / b2 ) (h1 / h2 )

12. Hazard Map of Inundation Contours based on Field Measurements of IOT
Locations of Data Collection for the City of Galle
At least one location for each 250m x 250m area; 138 Locations in total;
Information on Inundation Depth and Flow Direction
after Dr.N.Wijeratne

13. Deterministic Tsunami Hazard Modelling
Deepwater
Modelling, Ne
ar-shore and Inundation Modelling
(1) To study overall exposure of the island
(2) Simulate the IOT and 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.

14. Project “HyperDEM”
Funded by the Italian Government
3-D PERSPECTIVE VIEW OF THE DUTCH FORT IN
GALLE
DIGITAL DIGITAL
SURFACE MODEL TERRAIN MODEL

15. Modelling of a ‘ credible scenario’ provides
Key Parameters relating to inundation

16. Modelling of ‘different credible scenarios’ provide a
Data Base of the Key Parameters relating to
inundation leading to a clear understanding of
hazard and development of ‘critical scenario’
Key Parameters
Inundation Height
Distribution of Inundation level
Velocity of the propagating wave
Currents
Intrusion length
Run-up (where applicable)
Flood volume (if possible) IOT

17. Hazard Maps of Inundation Contours
based on Inundation Modelling of different scenarios
IOT
Anuga Model (GeoScience-Australia)

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

19. Probabilistic Tsunami Hazard Modelling
Example of Offshore Tsunami Hazard for Sri Lanka
Low hazard end-member High hazard end-member
For Sri Lanka, the
low-hazard and high-
hazard maps are very
similar in
character, with
hazard maximum
along the east coast
and the high hazard
case greater than the
low by about 30%.

20. Probabilistic Tsunami Hazard Modelling
Example: Deaggregated Tsunami Hazard for Sri Lanka
Deaggregated hazard displays the relative contribution of different
sources to the tsunami hazard at a particular location.
Low-Hazard Case High-Hazard Case
Both Low- and High-hazard cases show that tsunami hazard in Sri Lanka
is dominated by events in North-Sumatra/Nicobar Islands.
Probably, this means that the 2004 IOT was the ‘worst-case’ scenario
for Sri Lanka..

21. Risk – Superposition of Hazard and Vulnerability
+
=

22. + Hazard Analysis-
Event based
=
P4

23. + Hazard Analysis-
Multiple hazard
= scenario based
P4
P3
P2
P1

24. 3 Vulnerability
Vulnerability represents the
proneness of society and its full
structure to be affected by the
hazard.
Components of Vulnerability (1D approach)
1--Human, Cultural and Psychological
2--Physical/Structural
3--Socio-Economic
4--Environmental
5--Functional
6--Administrative

25. Examples of Vulnerable Public Infrastructure and Sectors within the City of Galle
• Bus Terminal.
• Main Street – commerce.
• 4 Schools. • Commerces, Road to Colombo.
• Mahamodera hospital • Commerces, Road to Matara.
• School of Nursing • Area in front of Post Office.
• Train Station • Fishing boat areas (3).
• District Admin. Building. • Sambodhi Hospital (for children).
• Municipal Council Building. • Fish market, fruit market,
vegetable market.
after Juan Carlos Villagran

26. Vulnerability - The Sector Approach
Detailed Approach towards Vulnerability Analysis
Geographical Level Dimension
r
er la
nt icu
c e a rt
National
or a p
State or
lit of
Province
ci y
fa ilit
y
District or
th b
a l e ra
Municipal
he uln
Local or
V
Community
Single unit or
house
Human being
Dimension of Sectors
Physical
re
ce
n
th
e
e
g
y
F try
es
ns
io
ur
nc
in
rg
tu
al
er
lin
at
s
io
ct
us
He
ul
In Ene
Functional
m ina
m
du
uc
at
ru
fe
ric
Ho
m
In
ic
Li
st
Ed
Co
Ag
Economic
un
fra
s ic
Human condition / Gender
Ba
m
co
Administrative
le
Te
Environmental
nt f
ne n o
s
po sio
The vulnerability of the particular health facility is to be determing via
om n
C ime
the assessment of physical, functional, economic (if private), human
D
condition / gender; administrative, and environmental components.
after Juan Carlos Villagran

27. 4 Capacity, Resilience and Preparedness
Key Areas
-Awareness and Education
-Preparedness
-Early Warning
-Response
-Evacuation / Safe Places
-Evacuation Structures
-Tsunami Resilient Infrastructure
Building a Tsunami Resilient Community
A community based approach was adopted
28th March 2005-
Successful evacuation

28. Other information used in the analysis:
•Sources of income and household economic level
•Condition of the buildings
•Profile of the occupants
•Condition of the infrastructure facilities etc
•Community knowledge base via their participation
Community participation in the vulnerability assessment

29. 5 Initial Risk Analysis
Step 1- Appraoch
R= ( Hazard x Vulnerability x Deficiencies in Preparedness)
Simplified approach towards Hazard Analysis - based on IOT.
Hazard and Vulnerability
Vulnerability –Critical parameters used.
Assessment
•Only the elements that can be easily identifiable, quantifiable and spatially
presentable were considered.
•Total risk (that the community is exposed) is analyzed as a combination of
hazard and vulnerability.
Hazard Map + Vulnerability Map = Risk Map

30. Step 2- Tsunami Hazard Map
Inundation Map -----------> Hazard Map
Levels of Tsunami Hazard
High Hazard Level – Inundation level above 0.5m with high flow speeds.
Medium Hazard Level – Inundation 1m to 2m with low flow speeds.
Low Hazard Level – Inundation less than 1m and low flow speeds.
Zero Hazard Level – No inundation (no buffer zones are allocated)

31. Development of Critical Hazard 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

32. Inundation Field Studies Mathematical Modelling
Map
Hazard
Map

33. Tsunami Hazard Map
Hazard in water areas is not assessed.

34. Step 3- Vulnerability Assessment/ Levels of Vulnerability
Vulnerability Assessment was based on the vulnerability arising due to critical parameters only
•Exposure to the hazard
•Distance from the sea High Vulnerability
•Elevation Medium Vulnerability
•Status of infrastructure facilities etc Low Vulnerability
•Capacity to evacuate.
Zero Vulnerability
•Impact on livelihoods,

35. Vulnerability Assessment
Vulnerability Assessment was based on the vulnerability arising due to the location,
infrastructure and livelihood
High vulnerability
Short distance and direct exposure to the sea,
Low elevation,
Inability to evacuate quickly,
Easily damageable infrastructure facilities etc.
Easy disruption to livelihoods,
Medium vulnerability
Low vulnerability
Zero vulnerability
Far away from the sea,
High elevation,
No possibility of isolation during a tsunami,
Hazard resistant infrastructure,
Livelihoods which may not be effected by the disaster etc.

36. Tsunami Vulnerability Map
Vulnerability in water areas is not assessed.

37. Step 4-Risk Map
Hazard
Vulnerability
Risk
37

38. Tsunami Risk Map

39. Information and Maps
6
for the benefit of the community
Information relevant for disaster risk reduction
-Disaster Awareness/ Preparedness Education
-Disaster Management Maps
• Residents’ Preferred Evacuation Routes and Safe Areas
• Information to establish better Evacuation Routes and
Safe Areas

40. Tsunami Education Programme Preparation of Tsunami Evacuation
Plans with the
participation of community
Typical Tsunami Education
Materials on Disaster
Awareness and Preparedness

41. Risk Management
Mitigate the impact Mitigate exposure Promote successful
of the hazard and vulnerability evacuation from
(Mitigation Options) to the hazard hazard where
necessary
-Land Use Planning -Early Warning System
-Physical (Local and Regional)
Interventions
-Regulatory interventions
(Artificial such as set back of defense -Public Warning System
Methods, Natural line
Methods and -Evacuation Routes & Structures
Hybrid Methods) -Hazard resilient buildings
and infrastructure -Community Education,
Maps for their benefit
and Preparedness

42. Tsunami Breakwaters- Integrating Mitigation with port development projects
Galle City and the Port
Detailed Topographical Data (LiDAR Surveys)
Full 3-D reconstruction of the urban area of Galle. In foreview, the Dutch Fort

43. Tsunami Breakwaters Two Multi –purpose berths (240 m x 2) to be developed
Depth -14 m
Integrating Hazard Mitigation Outer breakwater 800 m
with port development Inner Breakwater 350 m

44. Inun
Dept
date
(m)
h
d
0.3
Simulated Tsunami Flood Area of Galle Bay for Present Condition

45. (m)
h
Dept
d
date
Inun
0.3
Simulated Tsunami Flood Area of Galle Bay with Galle Port Development

46. Existing
with Harbour

47. Advertisement from the Economist

48. Managing tsunami risk is certainly a fine art