Flood Damage Assessment in Taipei City

1. Flood Damage Assessment in
Taipei City, Taiwan
M.H. Hsu, M.Y. Tsai, Y.C. Lin
National Taiwan University, Taiwan
A.S. Chen, M.J. Hammond, S. Djordjević & D. Butler
University of Exeter, UK
9th International Conference on Urbn Drainage Modelling
Belgrade 2012

2. Outline
• Introduction
• Hydraulic modelling
• Flood damage assessment
• Discussions
• Conclusion

3. Introduction
Image source: CWB, Taiwan

4. Taipei City

5. • Taipei City
–272 km2 ; 2.6 M inhab.
– 9,600 inhab./km2
• Central Taipei Area
–120 km2; 1.7 M inhab.
–14,200 inhab./km2
Area and population
Songshan
Xinyi
Zhongshan (north)
Zhongzheng
Datong
Wanhua
Wenshan
Nangang
Neihu
Shilin
Beitou
Daan
Zhongshan
(south)
4,000 – 5,000
5,000 – 8,000
8,000 – 10,000
20,000 – 22,000
Population density
(unit : person/km2)

6. Hydrology and hydraulic attributes
• 200yr levees
• 25 drainage networks
(5y, 78.5mm/h)
• 900cms pumping
capacity
• 100 + mm/h by
typhoons

7. Hydraulic modelling
• Coupled 1D/2D model
– 1D SWMM
– 2D UIM
• Trunk sewer considered
• Pluvial flooding only
• Uniform spatial rainfall
distribution
• 24 hours events

8. Inundation hazard map (10y)

9. Inundation hazard map (25y)

10. Inundation hazard map (50y)

11. Inundation hazard map (100y)

12. Inundation hazard map (200y)

13. Flood damage assessment
Damage
Depth
Depth-Damage
Curves (DDC)
Land uses

14. Land uses

15. Depth-Damage Curves (DDCs)
• Field investigations
• Tax revenue office
–Flood damage claim reports of individual
household and business (aggregated)
• Wang, et al., 2003. Establishment of Systematic Models for
Flood Damage Evaluation.
• Su et al., 2005. A Grid-Based GIS Approach to Regional Flood
Damage Assessment.

16. Depth-Damage Curves (DDCs)
0
200
400
600
800
1000
1200
0 1 2 3 4
Damages
(
$US
/m2)
Flood depth(m)
Residential Zone
Industrial Zone
Cultural, School
Retail Business
Wholesale
Business
Commercial
Source : Wang, R. Y. et al., 2003. Establishment of
Systematic Models for Flood Damage Evaluation.

17. Flood damage map (10y)

18. Flood damage map (25y)

19. Flood damage map (50y)

20. Flood damage map (100y)

21. Flood damage map (200y)

22. Shops and business office buildings

23. Shops in old communities

24. Commercial and Industrial

25. Flood damage assessment
Return period
(year)
Inundated area
(Km2)
Flood damage
(US $ million)
Res. Com. Ind. Gov. Total
5 0.93 41.7 12.6 3.7 15.6 73.7
10 2.40 121.0 57.7 12.3 64.1 255.0
25 3.22 234.1 114.2 23.4 128.4 500.1
50 4.01 323.2 166.4 31.8 199.4 720.8
100 5.43 409.7 211.2 41.5 271.7 934.1
200 9.68 499.7 269.5 53.6 319.5 1,142.3
500 31.13 623.6 402.0 74.4 384.8 1,484.9

26. Flood damage EP curve
0
500
1,000
1,500
/通用格式
/通用格式
/通用格式
/通用格式
/通用格式
/通用格式
$
USD
(million)
Exceedane probability
Household
Commercial
Industry
Government
Total flood damage

27. Flood damage assessment
Return period
(year)
Inundated area
(Km2)
Flood damage
(US $ million)
Res. Com. Ind. Gov. Total
5 0.93 41.7 12.6 3.7 15.6 73.7
10 2.40 121.0 57.7 12.3 64.1 255.0
25 3.22 234.1 114.2 23.4 128.4 500.1
50 4.01 323.2 166.4 31.8 199.4 720.8
100 5.43 409.7 211.2 41.5 271.7 934.1
200 9.68 499.7 269.5 53.6 319.5 1,142.3
500 31.13 623.6 402.0 74.4 384.8 1,484.9
Average Annual Flood Loss(AAFL)
Expected Annual Damage (EAD) 31.98 15.58 3.22 17.93 68.70

28. On-going studies
• Damage assessment for individual buildings
• Resolution and accuracy
• DDCs for other land uses to be determined
• Roadside parking
• Basements and underground infrastructures
• Urban redevelopment
• Social-vulnerability assessment

29. Concluding remarks
• Flood damage of various rainfall periods
• Average annual flood loss (AAFL)/
Expected Annual Damage (EAD)
• High risk areas identified
• Needs of better/detailed data
• Potential applications to various impact

30. Acknowledgements
• CORFU project is funded by the European
Commission through Framework
Programme 7, Grant Number 244047.
• Taipei case study is funded by the
National Science Council, Taiwan (NSC
99-2915-I-002-120).

31. Further information
• http://corfu7.eu/
• Contact:
• a.s.chen@ex.ac.uk
• mhhsu@ntu.edu.tw