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International Conference on Climate Change

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International Conference on Climate Change Impact of Sea Level Rise on storm surge in Hong Kong and the Pearl River Delta by WONG, Agnes K.M. LAU, Alexis K.H. – PowerPoint PPT presentation

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Title: International Conference on Climate Change


1
International Conference on Climate Change
Impact of Sea Level Rise on storm surge in Hong
Kong and the Pearl River Delta by WONG, Agnes
K.M. LAU, Alexis K.H. GRAY, Joseph P. (The Hong
Kong University of Science and Technology) 31
May 2007
2
  • Did you know that the Pearl River Delta is
    already under threat from severe flooding?

3
Guangzhou in flood due to heavy rain.
4
Guangzhou in flood due to astronomical tide
School is cancelled for 100,000 students
June 2005 NOT rain related
5
Coastal Flooding
  • Astronomical tide
  • Shape of coast
  • Accumulated rain water
  • Tropical cyclone
  • Global warming (sea level rise)
  • Storm surge

6
Storm Surge
  • The abnormal rise in the ocean level associated
    with typhoon landfall.

7
Global Situation
  • Intergovernmental Panel on Climate Change (IPCC)
    report in 2007
  • An average rate of 1.8mm/yr for 1961-2003
  • Faster rate of 3.1mm/yr for 1993-2003
  • Total sea level rise for 20th century is
    estimated to be 0.17m

8
Time series of global mean sea level
IPCC 2007
9
Local Situation
Rate of sea level rise (mm/yr) HK Global (IPCC, 2007)
1961 2003 2.8 1.8
1993 2003 7.2 3.1
(HKO, 2004)
The observed rate of sea level rise in Hong Kong
is faster than the global average report by the
IPCC (2007)
10
IPCC (2007) Report
  • Storm surges are especially serious when they
    coincide with high tide. Changes in the frequency
    of occurrence (i.e. return period) are affected
    both by changes in mean sea level and in the
    meteorological phenomena causing the extremes.
    There is evidence for an increase in the
    occurrence of extreme high water worldwide
    related to storm surges

11
HKOs findings
  • Hong Kong Observatory (HKO) research in 2004
  • The 50 yr return period would be shortened to
    about 3 yrs if the sea level rises by 48cm in
    2100
  • A 50yr event could even become an annual event if
    sea level rises by 88cm

12
Practical use of return period
  • Formation levels for reclamations
    - streets and pavements
  • Flood defence levels for critical facilities
  • - building basements, MTR
  • Crest levels for seawalls and river banks
  • Tailwater levels and other hydraulic design
  • - stormwater and sewage systems

S. Buttling M.L. Chalmers
13
Design Life
  • Normally, the extreme environmental conditions
    for structures having a design life of 50 years
    should be taken as those having return periods of
    100 years.

Port Works Design Manual Part 1
14
Objective of this study
  • To see how the probability of destructive
    flooding (return period of extreme flooding
    events) changes with increasing mean sea level
  • To understand the relationship between sea level
    rise and storm surge

15
Data
  • Sea Level records around HK from HKO
  • Period 1965 - 2006

16
Methodology
  • Gumbel cumulative distribution - extreme
    value type I
  • Parameter estimation with the moment method
  • It is used to find the maximum of a number of
    samples of various distributions. It is useful in
    predicting the chance that an extreme flood will
    occur.

17
Significant increase in extreme value in last 20
years
Extreme value ranged between 3 to 4 meters
18
Current 20 year event
Current return period for a 3.2 m event (20 yr)
19
Current 100 year event
Event level used for a marine work with a 50yr
design life
20
Population annually affected by flood
Robert J. Nicholls 2004
21
(No Transcript)
22
Land Use Map in PRD Red highly developed area
Flooding of 3m
23
(No Transcript)
24
Economic Impacts
Region Predicted losses for a 30cm rise (2000) in RMB Predicted losses for a 30cm rise (2030) in RMB Predicted losses for a 1m rise (2000) in RMB Predicted losses for a 1m rise (2030) in RMB
PRD 22.6 Billion 56 Billion 104.4 Billion 262.5 Billion
Economic Losses from sea level rise in the PRD
Warrick, Barrow Wigley
25
Summary Discussion
  • The PRD is already susceptible to severe flooding
  • The observed sea level rise in the region is
    faster than the global average
  • The sea level rise projected by the IPCC results
    in a significant decrease in the return period in
    the region, implying a significant reduction of
    the design life of coastal constructions
  • We need to act swiftly to mitigate the flooding
    potential caused by climate change

26
Action Items
  • Building regulations should be reviewed to
    reflect the potential risks related to climate
    change
  • Environmental responsible policies should be
    adopted to reduce our contribution to Global
    Warming
  • Further research work should be done to better
    understand the rise of sea level and its impact
    on the region

27
Acknowledgment
  • Prof. S.C. Kot for his guidance
  • Dr. Jimmy Chan for his graphics
  • Hong Kong Observatory for provision of historical
    sea level data around Hong Kong
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