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Climate Change related increase
in flood risks for HK and the PRD
Qiwei Yu, Alexis KH Lau, HY Lau, W BarronThe Hong Kong University of Science and Technology
Gabriel NC LauThe Chinese University of Hong Kong
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Daily maxima sea level at NPQB (1954-2012)
Threshold Number of
case
Approximate
return period
>340 cm 1 60
>330 cm 3 20
>320 cm 7 8
>310 cm 10 6
>300 cm 20 3
>290 cm 56 1
HKO Sea Level Data
Return period is a critical
Engineering design parameter
Threshold Number of caseApproximate
return period
Threshold – 290 cm
(current annual event)
>340 cm 1 60 50 cm
>330 cm 3 20 40 cm
>320 cm 7 8 30 cm
>310 cm 10 6 20 cm
>300 cm 20 3 10 cm
>290 cm 56 1 0
Projected Sea level rise
from 2000
Future annual
maximum sea level
Return period
by 2100
2030 +10 cm 300 cm ~3
2050 +20-25cm 310-315 cm ~6-7
2100 +40-80cm 330-370 cm 20-100+
Global Active Archive of Large Flood Events
---Dartmouth Flood ObservatoryDuration - Derived from start and end dates.
Known Dead - News reports are usually specific about this, but occasionally there is only mention of 'hundreds' or
'scores' killed
Number Displaced - This number is sometimes the total number of people left homeless after the incident, and
sometimes it is the number evacuated during the flood. News reports will often mention a number of people that are
'affected', but we do not use this.
Damage (US $) - This number is never more than an estimate and we use no independent criteria for determining such.
Instead we accept the latest and apparently most accurate number available in all the relevant sources.
Main Cause - One of eleven main causes is selected: Heavy rain, Tropical cyclone, Extra-tropical cyclone……
Severity Class - 1, 1.5, 2.Class 1: large flood events: significant damage to structures or agriculture; fatalities; and/or 1-2
decades-long reported interval since the last similar event. Class 1.5: very large events: with a greater than 2 decades
but less than 100 year estimated recurrence interval, and/or a local recurrence interval of at 1-2 decades and affecting
a large geographic region (> 5000 sq. km). Class 2: Extreme events: with an estimated recurrence interval greater than
100 years.
Geographic Flood Extents (sq km) - This is derived from our global map of news detected floods. Polygons representing
the areas affected by flooding are drawn in a GIS program based upon information acquired from news sources
Flood magnitude=log(severity *duration*area)9
1. Data ellipse outlier
detection-A clear increase trend
and the data is
concentrate in the
ellipse (0.9)
2. From the origin-If flood magnitude is 0,
there has no damage
due to flood
3. Log-linear
regression
estimation
World Development Indicators ( Word Bank, Average of 1985-2012)1
Country damage_rate GDP per capita Urban population (%) ……………. Employment ratio Telephone lines
China 3.0 1518.0 35.6 . 73.3 11.4
United States 3.2 33184.2 78.5 . 61.4 56.4
Philippines 3.0 1167.4 47.8 . 59.8 2.8
Vietnam 2.9 544.5 24.4 . 76.4 5.2
. . . . . . .
. . . . . . .
. . . . . . .
Canada 3.6 27455.5 78.6 . 60.5 58.0
Korea, Rep. 3.7 11849.5 77.7 . 58.9 43.7
Argentina 2.7 6307.0 89.4 . 52.2 17.8
Fiji 3.7 2681.1 46.4 . 56.1 9.9
Japan 2.8 33061.6 81.6 59.5 46.6
New Zealand 3.2 17967.4 85.4 . 61.5 43.9
1. WDI take into consideration only if it has more than 20 years record
Categorized countries by Population density & Urban population (%)
-Deaths/Displaced
-Factor analysis
-Identify the indicators represent
the characteristic of the country
-Where is Hong Kong & PRD
locate?
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Correlated indicators
Death: • Rural population (% of total) (0.58)
• Population density (people per sq. km of land area) (0.48)
Displaced:• Population density (people per sq. km of land area) (0.65)
• Rural population (% of total) (0.52)
Cor (Urban population, Population Density)≈0.28
Economic Damage:• GDP per capita (constant 2005 US$) (0.43)
• Telephone lines (per 100 people) (0.52)
Cor (GDP,per capita & Telephone lines)=0.95
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Impact for Hong Kong 2000 2030 2050 2100
Projected Sea level rise
from 20000 cm +10 cm +20-25 cm + 40-80 cm
Return Period (years)
in the future1.5 1.5 1.5 1.5
Equivalent Return
Period (years) in 20001.5 ~ 3 6 – 7 20 – 100+
Flood magnitude 3.5 3.5+ 4 6 - 7
Number of deaths < 5 ~ 5 ~ 20 20 – 60+
Number of people
displaced< 400 400+ 1,000+ 5K – 150K
Economic loss
(Million HKD)< 25 25+ 60 – 600 800 – 6000+
Impact estimates ASSUMED no protective measure being done in HK
Year 2030 2050 2100
Return period at present 3 6~7 20-100+
Deaths
Hong Kong ~ 10 ~ 20 20 – 60+
PRD ~ 30 ~ 40 100 – 700+
Displaced
Hong Kong Up to 400 Up to 1,000 5000 – 150,000
PRD Up to 4,000 Up to 15,000 0.2 – 2+ million
Economic Damage (HK Dollars)
Hong Kong < 25 million 60-600 million 800–6000+ million
PRD < 10 million 30–150 million 200–3000+ million
Recovery duration
Hong Kong & PRD Several days <1 month Several months
(>4 months)
Projected annual flood damages for Hong Kong & PRD in 2030, 2050
and 2100 without adaptation (flood magnitude: 3.5, 4, [6-7])
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