Transcript Presentation - International Flood Initiative

4th International Symposium on Flood Defence
Toronto, Ontario, Canada, May, 6-8, 2008
RIVER FLOODS IN THE CHANGING
CLIMATE – OBSERVATIONS AND
PROJECTIONS
Zbigniew W. Kundzewicz
Research Centre for Agricultural and Forest Environment,
Polish Academy of Sciences, Poznań, Poland
Potsdam Institute for Climate Impact Research,
Potsdam, Germany
Contents
Introduction
Multi-factor context
Observations
Projections
Adaptation
Concluding remarks
Source: Dartmouth
Floods Observatory
Canada: Heavy rain combined with melting of the heaviest
winter snow accumulation in memory. Floods on already
swollen rivers. St John River at Fort Kent at record high level,
surpassing 1979 record crest. Worst flood in 80 years of record
keeping. A "greater than a 100-year event" in Fort Kent. Damage
to roads and bridges.
The global decline in aggregate deaths and death rates due to extreme
weather events during the 20th century suggest that adaptation measures
to cope with some of the worst consequences of such events have been
successful.
[IPCC AR4 WG II Ch.1]
Insured and total property
losses caused by weather
events ($45 billion and $107
billion in 2004, respectively)
are rising faster than
premiums, population, or
economic growth. Data
exclude health and life
insurance premiums and
losses. Inflation-adjusted
economic losses from
catastrophic events rose by 8fold between the 1960s and
1990s and insured losses by
17-fold.
[Mills, 2005]
Contents
Introduction
Multi-factor context
Observations
Projections
Adaptation
Concluding remarks
Reasons for changes in flood risk and vulnerability
(i) Changes in
socio-economic
systems
Land-use change, increasing exposure and damage
potential – floodplain development, growing wealth
in flood-prone areas, changing risk perception
(ii) Changes in
terrestrial systems
Land-cover change - urbanization, deforestation,
elimination of natural inundation areas (wetlands,
floodplains), river regulation – channel straightening
and shortening, embankments), damming rivers,
adverse changes of conditions of transformation of
precipitation into runoff
(iii) Changes in
climate and
atmospheric system
Holding capacity of the atmosphere, intense
precipitation, seasonality, circulation patterns
Source: Kundzewicz & Schellnhuber, 2004
1000-year flood
1000-year flood
Old 1000-year flood
New 1000-year flood
Impacts of land-use change on floods
Precipitation
Discharge
urbanized area
rural area
Time
Water holding capacity of the atmosphere
Clausius-Clapeyron equation
des(T) / es(T) = L dT / R T2
where es(T) is the saturation vapor pressure at
temperature T,
L is the latent heat of vaporization,
and R is the gas constant.
T  es(T) 
o
1C
6-7%
Contents
Introduction
Multi-factor context
Observations
Projections
Adaptation
Concluding remarks
Contribution to total
annual precipitation from
very wet days (95th
percentile and above).
[IPCC WGI AR4, 2007,
Groisman et al., 2005,
Alexander et al., 2006]
Source: CHMU
Maximum water levels, Elbe at Dresden. Source: Grünewald
Record level of Elbe at Dresden: 940 cm on 17 August 2002
Linström & Bergström (Hydrol. Sci. J., 2004)
Conclusions from a study of trends in 61 river
flow series in Sweden:
■ Flood magnitude increased substantially
between 1970 and 2002, but similar conditions
were experienced in 1920s.
■ Flood peaks in old data are probably
underestimated.
■ The largest flow increase was found in less
reliable data series.
■ It is therefore difficut to conclude that flood
levels are increasing in a statistically significant
way.
Radziejewski & Kundzewicz (Hydrol. Sci. J., 2004):
♦ Failure to detect a significant trend does not
mean the absence of change.
♦ Examination of detectability of artificially
introduced, hence fully controlled, trends in time
series leads to the following common-sense
results:
♦ If a change is weak and lasts for a short time, it
is not likely to be detected. If a change is
stronger and lasts longer, the likelihood of
detection grows.
Maximum annual flow
Karjaanjoki, Lohjanjarvi-Peltokoski (SF)
Rhine, Kaub (D)
WCP-Water
y = 0.4228x + 30.568
6855500
6335100
2
R = 0.1504
y = 16.839x + 3684.5
2
R = 0.0871
140
8000
120
7000
100
6000
80
5000
4000
60
3000
40
y = -1.9713x + 822.71
6335301
1800
1999
1995
1991
R2 = 0.0216
600
1600
1987
1983
1979
1975
1967
1963
1971
y = 0.3914x + 104.45
6142100
2
R = 0.0766
1959
1955
1951
1947
1943
1939
1935
1998
1994
1990
1986
1982
1978
1974
1970
1966
1962
1958
1954
1950
1946
0
1942
0
1938
1000
1931
2000
20
500
1400
400
1200
1000
300
800
200
600
400
Main, Schweinfurt (D)
1997
1992
1987
1982
1977
1972
1967
1962
1957
1952
1947
1942
1937
1932
1927
1922
1917
1998
1989
1980
1971
1962
1953
1944
1935
1926
1917
1908
1899
1890
1881
1872
1863
1854
0
1845
0
1912
100
200
Source: Kundzewicz et al. (2004) Morava, Moravicany (CZ)
Year of occurrence of maximum flow (Source: Kundzewicz et al., 2004)
The overall maxima for the
period 1961-2000 occurred
more frequently in 1981-2000
(46 times) than in 1961-1980
(24 times)
WCP-Water
Contents
Introduction
Multi-factor context
Observations
Projections
Adaptation
Concluding remarks
Difference between 1961-1990 and 2070-2099 (A2, HadRM3-P)
Mean precipitation
Annual maximum precipitation
<-1.5
(-1.5; -1.25)
(-1.25; -1.0)
(-1.0; -0.75)
(-0.75; -0.5)
(-0.5; -0.25)
(-0.25; 0)
0
(0; 0.25)
(0.25; 0.5)
(0.5; 0.75)
(0.75; 1.0)
(1.0; 1.25)
(1.25; 1.5)
>1.5
Source: Kundzewicz et al. (2004)
-350; -300
-300; -250
-250; -200
-200; -150
-150; -100
-100; -50
-50; 0
0
0; 50
50; 100
100; 150
150; 200
200; 250
Changes in extremes based on multi-model simulations from
nine global coupled climate models. L) Globally averaged
changes in precipitation intensity (defined as the annual total
precipitation divided by the number of wet days) for three
scenarios. R) Changes of spatial patterns of precipitation
intensity based on simulations between two 20-year means
(2080–2099 minus 1980–1999) for the A1B scenario. (IPCC AR4)
2.3
1.8
1.3
hg3a2a
0.8
hg3b2a
0.3
-0.2
10
20
30
40
50
60
70
80
90
100
-0.7
Changes in percentiles of precipitation, Poznań grid, HadRM3 (20702099 vs 1961-1990).
Source: Kundzewicz et al. (2004)
Changing probability of extreme seasonal precipitation in
boreal winter. The ratio of probability of a very wet winter for
CO2 doubling vs present
[Palmer & Räisänen, 2002]
[Milly et al., 2002]
Contents
Introduction
Multi-factor context
Observations
Projections
Adaptation
Concluding remarks
Flood protection and management strategies modify either flood waters,
or susceptibility to flood damage and impact of flooding.
Protect
[Absolute protection does not exist. Japan – superdikes]
Accommodate
[Living with floods, learning from them]
Retreat
[The state/province purchases land and property in flood-prone areas]
Examples of measures: structural/technical protection measures - dikes, relief channels,
enhanced water storage; watershed management (“keep water where it falls” and reduce
surface runoff and erosion), or increase of system resistance: flood forecasting and
warning; regulation through planning, legislation and zoning; flood insurance;
relocation of population living in flood-risk areas; flood proofing on location.
European Union Floods Directive
• Preliminary flood risk assessment (including assessment of the
projected impact of climate change trends; forecast of estimated
consequences of future floods, …).
• Preparation of flood maps and indicative flood damage maps,
covering the geographical areas which could be flooded with a
high probability (return period of 10 years); with a medium
probability (100 years), and with a low probability (extreme
events).
• Preparation and implementation of flood risk management
plans, aimed at achieving the required levels of protection.
Water managers in a few countries have begun to
consider the implications of climate change explicitly in
flood management.
In the UK and in Bavaria design flood magnitudes
have been increased by 20% and 15%, respectively, to
reflect the possible effects of climate change.
Measures to cope with the increase of the design
discharge for the Rhine in the Netherlands from 15 000
to 16 000 m3/s must be implemented by 2015 and it is
planned to increase the design discharge to 18 000
m3/s in the longer term due to climate change.
ERA-NET CRUE
(COORDINATION DE LA RECHERCHE SUR LA
GESTION DES INONDATIONS FINANCÉE DANS
L’UNION EUROPÉENNE)
• Inter-comparison of national research programmes
• Identification of good practice on programme
identification and management
• Dissemination methods for current national research
results
• Identification of opportunities and gaps in research
• Pilot common calls for research
• European research agenda for flood risk mitigation
Contents
Introduction
Multi-factor context
Observations
Projections
Adaptation
Concluding remarks
♦ The impact of climate forcing on flood risk is complex
and depends on the flood generation mechanism.
♦ Higher and more intense precipitation has been
already observed and this trend is expected to strengthen
in the warmer world, directly impacting on flood risk.
♦ However, snowmelt and ice-jam related floods have
been decreasing over much of Europe.
♦ It is difficult to disentangle the climatic change
component from strong natural variability and direct
human impacts.
♦ IPCC (2001): „The analysis of extreme events in both
observations and coupled models is underdeveloped.”
„The changes in frequency of extreme events cannot be
generally attributed to the human influence on global
climate.”
Acknowledgements to co-authors of:
IPCC WGII Fourth Assessment Report
Chapter 3: Freshwater Resources and their Management
[www.ipcc.ch]
Coordinating Lead Authors
Zbigniew W. Kundzewicz (Poland) and Luis Jose Mata (Venezuela)
Lead Authors
Nigel Arnell (UK), Petra Döll (Germany), Pavel Kabat (The Netherlands),
Blanca Jimenez (Mexico), Kathleen Miller (USA), Taikan Oki (Japan), Zekai
Sen (Turkey), Igor Shiklomanov (Russia)
Contributing Authors
Jun Asanuma (Japan), Stewart Cohen (Canada), Mark Nearing (USA), Richard Betts (UK), Christel
Prudhomme (UK), Roger Pulwarty (Trinidad and Tobago), Roland Schulze (South Africa), Renoj
Thayyen (India), Nick van de Giesen (The Netherlands), Henk van Schaik (The Netherlands), Tom
Wilbanks (USA), Robert Wilby (UK)
Review Editors
Alfred Becker (Germany), James Bruce (Canada)