Pluvial flooding presentation 2010
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Transcript of Pluvial flooding presentation 2010
![Page 1: Pluvial flooding presentation 2010](https://reader034.fdocuments.in/reader034/viewer/2022042518/55575f1cd8b42a94728b4824/html5/thumbnails/1.jpg)
UN
ESC
OIH
P-H
ELP
Ce
ntr
e fo
r W
ater
La
w, P
olic
y &
Sci
ence
Demographic and climatechange influences on future
pluvial flood risk
Prof Alan Werrity and Prof Donald Houston (University of St Andrews)
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Introduction
• What is pluvial flooding?
• Appraisal of current pluvial flood risk difficult
• Appraisal of future risk even more difficult!!
• Hydrological and climate change influences
• Demographic and social influences
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The determinants of flood risk (based on McLaughlin, 2011)
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Appraisal of Current flood risk
1. Where is the hazard?
2. Where is the exposure?
3. What receptors are most vulnerable?
Most effort has gone into 1 & 2
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Appraisal of Future flood risk
1. Change in hazard
2. Change in exposure
3. Change in vulnerability of receptors
Most effort has gone into 1
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Current flood risk (SEPA, 2011)
• Hazard + Exposure = – 133k properties at flood risk (5%)
• Fluvial: 64%
• Coastal: 23%
• Pluvial: 13% (but probably a lot higher)
• UNCERTAINTY in extent of pluvial hazard
• What about population?
• What about vulnerability?
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Vulnerability and current exposure (Walker et al 2006; Werritty et al 2007; Houston et al 2011)
• River flooding:
– Socially deprived groups slightly under-represented
• Coastal flooding:
– Socially deprived groups over-represented
• Surface water flooding:
– Socially deprived groups slightly over-represented
• UNCERTAINTY: Social deprivation is a crude proxy for flood vulnerability
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Future pluvial flood risk
• Change in hazard
– UK uplift in extreme daily rainfall: 8%
– UK uplift in extreme hourly rainfall: ???
• Change in exposure:
– UK population growth 1990-2050: 48%
– 1.2 million additional people at pluvial flood risk (Houston et al 2011):
• Climate change: 300k
• Population growth: 900k
• Change in vulnerability: ???
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Increase in pluvial flood risk
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
Climate change 1990-2050
Demographic change
2001-33
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Level of certainty in pluvial flood risk appraisal (Low, Moderate, High)
Current Future
Hazard Moderate
Moderate
Exposure Moderate
Low
Vulnerability Moderate
Low
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Vulnerability and future risk
• Population ageing
• Insurance withdrawal/higher premiums?
• Flood risk areas blighted?
• Developed for social housing?
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Conclusions
• More emphasis in flood risk appraisal required on: – Population – Population growth – Demographic change
• More research required on
– Extreme rainfall under climate change – Surface water flooding modelling – Population change in flood risk areas – Social vulnerability to flooding
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References
• Houston, D., Werritty, A., Bassett, D., Geddes, A., Hoolachan, A. and Macmillan, M. (2011) The Invisible Hazard: pluvial flood risk in urban areas. York, Joseph Rowntree Foundation. (Due for publication summer 2011).
• Walker G, Burningham K, Fielding J, and Smith G (2006) Addressing Environmental Inequalities: Flood Risk. R&D Technical Report, SC020061/SR1, Bristol, Environment Agency.
• McLaughlin, M. (2011) Nation Flood Risk Assessment. Presentation to SNIFFER Flood Risk Management Conference, Edinburgh, March 2011.