climate change risk assessment: 2017 assessing future flood risk … · 2015. 6. 2. · climate...
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Climate Change Risk Assessment: 2017
Assessing future flood risk across the UK (England, Wales, Scotland and Northern Ireland)
Presentation to the FoRUM Workshop Paul Sayers and Matt Horritt
17 March 2015
Flood Hazard
Research
Centre Prof. Edmund
Penning-Rowsell
University of
Newcastle Prof. Chris Kilsby
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Outline of presentation
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Introduction to the CCRA
Approach to assessing future flood risk at a UK scale
Opportunities the approach may provide for NaFRA
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Introduction to the CCRA
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CCRA 2017: Background
Under the UK Climate Change Act
The Climate Change Committee must undertaken a Climate Change Risk Assessment (the CCRA) every 5 years and then produces a policy programme to address those risks
The Adaptation Sub-Committee advises on this assessment and scrutinises the implementation of the policy programme
The first CCRA was completed in 2012
The second CCRA is due for publication 2017 (the flood risk component of this is the subject this talk)
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CCRA 2017: Aims
To assess the priority risks (opportunities and threats) for the UK from current and future climate change
Assess how climate interacts with socio-economic factors in affecting risk
How the effects of different adaptation scenarios could alter future risk
How climate change overseas could affect the UK
To provide a single report covering England, Wales, Scotland and Northern Ireland.
To use this to inform Government policy on future priorities for adaptation policy
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Approach to assessing future flood risk at a UK scale
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Context of the analysis
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Flood sources of interest
All sources of flood risk across the UK, including:
Coastal
Fluvial
Surface water
Groundwater
Permeable Superficial Deposits
Clearwater (Chalk and other aquifers)
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Future changes of interest
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2020s,2050s,2080s
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Flood Risk metrics of interest
Property (residential and non-residential)
People
Agriculture (Best and Most Versatile and Not)
Infrastructure (a range of critical infrastructures)
Natural capital (SPA and SACs)
Note: Erosion risk is outside of scope
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Analysis approach
Future flood explorer:
Using available information across the UK to create an emulator of the UK flood risk system
Look up tables of probability and impact are created offline
As no spatial analysis is run real time (the FFE works purely from impact tables) it is quick (almost instant to run)
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FFE - Limitations and assumptions
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Assumption/Limitation Comment/Mitigation
Changes in risk are appropriately resolved at a Flood Area (FA) scale and 1km grid.
The UK FFE will characterise the input data, climate change, defences, damages and adaptation at a FA scale for ‘on floodplain’ areas and at a 1km grid for ‘off floodplain’ areas.
Sources of flooding will be treated as independent
Not ideal but a practical assumption here – a potential future enhancement
Available input data covers a sufficiently wide range of conditions to make the explorer credible.
To maximize credibility of the UK FEE we will mine all available data – using undefended and defended data, all future and present day analysis – and make sensible assumptions to condition the emulation
The UK FFE provides a good representation of the national risk
We will verify the UK FFE against: • ‘Unused’ runs of the models upon which is
based (e.g. LTIS – but comparison is not direct)
• Observed events – namely the 2007 event
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Spatial schema (Calculation Areas in the UK FFE)
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Flood Area Fluvial, Coastal, pluvial and Groundwater risks
1km Grid Surface and Groundwater risks
Representative type, standard of protection and condition grade (in defended and undefended areas)
Impacts are aggregated to the calculation area in a way that reflects the spatial variation in probability and receptors
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Steps in the creation of the UK Future Flood Explorer (FFE)
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Step 1: Gathering the input data
The FFE utilises available data:
Flood probability (defended, undefended and probabilistic analysis)
Flood defence assets (standards, condition, type)
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+ Groundwater
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Step 1: Gathering the input data
The FFE utilises available data:
Receptors
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Step 2: Building the impact curves
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Step 3: Build the FFE emulation rules
Changes in increases in storm loads:
% increase in river flows
% increase in urban and rural run-off
sea level rise (m)
Changes in defence performance/protection:
Reducing/increases in Standard and Condition Grade
Changes in exposure
Number of properties and occupancy
Changes vulnerability
The damage incurred if a receptor is flooded
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Step 4: Validate the FFE risk estimates
Looking at emulator outputs for some real events:
2007 flooding in England and Wales
Surface water flooding 2000-2010 in Belfast
And comparing with outputs of other analysis (for example comparing estimates of future national risks with those from LTIS)
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Spatial coherent events
Exploring future coherent events under climate change
(example only shown opposite)
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‘What if’ the 2007 event reoccurred in 2080s
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Step 5: Explore alternative adaptations
Within the FFE there are
Adaptation levers (individual actions)
These are used to construction
Adaptation scenarios
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Example adaptation levers
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Adaptation affecting the probability of flooding:
Formal defences (river and coastal defences)
Coastal foreshore management (realignment)
Rural land management (storage and run-off)
Urban land management (run-off)
Adaptation affecting the extent to which receptors are exposed to flooding
Spatial planning (development control)
Adaptation affecting the vulnerability of those exposed.
Receptor level protection measures (both resistance and resilience)
Forecasting and warning
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Example adaptation scenarios
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Additional analysis to explore the impact of sea level rise on the ‘vulnerability’ of the existing defence line and estimate the potential area that could be inundation if the current defence line (in areas identified as ‘highly vulnerable’) were lost.
Note: No consideration of the cost of maintaining or retreating the line at this stage
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Additional coastal analysis
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Within the FFE we are developing...
A simplified (first pass) relationship between mean sea level = length of highly vulnerable defences
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….and assessing what if ’highly vulnerable’ defences were lost/abandoned...
Tidal inundation only (no waves)
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Lincolnshire +0m
Lincolnshire +0.5m
Scotland +0m
Scotland +0.5m
Severn +0m
Severn +0.5m
Solent +0m
Solent +0.5m
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Opportunities the approach may provide for NaFRA
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Opportunities: FFE and NaFRA
The FFE is
Very fast to run UK wide (effectively instant)
A bottom up assessment. – Utilises the results from local modelling
– The input data (on flood inundation, impacts) is recognisable locally.
– Capable of including all sources
– Capable of estimates damages associated with spatial coherent events
Recognises benefits of defences and conditions in reducing risk
Only as good as the input data
Is currently limited by assumptions of independence of different sources and no attempt to estimate depth or velocity – both could be relaxed.
It would not replace local analysis – in fact it relies upon it!
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More questions…..please contact
Paul Sayers
Skype: floodsman
Telephone: 01865 600039
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