Estimating societal risk: modelling and outputs www.hsl.gov.uk Dr Mike Wardman

Estimating societal risk:
modelling and outputs
Dr Mike Wardman
HSL
www.hsl.gov.uk
www.hsl.gov.uk
AnAn
Agency
of theof
Health
and Safety
Executive
Agency
the Health
and
Safety
Executive
Modelling
• Workbench tool Excel workbook/C code
• Inputs required
– Scenarios
– Weather
– Population
• Dispersion calculations
– Generate footprints
• Calculate fn pairs
– Overlay footprints - fatalities
– Calculate frequency
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Scenarios
• Set of scenarios used:
– Reduced set for ranking
– Land use planning scenarios
• Specify
– Substance
– Event frequency
– Instantaneous/continuous release
– Size/Rate and duration
– Release coordinates
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Weather
• 12 sector wind rose
• Data available for range
•
of stations closest to site
used
Weather conditions
– e.g. F2, D5, B2, D2
• Probability
– Sector
– Weather conditions
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Population
•
•
•
•
National Population Database (NPD) used
100m grid resolution
Extent determined by hazard range
Produces grid
0
0
0
2.69
0
115.28
7.86
858.4
486.27
0
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5.42
0
2.69
2.69
2.62
7.86
0
10.48
5.52
5.52
0
5.38
2.69
72.26
8.07
2.69
0
2.62
5.52
0
0
0
272.1
1061.4
123.11
109.43
0
0
27.6
0
0
10.28
2.35
14.1
0
11.75
0
2.35
2.76
0
0
5.14
5.14
4.7
2.35
2.96
2.35
0
25.1
2.51
2.57
0
8.84
11.05
4.56
2.35
0
0
65.74
102.04
0
4.42
2.21
14.8
11.84
0
0
0
692.46
344.58
21.84
11.05
32.17
74.25
5.74
2.78
0
0
393.44
108.68
5.46
2.73
21.62
631.68
30.58
2.51
2.51
0
7.53
0
2.73
71.96
33.12
50.01
5.29
5.02
60.96
844.76
0
2.46
20.22 26.1
89.49 15.72
5.46 10.48
397.69 13.99
140.97 53.98
73.23 80.96
1158.82 2.48
4002.68 2256.72
1244.61 391.1
0 8.74
NPD Database
•
•
•
GIS based analysis tool, hosted at HSL
Data for England Scotland and Wales
Different Populations available:
– Residential (day/night time term/non term time)
– Sensitive populations (Schools, Hospitals, Care
Homes, Prisons)
– Workplace (based on Census Output Area, COA)
– Retail (town centre, out of town developments)
– Transport (Motorway, dual/single carriageway A
roads)
– Leisure (stadium, theme parks, camping grounds)
•
Gives vulnerability, location, time
differentiation
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National Population Database
•
Residential Layer - Night time population ~
504
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Dispersion
• Parameterised dispersion used
– Generated from integral models
– Defines footprints dimensions
Min Distance
Max Width
Distance to Max
Width
Max Distance
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n values (fatalities)
•
Footprints generated for:
– Indoor/outdoor
– 1%, 10%, 50% fatality doses
– Each weather condition
• D5, F2, …
– Different population sets (day/night)
•
Overlay population data to
calculate n values
– Combine indoor/outdoor and doses
– Fraction of the population covered
at each dose
•
Cover all sectors of windrose
– 1 degree steps used
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f values (frequencies)
• Frequencies calculated
taking account of:
– Weather condition probability
e.g. 80% D5, 20% F2
– Bias factor for each wind
direction from wind rose
– Different populations
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Outputs
• Numerical
– Expectation Value
– Risk Integral (scale aversion)
• Graphical
– Cumulative FN Curve
• Geographical
– Risk combined from each footprint (area plot)
– Risk from each grid location (hot spots)
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Numerical
• Expectation Value, EV
– Σ f.n
• Risk Integral, RI
– RI is based on EV with factor a to reflect
scale aversion
– Σ f.na
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Graphical
• FN curve
– cumulative frequency of N or more fatalities
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Geographical Output
• Based on numerical
representation
– EV
– F.N
• Value at grid location
•
shown
Types
– Hot Spots plot
– Area plot
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Hot Spots
• Risk at each grid location
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Area plot
• Cumulative risk of overlaid footprints
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