The Addition of Great Britain Storm Surge to AIR's Extratropical

Home , Cyclone Anne (2014), North Sea flood of 1953

The Addition of Great Britain Storm Surge to AIR’s Extratropical Cyclone Model for Europe

Richard M. Yablonsky, Ph.D. Alastair Clarke, Ph.D.

Introduction

Updates to the Hazard Component

Hazard Model Validation

Updates to the Vulnerability Component

Modeled Losses

Upcoming Software Changes

2000 2010 2013 2019

Addition of Great Britain Great Britain Great Britain Great Britain Exposure Vulnerability Storm Surge Update Update to EU ETC

2019 Update: Previously: Storm Surge sub-peril in the AIR AIR Coastal Flood Model for Extratropical Cyclone Model Great Britain for Europe

Sea Defenses Topography

Shallow Water Deep Sea Wind Pressure

Bathymetry

in Great Britain Historical Storm Tracks Latitude

Storm Anne (2014): West Coast Example* Storm Xaver (2013): East Coast Example** *another example is Storm Undine (1991) **another famous example is North Sea Flood (1953)

Southerly wind pushes water into Northerly wind pushes water into Irish Sea the Channel

• Expanded domain covers all Hydrodynamic Domain Coarse of England and Wales Mesh Fine Mesh: • Uses Delft3D Flexible Mesh Current Coverage • Dynamic simulation of tides New Coverage and surge • Driven by wind and pressure from EU ETC model catalog (see Keshtpoor, Carnacina, and Yablonsky, 2019: New Statistical Approach to Select Coastal Flood-Producing Extratropical Cyclones from a 10,000-Year Stochastic Catalog. J. Waterway, Port, Coastal, and Ocean Eng.) • Surge depth at 10-meter resolution via downscaling and topography subtraction

• Data can be mapped to a Manning friction coefficient

• Helps to ensure proper flood extent over land

• Particularly challenging in urban areas

UK Environment Agency Spatial Flood Defences Dataset • 2016 vintage defense data set for the entire United Kingdom: defined crest heights, material, quality condition, and design type • Undefined heights were extracted from 2- to10- meter topography (DTM) sources

• The Thames Barrier was completed in 1984

• During construction, flood defenses were raised by ~2 meters for ~30 km downstream to match the Barrier

• Defenses for ~5 km upstream were also raised to increase protection and match protection of Central London

©2019 AIR Worldwide CONFIDENTIAL—FOR WEBINAR ATTENDEES ONLY 16 16 Storm Surge Model Validation at Great Britain Tide Gauges for Four Storms Four Storms Combined: 1953, Undine, Xaver, and Anne Total water level Wind setup (no tide)

Perfect line Modeled Water Elevation (Meters) Elevation Water Modeled

RMSETWL= 0.32 m RMSE = 0.28 m Tide Gauge Locations WS Observed Water Elevation (Meters) ©2019 AIR Worldwide CONFIDENTIAL—FOR WEBINAR ATTENDEES ONLY 17 17 Modeled Pressure, Wind, and Surge During North Sea Flood of 1953 a) SLP (mb) b) U (m/s) 20 1030 a) Sea level pressure 60 1020 10 1010 b) West-to-east wind 55 1000 0

speed (U) ~180 meters 990 ) above ground ° 50 980 -10

c) V (m/s) d) Surge (m) c) South-to-north wind 20 2 speed (V) ~180 meters Latitude( 60 10 1 above ground 0 55 0 -10 d) Water level due to -1 -20 wind setup (without 50 -30 -2 tide) -10 0 10 -10 0 10 Longitude(°)

©2019 AIR Worldwide CONFIDENTIAL—FOR WEBINAR ATTENDEES ONLY 18 18 Modeled Water Level Near Thames Barrier from a Storm Like the 1953 North Sea Flood 8 ~7.3 m (height of Thames Barrier) Tide Only Surge Only 6 Linear Tide & Surge ~5.4 m (like North Sea Total Water Level 1953 storm) 4

-2

Thames Barrier

Hull, UK

Humber River

Boston, UK Boston, UK

The Haven River The Haven River

Insufficient resolution (~220 m) Sufficient resolution (up to 35 m) for water to reach Boston, UK for water to reach Boston, UK ©2019 AIR Worldwide CONFIDENTIAL—FOR WEBINAR ATTENDEES ONLY 24 24 Updates to the Vulnerability Component

Building and Component Damage Functions for a Retail Shop Building Building Structure Services Fixtures and Fittings Overall Building Coverage

Structure Fixtures Services

60% 40% 20%

0% Mean Damage Ratio Damage Mean

Flood Depth

Residential Commercial 3 2.5 2 1.5 1

0.5 Relative VulnerabilityRelative 0 Previous Version Updated Version

• Addition of marine cargo, marine hull, industrial facilities, wind turbine, and builder’s risk Marine • Incorporation of unknown damage functions at CRESTA level • Updated secondary damage distributions Industrial Facilities ©2019 AIR Worldwide CONFIDENTIAL—FOR WEBINAR ATTENDEES ONLY 28 28 67K Claims from Four Historical Floods Inform the Latest Secondary Uncertainty Distributions

Previous Updated

Mean Damage

Ratio

Probability Damage Damage Ratio

Flood Depth Damage Ratio • Distinct secondary uncertainty • In the new model, there is lower distributions for Residential and probability of zero or full Commercial risks damage

Custom Flood PresenceFoundation of Floor of Protection BasementType Interest

London, UK • Utilized best available building footprint data sets to accurately locate risks • Updated construction splits, replacement costs, coverage splits, and policy conditions • Improved automobile valuation methodology • Identified high-value industrial facilities

1 km

90 m

1 km

Model Ground-Up Estimated 9 8 7 6 5 4 3 2

Losses (GBP Losses (GBP Billions) 1 0 North Sea Flood (1953 Vintage)

Model Insured Observed 450 400 350 300 250 200 150 100

Losses (GBP Losses (GBP Millions) 50 0 Undine (1991) Xaver (2013 Vintage) Anne (2014) Flood Events Observed Data Sources: UK Met Office, Munich Re, ABI ©2019 AIR Worldwide CONFIDENTIAL—FOR WEBINAR ATTENDEES ONLY 36 36 Exceedance Probability of Insurable Gross Loss

1953 X

X = No SoP 1953 V V = Vintage SoP

M = Modern SoP Loss

1953 M 2013 V 2013 M 1991

2014

1953 M V = Vintage SoP

M = Modern SoP Loss

2013 V 2013 M

1991 2014

AOL 2 4 5 10 15 20 50 100 Return Period (Years)

Residential, Commercial, Industrial, Agriculture, and Auto Lines of Business

Wind Only

Loss Wind & Updated Surge

AAL 2 5 10 20 25 50 100 200 500 1,000 Return Period (Years)

Residential, Commercial, Industrial, Agriculture, and Auto Lines of Business

Wind & Previous Surge

Loss Wind & Updated Surge

AAL 2 5 10 20 25 50 100 200 500 1,000 Return Period (Years)

Touchstone 2018

* Europe Extratropical Cyclone is still categorized as a “Tropical Cyclone” peril in Touchstone

Touchstone 2019

1) Events in the Database are tagged as either Extratropical Cyclone (E), Surge (S) or Combined (C). 2) In Touchstone® 2019, you can run the previous and new versions of the GB storm surge model 3) Users can apply financial terms on combined wind and surge losses in Touchstone and CATRADER®/Touchstone ReTM 4) CATRADER/Touchstone Re users can also get losses for the GB surge-only catalog 5) Exported CLFs will be for European ETC (even storm surge-only runs)

Expanded model coverage to include all of England and Wales

Updated with modern-day levee information to improve surge footprints

Enhanced damage functions using claims and peer-reviewed literature

Greater selection of primary and secondary characteristics to represent your risk