Inland flood risk:
A growing global threat
for re/insurers

Global flood hazard has already taken centre stage in 2019, with communities in Brazil, Queensland, the US, Canada, Iran and south-east Africa experiencing extreme flood events, as a result of heavy rainfall, that have had major social and economic impacts.

These events demonstrate that inland flood continues to pose a very real and serious threat. In fact, JBA estimates that a quarter of the world’s population will be at risk to inland flood by 2020, with climate projections suggesting increased flood risk in future.

The insurance community needs the right tools to better understand and manage this hazard. This blog looks at what data is available to help them do so.

The impact of inland flood

2018 saw major losses for the global re/insurance industry, with natural catastrophe losses estimated at around USD $155 billion, resulting in the fourth-highest insurance payout on sigma records (Swiss Re, 2019).

These natural catastrophes also have wide ranging social impacts, with inland flood playing a major role. At the time of writing, 94 flood events can be attributed to heavy rainfall since the beginning of 2018, causing 675 fatalities and displacing 174,000 people (Dartmouth Flood Observatory, 2019). In particular, Kerala, India, hit the headlines in 2018, when the state received 255% more rainfall than the monthly average in August (Madaan, 2018). The floods were described as the worst the state had experienced in a century, with 433 reported deaths and 1.4 million people displaced (Jacob, 2019).

How can re/insurers begin to better understand inland flood risk?

With this continuing threat to local communities and the global market, it’s vital that re/insurers can better understand and manage flood hazard.

The need for global consistency

Most available flood data is built using a country-specific approach, with flood maps detailing flood extents and depths for a single country using different modelling methods. This approach doesn’t allow for consistency in analysis of flood hazard at different locations that may cross political or geographical boundaries; for example, when assessing flood hazard in Laos and Cambodia using maps with different methodologies, it may impact decisions in underwriting, pricing, risk selection and portfolio management across the two countries.

As a result, re/insurers must have access to data, such as JBA’s Global Flood Maps, which enable them to compare risks globally based on a consistent source of information.

Scientifically-backed data

During the development of maps, this globally consistent methodology must also be scientifically robust for re/insurers to make the best decisions regarding flood exposure.

Digital elevation data have a significant impact on the resulting flood map. Good quality data ensure that flood maps represent the terrain and subsequent flow path of water as realistically as possible, rather than over- or underestimating the hazard. To ensure flood is most realistically represented, JBA uses the best quality elevation data available in each country, with many of the world’s high-risk areas modelled using lidar data or other bare earth terrain models, without losing the global consistency of the maps’ resolution.

Another important input in the modelling process is observed river and rainfall gauge data. JBA makes use of this data in its Global Flood Maps. Gauge data enables us to study patterns from historical floods to calculate the probability of a certain river flow or rainfall amount occurring in that catchment each year. It also allows us to understand the relationship between catchment characteristics and flood hazard, which we can apply to areas where no data is available, to ensure we represent global flood risk effectively and consistently.

Finally, JBA’s Global Flood Maps represent flood hazard by using sophisticated 2D hydrodynamic modelling. Inland flood is very complex and changes over small distances, with lots of factors (including ground height, land use and drainage systems) affecting the flow path of water, which can most effectively be represented using these complex models.

A fuller view of the risk

Flood data is now available at 30m resolution, representing the major sources of flood hazard more comprehensively, including multiple flood types, extents and depths for a range of return periods.

River and surface water flooding often coincide, with each flood type behaving differently and having diverse impacts. As a result, it’s vital for flood mapping to represent the complex interplay between river and surface water flooding; JBA’s Global Flood Maps provide the opportunity to separately view the impact of surface water in flood assessments which, when compared to claims data, can provide a better insight into the potential drivers of loss. Similarly, global defence data enable users to view how river defences may impact on flood exposure, giving them the ability to decide which defences to incorporate in flood assessments, and have their own view of the risk.

To understand the full range of flood severities, flood maps must also provide information on various extents and depths of flooding. JBA’s Global Flood Maps cover six return periods, from 20-year to 1,500-year, demonstrating the different severities a re/insurer may be exposed to. The associated water depths for each return period are also important for a more specific exposure assessment: if there’s a chance of a property being flooded by three inches of water, a re/insurer may decide it’s a risk worth taking, while the decision may be entirely different if it’s a chance of being flooded by three feet of water.

Finally, the JBA Global Flood Maps are modelled at 30m resolution globally, in order to represent the hazard at the most appropriate scale worldwide. This enables users to identify locations at low and high risk from flood hazard, gain an overview of the overall flood hazard and understand which locations may benefit from a more in-depth analysis.

How can JBA help?

JBA’s Global Flood Maps enable users to better understand and manage global flood hazard for more profitable and effective business decisions now and in the long term. For more information on the JBA Global Flood Maps, please get in touch or read our executive briefing.

The maps can also be used alongside our catastrophe models and Global Flood Event Set for a consistent view of the risk across the risk-transfer chain. Keep an eye out for our upcoming blog series to find out more about our catastrophe models and event set.

References

Brakenridge, G.R. 2019. Global Active Archive of Large Flood Events. [online] Dartmouth Flood Observatory, University of Colorado. Available at: http://floodobservatory.colorado.edu/Archives/index.html [Accessed 6 May 2019].

Jacob, N. 2019. Kerala on the road to recovery. India Today. [online] 1 April 2019. Available at: https://www.indiatoday.in/magazine/the-big-story/story/20190401-on-the-road-to-recovery-1483607-2019-03-22. [Accessed 2 May 2019].

Madaan, N. 2019. In just 20 days, Kerala gets highest August rains in 87 yrs. The Times of India. [online] 21 August 2018. Available at: https://timesofindia.indiatimes.com/india/in-just-20-days-kerala-gets-highest-aug-rains-in-87-yrs/articleshow/65480279.cms [Accessed 2 May 2019].

Swiss Re. 2019. Confronting the cost of catastrophe. [online]. Available at: https://www.swissre.com/risk-knowledge/mitigating-climate-risk/natural-catastrophes-affecting-more-people-what-can-do-to-help.html [Accessed 14 May 2019].

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