Enhanced risk models with Global Flood Zones

Flooding is a global hazard, and it occurs more frequently and affects more people and properties than any other natural peril. More than 3,500 people lost their lives due to flooding in 2017, meaning floods were responsible for more than 40% of all natural catastrophe casualties last year, according to Swiss Re's recent sigma report. In addition, the floods caused by Hurricane Harvey were a grim reminder that flood events can also cause huge economic and insured losses. While Harvey was an exceptional event in many ways, unfortunately, the number of flood victims in 2017 was not exceptional at all – in 2016, it was only slightly lower with 3336.

Knowing the areas with elevated flood risk is crucial to increase flood resilience and ultimately reduce the impact of flood events. Such information is the basis for raising risk awareness, enforcing zoning laws, deciding on where to build flood protection measures, and pricing insurance accurately – all of which contribute to increased flood resilience. However, for a long time there was no globally consistent flood hazard information available.

That changed in 2012, when Swiss Re filled this gap with the release of the Global Flood Zones (GFZ), the first worldwide flood maps in the insurance industry. Since then a lot of water has flowed under the bridge. In recent years, advances in technology have allowed for significant improvements, particularly to the quality of digital elevation models, the most important input when calculating GFZ.

Swiss Re acquired one of the most accurate commercially available elevation data products, which integrates high-resolution worldwide LiDAR data into a globally consistent elevation data set on a 30-meter resolution. The latest GFZ release makes use of this data set, and based on these material improvements in data quality and the higher resolution, Swiss Re recalculated all flood maps globally. These new maps are now an even more powerful tool to provide detailed flood hazard information for any location worldwide and enable flood solutions.

This newest version of GFZ (v3) is available in CatNet, Swiss Re's natural hazard atlas, for our clients since April 2018. The zones are available for the entire world on a 30m resolution.

Comparison of the previous version of GFZ on a 90m resolution (above) and the more detailed GFZ v3 on a 30m resolution (below).

Article by Konrad Schoeck, Flood Lead, Cat Perils, Swiss Re

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