New global dataset to support the hundreds of millions of people threatened by sea-level rise

Published: 27 June 2016

Extreme sea-levels - which can cause catastrophic floods - have been mapped with greater accuracy than ever before in a new study by Dutch researchers (Vrije Universiteit Amsterdam and Deltares), published today in Nature Communications. This allows for a much better mapping and understanding of the risks faced by the more than 600 million people living in low-lying coastal areas.

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Great step forward

The research presents a new global dataset of extreme sea-levels around the world’s entire coastline, the Global Tide and Surge Reanalysis dataset (GTSR). GTSR is the first global near-coast dataset based on hydrodynamic modeling, and as such is a great step forward in understanding how coastal communities are threatened by coastal floods. Using the new extreme sea levels, the researchers from the Institute for Environmental Studies (IVM) at the Vrije Universiteit Amsterdam and research institute Deltares found that 76 million people are potentially exposed to a 1-in-100 year flood. Sanne Muis, lead-author of the paper, says: “As the world’s population continues to grow, and sea-level rises, the number of people potentially affected by coastal floods will increase even further. To combat this upward trend in risk, it is essential to have accurate data on sea-level extremes around the world, which can support decision-makers in developing effective adaptation strategies. To assist in this, we have made the 1-in-100 year extreme sea-level dataset freely available online”.

Mission impossible

At the regional-scale, hydrodynamic modeling is the state-of-the-art method to assess flood hazard. Recent technological advances have finally made it possible to apply this approach at a global-scale. The Global Tide and Surge Model (GTSM), developed by co-author Martin Verlaan from Deltares, was forced with wind speed and atmospheric pressure data for the period 1979-2014. Verlaan: “When I first started working on a global hydrodynamic model, many colleagues said it was a mission impossible. However over the last years more and more computational power has become available, as well as global datasets needed to run these models. A large boost to this research was given by the implementation of unstructured grids in the Delft3D software, which make it possible to refine the resolution of the model towards the coast. As a result GTSM has a uniquely high resolution near the coasts but at the same time is computationally very efficient.”

Importance for future studies

Validation shows the modelled sea-levels are very accurate, and that the performance of GTSR is similar to that of many regional hydrodynamic models. The GTSR dataset can therefore be used in important studies to assess society’s risk of flooding. GTSR may also be essential for assessments of the impact of sea-level rise; its application to project future risk may result in changed insights in the areas at risk.