Coastal flood risks set to increase as the climate warms: new study combines recent advances of global modelling

Published: 4 August 2020

By the end of the century, tens of millions more people and trillions of dollars more of the world economy will be at risk of being flooded. This is shown by a new study “Projections of global-scale extreme sea levels and resulting episodic coastal flooding over the 21st Century” in Nature’s Scientific Reports. The study was led by researchers from the University of Melbourne in collaboration with Deltares (Rosh Ranasinghe and Sanne Muis), IHE Delft Institute for Water Education, Vrije Universiteit Amsterdam, University of East Anglia and the Global Climate Forum in Germany.

Projections of episodic coastal flooding over the next 100 years

The study combines global models of tide, storm surge, and wave setup with regional sea-level rise projection to obtain projections of episodic coastal flooding over the coming century. Co-author Sanne Muis, researcher at Deltares and the Vrije Universiteit Amsterdam, says: “This new study brings together recent advances of global modelling, including surge data derived from the Deltares Global Tide and Surge Model based on Delft3D FM. The study provides a comprehensive analysis of global risks to coastal flooding and identifies which coastal regions may be threatened by sea-level rise.”

Tides, storm surges and seal level rise

Results show that the extent of global flooding is primarily determined by tides and storm surges, but sea-level rise can increase the frequency of coastal flooding. Under a high-emission scenario, a 1 in 100-year flood today can become a 1 in 10-year flood by the end of the century. Without coastal protection, it is estimated that by 2100 the global population exposed to coastal flooding could be up to 4.1% of the world’s population, and that the assets threatened by flooding could be worth up to 20% global GDP. This is an increase of 52% of the global population and 46% of global assets at risk compared to present day.

Global “hotspot” regions of changes in episodic coastal flooding in 2100 for RCP 8.5

Increase preparedness

The findings underscore the importance of climate mitigation and adaptation. Lead author Ebru Kirezci says: “Our research shows that large parts of communities residing in low-lying coastal areas are at risk of being devastated so we need urgent action. Vulnerable areas need to start building coastal defences, we need to increase our preparedness, and we need to be following strategies to mitigate climate change.”

 

Full article in Nature Scientific Reports:

“Projections of global-scale extreme sea levels and resulting episodic coastal flooding over the 21st Century”

By: Ebru Kirezci, Ian R. Young, Roshanka Ranasinghe, Sanne Muis, Robert J. Nicholls, Daniel Lincke & Jochen Hinkel