24 Jan 2023
 | 24 Jan 2023
Status: this preprint is currently under review for the journal NHESS.

The potential of global coastal flood risk reduction using various DRR measures

Eric Mortensen, Timothy Tiggeloven, Toon Haer, Bas van Bemmel, Dewi Le Bars, Sanne Muis, Dirk Eilander, Frederiek Sperna Weiland, Arno Bouwman, Willem Ligtvoet, and Philip J. Ward

Abstract. Coastal flood risk is a serious global challenge facing current and future generations. Several disaster risk reduction (DRR) measures have been posited as ways to reduce the deleterious impacts of coastal flooding. On the global scale, however, efforts to model the effects of DRR measures (beyond structural) in the future are limited. In this paper, we use a global-scale flood risk model to estimate the risk of coastal flooding, and to assess and compare the effectiveness and economic performance of various DRR measures, namely: dykes and coastal levees, dry-proofing of urban assets, zoning restrictions in flood-prone areas, and management of foreshore vegetation. To assess the effectiveness of each DRR measure, we determine the extent to which they can limit future flood risk as a percentage of regional GDP to the same value as today (the so-called relative-risk constant objective). To assess their economic performance, we estimate the economic benefits and costs. If no DRR measures are taken in the future, we estimate expected annual damages to exceed $2 trillion USD by 2080, directly affecting an estimated 15 million people. Over 90 % of sub-national regions in the world can achieve their relative-risk constant targets if at least one of the investigated DRR measures is employed. At the global scale, we find the effectiveness of dykes and coastal levees in achieving the relative-risk constant objective to be 98 %, dry-proofing to be 49 %, zoning restrictions to be 11 %, and foreshore vegetation to be 6 %. In terms of direct costs, the overall figure is largest for dry-proofing ($151 billion) and dykes and coastal levees ($86 billion), much more than those of zoning restrictions ($27 million) and foreshore vegetation ($366 million). While zoning restrictions and foreshore vegetation achieve the highest global benefit-cost ratios, they also provide the least benefits overall. We show that there are large regional patterns in both the effectiveness and economic performance of modelled DRR measures. Future research could assess the indirect costs and benefits of these four and other DRR measures as well as their subsequent hybridisation.

Eric Mortensen et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on nhess-2022-284', Anonymous Referee #1, 03 Mar 2023
  • RC2: 'Comment on nhess-2022-284', Anonymous Referee #2, 21 Apr 2023

Eric Mortensen et al.

Eric Mortensen et al.


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Short summary
Current levels of coastal flood risk are projected to increase in coming decades due to various reasons, e.g., sea-level rise, land subsidence, and coastal urbanisation; action is needed to minimize this future risk. We evaluate dykes and coastal levees, foreshore vegetation, zoning restrictions, and dry-proofing on the global scale to estimate what level of risk reductions are possible. We demonstrate that there are several potential adaptation pathways forward for certain areas of the world.