Compound risk of river and coastal floods in global deltas and estuaries

Flooding in deltas and estuaries is driven by the interactions of oceanographic, hydrological, and meteorological phenomena such as extreme rainfall, river discharge, storm surge, and wave action. When these co-occur in space and time, they can exacerbate the flood extent, depth, and duration locally, resulting in a so-called compound flood event.

Compound Risk
© Henk de Boer

These events have the potential to cause large social and economic impacts and can directly or indirectly impact flood emergency response and infrastructure. This study shows the impact of these concurrent events on global flood risk and evaluates potential strategies for reducing this risk. Current global flood risk models assess either river or coastal flood risk, neglecting extreme compound river and coastal flood risk processes. This is problematic, as ignoring the temporal dependence between river and coastal floods could lead to underestimations of risk. To address these issues, the objectives of the proposed research are to:
  • Develop the first globally applicable model for consistently assessing flood hazard at the river-coast interface.
  • Improve our understanding of the influence of compound river and coastal flood events on flood risk.
  • Develop a new integrated global flood risk assessment framework, tailored to highly populated regions at the river-coast interface.

This research is conducted in collaboration with Deltares.

Contact information: Prof. Philip Ward, Dirk Eilander and Anaïs Couasnon

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  • Ward, P.J., Couasnon, A., Eilander, D., Haigh, I.D., Hendry, A., Muis, S., Veldkamp, T.I.E., Winsemius, H.C. &, Wahl, T. (2018). Dependence between high sea-level and high river discharge increases flood hazard in global deltas and estuaries. Environmental Research Letters, 13, 084012. doi:10.1088/1748-9326/aad400
  • Hoch, J. M., Eilander, D., Ikeuchi, H., Baart, F., and Winsemius, H. C.: Evaluating the impact of model complexity on flood wave propagation and inundation extent with a hydrologic–hydrodynamic model coupling framework. Nat. Hazards Earth Syst. Sci., 19, 1723–1735.
  • Couasnon, A., Eilander, D., Muis, S., Veldkamp, T. I. E., Haigh, I. D., Wahl, T., Winsemius, H. C. & Ward, P. J. (2020). Measuring compound flood potential from river discharge and storm surge extremes at the global scale. Nat. Hazards Earth Syst. Sci., 20, 489–504.
  • Muis, S., Lin, N., Verlaan, M., Winsemius, H.C., Ward, P.J. & Aerts, J.C.J.H. (2019). Spatiotemporal patterns of extreme sea levels along the western North-Atlantic coasts. ScientificReports, 9, 3391. doi:10.1038/s41598-019-40157-w
  • Zscheischler, J., Westra, S., Van den Hurk, B.J.J.M., Seneviratne, S.I., Ward, P.J., Pitman, A., AghaKouchak, A., Bresch, D.N., Leonard, M., Wahl, T. & Zhang, X. (2018). Future climate risk from compound events. Nature Climate Change, 8, 469–477.doi:10.1038/s41558-018-0156-3
  • Winsemius, H.C., Jongman, B., Veldkamp, T.I.E., Hallegatte, S., Bangalore, M. & Ward, P.J. (2018). Disaster Risk, Climate Change, and Poverty: Assessing the Global Exposure of Poor People to Floods and Droughts. Environment and Development Economics, 23. 328–348. doi:10.1017/S1355770X17000444
  • Wahl, T., Ward, P.J., Winsemius, H.C., AghaKouchak, A., Bender, J., Haigh, I.D., Jain, S., Leonard, M., Veldkamp, T.I.E. & Westra, S. (2018). When Environmental Forces Collide. EOS, 99.doi:10.1029/2018EO099745