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Coastal wetlands mitigate storm flooding and associated costs in estuaries

September 2, 2021
News item image The study found that saltmarshes mitigate storm flooding and associated costs in estuaries via multi-scale processes.

A recent study published in Environmental Research Letters has found that estuary wetlands such as saltmarshes reduce flooding more than previously thought. The authors created numerical hydrodynamic models of eight Welsh estuaries to simulate storms of varying intensity and coupling flood predictions to damage valuation. They found that in all cases estuary wetlands reduced flooding, with vegetation reducing average flood extents by 35% and the amount of damage caused by 37%. The modelled wetlands also reduced water levels by up to 2m in upstream areas, and could save up to £27m in avoided damage per estuary during a large storm.

As storm-driven coastal flooding increases under climate change, wetlands such as saltmarshes are held as a nature-based solution, but previously there was scarce evidence supporting wetlands’ storm protection role in estuaries. The results of this study therefore fill that knowledge gap, and show that saltmarshes play a generalised role in mitigating storm flooding and associated costs in estuaries via multi-scale processes. Ecosystem service modelling must therefore integrate these processes, or risk grossly underestimating the value of nature-based solutions to the growing threat of storm-driven coastal flooding that are increasing due to climate change.

The study result also highlights the need to protect wetlands that are facing growing threats from development. Of the largest 32 cities in the world, 22 are built on low-lying land around estuaries; putting them at increasing risk of flooding in a warming climate. Wetland habitats can be regenerated through active nourishment of sand bars, planting of wetland grasses, as well as integrating marsh conservation into coastal planning to reduce development and use of man-made flood defences along estuaries.

Find out more in the full published article.