Abstract
Exposure to coastal flooding is increasing due to growing population and economic activity. These developments go hand-in-hand with a loss and deterioration of ecosystems. Ironically, these ecosystems can play a buffering role in reducing flood hazard. The ability of ecosystems to contribute to reducing coastal flooding has been emphasized in multiple studies. However, the role of ecosystems in hybrid coastal protection (i.e. a combination of ecosystems and levees) has been poorly quantified at a global scale. Here, we evaluate the use of coastal vegetation, mangroves, and marshes fronting levees to reduce global coastal protection costs, by accounting for wave-vegetation interaction.The research is carried out by combining earth observation data and hydrodynamic modelling. We show that incooperating vegetation in hybrid coastal protection results in more sustainable and financially attractive coastal protection strategies. If vegetated foreshore levee systems were established along populated coastlines susceptible to flooding, the required levee crest height could be considerably reduced. This would result in a reduction of 320 (range: 107-961) billion USD2005 Power Purchasing Parity (PPP) in investments, of which 67.5 (range: 22.5- 202) billion USD2005 PPP in urban areas for a 1 in 100-year flood protection level.
Highlights
Exposure to coastal flooding is increasing due to growing population and economic activity
In the short term, the structural loss of wetlands is likely to result in extra investment costs for coastal infrastructure, and in the long term it may lead to widespread loss of coastal lands and relocation of millions of people inhabiting coastal areas
While these studies exemplify the role of coastal vegetation as ecosystem services to reduced flood risk, the potential of combining coastal vegetation with traditional flood defence measures so-called hybrid or green/ grey protection)—has not been assessed on a global scale
Summary
Exposure to coastal flooding is increasing due to growing population and economic activity. Few global studies have been based on process-based wave modelling, and those that have taken this approach focused on mangroves only[23] While these studies exemplify the role of coastal vegetation as ecosystem services to reduced flood risk, the potential of combining coastal vegetation with traditional flood defence measures so-called hybrid or green/ grey protection)—has not been assessed on a global scale. Such an assessment is important because hybrid protection can be very effective. As forcing, we used wave heights and periods from a re-analysis of ERA-Interim[33] and extreme water levels from a global tide and surge model[34]
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