Print Email Facebook Twitter Salt marshes for flood risk reduction Title Salt marshes for flood risk reduction: Quantifying long-term effectiveness and life-cycle costs Author Vuik, V. (TU Delft Coastal Engineering; HKV Consultants) Borsje, Bas W. (University of Twente) Willemsen, Pim W.J.M. (University of Twente; Universiteit Utrecht; Deltares) Jonkman, Sebastiaan N. (TU Delft Hydraulic Structures and Flood Risk) Date 2019-04-01 Abstract Flood risks are increasing worldwide due to climate change and ongoing economic and demographic development in coastal areas. Salt marshes can function as vegetated foreshores that reduce wave loads on coastal structures such as dikes and dams, thereby mitigating current and future flood risk. This paper aims to quantify long-term (100 years) flood risk reduction by salt marshes. Dike-foreshore configurations are assessed by coupled calculations of wave energy dissipation over the foreshore, sediment accretion under sea level rise, the probability of dike failure, and life-cycle costs. Rising sea levels lead to higher storm waves, and increasing probabilities of dike failure by wave overtopping. This study shows that marsh elevation change due to sediment accretion mitigates the increase in wave height, thereby elongating the lifetime of a dike-foreshore system. Further, different human interventions on foreshores are assessed in this paper: realization of a vegetated foreshore via nourishment, addition of a detached earthen breakwater, addition of an unnaturally high zone, or foreshore build-up by application of brushwood dams that enhance sediment accretion. The performance of these strategies is compared to dike heightening for the physical boundary conditions at an exposed dike along the Dutch Wadden Sea. Cost-effectiveness depends on three main factors. First, wave energy dissipation, which is lower for salt marshes with a natural elevation in the intertidal zone, when compared to foreshores with a high zone or detached breakwater. Second, required costs for construction and maintenance. Continuous maintenance costs and delayed effects on flood risk make sheltering structures less attractive from a flood risk perspective. Third, economic value of the protected area, where foreshores are particularly cost-effective for low economic value. Concluding, life-cycle cost analysis demonstrates that, within certain limits, foreshore construction can be more cost-effective than dike heightening. Subject Flood riskLife-cycle costsNature-based solutionsSalt marshSea level rise To reference this document use: http://resolver.tudelft.nl/uuid:c8e8d1aa-78ea-4839-bab0-1d658e8d7ea8 DOI https://doi.org/10.1016/j.ocecoaman.2019.01.010 Embargo date 2019-08-01 ISSN 0964-5691 Source Ocean & Coastal Management, 171, 96-110 Bibliographical note Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public. Part of collection Institutional Repository Document type journal article Rights © 2019 V. Vuik, Bas W. Borsje, Pim W.J.M. Willemsen, Sebastiaan N. Jonkman Files PDF 1_s2.0_S0964569118307026_main.pdf 7.25 MB Close viewer /islandora/object/uuid:c8e8d1aa-78ea-4839-bab0-1d658e8d7ea8/datastream/OBJ/view