Abstract
Effective adaptation to sea-level rise is critical for future flood protection. Nature-based solutions including salt marshes have been proposed to naturally enhance coastal infrastructure. A gently sloping grass-covered dike (i.e. Wide Green Dike) can be strengthened with clay accumulating locally in the salt marsh. This study explores the feasibility of extracting salt-marsh sediment for dike reinforcement as a climate adaptation strategy in several sea-level rise scenarios, using the Wide Green Dike in the Dutch part of the Ems-Dollard estuary as a case study. A 0-D sedimentation model was combined with a wave propagation model, and probabilistic models for wave impact and wave overtopping. This model system was used to determine the area of borrow pits required to supply clay for adequate dikes under different sea-level rise scenarios.For medium to high sea-level rise scenarios (>102 cm by 2100) thickening of the clay layer on the dike is required to compensate for the larger waves resulting from insufficient marsh accretion. The model results indicate that for our case study roughly 9.4 ha of borrow pit is sufficient to supply clay for 1 km of dike reinforcement until 2100. The simulated borrow pits are refilled within 22 simulation years on average, and infilling is projected to accelerate with sea-level rise and pit depth. This study highlights the potential of salt marshes as an asset for adapting flood defences in the future.
Highlights
IntroductionMany studies (Borsje et al, 2011; Möller et al, 2014; Temmerman et al, 2013; van Loon-Steensma, 2015; van Loon-Steensma et al, 2016; Vuik et al, 2018) stress the capacity and importance of specific coastal ecosystems such as salt marshes and mangroves to dampen wave action and preserving foreshores
This study explores the feasibility of extracting sediment for dike reinforcements from the fringing salt marshes as a climate adaptation strategy in several sea-level rise scenarios, using the Wide Green Dike in the Dutch sector of the Dollard bay in the Ems estuary as a case study
In the lowest sea-level rise scenario, the marsh accretes in pace with sea-level rise
Summary
Many studies (Borsje et al, 2011; Möller et al, 2014; Temmerman et al, 2013; van Loon-Steensma, 2015; van Loon-Steensma et al, 2016; Vuik et al, 2018) stress the capacity and importance of specific coastal ecosystems such as salt marshes and mangroves to dampen wave action and preserving foreshores. Incorporating these systems into coastal management could reduce the need for more costly flood protection measures in the future. Nature-based flood-protection measures have emerged as a potential adaptation option
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