Abstract
Abstract. Coastal lowlands and estuaries are subjected to increasing flood risks during storm surges due to global and regional changes. Tidal wetlands are increasingly valued as effective natural buffers for storm surges by dissipating wave energy and providing flood water storage. While previous studies focused on flood wave attenuation within and behind wetlands, this study focuses on the effects of estuarine wetland properties on the attenuation of a storm tide that propagates along the length of an estuary. Wetland properties including elevation, surface area, and location within the estuary were investigated using a numerical model of the Scheldt estuary (Belgium, SW Netherlands). For a spring tide lower wetland elevations result in more attenuation of high water levels along the estuary, while for a higher storm tide higher elevations provide more attenuation compared to lower wetland elevations. For spring and storm tide a larger wetland surface area results in a better attenuation along the estuary up to a threshold wetland size for which larger wetlands do not further contribute to more attenuation. Finally a wetland of the same size and elevation, but located more upstream in the estuary, can store a larger proportion of the local flood volume and therefore has a larger attenuating effect on upstream high water levels. With this paper we aim to contribute towards a better understanding and wider implementation of ecosystem-based adaptation to increasing estuarine flood risks associated with storms.
Highlights
Deltas and estuaries worldwide are subjected to an increasing risk of flooding disasters
In this paper we present a 2-D hydrodynamic model that has been calibrated and validated for tides and storm tides in the Scheldt estuary (Belgium and SW Netherlands), and use the model to investigate the effect of scenarios with different intertidal wetland properties, including wetland elevation, size and location along the estuary, on along-estuary attenuation of tides and storm tides
All these studies focussed on the attenuation of storm surges that propagate through coastal wetlands, which we call here within-wetland attenuation, while to our knowledge few scientific studies exist on the effects of intertidal wetland properties on storm tide attenuation along estuaries, a mechanism we call here along-estuary attenuation (Fig. 1)
Summary
Deltas and estuaries worldwide are subjected to an increasing risk of flooding disasters. Global climate warming accelerates sea level rise (Church et al, 2013) and there is growing consensus that it increases the intensity of storms and associated storm surges (Emanuel, 2005; Webster et al, 2005; Knutson et al, 2010; Lin et al, 2012; Grinsted et al, 2013) These global change effects combined with regional changes, including growing coastal populations and land subsidence, expose low-lying deltas and estuaries to increasing storm surge flood risks (Hanson et al, 2011; Hallegatte et al, 2013). An increasing number of studies shows that these wetland ecosystems can reduce the height of storm surges due to their dense vegetation and the friction they exert on landward propagating flood waves
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