Sediment deposition is one of the key mechanisms to counteract the impact of sea level rise in tidal freshwater wetlands (TFWs). However, information about sediment deposition rates in TFWs is limited, especially for those located in the transition zone between the fluvially dominated and tidally dominated sections of a river delta where sedimentation rates are affected by the combined impact of river discharge, wind, and tides. Using a combined hydrodynamicmorphological model, we examined how hydrometeorological boundary conditions control sedimentation rates and patterns in a TFW located in the Rhine-Meuse estuary in the Netherlands.The modelling results show that net sedimentation rate increases with the magnitude of the river discharge, whereas stronger wind increasingly prevents sedimentation. Sediment trapping efficiency decreases for both increasing river discharge and wind magnitude. The impact of wind storms on the trapping efficiency becomes smaller for higher water discharge. The spatial sedimentation patterns are affected by all controls. Our study illustrates the importance of evaluating both the separate and the joint impact of discharge, wind, and tides when estimating sedimentation rates in a TFW affected by these controls. Such insights are relevant to design measures to reactivate the sedimentation process in these areas. Wetlands also provide various ecosystem services to human wellbeing, for example, the provision of food (e.g., fish) and recreational opportunities, and regulating water quality (Millennium Ecosystem Assessment, 2005). TFWs are vulnerable to sea level rise (SLR) through both increased risk of inundation and possible salt water intrusion (e.g., Anderson & Lockaby, 2012;Burkett & Kusler, 2000).Enhanced sedimentation is considered an effective strategy to prevent further wetland loss in case horizontal wetland migration to higher zones is not possible (Darke & Megonigal, 2003;Kirwan & Megonigal, 2013;Paola et al., 2011). Previous research has indicated that sedimentation rates of wetlands may in general be controlled by factors such as the supply of fluvial sediments (Neubauer, Anderson, Constantine, & Kuehl, 2002;Siobhan Fennessy, Brueske, & Mitsch, 1994), tide, wind (Delgado, Hensel, Swarth, Ceroni, & Boumans, 2013Orson, Simpson, & Good, 1990), vegetation cover (Brueske & Barrett, 1994Darke & Megonigal, 2003;Nardin & Edmonds, 2014;Nardin, Edmonds, & Fagherazzi, 2016;Pasternack & Brush, 2001), wetland shape properties such as average depth/wetland elevation, distance to tidal creeks, and wind fetch lengths (Hupp & Bazemore, 1993;Hupp, Demas, Kroes, Day, & Doyle, 2008;Mitsch et al., 2014;Temmerman, Govers, Wartel, & Meire, 2003b). --------------------------------------------------------------------------------------------------------------------------------This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Tidal freshwater wetlands are threatened by climate change, especially by rising sea levels. Until now, research in these wetlands has focused mostly on determining historical and present-day accretion rates without analysing the influence of climate change on future developments. We study a recently constructed freshwater wetland under influence of tides, wind, and riverine discharges and carry out a scenario analysis to evaluate the impact of climate change on morphodynamics. We use a numerical model that describes the hydrodynamics and morphology in the study area and includes the impact of vegetation and carry out transient scenario runs for the period 2015-2050 with gradually changing boundary conditions. We conclude that the simulated accretion rates are significantly lower than the rate of sea level rise, meaning that the wetland will gradually convert to open water. We also find that the morphological changes can largely be attributed to morphological stabilization of the constructed wetland and not to climate change. Wind plays an important role through resuspension and redistribution of fine sediment, and neglecting it would lead to a significant overestimation of accretion rates on the flats. Depending on wetland location and properties, flooding and sedimentation in TFWs are governed by the combined influence of tides, riverine discharges, and wind (Verschelling, Van der Deijl, Van der Perk, Sloff, & Middelkoop, 2017). Drowning mechanisms and measures that mitigate the impact of climate change (CC) in these areas, therefore, differ significantly from those in coastal areas, especially if CC also impacts river discharges and wind. Most research in TFWs has focused on understanding historical and present-day sedimentation rates and patterns and has shown that sedimentation rates depend on factors -----------------------------------------------------------------------------------This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
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