The impact of climate change on the morphology of a tidal freshwater wetland affected by tides, discharge, and wind

Abstract

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.

Enhancing effectiveness of tidal river management in southwest Bangladesh polders by improving sedimentation and shortening inundation time

“…Depoldering and controlled flooding are not new concepts. The Netherlands, the inspiration for the polders in the coastal areas of Bangladesh, has used depoldering in the 'Room for the River' project to facilitate river discharge for flood prevention (van Staveren et al, 2014, van der Deijl et al, 2018, Verschelling, 2018. Controlled flooding is also used in the Mekong delta to reduce the peak discharge in the river and bring sediments and nutrients to the flood plain (van Staveren M.F.…”