Saltmarsh restoration: a sedimentary perspective

Coastal wetlands are globally important systems, offering a range of ecosystem services including wildlife habitat and coastal flood defence. However, these environments are threatened by erosion and rising sea levels, along with reclamation and degradation by anthropogenic activity. To compensate for the loss of wetland habitat, such as saltmarsh, and to improve the sustainability of flood defences, coastal engineers and managers have implemented a number of schemes to re-create, restore and construct new intertidal habitat. This includes an approach known as managed realignment and involves re-locating the land / sea border by de-embanking, lowering or breaching flood defences, thereby allowing inundation of the coastal hinterland. In the UK, nearly 60 managed realignment sites have been constructed, however there is growing evidence that saltmarshes in these sites have lower biodiversity and ecosystem service delivery than natural sites. This may have consequences for the level of coastal flood defence and ecosystem functioning, with variations in the physical sediment characteristics, morphological evolution, topographic complexity, sub-surface hydrology and geochemistry proposed as possible explanations for these differences. In this presentation I will share the findings from almost ten years of research into the post-breach sedimentological development of managed realignment sites, along with an assessment of unmanaged realignment; an alternative form of saltmarsh restoration which may mitigate some of the issues found in managed realignment sites. I will also share preliminary findings from my on-going research into other methods of saltmarsh restoration to provide an evaluation of our current approach in the UK from a sedimentary perspective, and identify where further research is required.