The Adur Estuary represents a regionally rare and significant area of saltmarsh in Sussex, southern England. The estuarine plant communities are unusual due to the relative scarcity of cord-grass, Spartina spp. The large area of intertidal mudflats within the estuary are important for a variety of wading birds. Saltmarsh and mudflat habitat within the Adur Estuary exists due to a complex relationship between sediment supply, tidal action, wind-wave and elevation relative to tidal inundation. In order to compensate for habitat loss directly caused by construction of flood defence tidal walls in 2019, and indirectly through coastal squeeze, the Shoreham Adur Tidal Walls (SATW) Scheme has constructed an intertidal habitat restoration area of 1.32 ha. This area of salt marsh forms part of Adur Estuary Site of Special Scientific Interest (SSSI) which is a designation of national importance. The Adur Estuary SSSI represents a significant proportion of the saltmarsh extent between Chichester and Sandwich Bay. The existing vegetation within the site comprises pioneer communities consisting of open areas with extensive mudflat channels and Salicornia europaea, and Aster tripolium, merging into lower marsh communities with Puccinellia maritima. Halimione portulacoides is the most abundant species over the middle of the marsh, while the upper saltmarsh areas are dominated by Atriplex spp., with a vegetative cliff along its low water edge, grading into a number of grazing marsh communities dominated by Elytrigia spp. These communities form a self-sustaining ecosystem that are covered on a daily basis by all tides with the exception of low spring tides, when only part of the lower community is submerged.
There is a diverse network of mudflats, creeks and pans within the estuary. The mudflat creeks perform an important function by absorbing tidal energy and delivering crucial sediment to develop the saltmarsh community.
The aim of this project is to evaluate the evolution of saltmarsh habitat from ecological and sedimentary perspectives following construction of the tidal walls, using field surveys, drones, elevation monitoring, and computer modelling. The colonisation of the compensatory habitat has already seen the establishment of pioneer species, as these are generally the quickest to colonise and are prevalent in the site. Future sea level rise will also impact saltmarsh zonation and this should be included in the modelling.
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