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Title: Definition of the Extent and Vertical Range of Saltmarsh
Author: A Hough
Author: C Spencer
Author: S Lowthb
Author: S Muddiman
Author: Environment Agency
Document Type: Monograph
Annotation: Environment Agency Project ID:EAPRJOUT_519, Representation ID: 180, Object ID: 1858
The aim of this project is to provide a concise and widely applicable definition of the vertical range of saltmarsh and to identify links between saltmarsh, coastal fauna and coastal processes. The need for such a definition has arisen during recent flood defence realignments including the set-back of defences and the creation of new areas of saltmarsh. Saltmarsh usually supports a range of plant communities, the species and communities present changing with increasing elevation of the marsh and so decreasing frequency of tidal inundation. The ecological importance of saltmarshes is recognised by their inclusion in many sites of nature conservation importance and by lower saltmarsh zones (with cord-grass, Spartina and glasswort, Salicornia) being considered as important in the European Community Habitats Directive. Prior to determining the vertical range of saltmarsh, it is necessary to derive a clear definition of ‘saltmarsh’. A widely accepted definition of the lower limit of saltmarsh was taken as the lower limit of terrestrial vegetation. The species recorded at the lowest levels of the tidal profile is cord-grass Spartina. A formula for calculating the lower limit (LL) of Spartina colonisation has been adopted after Gray et al (1989) and is presented. The upper limit of saltmarsh is marked by a transition to non-saline habitats. Previous definitions of the upper limit of saltmarsh focus on tidal submergence and the salinity of the soil, the consensus being in the region of Highest Astronomical Tide (HAT). Consequently a conservative assessment was made of actual tidal levels at Holland on Sea in relation to predicted HAT at the nearby Standard Port of Walton on the Naze. On the basis of this data, multiplication of HAT by a factor of 1.23 would provide an estimate of the upper extent of seawater influence. This would allow the development of a full transition zone providing a ‘natural’ environment within which to accommodate surge tide events and, accordingly, provide important habitat for species and communities of flora and fauna.
Publisher: Environment Agency
Subject Keywords: Salt marshesCoastal watersTerminologyStandardsBrackishwater environmentMarine environment
Extent: 21
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