Saltmarsh Change Summary:
The Saltmarsh Change layer shows the recent change in saltmarsh extent across England, since a baseline survey was completed in 2006 to 2009.
Dataset Descpription:
The Saltmarsh Change layer was created by comparing the 'baseline' version of Saltmarsh Extent with its 'most recent' version. The baseline version was mapped from aerial imagery, primarily collected between the 2006 and 2009. The most recent version is based on imagery between 2006 and 2019. Since the production of the baseline (in 2006-09), approximately 80% of England's saltmarsh has been remapped using later imagery. This dataset allows users to easily identify the differences between the two versions of the mapped extent, and identifies where areas of gain and loss have occurred. Each feature within the dataset contains one of the following attribute classes:
• Gain
• Loss
• No Change
• Not Remapped
Limitations & Other Guidance:
The dataset does include some, but not all marsh, created at recently breached managed realignment sites. Sites such as Steart Marshes, Salt Fleet Flats Reserve and Allfleet's Marsh have been included. However, other sites such as Medmerry (Sussex coast), Greatham (Tees Estuary) and Hesketh Out Marsh (Ribble Estuary) are yet to be included. It is intended that all such sites will be included in an update to be published in spring 2021.
Users should refer to the 'Year' attributes for the timing of image capture of both the 'baseline' and 'most recent' survey.
Users should bear in mind that some instances of change may be a result of the seasonal differences in the timing of image capture. The month of image capture of any feature can be identified using the attribute table.
Further Information:
The dataset provides valuable evidence of where saltmarsh is accreting and eroding across the whole of England, which is vital for flood and coastal risk management, and for ecological monitoring and reporting.
Saltmarsh extent has been interpreted (using a consistent technique) from aerial imagery, primarily collected through the Regional Coastal Monitoring Programmes, and other estuarine and coastal strategy monitoring programmes. The demarcation of the landward extent is aimed to be the point at which the upper most zones give way to terrestrial plants (often at the foot of a seawall), and where saltmarsh plants become ≤5% of the predominantly terrestrial community. At the seaward end, the final demarcation is aimed to be where the saltmarsh vegetation cover has become so sparse it only represents <5% of the ground cover. Mapped extents have been ground-truthed using data collected by the Environment Agency and Natural England. Attribution statement: © Environment Agency copyright and/or database right 2015. All rights reserved.