Managing Wetland Heritage - Maps and Advice
This section contains maps developed to demonstrate the importance of wetlands to the historic environment. The map below shows priority areas for the wetland historic environment.
The reasons why wetland heritage is so important (and requires specific management strategies) is because waterlogged environments offer incredible preservation of archaeological remains and palaeoenvironmental data. These are finite, fragile and non-renewable resources which cannot be re-created, but wetland enhancement and restoration can often improve the chances of long term preservation.
The areas shown on the map above are where there is the greatest potential of encountering well preserved and significant wetland archaeological and palaeoenvironmental remains. These areas are defined in characterisation data from an English Heritage funded project (Archaeological Wetlands GIS) provided by the University of Exeter, derived from soils data. The criteria that have been used to produce this map are those soils which have a high potential for the survival of deeply buried, waterlogged archaeological material, where palaeoenvironmental records of national importance are known to exist. These data were also integrated into the Wetland Vision ‘future potential for wetlands’ map, see map below.
The wetland vision project has also used data from another English Heritage funded project carried out by the University of Exeter called the Heritage Management of England’s Wetlands (HMEW). As part of this project, lists of key / types wetland sites (list A), and sites of national importance (list B) were drawn up, containing in total around 200 sites (further information about the project can be found on the HMEW website (http://sogaer.exeter.ac.uk/archaeology/research/rhmew.shtml). Lists of these sites are available on the Downloads page.
Some of the sites fall inside areas of existing wetland, whilst almost all of the rest lie in areas of future wetland potential. Achieving our goals to restore wetland habitats and create more wet areas thus has the potential to also secure the long term future of these important wetland archaeological and palaeoenvironmental sites. There is significant parity between heritage and habitats in the vision, which is aptly demonstrated by comparing the list A & B sites with wetland SSSIs. Nearly 25% of the wetland archaeological sites fall within the boundaries of wetland SSSIs; 32% within all types of SSSI. Undoubtedly, a shared, and wetter future for these sites will bring benefits to both the natural and the historic environment.
For a list of these sites as an Excel table go to the Downloads page or visit: http://www.wetlandvision.org.uk/userfiles/File/HMEW%20List%20A%20and%20B%20Wetland%20Sites%20and%20Landscapes%20Final%20Without%20GridRefs.xls
Managing wetland heritage within wetland restoration and recreation schemes
Although wetland archaeological and palaeoenvironmental deposits will benefit from the restoration or recreation of new wetland habitats (because their survival depends on high water levels which create anaerobic conditions), there are a number of important considerations that need to be taken into account in any wetland scheme. Wetlands, in the areas shown on the map above as priority areas for the historic environment are likely to contain archaeological or palaeoenvironmental resources which can, if considered early enough in a scheme design, be successfully integrated into future wetlands. If early consideration is not given to these issues, there is a potential for wetland schemes, in particular ditch re-profiling, pond or scrape creation and within upland areas grip blocking with locally ‘borrowed’ peat, to cause damage to these sites.
It is vital therefore that contact is made with local authority historic environment staff early on in any scheme design (contact details can be found at http://www.algao.org.uk/Association/Members.htm). These individuals will be able to give advice on known sites and the potential for other, unknown sites to occur in the vicinity. They may also recommend various levels of archaeological investigation that should be carried out in order to understand the site better before any intrusive ground works begin. These investigations might start with a desk-based assessment, which would consider all available, current information, and may also involve analysis of aerial photographs. More recent applications, such as Lidar (see below), which has been shown to be successful in elucidating former wetland deposits (such as palaeochannels) in river valleys, may also be recommended.
Left-hand image: Colour-shaded Lidar digital surface model of the Middle Trent at Gunthorpe. The pale grey shows the previous channels and the complex geomorphology of the floodplain. These palaeochannels are known to contain well preserved palaeoenvironmental material. Image Copyright York Archaeological Trust. Right-hand image: Harding’s alignment, a Bronze Age timber structure in the Somerset Levels, during evaluation in 2003, photograph by Richard Brunning.
Some form of ground investigation may also be needed in advance of wetland creation ground works. Hand augers, or trial pits are quick and effective assessment methods in wetland landscapes. Clearly, archaeological investigations will take both time and money, and so sufficient consideration and resourcing of these issues is essential in any wetland project.
A lot of wetland archaeology has been put at risk in recent years by drainage and ploughing, which in some areas has led to ground reduction and peat shrinkage. In places, archaeological sites sit above the water table for at least part of the year, Re-wetting these sites as part of wetland creation schemes can be beneficial to archaeological and palaeoenvironmental sites, but water levels need to be sensitively managed to ensure that these sites stay waterlogged year round; regular fluctuations of wet and dry conditions can, in some cases exacerbate degradation, putting sites further at risk. Advice on the best ways to ensure in situ preservation of archaeological sites within wetland schemes can be sought from the relevant English Heritage regional archaeological science advisor (for contact details see http://www.dur.ac.uk/eh.rsa/index.html).
Notwithstanding the issues raised above, wetland restoration and recreation can lead to significant improvements in the potential for long-term preservation of wetland heritage. The key to success is to ensure that it is considered early on in the planning for these projects.
For more information go to the Downloads page.