Rapid Coastal Zone Assessment and Beyond - research and management of the Essex Coast
Rapid Coastal Zone Assessment and Beyond - research and management of the Essex Coast
The coastline of England is around 8,500Km long about 8% of which is in Essex. The Essex coast is of great importance for nature conservation, and consequently over 80% is designated as a series of Sites of Special Scientific Importance (SSSI). The coastal zone also contains an important legacy of historic assets, of many dates and types. They are vulnerable to a wide range of threats, resulting from both development pressures and natural erosion. The latter is now thought to be accelerating as a consequence of global warming and changes in sea level.
In the early 20th century pioneering archaeological studies of the Essex coast revealed important prehistoric sequences particularly at Hullbridge and Clacton (Warren 1935 et al). Work by amateur archaeologists in the 1970s in the Crouch estuary focused renewed attention on the Essex coast. During the 1980s English Heritage funded survey work of much of the inter-tidal zone of the Essex coast carried out by Essex County Council. Known as the 'Hullbridge Survey' (Wilkinson and Murphy 1995) this work revealed a remarkable range of archaeological sites and deposits and was in effect a prototype Rapid Coastal Zone Survey. In the 1990s the work of the National Mapping Project in Essex focused attention a variety of mainly medieval and post-medieval remains on the salt marshes, and present and former grazing marsh. This work was augmented by a sustained campaign new aerial survey of the coastal zone. Building on the work of amateur investigators, at two key sites, Sales Point and Collins Creek the aerial survey revealed a series of 6 very large timber fish traps in the Blackwater estuary (Strachan 1998). Ground based survey was undertaken at the vast complex at Collins Creek (Hall and Clarke 2000), and radiocarbon dates from that site and two others in the Blackwater indicate a Middle Saxon date.
In response to the publication of Frameworks for our Past (Olivier 1996) A Regional Archaeological Research Framework for the Greater Thames Estuary (Williams and Brown 1999), was prepared by Essex County Council, GLAAS, and Kent County Council. This defines the estuary zone as running from Whitstable in Kent to Clacton in Essex, and upstream to Tower Bridge. Given its great historical and archaeological value, and the scale of the threats to its historic environment, the Greater Thames Estuary was identified in England's Coastal Heritage (Fulford et al 1997) as a national priority area for coastal zone studies.
As part of the implementation of the Research Framework and England's Coastal Heritage, further field survey was funded by English Heritage. This work comprised 1. new survey and 2. monitoring of previously recorded sites and deposits. The help and co-operation of numerous individuals and landowners is gratefully acknowledged. The help co-operation and interest in the project of English Nature has been especially useful in undertaking the fieldwork.
New Survey
Whilst the Hullbridge Survey had covered much of the Essex coast, it had concentrated largely, but not entirely, on areas with prehistoric sites and deposits. The new work was targeted and previously unsurveyed areas of the coast which were at particular risk from erosion and or development and appeared likely to contain Roman Medieval or post medieval sites and deposits. The areas examined comprised; Pyefleet and Strood Channels at Mersea, Benfleet and Holehaven creeks at Canvey and the creeks around the southern part of Foulness between the Thames and the Roach estuaries. Survey was carried out by Essex County Council Field Archaeology Unit during . In each case the work involved local groups and individuals, whose help and detailed local knowledge often proved invaluable to the success of the project. Survey of these relatively small areas recorded 264 archaeological sites and deposits (of which 96% had not previously been recorded on the Essex Heritage Conservation Record) to complement the thousands of records existing records for the Essex coast derived from earlier surveys. Sites recorded included earthworks, oyster pits, Red Hills, wrecks, relict seawalls, wharves and jetties.
Monitoring
Selected sites recorded during the Hullbridge survey in the 1980s were revisited to assess changes which have occurred since initial recording. The locations were chosen to give a range of sites, submerged land-surfaces, peat deposits, wooden structures, red hills and submerged forests in a variety of estuarine conditions and tidal ranges. At one site, Rolls Farm, in the Blackwater estuary, a programme of detailed sampling and repeat planning is taking about every three months. The aim is to provide an indication of the rate of erosion of various sites and deposits, and the occurrence of new exposures. The data will be used to inform long-term conservation and recording strategies.
The sites revisited were:-
Fenn Creek, Crouch Site 4: The site comprises a stratigraphic sequence of submerged landsurface, peats and associated deposits, and is one of the type sequences in the Crouch estuary, first recorded in 1911. The lower palaeosoil contained a flint assemblage, largely Mesolithic in date, but with some Neolithic artefacts also present.
The monitoring established that the full vertical sequence of deposits noted in the earlier studies were still present on site. However, the vertical face had retreated a maximum of 5m over a period of 19 years since the site was recorded by the Hullbridge survey. In addition shifting gravel banks had buried portions of the site. The Crouch is used for yachting, and there are a number of vessels moored on or near the site, which are also causing damage to palaeosols.
The Stumble, Blackwater estuary: The Stumble is an expanse of intertidal mudflats located between Osea Island and the mainland. A large area of submerged prehistoric landsurface, with extensive remains of Neolithic settlement with extraordinarily well preserved cereals and other plant remains and very large assemblages of pottery and flint, together with later wooden structures. The site was first located during the 1985 season of the Hullbridge survey, and was sampled by a series of small excavations in subsequent years.
The monitoring of the Stumble has identified a number of areas in which active erosion is taking place. The results clearly show that there has been vertical erosion across the flats. A greater area of old land surface has been exposed in comparison to the previous studies. Dense concentrations of Neolithic finds were located, new exposures indicated that Neolithic settlement extended well to the west of the areas recorded in the 1980s. It appears that the Neolithic site is being slowly eroded, while overlying peat deposits, associated with tree stumps, noted in the 1980s have been considerably reduced in extent. In addition there is some deposition taking place, which masks the old land surface in places. This material is course slightly silty sand, containing a high proportion of shells. However this deposit is unconsolidated and regularly shifts with the tide, thus providing little protection for the underlying deposits. To the north, towards the shore wooden structures were located. Here erosion of the salt marsh is clear to see, and it has retreated at least 10m since the OS maps were last updated. This erosion is likely to expose more of the wooden structures.
Lion Point, Jaywick: The exposure between Jaywick and Dovercourt of a later Neolithic land surface, with a range of settlement evidence, was extensive when first recorded in the early of the 20th century. Substantial fragments still survived when the Hullbridge Survey recorded the area in the mid 1980s.
The revisit showed that archaeological deposits were no longer visible at Jaywick. The area towards the shoreline, where the majority of the archaeological deposits were noted by previous surveys, beach recharge has sealed surviving archaeological deposits beneath a substantial deposit of sand.
Arlesford, Colne Estuary: When recorded by the Hullbridge survey saltmarsh in this area was eroding and slumped sediment overlay a firm clay beach, within which a number of wooden structures were located.
During the revisit five groups of timbers and a number of what appeared to be isolated posts were located, clearly different from those recorded in the 1980s. Erosion at this location is very great with severe loss of salt marsh, which has lost much of its consolidating vegetation.
Purfleet Thames Estuary: The site was recorded by the Hullbridge Survey in 1986, on the Thames foreshore to the west of the confluence of the Mar Dyke. A single bed of wood peat, up to 1m thick, contains ash, alder, yew and other trees, both roots and trunks. Estuarine sediments underlie this deposit, containing some drifted tree trunks.
The following sequence of events is suggested
- Initial sedimentation in an estuarine environment during the Thames II transgression (estuarine deposits)
- Tilbury III regression; a soil horizon forms, which later develops in woodland. Artefacts would suggest some human activity.
- Conditions became wetter, wood peat formed above the sediments.
In September 2001 the site was relocated, at that time, the wood and peat deposits at this site stretched for some 400m, for ease of description this has been split into three sections, west, east and central. The western section of the peat deposit has been eroded in comparison to the earlier plans. It contains the vast majority of the tree stools and trunks in the survey area. The peat has eroded in two distinct shelves. The first is approximately 0.2m high, close to the low water mark. This deposit then gradually rises for c. 6m, before there is another shelf, c. 0.5m high. The top of this represents the highest level of the deposit. Concrete blocks and recent silt associated with the modern sea wall mask the area to the north. The central section of the site is the most altered. It has been almost completely covered with concrete blocks, presumably placed to re-enforce the sea wall. The remains of some of the trees can be seen poking up from the blocks. The eastern section of the deposit has also been eroded. Reference to the published photographs would also suggest that the deposit was much wider when first surveyed. The exposure of peat in this section now runs for 80m, and extends for a maximum of 8m from the base of the sea wall. Exposures of the paleosol were located to the south of this peat bed. There are small roots and rootlets visible in this deposit.
Coastal erosion is clearly a major threat in this area; the exposures of peat are certainly less expensive than they were in the 1980s. Comparison of photographs would also suggest that there are now more trees exposed. In the western section of the site only 0.2m of peat remains in some areas. The tidal erosion in the area is added to by the wash from large vessels, the effects can easily be seen and felt on site.
Rolls Farm, Blackwater Estuary: Rolls Farm is the site of a multi-period complex, located on the north shore of the Blackwater about 4Km east of The Stumble. The site was first located and recorded during the Hullbridge survey in the mid 1980s. An earlier Neolithic settlement site was located at approximately -1.5mOD, on an extensive area of submerged landsurface eroding out from under the edge of the lower peat shelf, close to the level of mean low water. Nine Bronze Age brushwood structures, comprising sections of trackways and platforms were located 80m to the north of this occupation scatter. To the west of the main exposures of the Neolithic and Bronze Age site there is a substantial red hill, part of a line of such features spaced around 300-350m apart. To the south of this red hill is a line of posts part of a relict sea wall.
The Rolls Farm complex has been monitored regularly over three years (2001-3) using methodologies which were adapted to suit each site and could be easily replicated. An area of the lower peat surface and Neolithic old land surface was chosen for study, as
close as possible to that examined in the earlier survey. A transect was placed north south across this, using metal grid pegs marked with the present surface level, so that the amount of vertical erosion could be measured. The edge of the peat in relation to this grid line was planned; to allow the degree of horizontal erosion to be measured. The old land surface was divided into 1m wide collection units, again so that relative finds densities could be compared. Bronze Age wooden structures and associated creek systems were located close to the marsh edge. Two areas in which wooden structures were present were planned in detail and the present surface level was marked on the grid pegs. The red hill was planned using and the grid pegs marked, it was clear that considerable erosion had taken place. The line of posts associated with a relict sea wall was also planned.
Samples of the wooden structures were taken from top and bottom surfaces, and from wood still buried in sediment. % water content of the wood samples will be determined by drying for 12 hours at 105 degrees centigrade. Samples will be inspected macroscopically to assess induration by mineral replacement, colour (indicative of oxidation state of iron minerals), damage by boring organisms, and any algal growth. Sections will be examined microscopically, recording presence/absence of framboids and intra-cellular mineral concretions, degree of fissuring, deformation and preservation state of cellular structure.
Microscopic comparison of preservation of buried and exposed wood, from the same component will also be undertaken. Aspects to be recorded include fissuring and distortion, preservation of fine structures (e.g. vessel perforation plates) and extent of oxidation of sulphides. These studies will provide information on the destruction of the overall structure and more detailed information on degradation of cell structure. Correlation with physical parameters should indicate which are the critical factors for information loss. Both newly exposed and weathered wood samples will be taken. Measurement of the tidal flow off the site was also undertaken.
The project has supplied a range of data on long-term changes to archaeological sites and deposits in the intertidal zone. It is anticipated that the project will make a significant contribution to informing decisions on heritage management with regard to, natural erosion, development proposals and schemes of nature conservation/enhancement. A full assessment report will be submitted in March 2004.
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Hall, R. L. and Clarke, C. P. |
2000 |
'A Saxon inter-tidal timber fishweir at Collins Creek in the Blackwater estuary' Essex Archaeol. Hist. 3,125-137 |
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Fulford, M., Champion, T. and Long, A. (eds.) |
1997 |
England's Coastal Heritage: a survey for English Heritage and the RCHME, English Heritage Archaeol. Rep. 15 |
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Olivier, A. |
1999 |
Frameworks for Our Past: A review of Research Frameworks |
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Strachan, D. |
1998 |
'Inter-tidal stationary fishing structures in Essex' Essex Archaeol. Hist. 29, 274-282 |
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Warren, S. H. , Piggott, S., Clark, J. G. D., Burkitt, M. C., Godwin, H. and Godwin, M.E. |
1936 |
'Archaeology of the submerged landsurface of the Essex Coast' Proc. Prehist. Soc. 2,178-210 |
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Williams, J.J. and Brown, N.R. (eds.) |
1999 |
An Archaeological Research Framework for the Greater Thames Estuary |
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Wilkinson, T.J. and Murphy, P. |
1995 |
The Archaeology of the Essex Coast: Volume 1, The Hullbridge Survey Project E. Anglian Archaeol. 71 |
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