LANGSTONE - CHICHESTER HARBOURS, SOLENT REGION, SOUTH COAST, UK

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1 PALAEO-ENVIRONMENTAL STUDY AREA P12 LANGSTONE - CHICHESTER HARBOURS, SOLENT REGION, SOUTH COAST, UK AN ASSESSMENT OF THE ARCHAEOLOGICAL AND PALAEO-ENVIRONMENTAL EVIDENCE FOR COASTAL CHANGE IN THE DROWNED BASINS OF LANGSTONE AND CHICHESTER HARBOURS, SOLENT REGION, UK Plate P12 Langstone Harbour, eastern Solent, UK (HR Wallingford Ltd. And Chichester District Council 1997) 1. LOCATION Langstone and Chichester Harbours are adjoined drowned river basins lying immediately east of the harbour and city of Portsmouth on the central southern coast of England (Plate P12). The two harbours are divided from each other by Hayling Island. This is an area of farmland and a modest seaside resort. 2. MODERN GEOGRAPHY Langstone Harbour and Chichester Harbour are physically connected but they are separately managed. The former is administered by the Langstone Harbour Board while the latter is managed by the Chichester Harbour Conservancy. The setting of the harbours are complicated by various administrative boundaries. Langstone Harbour lies in the county of Hampshire and its coastline is divided between the administrative boundaries of Portsmouth City Council and Havant Borough Council. Chichester Harbour spans the border between the counties of Hampshire and West Sussex; the county boundary emerging from the harbour mouth. The Hampshire shore lies within the remit of Havant Borough Council while in West Sussex the coastal zone falls within the remit of Chichester District Council. Hayling Island is part of the remit of Havant District Council and it is separated from the remainder of the district by a narrow tidal channel which is part of the drowned creek system. This channel is spanned by a short road bridge which was formerly accompanied by a single- 1

2 track railway bridge. The island is a low-lying area occupied by a farmland and a coastal village which has been expanded by bungalow development, holiday chalets and caravans. 3. THE CONTEMPORARY COASTAL PROBLEM The management problems of these two harbours are set out in the East Solent Shoreline Management Plan (HR-Wallingford 1998). There has been along history of submergence and coastal erosion within these harbours. This has been exacerbated by a die back of Spartina grass and diminution and erosion of the mud flats. The internal coastline is low-lying and mostly varies from shingle beaches to low undefended mud cliffs. There are also sections of embanked and defended pasture. In total, seven different types of coastline have been identified in this harbour and each has required its own management prescription. In Chichester Harbour a similar classification has been applied. Here the sectors of undefended coastline are notably larger. The recognition of the sevenfold shoreline classification represents an significant departure from the simple fourfold management prescriptions which have been generally adopted for most sections of the English coastline. There are conflicting interests in the management and uses of these harbours. The principal factors are nautical and recreational interests; the needs of nature conservation; the wish to protect adjacent farmland; and the prospect of rising sea-level and increased storminess. The prospects of relative sea-level rise are particularly perturbing given that the perceived local rate of downwarping in this particular region is notably high (Figures P12.1a and P12.1b). 4. KNOWN HISTORY AND PALAEO-ENVIRONMENTAL SETTING Langstone Harbour lies on the west side of the Hayling Island. It is a broad shallow inlet bordered by mudflats and a variety of modest retaining embankments. The embankments mostly protect adjoining reclaimed marshland. The western boundary of the harbour is Portsea Island. This is separated from the mainland shore in much the same way as Hayling. East of Hayling Island another narrow entrance gives access to a further drowned basin, This is Chichester Harbour a shallow inlet with three long arms penetrating arms the West Sussex coastal plain. The longest of these reaches 10km from the harbour mouth and it provides a navigable channel the margins of the Roman and medieval city of Chichester. At the head of this creek lies Fishbourne Roman palace, an exceptionally fine Roman villa which once maintained important maritime connections. The character of the drowned landscape within these harbours is best understood from the palaeo-environmental history which has recently been assembled at Langstone by Allen, Scaife and Dix (Allen & Gardiner, forthcoming). On the open coast of this region other pioneer work has been carried by Wallace (who has sought underwater evidence for the former character of the shoreline prior to the advance of the sea in historic times (Wallace 1999). Allen, Scaife and Dix summarise the palaeo-environmental setting as a single biological system comprising connected tidal basins drained at low water by a system of channels. The bedrock of the harbour is varied where it crosses the strike of the Portsdown anticline. The oldest strata is represented by the Upper Chalk which underlies the innermost northern reaches of the harbour. Passing southwards the harbour crosses the rocks of the Lower and Upper London Tertiary Groups, the principal components being the Reading Beds and the London Clay. Near the harbour mouth the bedrock gives way to sandstones of the Lower and Middle Eocene Bracklesham Group. The main channel systems within the harbours largely follow old incised palaeo-channels of Pleistocene and Early Holocene date. Off-shore, peats and sediments concealed within these channels relate to a Solent Transgression which has been attributed to a principal phase of sea-level rise between 8000 and 6000 years BP (Nicholls, 1987; Allen & Gardiner forthcoming). 5. ARCHAEOLOGICAL AND PALAEO-ENVIRONMENTAL STUDIES AND POTENTIAL The archaeological potential of Chichester Harbour was first recognised in 1982 when an exploratory coastal survey was carried out in the West Sussex arm of the harbour system 2

3 (Cartwright 1984). In 1993 Hampshire County Council turned its attention to Langstone Harbour and a collaborative survey project was set up which was to include Wessex Archaeology and the University of Portsmouth. Underwater inspections were also commissioned from the Hampshire and Wight Trust for Maritime Archaeology. Like the Wootton-Quarr survey in the Isle of Wight some difficulty was experienced in differentiating between cohesive archaeological sites in the intertidal zone and individual component structures. Nevertheless, some 26 recognisable sites were identified and mapped while a number of these were also recognised to be broad archaeological areas in which many more individual features or structures were present. Coring and sub-bottom prospection was also carried out over the submerged palaeo-channels and this enabled a reconstruction to be proposed for the Holocene evolution of the harbour system. See Figures P12.2a, P12.2b and P THE DESK-TOP ASSESSMENT SCORES A total of 60 sites were identified offering a potential contribution to the understanding of coastal, environmental and climatic change (see Appendix P12.1). 7. CURRENT APPROACH TO IDENTIFICATION AND PROTECTION OF THE ARCHAEOLOGICAL RESOURCE The identification of the archaeological resources within these linked harbours has followed separate lines of enquiry. The targeted interdisciplinary survey in Langstone Harbour has identified prehistoric and historic structures in the intertidal zone which are subject to threat of diminution and loss. Some of these threats are caused by natural processes including those of wave attrition, bed erosion, the die-back of Spartina grass and diminution of the mud banks and the intra-harbour islands. Most of these processes are similarly damaging to ecology of the harbours and particular concern has been expressed over threat to designated bird habitats. These are issues which are currently being examined by the Langstone Harbour Board. The results of the Langstone Harbour archaeological survey has yet to reach final publication and the newly surveyed sites have yet to be integrated into the Hampshire Sites and Monuments Record. For this reason the LIFE assessment is the archaeological resources of the harbour has been based upon the logged desk-top knowledge held within the SMR and not the sum of the new field information which has been gained through the recent survey. This omission has been deliberate for like the recent intertidal survey at Wootton-Quarr it has allowed a distinction to drawn between the perceived resource and the greater body of information which demands interpretation in the field. While archaeological and palaeo-environmental fieldwork has progressed in Langstone Harbour since 1994, an East Solent Shoreline Management Plan has been compiled (HR- Wallingford 1997). This plan has reviewed the geological evolution of the harbours and the coastline, observing that various organic deposits in the old river channels within the harbours can be related to ancient sea-levels. It also notes that traces of earlier relict beach bases have been identified off-shore in Bracklesham and Hayling Bays. The plan concludes that marked changes have occurred in the historic period (the last 2000 years) and that during this time the former barrier beaches in Bracklesham and Hayling Bays have been driven progressively shore-wards. Much of this hypothesis concurs with the pioneering work of Wallace (1999) who has used underwater observations and the evidence offered by place-names to propose the configuration of the coast in Saxon and medieval times. The shoreline management plan also acknowledges that archaeological sites within this region are a finite and non-renewable resource and that further work and identifying, mapping and classifying sites is needed. Remarkably, the plan seems to consider that this work is only necessary to ensure survival. No mention is made of the need to interrogate archaeological, or indeed palaeo-environmental, evidence. This is surprising given that there is a need to establish the precise timescale and magnitude of the very considerable coastal changes which are so weakly understood during and before the past 2000 years. Where evidence for the historical 3

4 evolution of the harbour system is presented in the plan it is heavily focussed upon the history of land reclamation. It is surprising to find that no reference is made to the research of the Langstone Harbour archaeological survey which was on-going during the compilation of the management plan. In the conclusions of the Langstone Harbour survey the contribution of archaeological and palaeo-environmental evidence to the reconstruction of the Holocene evolution of the harbour is firmly seized. The deep incised palaeo-channels within the floor of harbour are seen to be freshwater peat environments during Late Mesolithic times (c cal BC). It is calculated that at this time the contemporary coastline still lay some 30km to the south.. By Late Neolithic/Early Bronze Age times (c cal BC) the shoreline still lay some distance to the south but the sea now seems to have been exercising its tidal influence over at least some of the rivers of this region. Consequently, the channels within the Langstone basin were now acquiring a more shallow gradient with the help of accruing silts. The project team note an absence of adequate peat samples and pollen evidence for this particular period. This emphasises the need to persist in the monitoring and pursuit of further evidence within the eroding environment of the harbour. By the Middle-Late Bronze Age (c cal BC) the streams of the Langstone basin were becoming choked with peat and sediment and there is some evidence to suspect the beginnings of saltmarsh. The low-lying areas of the basin now accommodated fresh water pools, mires and alder carr while drier land supported grassland and poor meadow with stands of oak, alder yew and willow. This environment was an attractive habitat for human communities who had now become sufficiently active within the area to establish a cremation cemetery. The effective marine incursion into the Langstone basin and the initial forming of the harbour is now suspected to have taken place either in the Iron Age or the Romano-British period. The research team emphasise that this advance was achieved by progressive erosion rather than drowning. The best definition that can currently be offered is that... Langstone was not a marine inlet of any size until about the Iron Age (after 800BC). This observation seems to be equally applicable to Chichester Harbour which gained supremacy as a focus for human occupation in the Late Iron Age and Early Roman periods when its advantages as a maritime route seem to have been fully realised (Allen & Gardiner, forthcoming). 8. CURRENT APPROACH TO IDENTIFICATION AND PROTECTION OF THE PALAEO- ENVIRONMENTAL RESOURCE The coastal change chronology currently assembled for Langstone Harbour has been based upon evidence gained from marine palaeo-mollusca, sediments and peats contained within the eroding channels of the harbour. A vital source palaeo-environmental information has been the pollen content of the peats but the survey report also records that difficulties were encountered in locating sufficient peat deposits in the right stratigraphic and chronological contexts. This has impaired the chronological coverage of the pollen record. Elsewhere the report observes that disturbances across the harbour, such as pipes and thrust-bored tunnels, pose a potential threat and that the narrow deposits of peat in buried channels are susceptible to these activities. Oyster trawling and dredging are common activities in the harbour and it is surprising to find that these activities have not prompted a case for monitoring. 9. SUCCESSES AND PROBLEMS IDENTIFIED BY THE LIFE PROGRAMME The use of a high resolution global positioning system (GPS) was an outstanding advantage to the Langstone Harbour archaeological team. This overcame many of the severe impediments of measuring and recording in intertidal mud. Accessing remote locations during the restricted times offered by a seasonally controlled tight tidal window. was a further practical difficulty. The use of a global information system (GIS) within the Department of Geography at the University of Portsmouth was another distinct advantage. Further successes were achieved where notable 4

5 contributions were made by volunteer recorders, particularly the divers of the Nautical Archaeological Society who were able to extend direct observations underwater. Where problems were perceived they concerned three issues. The high level of habitat conservation required for the wild bird colonies in Langstone Harbour was not always compatible with the management needs for the archaeological resources. Some of the latter required monitoring visits and interventions which could be potentially detrimental to the bird habitats. A second issue concerned the continuing exposure and destruction of archaeological and palaeo-environmental material within the harbours by natural processes. While the field survey commissioned by Hampshire County Council had identified this problem no clear remit or provision had been set within local government to enable regular monitoring and recording to proceed. This problem had also been identified in the Isle of Wight coastal Audit (Loader & Basford 1999) and in the Northumberland coastal survey (NCC 1994) where it had been observed that: single surveys could offer little more than a preliminary inspection of the archaeological resource and the problems affecting it and that: regular programmes of fieldwork are required if a full and accurate picture of the coast is to be generated. Such programmes should be devised in such a way that they can be repeated over significant periods of time, allowing for observations in different conditions and at different times of the year (paraphrase). The third problem identified in this study has been perceived to be a lack of communication between the commissioners and compilers of the shoreline management plan and the archaeological and palaeo-environmental researchers engaged in innovative coastal field survey. This review has concluded that both of these tasks had generally proceeded in isolation. Some of the contributory reasons to this problem seem to stem from weak guidelines on the historic environment given in Central Government s advice on the preparation of shoreline management plans (MAFF 1995; see also review by Wessex Archaeology 1999). Other contributory factors might be attributable to the separate funding and administrative frameworks for coastal management and coastal archaeology. Where coastal archaeological survey was initiated in this instance, the initiative came from Hampshire County Council acting as the Strategic Planning Authority and the host of the County Sites and Monuments Record. Where objectives were defined within this survey they were essentially guided by Planning Policy Guidance on archaeology (PPG16) and Planning Policy Guidance on Coastal Planning (PPG20). Neither of these guidelines were cross-referenced to the need to identify and interrogate archaeological and palaeo-environmental evidence pertinent to the nature, scale and pace of coastal change or the planning of appropriate coastal defence policies. Where shoreline management policies were defined on this coast the initiative lay with the District Councils acting in their role as operating authorities for the purpose of coastal protection. The documents of the Shoreline Management Plan acknowledged the collective participation of these councils as well as the Environment Agency and English Nature but they have not included Hampshire County Council, West Sussex County or English Heritage. 10. SOCIAL INCLUSION AND COMMUNITY INVOLVEMENT Like other coastal projects cited in the Solent region the Langstone Harbour survey drew notably upon the voluntary participation of underwater recorders from the Nautical Archaeological Society as well as the observations and assistance provided by the fishing community. The voluntary underwater survey activity was co-ordinated by the Hampshire and Wight Trust for Maritime Archaeology and the modest staff of Nautical Archaeological Society. Both of these organisations were charitable bodies dependent upon voluntary donations. Considerable time was expended by the professional archaeological staff of these bodies in organising survey tasks as training events. While improving public benefit from participation this type of involvement incurred penalties concerning loss of efficiency in the deployment of professional time. Where on-going monitoring is required in the coastal zone this is a common problem where no provision has been made to sustain and satisfy public interest. 5

6 11. CONCLUSION AND KEY ISSUES In summary, this case study exemplifies some of the missed opportunities which can arise when divergent interests and energies are expended on two lines of coastal research while both are operating without the benefit of a common data-sharing forum. Nevertheless, the prompt production of the East Solent Shoreline Management Plan with its option for a five-yearly review, and the impending publication of the Langstone Harbour archaeological report (Allen & Gardiner, forthcoming) augurs well for a well co-ordinated approach by archaeologists, palaeoenvironmental scientists and coastal managers in the future. The promotion of public participation in the harbour survey project was temporarily rewarding and beneficial to the community but a disturbing lacuna arose when a need for on-going monitoring could not be fulfilled once the initial survey project had been concluded. This problem of sustaining the expectations of the public, averting disappointment amongst participants and addressing the on-going process of future losses has yet to be resolved. Its root lies in the lack of a clear statutory remit for the archaeological services of local authorities. Where long-term timetables of coastal changes and the sustainability of the historic environment need to be grasped, a lack of a specific remit within these authorities admits the processes of prevarication, hesitancy and delay where fieldwork. monitoring, analysis and mitigatory measures are required The archaeological survey of Langstone Harbour is an exemplary coastal survey project. Ii is particularly notable because it represents a well-focussed study of past human experience of coastal change. It has been conducted in an area which remains susceptible to flooding and coastal erosion and it has been essentially commissioned by the former strategic planning authority for the region. The archaeological and palaeo-environmental studies in Langstone Harbour make an interesting comparison with the neighbouring natural harbour of Portsmouth. Here, the imposition of environmental stress by human impacts are higher and the opportunities for flooding and damage to property are also increased. Despite these criteria the record of monitoring, field assessment, intervention and analyses has been very weak. in the intertidal and sub-tidal zones of the harbour. The LIFE case-study of Portsmouth Harbour identifies a marked inconsistency in the recognition and protection of the historic environment where archaeological resources extend beyond the tidal boundary. This is exemplified at the Roman shore fort at Porchester where the area designated for protection as a Scheduled Ancient Monument is restricted to terrestrial limits. Archaeological evidence gathered from past dredging events in the harbour and analogy with neighbouring historic anchorages in the Solent, at Yarmouth Roads and Mother Bank, suggest that the preservative qualities of the seabed make the intertidal and sub-tidal environs of the fort an area which deserves and equal level of protection. A weakness can be identified in the current wording of the Ancient Monuments and Archaeological Areas Act This Act provides protection for a monument or archaeological site only within the area of its proven extent. The example of Porchester shows that there is need to provide protection over an area which is sufficient for the effective protection of an ancient monument and its setting. This latitude should include both the intertidal and sub-tidal zones. 12. BIBLIOGRAPHY Allen, M. J., & Gardiner J., forthcoming. Our changing coast; an interdisciplinary survey of Langstone Harbour, Hampshire. Council for British Archaeology, monograph. Cartwright C., Field survey of Chichester Harbour 1982, Sussex Archaeological Collections 122, HR-Wallingford East Solent Shoreline Management Plan. (A commissioned report for the coastal operating authorities). 6

7 MAFF Shoreline management plans; a guide for coastal defence authorities. Ministry of Agriculture, Fisheries and Food/Welsh Office. Nicholls R. J., Evolution of the upper reaches of the Solent River and the formation of Poole and Christchurch Bays in K.E. Barber (ed.), Wessex and the Isle of Wight - field guide. Quaternary Research Association. Cambridge ACKNOWLEDGEMENTS The authors gratefully acknowledge the support of Dr Mike Allen and Dr Julie Gardiner of Wessex Archaeology for the use of their forthcoming detailed study of Langstone Harbour. 7

8 Based upon the 1991 Ordanance Survey 1:50,000 scale Landranger map with the permission of the Controller Based upon the 1991 Ordanance Survey 1:50,000 scale Landranger map with the permission of the Controller of Her Majesty's Stationary Office, Crown copyright. HR Wallingford AL of Her Majesty's Stationary Office, Crown copyright. HR Wallingford AL Archaeological and palaeoenvironmental sections and bore-holes. Approximate extent of potential flood area (present day 1:200 year sea level) Moderate Low 14th century land-loss N Erosion risk Approximate extent of potential flood area (present day 1:200 year sea level) N Moderate Low Figure P12.1a Flood and erosion risk in Langstone Harbour. The location of palaeo-environmental investigations into earlier drowned land surfaces is also indicated (HR Wallingford Ltd. and Chichester District Council 1997). Erosion risk Figure P12.1b Flood and erosion risk in Chichester Harbour as recognised in the Eastern Solent Shoreline Management Plan.The historically documented loss of land in the early 14th century is also indicated (HR Wallingford Ltd. and Chichester District Council 1997).

9 N N Scheduled Ancient Monuments Site of archaeological / historic interest Area of multiple sites Area of outstanding natural beauty scale (km) Figure P12.2a Historic sites and landscape conservation areas, Langstone Harbour (HR Wallingford Ltd. and Chichester District Council 1997). Figure P12.2b Historic sites and landscape conservation areas, Chichester Harbour (HR Wallingford Ltd. and Chichester District Council 1997).

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11 Plate P12a Cultural items of all ages are strewn on the seabed of ancient anchorages at the approaches to Europe s historic ports and harbours. The content, age and condition of these items can be an index of past depositional conditions, bed movement and coastal change. Fishing and navigational dredging can be readily destructive of these resources. With good liaison and practical inducements to report, the loss of this information can me mitigated. 8