ENVIRONMENT AND LAND USE IN THE LOWER LEA VALLEY c.12,500 BC—c.AD 600: INNOVA PARK AND THE FORMER ROYAL ORDNANCE FACTORY, ENFIELD Kevin Ritchie, Michael J Allen, Catherine Barnett, Nicholas Cooke, John Crowther, Rowena Gale, Michael Grant, Grace P Jones, Stephanie Knight, Matt Leivers, Jacqueline I McKinley, Richard I Macphail, Lorraine Mepham, Robert G Scaife, Chris J Stevens and Sarah F Wyles SUMMARY INTRODUCTION Excavations revealed aspects of the changing Archaeological investigations were carried environment of the floodplain of the Lower Lea Valley out on land at the former Rammey Marsh from the Late Glacial to the early historic periods. Sewage Treatment Works (Site ; centred Evidence for land use mostly related to activity on NGR 536800 99200) and the former along the western bank of a former stream. Wooden Royal Ordnance Factory (Site 2; centred revetments (the earliest dated one being Early Bronze on NGR 537300 98600) in the London Age), ditches, gullies, pits, a droveway, land surfaces Borough of Enfield (Fig 1). Both study sites and associated ‘midden-like’ deposits provided evidence are located upon the River Lea floodplain, for seasonal or periodic use and, arguably, habitation, with Site west of the present course of the dating principally from the Middle to Late Bronze Age. River Lea, and Site 2 lying east of the River The economy of the site was focused on stock rearing, Lea Navigation and between two channels grazing and the exploitation of river resources. The of the present River Lea. The floodplain ‘midden-like’ deposits, identified as interleaved layers of lies at between 16m and 20m aOD, with silt, sand and gravel containing pottery, human and the valley side rising sharply to 30m aOD animal bone, as well as flint and bone tools, and other on the western edge and gradually to 50m objects, may be compared with similar, more extensive aOD on the eastern side. The underlying deposits from sites such as Runnymede Bridge, Surrey. geology is principally composed of Eocene There was no evidence of further activity until the London Clay, with the overlying deposits on Late Iron Age to early Romano-British period, when the valley floor mapped as Kempton Park a series of fish-traps, pits and a structure within an and floodplain gravels, with sands and gravel enclosure indicate renewed, again possibly seasonal, forming a series of river terraces. use of the area. An evaluation on the site of the former The redevelopment of Site took place in Royal Ordnance Factory produced evidence for the several stages between 1997 and 2001. Seven continuing importance of waterfront management in evaluations were undertaken, comprising 89 this floodplain environment, in the form of the wooden trenches, followed by five phases of targeted revetment of another stream channel, radiocarbon open-area excavation. The Phase I—III and dated to the late or post-Roman period. V excavations were located in the north of 2 Kevin Ritchie et al Fig 1. Site location, also showing previous investigations and finds Environment and Land Use in Lower Lea Valley c.12,500 BC—c.AD 600: two sites in Enfield 3 Site 1, an area now known as Innova Park. Allison et al 1952), and Enfield Lock (Bedwin The Phase IV excavation was located in the 99; Chambers et al 1996; Site 2, Fig 1). south of Site 1, now Innova Science Park During the middle and later Holocene (Wessex Archaeology 2003). A two-phase extensive aggradation of the floodplain archaeological evaluation was undertaken occurred through overbank flooding and at Site 2 (in April 997 and February 998 sedimentation on the valley floodplain. (Wessex Archaeology 1999)), which allowed During this phase the gravel topography the design of a mitigation scheme following would have become submerged and lost. which the site was redeveloped without Channel stability may have been maintained further excavation. Previous investigations but small tributary channels would have at Site 2 were undertaken by Essex County formed across the floodplain. Marshland Council (1989). Sediments, molluscs and development may have occurred during pollen were analysed from a number of certain parts of this phase (Bates 1997). boreholes, with radiocarbon dating also During the Bronze Age the floodplain was applied (Bedwin 99; Chambers et al 1996). largely open and maintained by grazing, This indicated a sedimentary sequence init- with probably larger but fewer watercourses iated in the early Holocene. within the Lea Valley. These channels were revetted and their course artificially defined palaeoenvironmental if not modified in places. In the Iron Age BackGround and Romano-British phases the floodplain remained open, with further modification The Lea Valley is well known for its Pleistocene of the natural watercourses. Further north deposits (Gibbard 1994). Prior to the Late (Carthagena Lock) the river channels eroded Glacial Maximum (when glaciation reached older deposits, resulting in material being its maximum extent, c.8000 BC), high-energy flushed down the valley. Seasonal flooding fluvial gravel deposition occurred punctuated occurred, but sedimentation was limited. by phases of lower energy organic sediment accumulation in a series of floodplain chan- ArchaeoloGY BackGround nels or depression fills (known as the Arctic Beds), dated 26000 to 21000 BC (Bates 997a; Activity in the Lea Valley has been recorded Gibbard 1994). The Arctic Beds are a discrete from the Palaeolithic onwards (Greater organic layer that contain ‘full glacial’ plant London Sites and Monuments Record; assemblages (Reid 949; Allison et al 952) Wessex Archaeology 1997; MoLAS 2000). and ‘steppe tundra’ fauna (Lister & Sher The Lea Valley has been identified as being 2001). of particular importance for the survival Towards the end of the last glaciation, of Mesolithic remains (Austin 997) and meltwater discharge from the fast-flowing appears to have been a favoured area for arctic river carved out the present floodplain settlement (Jacobi 1980; 1996), with activity of the Lea by downcutting from its earlier apparently attracted to riverine locations higher level and depositing reworked river (Reynier 1998). Remains of occupation have gravels across the valley floor (Gibbard been found within the organic peat deposits 1994). Erosion of the arctic bed deposits which began accumulating in the area also occurred in many areas, the remnants during the Mesolithic period. Such sites have of which can sometimes be observed as the potential for the survival of organic and rafted blocks within the basal gravel and environmental evidence. Mesolithic finds sands, while in other areas it was probably have been found within or below stratified completely scoured with no remnants left. As peat deposits in the Lea Valley, such as at the strength of meltwater discharge abated, Rikof’s Pit, Broxbourne (Warren et al 934; a series of braided streams would have Allison et al 1952) and Millmarsh Lane, developed across the valley floodplain. Enfield, where excavation recovered 120 Studies from Late Glacial/Early Holocene struck flints dominated by flakes and blades, deposits have been undertaken at a number including two early Mesolithic microliths (cf of sites within the Lea Valley, including MoLAS 2005, 25). Nazeing and Broxbourne (Warren et al 934; There is limited evidence for Neolithic 4 Kevin Ritchie et al settlements within the Lea Valley floodplain, perhaps reduced to a trickle or completely but this may be due to its burial under thick dry during the summer. It is noteworthy deposits of alluvium. Possible evidence for that a stream in this approximate location Neolithic woodland clearance is indicated has been recorded on historical maps of in a layer of soot and charcoal rich alluvium the area, its course not deviating greatly, at at Millmarsh Lane, Enfield (Lewis 1995). least in several centuries. It was diverted and Evidence of Late Neolithic/Early Bronze Age finally infilled when the sewage works were activity is present outside of the floodplain constructed. at Plevna Park, Edmonton (cf MoLAS 2005, 26) Report conventions and structure There has been a large number of Middle and Late Bronze Age finds from within the This report is presented as a continuous Lea Valley (MoLAS 2005). The presence chronological narrative incorporating the of wooden trackways and other sites within principal findings of a number of specialist peat deposits in east London indicates the reports. The full stratigraphic, finds and exploitation of the marshland and floodplain environmental archive from both sites will areas during the Middle and Late Bronze Age be deposited with the Museum of London; (Meddens 1996, 331—3; Thomas & Rackham Site 1 under the site code RMA97, and Site 2 1996). Further to this, the presence of three under the site code ONR97. isolated finds of Middle to Late Bronze Age Narrative sections relating environmental weapons (see Fig 1), recorded close to former evidence to the changing dynamics of the past channels of the River Lea, may be considered environment, the resources it could support in the light of the recognised pattern of and an interpretation of the economy are deliberate deposition of metalwork in similar based on numerous detailed analyses of the wetland locations (Bradley 1998). sedimentary sequences (Chisham 2004; Bates Artefacts recovered during gravel extract- 1997b), the soils and soil chemistry (Macphail ion immediately north of the study area & Crowther 2004), pollen (Scaife 2005), in 1952, which included in-situ wooden charcoal (Gale 2004), charred and water- stakes, were interpreted as a possible Iron logged plant remains (Stevens 2005), and Age landing-stage, fishing-weir or dwelling. snails (Allen 2005). Environmental analysis No particular concentrations of Roman or is restricted both temporally and spatially Saxon finds were known in the vicinity, but a by the limited number of archaeological now vanished medieval moated site and later features and deposits available, reflecting manor house, Norris Farm, lay immediately the overall low level of activity.