Severn Estuary Rapid Coastal Zone Assessment Survey PHASE 1 REPORT for English Heritage (HEEP Project No. 3885) David Mullin, Richard Brunning and Adrian Chadwick Version 3 Final, December 2009 Contents List of figures ......................................................................................................................... 5 Summary ............................................................................................................................... 7 Document Control Grid .......................................................................................................... 9 1 Introduction ...................................................................................................................11 2 Survey area ..................................................................................................................13 3 Methods ........................................................................................................................15 3.1 Introduction ...........................................................................................................15 3.2 Information sources and analysis ..........................................................................15 3.3 Coastal change .....................................................................................................15 3.4 Aerial photographs and Lidar data ........................................................................15 3.5 Appraisal of the success of project methodologies ................................................16 3.6 Recommendations for methodologies to be adopted in future projects .................17 4 The sedimentary background .......................................................................................19 5 Historic maps and charts ..............................................................................................21 5.1 Assessment of historic map data ..........................................................................21 5.2 Collection of historic chart data from the Hydrographic Office ...............................21 6 Previous research into the archaeology of the English Severn Estuary.........................23 6.1 The right bank: Introduction ..................................................................................23 6.2 Beachley to Lydney ...............................................................................................23 6.3 Lydney to Maisemore ............................................................................................25 6.4 The left bank: Introduction .....................................................................................27 6.5 Maisemore to Sharpness ......................................................................................28 6.6 Sharpness to Aust .................................................................................................32 6.7 Aust to Portishead .................................................................................................34 6.8 Portishead to Brean Down including Steep Holm ..................................................37 6.9 Brean Down ..........................................................................................................38 6.10 Brean Down to Hinkley Point.................................................................................38 - 1 - 6.11 Hinkley Point to Gore Point ...................................................................................40 6.12 South West Archaeological Research framework ..................................................42 7 HER/SMR, NMR and other datasets .............................................................................47 7.1 Summary ..............................................................................................................47 7.2 Prehistoric .............................................................................................................48 7.3 Roman ..................................................................................................................49 7.4 Early medieval ......................................................................................................50 7.5 Medieval ...............................................................................................................50 7.6 Post-medieval .......................................................................................................51 7.7 Modern .................................................................................................................51 7.8 Undated/uncertain .................................................................................................52 7.9 Wrecks ..................................................................................................................52 7.10 Scheduled Monuments .........................................................................................52 8 Areas of high archaeological potential ..........................................................................55 8.1 Areas of greatest significance ...............................................................................55 8.2 Areas of low record density ...................................................................................55 8.3 Research themes ..................................................................................................56 9 Threats to the archaeological resource .........................................................................57 10 Coastal change on the English side of the Severn Estuary from the Palaeolithic to the present day by Richard Brunning .........................................................................................59 10.1 Introduction ...........................................................................................................59 10.2 Pre-Anglian and lower and middle Palaeolithic sea level changes (Oxygen Isotope Stages 17-6) .....................................................................................................................59 10.3 Ipswichian warm stage (c. 135-110ka BP) OIS 5e ................................................60 10.4 Devensian glaciation (c. 110-10.5ka BP) ..............................................................61 10.5 The Holocene (c. 10.5ka BP – present) ................................................................61 10.6 Early Holocene c. 8,500-5,000 cal. BC ..................................................................62 10.7 Transition from lower to middle Somerset Formation c. 5,000-1,500 cal. BC ........63 10.8 Transgressions and regressions of later prehistory c. 1,500 cal. BC- 0 cal. BC .....64 10.9 Roman coastlines .................................................................................................66 - 2 - 10.10 Late Roman transgression ................................................................................68 10.11 Early medieval reclamation ...............................................................................68 11 Mapping of borehole data .............................................................................................73 12 Digitising of cartographic data from historic OS mapping ..............................................75 13 The modern and projected coastlines: summary of FutureCoast data...........................77 14 Coastal management ....................................................................................................83 14.1 Management Principles .........................................................................................83 14.2 Shoreline Management Plans and the Tidal Severn Flood Risk Management Strategy ............................................................................................................................84 14.3 The Severn Estuary Shoreline Management Plan 2 (SMP2) .................................85 14.4 The North Devon and Somerset Shoreline Management Plan 2 (NDAS) ............ 102 14.5 The impact of major infrastructure projects .........................................................120 15 Identification of areas of deposition and erosion within the Severn Estuary ................ 123 16 Identification of specific sites and areas which would benefit from further research or fieldwork .............................................................................................................................125 17 Bibliography ................................................................................................................129 18 Project team and acknowledgements .........................................................................149 19 Abbreviations ..............................................................................................................150 Figures from ........ 151 Appendix A Historic maps and charts consulted in Records Offices - 3 - - 4 - List of figures 1 Extent of coastline 2 Survey Area 3 Sediments within the survey area (from Allen 2001) 4-13 All OS based mapping at 1:75,000 4 Beachley to Lydney and Sharpness to Severn Bridge 5 Lydney to Gloucester and Gloucester to Purton 6 Gloucester to Maisemore 7 Severn crossings to Avonmouth 8 Avonmouth to Clevedon 9 Clevedon to Brean Down 10 Brean Down to Burnham-on-Sea 11 Burnham-on-Sea to Kilve 12 Kilve to Minehead 13 Minehead to Porlock 14 County and Unitary Authorities 15 HER data at beginning of project: Prehistoric Period 16 HER data at beginning of project: