The History of Coastal Change in Somerset
The Somerset coastline, like every other coastline around the world, is not a static feature. Many natural and manmade forces are influencing it on a daily basis. Throughout time the coastline has advanced seawards as water has been trapped in building ice sheets and coastal marshes have been drained. It has also moved landwards when large amounts of ice water has melted from the ice caps to the north.
The maps below outline how the coastline has evolved over time. It is clear how dynamic the coastline has been in the past and how it is likely to continue changing shape in the future.
The pictures and text have been produced by Dr Richad Brunning of Somerset County Council Heritage Service.
1. 6 000BC
At the end of the last glaciation, 10 000 years ago, the sea level was much lower and the Severn Estuary was a dry river valley. As the ice melted sea levels rose and had flooded much of the present estuary by 6 000BC.
2. 5 000BC
The rising sea levels submerged the lowlands of Somerset creating intertidal mudflats and salt marshes further inland than Glastonbury and Langport.
3. 3 500BC
As the rate of sea level rise declined it was outpaced by the growth of freshwater peat created in reedswamps. By 3 500BC freshwater wetlands had pushed the coastline back at least as far as Brent Knoll and Chedzoy.
4. 700BC
In the later Bronze Age and early Iron Age periods the sea once again submerged large areas of the floodplain and by 700BC salt marshes extended as far as Godney (just north of Glastonbury) and Langport.
5. 280AD
In the Roman period the first sea and river defences were created. Many saltmarsh areas were reclaimed for agriculture and settlement. The coastline was pushed beyond its present line just south of Brean. The area south of Brent Knoll remained a saltmarsh where a huge salt-making industry was created.
6. 390AD
Sea levels continued to rise very slowly and before the end of the Roman period finally overcame the coastal defences, submerging the land in the Axe Valley and all the area that is now the clay 'levels' along the present coast.
7. 1 000AD
The coastal marshes were reclaimed from the sea by the Saxons using artificial flood defences to augment the natural dune barriers. By the Norman Conquest the coastline was very close to its present location or even perhaps a little further west in some places. The last big salt marsh, Brent Marsh, was reclaimed in the later 18th century.
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