Severn Estuary RCZAS NMP

The National Mapping Programme (NMP) components of this Rapid Coastal Zone Assessment Survey (RCZAS) project was carried out by Gloucestershire County Council staff based with the Aerial Survey and Investigation team in Swindon.  The Severn Estuary RCZAS project area is 538km² stretching along the eastern shore of the Severn Estuary; from the agricultural landscape in the upper tidal reaches of the River Severn at Gloucester, to the wooded coastline west of Porlock in Somerset.  The aerial survey focused on the intertidal zone and up to 1km inland.  The project aim was to assess the threat to historic and archaeological features from coastal erosion.

Some of the most significant archaeological features identified are the numerous coastal fish weirs and traps located in the intertidal zone of Bridgwater and Blue Anchor Bays, dating from the 10th century period to the 20th century.  These have been constructed in an intriguing variety of designs and materials.  Built of wood, stone or a mix of both; at least four morphological types of fish weir has been identified by the aerial survey.

These variations may reflect the availability of raw materials, changes in construction design over time, the types of fish being targeted, or a combination of these factors.  Detailed examination of air photographs reveal that these fish weirs were constructed and reconstructed and the raw material reused, especially those built of stone. Many fish weirs are visible overlying, intersecting or abutting each other.

Second World War military coastal crust defences were prominent features in the Severn Estuary intertidal zone, providing an interesting comparison with other military defences around Britain’s coastline such as those recorded by the Suffolk NMP aerial survey.  The aerial survey highlights the strategic importance of camouflage used to disguise coastal military defences, especially pillboxes. The historical air photographs are valuable as few surviving examples retain their original camouflage.  Numerous pillboxes were positioned along the coast between Porlock Weir and Blue Anchor, of which 28 were identified as a non-standard design known as an infantry section post, which were are a unique part of the coastal crust defences in the NMP survey.

Aerial photographs taken during the Second World War remain an important historical pictorial record of the nation’s defences, as most of the sites recorded were no longer visible within a few years of the war’s end. Using these wartime images has revealed anti-invasion defences of the Severn Estuary to be far more extensive than previously thought.

The NMP project included a trial lidar assessment of part of the flood plain of the River Parrett, Somerset and an area of possible Roman land reclamation at Elmore, Gloucesterhsire.  Overall lidar was shown to be complementary to aerial photographs in both the trial areas for the identification of archaeological sites and also for assessing their survival.

The images used on this page are copyright English Heritage unless specified otherwise. For further details of any photographs or other images and for copies of these, or the plans and reports related to the project please contact the NMR English Heritage's public archive.

For further information on a project or any other aspect of the work of the Aerial Survey team please contact us at: AerialSurvey@english-heritage.org.uk.