Monument record TQ 77 NW 1305 - The earthwork remains of four adjacent irregular mounds of varying size within Cliffe Marshes thought to be medieval saltern mounds

The earthwork remains of four adjacent irregular mounds of varying size (forming a raised area c.95m x 125m) seen centred as a group at TQ 7339 7825 within Cliffe Marshes thought to be medieval saltern mounds. The larger mounds measure c. 40m x 80m and 50m x 70m, with two smaller mounds of c.16m x 25m situated immediately to the south. The largest mound has a water-filled depression in the centre. These were mapped from a combination of RAF aerial photographs and Environment Agency lidar imagery as part of the English Heritage: Hoo Peninsula Landscape Project.

Saltern mounds are the result of large-scale salt manufacturing where brine was extracted from salt-rich sands and sediments, concentrated and evaporated using process known as sleeching. The discarded waste material from the process built up around the production area into a sizeable mound, often with a hollow in the centred where a hut stood. These medieval saltern mounds are typically described as `floriate' in form because of their irregular lobed formation of dumped waste. They often occur in clusters around former and surviving tidal water-courses within the marsh. There has been considerable reclamation and subsequent sea wall construction since the medieval period which has isolated these sites from the sea.

Many of these mounds were subsequently utilised as sheepfolds, sheep washes and stock refuges in the post medieval period because of their slightly elevated position in the readily flooded marshes.

Roman finds have been extracted from some of these sites, but are believed to be from the lower levels, and not associated with the mounds. Post-Roman flooding and silt deposition has resulted in Roman sites lying typically several feet below the current land surface. (1-2)

<1> Environment Agency, 2001, LIDAR TQ 7278 Environment Agency D0015733 APR-2001 (Digital archive). SKE57158.

<2> Royal Air Force, 1951, NMR RAF/540/458 4010 17-APR-1951 (Photograph). SKE58572.

<3> Historic England, Historic England Archive (Archive). SKE58569.