Erosion and deposition take place as a part of a river’s natural development. It appears that, as a general rule, gravel is deposited at the top of the foreshore, erosion takes place around the low water mark and relative stability prevails in the narrow area between the two. Erosion appears to be most active during the winter and spring months. Strong downstream flow appears to have a more erosive effect than the tidal ebb and flow.

The ‘natural’ factors affecting the flow of the river, and therefore both agradation and degradation, are many and various. The ‘natural’ erosion/deposition pattern is complicated further by the effects of human intervention. Any activity that effects the flow of the Thames will effect the rate of agradation and degradation of the foreshore deposits. Any disturbance of the deposits increases their exposed surface area and thus accelerates their degradation

In many of the zones surveyed during the 1996 – 1999 Thames Archaeology Survey, gravels were found to overlay 18th- and 19th-century features. This includes riverfront defences, the foundation of Fulham Old Bridge, gridirons and many of the watermen’s stairs and causeways. This suggests that the present profile and appearance of the foreshore is largely a result of changes over the last 100 years. It would appear that the rate of agradation and degradation has accelerated during that period. Activities likely to have contributed to this effect were foreshore consolidation, the removal of London Bridge and alterations to, or the replacement of, other bridges, the construction of the Embankments, locks and weirs, dredging, of both the navigation channel and for wharves and jetties, increased upstream abstraction and increased disturbance.

The effects of accelerated erosion over the winter and spring months was recognised on several regularly visited zones during the Thames Archaeological Survey. In some cases entirely new features were revealed, in others a timber pile might protrude a few more centimetres above the foreshore surface. Conversely, when downstream flows are slow, during the summer months, agradation is apparent and features can be covered beneath deposits of sand or silt.

There appears to be no clear pattern of erosion and agradation. Abstraction, encroachment and physical disturbance complicate the natural river regimen.

Adapted from ‘Report on the Thames Archaeological Survey 1996 – 1999’ by Mike D Webber