The Mobility of a Sand Bar Across an Estuarine Channel
Notes from a lecture by Dr R L Cloet.
Dr Cloet described his geology as ‘soft’. His research is in the Thames estuary as to how, why, when and where unconsolidated sand moves in the tidal waters. Since the Thames estuary is the busiest shipping channel in Europe it is important to follow the pattern of sand banks. Charting these has been going on since 1820, and since 1960 has been done twice a year, and only 200 charts are issued at a time, since they become out of date. It is essential that the Pilots of the Port of London have up-to-date information.
Off the Essex coast is a long sand bank, 40 by 20 by 5 Kms of pre-glacial origin, most of which has been static for a long time, but through which channels have formed.
The major shipping channel for London is the Edinburgh, which has been stable for some time, but the banks on either side change considerably, building out spits and shoals which do not act as one would expect.
Measurements have shown that more sand is brought in by the flow tide than is removed by the ebb tide. In general it is an area of stability, but there is a lot of sediment being moved and slow changes in the pattern of these sand banks. It is in a delicate balance which could be upset by careless dumping of waste material although dumping off-shore is still going on.