The Thames barrier

Abstract

This paper, presented at the International Symposium on El Paisaje del Agua organised in Madrid by Canal de Isabel II in October 1986, is based on the Verena Holmes Lecture of the Women's Engineering Society given by the author in 1983 in centres throughout the United Kingdom. It describes the background to tidal flooding in the estuary and the events leading to the commissioning in 1968 of hydraulic studies to predict how the construction and operation of a barrier at different sites would affect river levels, tidal currents and siltation in the Thames.Hydraulics Research, Wallingford, tackled the problem under six main headings: field measurements, continuous silt monitoring, laboratory tests on silt, computational modelling, physical modelling and desk studies. An account is given of a series of surveys undertaken at intervals between 1968 and 1981 to determine the present behaviour of the river under diurnal, bimonthly and seasonal differences in tidal range and river flow. The establishment in 1970 of stations for the continuous monitoring of suspended silt concentrations before, during and after barrier construction is described along with laboratory tests carried out to examine the properties of Thames mud. The silt monitoring still continues.Mention is made of the six physical hydraulic models used to examine the problems of flow and sediment redistribution associated with the Thames Barrier and flood-prevention investigation and of the first mathematical model ever developed to reproduce the movement of suspended silt in an estuary.The paper concludes with an account of site progress between 1971, when interim protection was provided for Londoners, and barrier completion 11 years later.