Introduction

Abstract

Historically estuaries have played an important part in the development of towns and cities. The use of ships for trade and transport meant that settlements naturally grew up around those estuaries offering both safe havens and easy access to the agricultural or industrial hinterland. The growth of major industries dependent on sea transport for bulk supply of raw material and distribution of the finished product has resulted in heavy concentrations of such industry in the upper reaches of many estuaries. The most significant of these industries are petroleum refining, petrochemicals, metal refining and food and drink production. All of these industries produce large quantities of potentially polluting effluent. Coupled with the sewage arising from the expanding populations these effluents caused a massive deterioration in the quality of many estuaries during the latter half of the 19th and the first half of the 20th century.