For centuries man has sought to achieve some beneficial change, usually for navigation, to tidal rivers or estuaries. In response to both pressure on land in coastal areas and to the increasing acceptance of the concepts of multiple land use, construction in areas of tidal waters has become more complex. Water storage, recreational and power generation schemes are typical examples.
With the optimum areas already utilized, construction work represents an increasingly difficult challenge in terms of site evaluation. Data required to achieve this objective include a wide range of aspects such as tidal cycles and sediment movement in terms of the likely modification following construction. These are essential for assessing the beneficial or damaging consequences of man-induced changes.
Three case histories are presented, summarized from existing literature, to illustrate the complex interplay and variable nature of tidal river and estuary systems. The purpose is to demonstrate the impact of changes following construction, and to show that these may have influenced decisions on details of the engineering scheme at the time of design, and the environment of the tidal reaches and the immediate surrounding areas.