The very word "barrages" is evocative. In the context of tidal waters it conjures up pictures of massive structures and environmental change. Barrages represent the engineer s success where King Canute failed to stop the tide coming in. They are hardly a new concept as man has for centuries tried to harness tidal power to drive his machinery, but a new breed of barrage is emerging, aimed at regenerating depressed urban areas. One of the primary aims of such schemes has been to drown "unsightly" mud flats. If you happen to be a wading bird used to enjoying the worms that live in intertidal mud flats you may not share that perspective. Indeed, many people today tend to side with the birds, fish and other ecological wonders and often find themselves in conflict with the promoters of a barrage scheme. How far are their fears justified? Are the negative impacts as bad as some people have predicted or even worse? How accurately can the impacts be predicted by scientific methods? Can the barrage be designed and its operation controlled to mitigate any negative effects as well as to optimise its primary objective? These issues are addressed in this book by authors drawing on their experience of research and practical experience.