No estuary is immune to change. Sea levels alter and the nature and position of an estuary varies as a consequence. The sediment that accumulates in these environments supports a highly productive food web which includes fish and birds such as the waders and wildfowl that are drawn to such habitat. Man also alters the environment of our estuaries. With towns and industry come the development of ports and the substantial physical change that accompanies land reclamation, dock developments and flood defences. Industry also brings a less attractive feature - the chemical changes due to discharges of wastes into the water course. The Humber is a classic example of an estuary. One of the largest estuaries in Britain, draining about one fifth of the area of England, it provides a fascinating illustration of the attractions to man and nature of these waterways. A DYNAMIC ESTUARY is deliberately multi-disciplinary in approach and reflects the many facets of the estuary. It describes its maj