Tidal changes and coastal hazards: Past, present and future

A review is presented of the nature of tidal changes and their importance i n the context of coastal hazards. This is done in order to illustrate the w ay in which tides do and may impact on the coast as a hazard and highlight the need for research to be carried out in this context. Three main aspects of tides are significant in this respect - these are: (1) tidal heights, i ncluding tidal range and the asymmetry or otherwise of the flood/ebb cycle; (2) tidal currents, the speed and direction of which affect sediment movem ent, sources and sinks; and (3) tidal mixing of fresh water with water of v arying levels of salinity and differing temperatures. A variety of tools, f rom geological data to modelling, and tide gauges to satellites, may be use d to assess tidal changes. Tides form the basis on which all other coastal processes operate and are therefore important with regard to the physical, chemical and biological hazards in the coastal zone. There is an urgent nee d to study tidal changes - both their nature and causes - in order to ensur e successful coastal management.