Construction of tidal power barrages could have serious consequences to the marine environment. The high productivity of the intertidal communities in the upper reaches is maintained in part by tidal flushing; these communities are also affected by changes in sediment type. Serious siltation problems could also shorten the lifespan of tidal power barrages. Computer simulation of sediment dynamics combined with programs designed to assess the effect of siltation on benthic communities will allow estimates of expected productivity losses to be made for some of the areas which have already been studied. -from Authors