The possible threats to western European coastal wetlands from tidal power generation were ascertained in this study by means of "desk-top" calculations and literature reviews. The physical characteristics of an estuary or embayment that may lead to economical tidal power generation were identified, the principal three being:- a macrotidal environment, i.e. greater than 4 metre tidal range,- a water depth along the barrage alignment of at least four metres,- a tidal prism behind the barrage alignment which is of sufficient magnitude. Using the "desk-top" Parametric Method which is based upon relationships amongst three of the key physical characteristics, the present study has tentatively identified 33 barrage alignments at 26 sites in western Europe which potentially offer economical tidal power generation. For each of these 26 sites, a provisional inventory of data relating to their natural resources was compiled. The inventory summarises the types of information available and their sources. Extreme variability exists between sites in the level of detail of such data. Possible effects on the biological importance of an estuary from a tidal power barrage were considered from the ornithological viewpoint. A literature review suggests that our understanding of the mechanisms controlling an estuary's bird community is relatively well advanced. However, a review of environmental impact assessments showed that none have been able to predict, with any confidence, the effect of a tidal power barrage upon bhds. This is due to a combination of factors: the lack of data on natural resources, an inadequate understanding of the interactive processes between the different estuarine components and an incomplete picture of the hydrological and sedimentation patterns post-barrage. An example of our current knowledge and its limitations is illustrated through a desk study of the ornithological implications of tidal power generation at the Burry Inlet, South Wales
