The impact on the inshore wave climate in the lee of a proposed 3km wave farm off the North Cornwall coast in the southwest UK has previously been modelled. The study estimated that an average decrease of less than 1% of significant wave height and a maximum decrease of 3% would occur with a 90% energy transmitting wave farm. While these results might be barely detectable at the shoreline, the prospect of larger wave farms, or wave farms sited closer to the shoreline, raises the question of when inshore wave climates become significantly impacted.
This paper summarises the results of a wave climate study that generalises the approach of the previous study, providing results applicable not just to one site, but to the wider field of wave farm development. The study comprises a much wider series of idealised SWAN model runs which aim to assess how the impact on inshore wave climates of a wave farm, considered in a simplified manner as a single object, is affected by four key variables: the length of the obstacle parallel to incoming wave crests, the distance of the obstacle from the shoreline, the percentage of wave energy transmitted through the obstacle, and the directional distribution of the local wave climate. The results show that there will always be a minimum percentage decrease in wave height in the lee of such an obstacle, even at substantial distances. This minimum varies with energy transmission and directional spread of the waves. The distance taken to reach this minimum is mainly dependent on the size of the obstacle. Although the modelling of an actual wave farm comprising arrays of devices would be more complex, the results allow a preliminary assessment of how far from the shoreline a wave farm should be sited to ensure wave height decreases are below a certain threshold.