A tsunami is a long wave which propagates with a depth far lower than its wavelength (non-dispersive conditions). The movement associated with this wave concerns the entire water column. Tsunamis are most frequently of geological origin (submarine earthquake, volcanic eruption, coastal or submarine landslide), meteorological origin, or triggered by asteroid impact. A tsunami causes the rapid, exceptional inundation of coastal areas by the sea, due to a temporary and abnormal rise in sea level.
In the case of a fixed-foundation offshore wind farm, only submarine and coastal landslides can trigger tsunamis. Wind farms cannot cause volcanic eruptions, earthquakes or asteroid impact. Coastal landslides or collapses result from the combined effects of geological (coastal sediment deficit, bedrock alteration), oceanographic (swell, tides, current) and meteorological (precipitation, frost) phenomena. Fixed-foundation wind farms can have a very minor influence on swell, currents and sediment transport which could destabilise coastal cliffs.
In order to estimate the probable influence of wind farms on sediment transport, experts have calculated scour, i.e. erosion at the base of the turbine. The scour depth can reach up to 1.7 times the diameter of the monopile and the scour distance 10 times the diameter. In the case of a gravity foundation with a 36 m diameter base, there is no major influence on the sediment dynamics beyond 360 m. For other types of foundation (jacket, monopile) which have a smaller diameter, this distance is shorter. As wind farms are located around ten kilometres from the coast, they cannot increase the risk of tsunamis caused by coastal landslides. Submarine landslides occur when the continental slope is steep. Fixed-foundation wind farms are located on a part of the continental shelf with a very low slope. A fixed-foundation offshore wind farm therefore cannot generate submarine landslides.
In short: fixed-foundation wind farms cannot trigger tsunamis.