Wave exposure (m2/s) was modelled, with a spatial resolution of 25 m, as an index using data on fetch (distance to nearest shore, island or coast), averaged wind speed and wind frequency (estimated as the amount of time that the wind came from one of 16 direction). Data on wind speed and direction were delivered by the Norwegian Meteorological Institute and averaged over a 10-year period (i.e. 1995-2004). The model is run using the program WaveImpact based on the method “Simplified Wave Model” (SWM) developed and described by Isæus (2004). The method is a fetch model, where the fetch values are adjusted to simulate refraction and diffraction effects. The estimated fetch values for each of the 16 directions are multiplied with the average wind speed in the given direction. The model has been run by NIVA for the whole Norwegian coast, and has been used as part of the habitat modelling of the National program for mapping biodiversity – coast (Bekkby et al. 2013). The model has also been applied in several research projects in Norway (e.g. Bekkby et al. 2008, 2009, 2014, 2015, Bekkby & Moy 2011, Norderhaug et al. 2012, 2014, Pedersen et al. 2012, Rinde et al. 2014). The model has also been run for Sweden (e.g. Eriksson et al. 2004), Finland (Isæus & Rygg 2005), the Danish region of the Skagerrak coast and the Russian, Latvian, Estonian, Lithuanian and German territories of the Baltic Sea (Wijkmark & Isæus 2010). The wave exposure values range from Ultra sheltered to Extremely exposed (cf Wijkmark & Isæus 2010, similar to the EUNIS system of Davies & Moss 2004).

Created by the EMODnet Seabed Habitats project consortium from data derived from NIVA Norway. The confidence assessment considered factors such as: • Quality of training data and methods used to construct the model. • Temporal resolution. • Spatial resolution Detailed information on the confidence assessment in Populus J. et al 2017. EUSeaMap, a European broad-scale seabed habitat map. Ifremer. http://doi.org/10.13155/49975