Wave Exposure Index

A wave exposure index converts fetch distance, prevailing wind speed and direction, and bathymetry into a single numeric or categorical rating of how much wave energy a candidate site experiences, used by engineers to specify mooring system strength, net and cage structural design, and whether a site requires submersible or surface cage technology rather than conventional floating pens. Sheltered fjord and bay sites with short fetch rate at the low end of most exposure scales and can use lighter, lower-cost mooring and standard surface cages, while open-coast and offshore sites exposed to long-fetch ocean swell rate at the high end, requiring heavier mooring grids, reinforced collar structures, and in the highest-energy sites, cages engineered to submerge below the surface wave zone during storms. Underestimating exposure at the design stage is a documented cause of catastrophic mooring or net failure during storm events, which is why most jurisdictions now require a formal wave exposure and mooring load calculation, often based on decades of wind and wave hindcast data, before licensing offshore expansion. As farms move from sheltered inshore waters to more exposed sites to access better flushing and reduce disease pressure, exposure-rated engineering has become as central to site planning as water chemistry.