Fetch Limited Sea

A fetch-limited sea is a wind-driven wave field whose growth is capped by the distance of open water the wind blows over rather than by wind duration or time. Within a limited fetch the waves cannot reach the fully developed state for the given wind speed, so significant wave height and peak period stay below their open-ocean maxima and rise with the square root of fetch. The condition governs waves in bays, fjords, lakes, and enclosed seas and underlies the fetch-limited branches of the JONSWAP and SMB wave-growth relations used in coastal design. Knowing the effective fetch lets engineers compute design wave height for sheltered sites.