Fetch

Synonyms

Fetch length

Definition

Fetch is the linear distance of open, unobstructed water lying beneath a wind traveling with a constant direction.

Overview

Fetch is calculated by measuring the distance from a point across open water of suitable depth for allowing wave travel, unobstructed by land masses including islands and shallow banks. Fetch is directional, and hence should include both a distance and orientation. Commonly, the fetch specified for a port is the maximum open water distance associated with a prevailing wind direction.

The fetch length is directly related to the height of waves, which can be generated by wind. Formation of waves requires the wind to frictionally interact with the water, transferring energy and overcoming both the inertia of the water and any existing waves traveling in different directions. Thus, the height of the waves generated increases with the fetch distance, as the duration of the wind–water interaction increases.

The maximum height of waves in...