What is a draft restriction?
A draft restriction limits how deep a ship may sit in the water, so it can carry less cargo through a canal or shallow channel.
Explainer, updated 2026-09-19 (19 September 2026).
Explainer
A ship’s draft is the depth of its hull below the waterline. The more cargo it carries, the deeper it sits. A draft restriction is a limit on the draft a ship may have to pass through a canal, lock or channel.
Why limits are set
Canals and channels have a fixed depth. If water levels fall, for example because of a drought feeding a lake that supplies canal locks, the authority may lower the maximum draft. Ships must then load less cargo, wait for other conditions, or take another route.
What it does to traffic
A draft restriction can reduce cargo per ship without stopping ships at all, so daily transit counts alone may understate its effect. Authorities sometimes also limit the number of ships per day. When we record a restriction we cite the authority’s own advisories for the dates and limits.
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