As a noun, a raised area of sand, mud or rock where depth is less than in the water around it, often enough to endanger a vessel. As a verb, it describes depth decreasing, as when a channel shoals between dredging campaigns. Hydrographers also speak of shoal soundings, shoal-biased surfaces and shoaling rates, and chasing the shoalest point over a shoal is the heart of development work.
Channel has shoaled 70 centimetres since the spring survey, mostly on the inside of the bend.
Also heard as
- shoaling
Related terms
Least depth
The shallowest depth over a wreck, rock or other feature, which is the value that gets charted.
Development
Extra survey work over a feature or shoal to pin down its least depth, shape and extent.
Shoal-biased
Favouring the shallower value whenever depths are generalised, so a chart never shows more water than exists.
DtoN
Danger to navigation: a newly found hazard reported urgently so charts and warnings change before the survey ends.