What is buoyage?
Buoys are a series of markers used to depict certain areas of a navigable channel. Their shape, colour and light signal are internationally recognised and enforced by the governing body IALA (International association of lighthouse authorities).
As such the buoyage system is often referred to as the IALA system. The UK and it's commonwealth countries operate under the 'A' scheme which is outlined below.
Types of buoy
All buoys can be separated in to 3 main categories:
- Lateral markers
- Cardinal markers
- Other markers
1. Lateral markers
Upon entering a navigable channel (or looking upstream) the PORT hand markers indicate the left of the channel and the STARBOARD markers the right.
The port hand markers are RED CANS
The STARBOARD hand markers are GREEN CONES ("Nuns")
GREEN buoys are ODD numbered
The numbering starts at the river mouth and increases upstream.
A ship should keep to the STARBOARD side on ENTERING the channel and to the PORT when LEAVING.
Where there are two possible channels one could take, the most preferable (wider channel, less hazards etc) is indicated with a preferred channel marker.
These are red and green cans where the colour of the central band indicates the preferred channel.
2. Cardinal markers
Cardinal markers indicate a danger area based on the points of a compass- North, East, South and West.
They may be placed at all points around a large (but isolated) point of danger (e.g. a wreck) or at fewer points to indicate a larger expanse.
They may be used to show:
- Submerged rocks
- The end of a shoal
- Sandbanks or other similar danger points
Cardinal marks are black and yellow with black top marks (if fitted).
N.B. The top marks point to the location of the black areas.
The important point to remember about cardinal markers is that they must be passed to the named side of the buoy.
[e.g a WESTERLY cardinal placed mid-river indicates that all ships must pass to the WEST of that mark.]
3. Other markers
A submerged wreck, isolated rock or similar hazard, with clear water surrounding, is indicated by a RED and BLACK Isolated danger mark.
Safe water marks are placed mid-channel to indicate a course of safe passage. They are RED and WHITE and the only type of buoy to have vertical stripes.
Special markers depict points of special interest, marked by a YELLOW buoy with a cross as the top mark.
They can be used to show:
- Areas dedicated to sporting use
- Waste outlet pipes
- Underwater cables
- Firing ranges