Aids to Navigation - Road Signs of the Waterway
Western Rivers Marking System (As Seen Entering From Seaward)
Note: The USWMS is presently merging with the U.S. Aids to Navigation System and will be discontinued on December 31, 2003. Vessel operators may encounter both types of systems during this transitional period.
Western Rivers Marking System is a variation of the standard U.S. Aids to Navigation System (ATONS) and is found on the Mississippi River and tributaries above Baton Rouge, and on certain other rivers which flow toward the Gulf of Mexico. Red daybeacons, lights, and buoys mark the starboard banks and limits of channels as vessels "return for sea" or proceed upstream. Green daybeacons, lights, and buoys mark the port banks and limits of navigable channels while going upstream. The Western River System varies of the standard U.S. system as follows:
- Buoys are not numbered.
- Passing daybeacons are not numbered but normally have an attached "Mile Marker" board that indicates the distance in statute miles from a fixed point (normally the river mouth).
- Diamond-shaped non-lateral dayboards checkered red-and-white or green-and-white, similar to those used in the U.S. Aids to Navigation System, are used as Crossing Daybeacons where the river channel crosses from one bank to the other.
- Lights on green buoys and on beacons with green daymarks show a single flash, which may be green or white.
- Lights on red buoys and on beacons with red daymarks show a double flash [Group Flashing (2)], which may be red or white.
- Isolated danger marks and Safe water marks are not used.
River Bank Names: When traveling downstream the banks are named "right" and "left". The right bank has green aids and the left bank has red aids, thus the west bank of the Mississippi is its right bank and it has green aids. To avoid confusion, commercial river traffic often calls the right bank the right descending bank and the left bank the left descending bank, expressed in this way, leaves no room for doubt.
Mile Markers: These markers are some of the most useful aids on a river. They are attached to daybeacons or displayed in other easily seen places. Since the U.S. Corps of Engineers erects them, they show distance in statute miles rather than nautical miles. With the exception of the Ohio River, mile markers indicate the distance up stream from the mouth of a river. Ohio River markers start at its headwaters and indicate the distance downstream. Mile Markers also help a vessel operator locate his/her position on a river chart.
Crossing Daybeacons: Because the navigable channels of rivers swing from bank to bank as the river bends, diamond-shaped crossing daybeacons are used to assist river traffic by indicating where the channel has changed from one side of the river to the other. Crossing daybeacons are always on the opposite side of the river. When a diamond-shaped crossing daybeacon is sighted, the vessel operator should head for the "diamond", and treat the color of the daybeacon as a channel mark (i.e. red mark keep to the left bank when traveling downstream).
River Buoys: Changes in river channels caused by fluctuations in water level, current speed and shifting shoals make buoys maintenance a continuous task for the Coast Guard. In wintertime where rivers freeze, buoys are lost or moved from position. Because of their somewhat temporary nature, river buoys do not have letters or numbers and are not usually shown on river charts.