While it’s difficult to define exactly where the river ends and the ocean begins, there is a clearly defined line that is often used for various legal and technical purposes.

On navigation charts, there is a line called the “COLREGS demarcation line” that is often used to define the boundary between river and sea.

COLREGS is navigation jargon for a 1972 agreement called the Convention on the International Regulations for Preventing Collisions at Sea. Basically, it spells out the traffic laws for ships at sea.

On navigation charts, the COLREGS demarcation line marks the point where vessels make the change from ocean navigation rules to inland navigation rules.

It’s sort of like driving on the interstate highway where one set of laws and speed limits apply, but when you pull off at an exit, you’re subject to different traffic laws on a side road.

The COLREGS lines are  usually a line between two navigation markers or other easily identifiable landmarks, to make it easy for navigators to mark. They are set by federal regulations and used by the Coast Guard to regulate navigation.

In the case of the Cape Fear River, the demarcation line runs from the abandoned “Old Baldy” lighthouse on Bald Head Island over to the Oak Island lighthouse.

The Old Baldy lighthouse is at approximately latitude 33°52.4′ N. longitude 78°00.1′ W.

Because the navigation lines are clearly defined on the charts, other state and federal agencies often use them as reference points.

For example, the N.C. Division of Marine Fisheries uses the COLREGS line to mark the boundary for fishing regulations. If you’re seaward of the line, the coastal fishing regulations apply. Inland of the line, inland fishing rules apply.

View chart here: www.charts.noaa.gov/OnLineViewer/11537.shtml

For more information:

www.ncfisheries.net/recreational/COLREGS.html

www.navcen.uscg.gov/mwv/regulations/33CFR080/33CFR80_acd05.htm#80.530

Date posted: January 27, 2010

User-contributed question by:
Morss Lippincott