Upstream Vs and downstream Vs are also hazards found on rivers. Upstream Vs indicate an underwater obstruction, and downstream Vs indicate an open channel.
An upstream V is formed by an obstruction in the water that creates a V that points upstream. The location of the V depends upon the depth of the obstruction.
- Sometimes the V may be right on top of the obstruction.
- If the obstruction is deeper, the V would be downstream from it.
A downstream V is formed when water is funneled (constricted) between two obstructions and forms a V that points downstream. A series of multiple standing waves are known as haystacks or wave trains. In urban areas, they may indicate multiple submerged vehicles.