River currents are caused by water travelling downhill. They are influenced by gradient, volume, and features.
- Laminar flow is the fastest water travelling with no restrictions in a straight line down a river.
- NFPA 1006 surface water rescue is defined as water flowing at less than 1 knot (1.15 mph). Water flowing faster than 1 knot would be considered swift water rescue.
- Helical flow is found along a shoreline and is a corkscrew or spring-like current that is constantly rolling and pushing out into the laminar flow. This spiral water flow can sweep a person off their feet and push them into the main current or make swimming back to shore a challenge.
- River left always refers to the left side of a river looking downstream.
- River right always refers to the right side of a river looking downstream.