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SOCIB / Rip currents

What is a rip and rip currents?

Rip currents are fast-moving flows, travelling seaward almost at right angles to the shore, creating a natural hazard for beach users, who suddenly find themselves in deep water. They typically extend from the shoreline, through the surf zone and past the line of breaking waves, and often they are perpendicular to the shoreline. Rip currents are the most important beach hazard and the cause of most rescues and many drownings a year. Rip currents do not put people under water; they pull people away from the shore. Rip current can be as narrow as 10 feet and as wide as 200 feet. They can extend hundreds of feet beyond the surf zone. Rip current speeds are typically 1-2 feet per second, but some can exceed 8 feet per second. The strength and the speed of a rip current increase as wave height and wave period increases. At Balearic Islands beaches there are rips currents although usually their magnitude and energy are lower than those described in more energetic oceanic environments.

Figure 1. Rip currents formation

How they are formed?

Rip currents can occur on many types of beaches under a variety of wave conditions and tidal levels. There are many causes of rip currents. Usually rip currents are generated simply by alongshore variation in breaking waves, other times they are forced by rock reefs or coastal structures. The two most commonly described are those rip currents controlled by the incident wave angles and those controlled by the bathymetry. Among the last group there are (a) rip currents associated to bar discontinuities and to bar morphology in large and straight beaches. (b) Rip currents are also commonly found near coastal structures (i.e. groins or piers) or (c) they are forced by wave height and water accumulation in embayed and pocket beaches. A commonly observed type of rip current is found associated to the presence of beach cups (d).

Figure 2. Rip currents induced by beach cusps.

Why are they dangerous?

A rip current can quickly pull a swimmer offshore. Rip current can even sweep the strongest swimmers away from the beach. Drowning deaths occur when people pulled offshore are unable to keep themselves a float and swim to the shore. This may be to a combination of fear, panic, exhaustion or lack of swimming skills.

How to identify rips?

Rips currents are very difficult to identify, but there are some clues such as:

a) Channel of churning, choppy water

b) Area with a drastic change in water colour

c) Line of foam, seaweed or debris moving away from the coast

d) A break in the incoming wave pattern

Figure 3. Rip current spotted at Cala Millor.

How to survive and stay in control?

Try to maintain calm
Instead of trying to swim back to the shore against the current, swim parallel to the shoreline across the current.
Swim and angle away from the current and towards shore.
If you can’t escape the rip current try to float or calmly tread water until the rip current decrease.
If you can’t arrive to the shore, face the shore, wave your arms and yell for help.

Figure 4. Rip currents safety sign.

References and recommended reading

Darlymple, R.A., MacMahan, J.H., Reniers, A.J.HM., Nelko, V. 2011. Rip currents. Annual Review of Fluid Mechanics, 43: 551-581

https://www.weather.gov/safety/ripcurrent-signs-brochures
https://www.weather.gov/safety/ripcurrent

Balearic Islands specific references:

Álvarez-Ellacuría, A., Orfila, A., Olabarrieta, M., Medina, R., Vizoso, G., Tintoré, J. 2010. A neashore wave and current operational forecasting system. Journal of Coastal Research, 26: 503-509.