Surf return current

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Mechanism: waves reach the beach across its entire width. Most of the water is only sucked back in one place due to the upstream shallows (sandbanks). This is where the surf backflow occurs.

Surf currents , also rip currents , rib currents or tractors are locally limited ocean currents that occur on coasts . They are the leading cause of bathing accidents on the seashore.

root cause

Basically, the waves of the surf are not associated with a directed current. Since sandbars often form in front of sandy beaches or because other obstacles such as rocks are in front of the beach , the water of the surf waves cannot flow back to the sea unhindered. At the gaps between the barriers, there is therefore a concentrated backflow of the water, through which bathers can be sucked out into the sea. Similar phenomena occur when currents running parallel to the beach are diverted into the open sea on groynes or headlands .

Danger to swimmers

This sign in San Diego (USA) explains that swimmers should first allow themselves to be driven out and then swim back laterally offset.

Since the current pulls the swimmer out to sea, inexperienced swimmers tend to panic swim against the current. There is a risk that they will then drown from exhaustion. The flow speed can be up to 9 km / h (about 5 knots ) - for comparison: the swimming world record over 400 m is 6.55 km / h (record set in 2009). That is why it makes sense to swim out across the current in calmer water or to drift into the sea first and then swim back laterally offset.

Scuba divers , snorkelers , boaters and surfers , on the other hand, like to use such back currents to get out to sea without much effort.

Signs of rip currents

Notes on rip currents:

Example of a surf backflow: foamed water is driven out into the sea
  • The water appears calmer as the return current dampens the surf.
  • Changes in the color of the water relative to the environment, for example the water appears darker due to the lack of foam crowns or lighter due to the spray drifting into the sea .
  • Seaweed drifting out quickly
  • Rib currents often form near a bay or groyne .
  • The rip current changes the sea floor, a channel towards the sea is visible.

European waters

The risk on beaches in the North and Baltic Seas is generally lower, as the water waves in these tributaries have less kinetic energy and the return currents are therefore smaller than on beaches that are directly adjacent to the oceans . Nevertheless, there are several deaths every year on the beaches of both the Baltic Sea and the North Sea, in which the current has drawn careless bathers out into the sea.

Web links

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  1. ↑ a b "How to survive beach rip currents" video from the University of South Wales, Australia
  2. ↑ Swimming accidents in the Baltic Sea: three dead in two days. In: Spiegel Online . July 10, 2014, accessed May 10, 2019 .