What is a back current
Backwash is a strong current directed perpendicularly from the shoreline to the open ocean, sea or lake. It is considered one of the most dangerous natural phenomena. Its insidiousness lies in the fact that it occurs very close to the shore – where no one expects danger.
Usually, the reverse current is formed in areas where there are sandbars, shoals, reefs, breakwaters, dikes or piers. Due to the peculiarities of the relief, water can not return to the reservoir evenly, so the main stream rushes at high speed into the strait between the obstacles and dies out immediately after them.
The return flow is found on beaches with both hard (rocky) and soft (sandy or muddy) bottoms.
The width of the reverse current sometimes reaches 45 metres, but most often does not exceed 9 metres. The water flow can move at a speed of 8 kilometres per hour.
Specialists distinguish different types of backflow. For example:
Channel, which occupies deep places between sandbanks and stays there for days, weeks or even months.
Boundary current, which occurs near headlands and structures, such as jetties and piers, that extend into the sea or lake.
Sudden, which forms instantly when the size and frequency of waves begin to increase rapidly. Such a current is short-lived and can appear and disappear in a variety of places. Because of its unpredictability, this type is considered one of the most dangerous.
How to recognise it
With a backward current, you can usually notice:
A band of churning water perpendicular to the shoreline;
a patch of water near the shore that is darker or lighter than the rest of the water surface;
foam floating rapidly away from the shore;
gaps in the surf line a few metres wide where there are no waves.
Abroad, rip currents are known by the phrase rip currents. If you see it on flags and signs, you should not enter the water. If there are no warnings, it is worth checking with lifeguards.
