A rip current , often called rip , or by erroneous rip tide , is a specific type of waterflow that can occur near the beach with crashing waves. Rips are strong, localized, and narrow water currents that move directly from the shore, cutting out broken waves like a river flowing into the sea, and strongest near the surface of the water.
Rip currents can be harmful to people in the water. Swimmers are trapped in rips and who do not understand what is going on, and who may not have the necessary water skills, may panic, or run out of steam by trying to swim directly against the flow of water. Due to these factors, tears are the main cause of rescue by coast guard on shore, and tears are the cause of an average of 46 deaths due to drowning per year in the United States.
Rip currents are not the same as currents, though some people use the last term wrong when it means rip currents. Contrary to popular belief, neither tearing nor short-circuiting can pull someone down and hold it under water. Tears only carry floating objects, including people, out of the broken wave zone.
Video Rip current
Causes and events
The shape of the torn current due to the wind and waves breaks the surface water into the land, and this causes a slight increase in water levels along the coast. This excess water will tend to flow back into the open water through the least resistant route. When there is a slightly deeper local area, or a break in a sand bar or offshore reef, this can allow water to flow offshore more easily, and this will initiate a rip current through the gap.
Water driven near the shore flows along the coast to rip out as "feed stream", and then excess water flows out at the right angle to the shore, in a tight stream called the "neck" of the rip. "Neck" is the fastest flow place. When the water in the rip current reaches beyond the broken wave lines, the flow spreads sideways, loses power, and disappears in what is known as the "head" rip.
Rip currents can often occur on the gradual shore where a breaking wave approaches the coastline parallel to it, or where underwater topography encourages outflow in certain areas. Rip currents can form on the shores of oceans, seas, and large lakes, whenever there is enough energy waves. The location of the tear current can be difficult to predict; whereas some tend to repeat always in the same place, others may appear and disappear suddenly at various locations along the coast. Appearance and loss of rip current depends on the lower topography and precise direction of the waves and the waves derived.
Rip currents can potentially occur wherever there is strong longshore variability in splitting. This variability can be caused by features such as sand dunes (as shown in the animated diagram), by docks and docks, and even by crossing the wagon train, and often located in places such as where there is a gap in the reef or low area. on a sandbar. Rip currents can deepen the channel through the sand clumps after forming.
Rip currents are usually quite narrow, but tend to be more common, wider, and faster, when and where the waves break out big and strong. Local underwater topography makes some beaches more likely to have rip currents; some beaches are famous for that matter.
Although rip tide is mistaken, in areas with significant tidal ranges, rip currents can only occur at certain stages of the tide, when the water is shallow enough to cause waves to break the sand rod, but deep enough for damaged waves to flow over the bar. (In parts of the world with large differences between tide and low tide, and where shorelines lined gently, the distance between bars and shorelines can vary from a few feet to a mile or more, depending on whether it is in high tide or low tide.)
A fairly common misconception is that rip currents can pull swimmers down, below the surface of the water. This is not true, and in fact the most powerful rip currents approach the surface, because the flow near the bottom is slowed by friction.
The surface of the rip current may appear as a relatively smooth water area, with no breaks, and this deceptive appearance can cause some coastal viewers to believe that this is a suitable place to enter the water.
Technical description
More detailed description involves radiation pressure. This is the force (or flux of momentum) given to the water column by the presence of waves. As swarms of waves and high rise before breaking, radiation pressure increases. To balance this, the average local surface level (water level with average wave) decreases; this is known as setdown . As the wave breaks and continues to decrease in height, the radiation pressure decreases. To balance this power, the average surface rise - this is known as settings . As the wave propagates above the sand dune with the gap (as shown in the main drawing), the wave breaks in the bar, leading to setup. However, parts of the waves that spread above the crack do not break, and thus the setdown will continue. So, the average surface above the bars is higher than the distance above it, and the strong flow out through the gap.
Maps Rip current
Signs and visible characteristics
Rip currents have a distinctive appearance, and, with some experience, they can be visually identified from the shore before entering the water. This is useful for coast guards, swimmers, surfers, sailors, divers and other water users, who may need to avoid tearing, or in some cases making use of current flow. Rip currents often look like roads or streams flowing straight into the sea, and it's easiest to notice and identify when the breaking wave zone is viewed from a high point of view. Here are some characteristics that can be used to identify rip visually:
- A real break in wave patterns - water often looks flat when torn, unlike broken wave lines on either side of the rip.
- "River" foam - rip surfaces sometimes look frothy, as currents carry froth from the waves into open water.
- Different colors - rips may differ in color from the surrounding water; often more opaque, more cloudy, or more confusing, etc., depending on the angle of the sun, the rip may appear darker or brighter than the surrounding water.
- It is sometimes possible to see that the foam or debris floating on the rip surface moves out, away from the shore. Conversely, in the surrounding area of ​​a ruptured wave, floating objects are pushed to shore.
This characteristic is helpful in learning to recognize and understand the nature of the rip current so that one can recognize the existence of a tear before entering the water. In the United States, some beaches have signs made by the National Oceanic and Atmospheric Administration (NOAA) and the United States Lifesaving Association, which explains what is meant by rip currents and how to escape. These signs are titled, "Rip Currents, Break the Grip of the Rip". Coastal adventurers can get information from the coast guard, who are always watching the torn currents, and who will move their safety flags so that swimmers can avoid rips.
Dangers to swimmers
Rip currents are a potential source of danger for people in shallow waters with waves crashing in the ocean, oceans and lakes. Rip currents are the direct cause of the 80% rescue performed by the coast guard.
Rip currents typically flow about 0.5 meters per second (1-2 feet per second), but they can be as fast as 2.5 meters per second (8 feet per second), which is faster than humans can swim. However, most rip currents are quite narrow, and even the widest rip currents are not very wide; The swimmer can easily get out of the rip by swimming at an angle right into the stream, parallel to the beach. Swimmers who do not realize this fact may be exhausted without trying to swim against the current. The current flow also fades completely in the rip head, outside the breaking wave zone, so there is a definite threshold as to how far the swimmers will be brought into the sea by the flow of rip currents.
In a torn stream, death by drowning occurs when a person has limited water and panic skills, or when a swimmer strives to swim to the shore against a strong rip current, eventually becoming exhausted and unable to survive.
According to NOAA, above the 10-year average, rip currents cause 46 deaths each year in the United States, and 64 people die in tear in 2013. However, the United States Rescue Association "estimates that the number of annual deaths due to rip currents on the coast our country exceeds 100. "
A study published in 2013 in Australia revealed that tears killed more people in the Australian territory than bush fires, floods, cyclones and combined shark attacks.
Management
A person trapped in a torn stream may notice that he is moving away from the coast very quickly. Often it is not possible to swim directly back to shore against tear current, so this is not recommended. Contrary to popular misconceptions, rip does not attract swimmers underwater, it just brings swimmers away from shore in a narrow band that moves. The tear is like a moving treadmill, which a swimmer can swim across the stream, parallel to the shore, in any direction, out of the rip current, which is usually not very wide. Once out of the rip, swimming back to shore is relatively easy in areas where the waves break and where floating objects and swimmers are being pushed towards shore.
Alternatively, swimmers who are trapped in a strong relax can relax and follow the current (either float or tread water) until the current disappears outside the surf line, and then they can signal for help, or swim back through the waves diagonally. far from the rip and headed for the beach.
It is important for beach swimmers to understand the dangers of tear currents, to learn how to recognize them and how to deal with them, and if possible to swim only in areas where coast guards are on duty.
Usage
Experienced and knowledgeable water users, including surfers, body tenants, divers, beach savers and kayak makers, will occasionally use rip currents as a quick and easy means of transportation when they want to get out of the crashing waves.
See also
- longshore drift
- Current statement - warnings issued by the US National Weather Service
- Undertow (water wave)
References
External links
- NOAA glossary term used in describing rip current
Source of the article : Wikipedia
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