Waves
[North shore big wave surfing scene]
At an outer reef miles from shore, a surfer on a surfboard holds onto a tow rope as he is pulled behind a jet-ski. A huge wave forms on the horizon and continues to grow as it approaches.
The jet-ski driver swings the craft around to pull the surfer in the same direction of the wave, which has now welled up to a monstrous size. The person on the surfboard lets go of the tow rope and surfs the giant wave.
The jet ski driver powers the craft out of harm’s way, and then quickly drives back around to retrieve the surfer.
[Photograph: Big wave surfing]
Hō a‘e ka ‘ike he‘enalu i ka hokua o ka ‘ale.
Show [your] knowledge of surfing on the back of the wave.
Talking about one’s knowledge and skill is not enough; let it be proven.
(Pukui: 1013-108)
Perhaps more than any other place in the world, Hawai‘i is famous for its large waves. Surfers, sunbathers, and visitors from all over the world flock to the Hawaiian Islands from all parts of globe for a chance to visit the famous surfing beaches, point breaks, and outer reefs.
During summer, large swells arrive from far to the south and break along the Hawaiian Islands’ southern shores. However, it is the giant north shore winter surf that is the source of legends.
Every winter, huge storms are generated off of the Asian landmass and grow over the
Types and Properties of Waves:
Technically, a wave is defined as any disturbance (energy) that moves over or through a medium, such as air or water. There are many different kinds of waves, from radio waves to sound waves, to tsunamis traveling 7,000 miles across the Pacific Ocean.
A wave’s speed is determined by the properties of the medium through which the wave is traveling. For example, sound waves move four times faster in water than they do in air, because water has a higher density than air.
A dolphin’s high frequency echolocation pulses (sound waves) have extremely small wavelengths, while a tsunami may have a wavelength of 50 to 300 miles (80 to 483 km), as well as a period as long as 30 minutes, and a speed through the ocean of more than 500 mi/hr (805 km/hr).
Anatomy of a Wave:
The highest point of the wave is called the crest and the lowest point is called the trough. The vertical distance between the wave’s crest and trough is the wave’s height. Waves also have a length, which is the distance from the crest of one wave to the crest of the next wave (the wavelength).
An ocean wave is really just energy moving through the water. A wave’s energy reaches to a depth equal to about one-half of its wavelength. If the water is shallower than that depth, the wave starts to collapse on itself, or break. In other words, a wave breaks when it reaches water that is about half as deep as the wave is long (which is also usually about half the wave’s height).
The time it takes one complete wave to pass a given point is known as the wave’s period. If the swell period is 14 or more, then it usually means sizeable waves were generated from a distant storm system, and are arriving in the
A wave period of 14 might bring waves with heights of about 6 to 10 feet (1.8 to 3 m) high. This wave height may vary considerably, especially considering that locals judge the waves height not by the face but by the back of the wave, which is about half as big as the face. In general, however, if the wave period is 14, there will be great surfing waves.
[Illustration: Diagram of wavelength, height, period, crest, and trough]
Ocean Weather Buoys
Four ocean buoys are placed hundreds of miles to the north, south, east and west of the Hawaiian Island chain. Each boat-shaped weather buoy is about 20 feet (6 m) long, weighs more than 14,000 pounds (6,350 kg), and is anchored to the ocean floor.
Real-time buoy data is transmitted each hour via satellite to National Oceanic and Atmospheric Administration (NOAA) meteorologists, posted on the Internet (http://seaboard.ndbc.noaa.gov/Maps/Hawaii.shtml) and reported on local news forecasts.
The ocean buoys report sea and air temperatures, barometric pressure, wind direction, wind speed, wave height, and wave and swell period at the buoy location. This provides fishermen with advance notice of high surf and possibly dangerous conditions, as well as alerting surfers when conditions may be particularly formidable.
For example, if the buoy to the north of the Hawaiian Islands (Buoy 51001—193 nautical miles west-northwest of Līhu‘e, Kaua‘i) reports that the height of the swell is 15 feet (4.6 m) with a period of 20 seconds, then surfers know there will definitely be big waves arriving on the north shore within several hours, and fishermen know it may not be the best time to go out to sea.
Be Careful—Avoid Dangerous Waters
The ocean can be a very dangerous place, especially when currents and waves make for difficult conditions. Drownings do occur, and at a rate that continues to confound officials.
On Kaua‘i alone, from 1970 to 2001, there were more than 200 reported drownings (including 63 from 1995-2002, with 12 in 1999, 12 in 2000 and 8 in 2001. Twenty-eight of these drownings occurred at just one Kaua‘i beach, Hanakāpī‘ai, and most of the victims were never recovered.
Another beach just miles away, Lumaha‘i, had 19 drownings. Most drownings occur in winter when big swells and strong currents are more frequent. Statistically, most victims of drowning in the Hawaiian Islands are male, from 30 to 50 years old.
With an estimated 18 million beach visitors on O‘ahu in 2001, there were 1,360 rescues, and first aid was given to 92,717 people. One particularly dangerous place is near the surf spot known as China Walls as well as the surrounding area for about 1 mile (1.6 km), including the area near Spitting Cave. In this stretch of water more than 24 people have drowned since 1977, with an estimated 50 more near drownings.
Beaches all over the island have potentially dangerous conditions, and often areas that seem safe pose potential hazards for people inexperienced in the water. On O‘ahu, in a period of less than one month—between June 6 and July 2, 2002—there were seven drownings, mostly tourists in shallow water. Two more persons died on July 19, 2002 near a spot called Witch’s Brew at the mouth of Hanauma Bay.
On June 30, 2002 an 18-year-old male became the third person since 1969 to die at Hālona Blowhole, a famous wave-generated spout of water on O‘ahu’s southeast shore near Hanauma Bay. As he leaned over the blowhole, a spout of water sent him flying up into the air and then down into the blowhole.
On April 13, 1986 an 18-year-old man fell into the Hālona Blowhole and died, and on July 24, 1969 a 26-year-old man died after falling into the blowhole. In 1967, a soldier from Schofield Barracks fell into the blowhole and survived. He later said that he found himself in a large cave before a wave arrived and caused him to hit his head. The next wave washed him out into the ocean where he was rescued.
Always stay behind railings and heed warning signs. Blowholes may be completely quiet one moment and the next moment sends an explosive plume of water more than 50 feet (15 m) into the air.
Water Safety
When venturing into the ocean in the Hawaiian Islands, be extremely careful, no matter how safe it may appear. Waves are often more powerful than they look, and currents along the shoreline may be hard to detect until you find yourself in a dangerous situation.
Always pause and look before going in the ocean. For at least 20 to 30 minutes before going in, patiently watch the ocean area where you plan on swimming. You need to observe the largest waves that are coming toward shore, and these “sets” may only be arriving every 30 minutes or so, so you must wait and see.
There is often an extended period of smaller waves or calm between the bigger sets, and this may be extremely deceptive, causing some people to think conditions are safe when they are not.
Things Aren’t Always As They Seem
Don’t always assume that just because there are numerous people in the water it’s safe to go in. Many Hawaiian Island residents have grown up around the water, and are experienced in dealing with powerful currents and waves that are extremely dangerous for inexperienced swimmers. Most of the drowning victims in the Islands are visitors, rather than the surfers and locals who frequent the ocean waters.
Many drowning victims are strong swimmers, but the powerful waves and ocean currents add another dimension to the situation, a dimension not always anticipated by those unfamiliar with the ocean. Visitors often overestimate their own abilities, and underestimate the ocean conditions.
E ‘au mālie i ke kai pāpa‘u, o pakī ka wai a pula ka maka.
Swim quietly in shallow water lest it splash into the eyes.
A cautioning to go carefully where one isn’t sure of conditions.
(Pukui: 267-33)
What To Do In a Rip Current—Remain Calm
If you do find yourself in trouble in the water, remain calm. Panic causes added difficulties in getting enough air, especially if you have to dive beneath waves.
If you are unable to swim closer toward shore or feel yourself being pulled out (away from shore), you are probably in a rip current. A rip current is an area where all the incoming water from the waves has found a channel to flow back out to sea. Rip currents tend to be fairly narrow and usually dissipate as they get farther from shore.
Don’t use up all your energy fighting the current. Instead the best thing to do is to calmly go with the flow as you slowly merge out of the rip current. Swim parallel to shore until you can feel that you are out of the current, and then make your way diagonally toward shore.
Some Tips on Water Safety—When In Doubt, Don’t Go Out!
Don’t swim alone, and always supervise children closely. Shorebreak waves are often very powerful, and body surfing or swimming even small waves, has the potential of causing extreme back and neck injuries if you are caught in the downward force of the breaking wave over a shallow sand area.
Sandy Beach is particularly known for this, making it one of the two most dangerous places on O‘ahu, along with China Walls (described above).
Water Safety—Key Things to Remember:
Ø If you get caught in a rip current, swim parallel to shore until you are out of it, then swim diagonally toward shore.
Ø Never turn your back to the waves when you are in or near the water! Occasional rogue waves have been known to surprise unwary swimmers.
Ø Swim with a buddy—never swim alone.
Ø Swim at beaches with lifeguards, and ask questions if you are unsure. It’s better to be safe than sorry.
Ø When in doubt, don’t go out—always be cautious around the ocean!
[Photograph: Big Waves]
