Jeffreys bay is one of the five most famous surfing destinations in the world and is ranked by some as second best in the world. It hosts a famous annual surfing event at Super Tubes during July. Spectators and professional surfers from all over the world flock to this event. Along the coastline the ideal waves can be found that is sought after by surfers.
The most important influence on wave shape is the topography of the seabed directly behind and immediately beneath the breaking wave. Each break is different, since each location’s underwater topography is unique. At beach breaks, sandbanks change shape from week to week. Local wind conditions will also affect wave quality, ideal conditions include a light to moderate “offshore” wind, because it blows into the front of the wave, making it a barrel or tube wave. Waves are Left Handed or Right Handed depending upon the breaking formation of the wave. Waves are generally recognized by the surfaces over which they break. For example, there are Beach breaks, Reef breaks and Point breaks.
Wave breaking and Types of breaks
Some waves undergo a phenomenon called “breaking”. A breaking wave is one whose base can no longer support its top, causing it to collapse. A wave breaks when it runs into shallow water or when two wave systems oppose and combine forces. When the slope, or steepness ratio, of a wave is too great, breaking is inevitable.
Four main types of breaking waves are identified by surfers or surf lifesavers. Their varying characteristics make them more or less suitable for surfing and present different dangers.
1. Spilling or rolling:
These types are the safest waves on which to surf. They can be found in most areas with relatively flat shorelines. They are the most common type of shore break. When the ocean floor has a gradual slope, the wave will steepen until the crest becomes unstable, resulting in turbulent white-water spilling down the face of the wave. This continues as the wave approaches the shore and the wave’s energy is slowly dissipated in the white-water. Because of this, spilling waves break for a longer time than other waves and create a relatively gentle wave. Onshore wind conditions make spillers more likely.
2. Plunging or dumping:
These break suddenly and can “dump” swimmers – pushing them to the bottom with great force. These are the preferred waves for experienced surfers.
These waves occurs when the ocean floor is steep or has sudden depth changes, such as from a reef or sandbar. The crest of the wave becomes much steeper than a spilling wave, becomes vertical, then curls over and drops onto the trough of the wave - releasing most of its energy at once in a relatively violent impact. A plunging wave breaks with more energy than a significantly larger spilling wave. The wave can trap and compress the air under the lip, which creates the “crashing” sound associated with waves. With large waves, this crash can be felt by beachgoers on land. Offshore wind conditions and long wave periods can make plungers more likely.
If a plunging wave is not parallel to the beach (or ocean floor), the section of the wave which reaches shallow water will break first, and the breaking section (or curl) will move laterally across the face of the wave as the wave continues. This is the “tube” that is so highly sought after by surfers (also called a “barrel”, a “pit” and “the greenroom”). The surfer tries to stay near or under the curling lip, often trying to stay as “deep” in the tube as possible while still being able to shoot forward and exit the tube before it closes. A plunging wave that is parallel to the beach can break along its whole length at once, rendering it unrideable and dangerous. Surfer refer to these waves as “closed out”.
3. Collapsing
Collapsing waves are a cross between plunging and surging, in which the crest never fully breaks, yet the bottom face of the wave gets steeper and collapse, resulting in foam.
4. Surging:
Surging breakers originate from long period, low steepness waves and/or steep beach profiles. The outcome is the rapid movement of the base of the wave up the swash slope and the disappearance of the wave crest. The form face and the crest of the wave remain relatively smooth with little foam or bubbles, resulting in a very narrow surf zone or no zone at all. The short, sharp burst of wave energy means that the swash/backwash cycle completes before the arrival of the next wave. Surging waves are typical of reflective beach states. These may never actually break as they approach the water’s edge, as the water below them is very deep. On steeper beaches, the energy of the wave can be reflected by the bottom back into the ocean, causing standing waves. These waves can knock swimmers over and drag them back into deeper water.
The Jeffreys Bay Surf Break is a very long, fast, tubing point break that breaks along the west side of the bay. In season, the break is regarded as one of the best point breaks in the entire world, in both consistency and quality. It has been divided up into several sections, including, from the top of the point: Kitchen Windows, Magna tubes, Boneyards, Supertubes, Impossibles, Tubes, The point and Albatross.
Supertubes breaks for about 300m or more and is regarded as the best part of the wave. On rare occasions, Boneyards can link up all the way to The Point for a ride of over one kilometre long. The optimal size wave faces is considered to be from about 1.2 - 3m. The most consistent waves occur between about May to mid-September coinciding with offshore winds. A South-West wind is best for optimal waves. Due to the sand dunes, the break is protected no matter how hard the South-West wind blows. East and South-East wind destroys the waves.
The answers to qualify for this Earth Cache can be found at the listed coordinates that will take you to a board walk:
To log this Earth Cache please email your answers to the following questions to the cache owner via our profile on the geocaching website. Please do not post any answers in your log:
- Based on what you have read about the different types of waves what type of seabed do you think is predominant on the Jeffereys Bay coastline? What do you base your answer on?
- Estimate the angle of the approaching waves relative to the shoreline.
- Looking at the first photograph above assume you are riding a wave from Supertubes and are traveling at right angles to the wave. The wave will take you past The Point and you will actually be traveling parallel to the coastline! [See last photograph]. Why do the waves NOT go onto the beach here? Explain your answer in terms of how you think the seabed and the shoreline influences this.
- What kind of waves and what kind of break (left or right) can be seen from the viewpoint? Explain your answer shortly.
- Estimate the length and the height of a wave while you are at ground zero.
- It would be great if you could share what you experienced during your stay in Jeffreys Bay in your log. This is not compulsory to qualify for a log.
- It would be nice to see a photo of you/team/GPS with the surf, but it is not compulsory to qualify for a log.
References:
https://en.wikipedia.org/wiki/Breaking_wave
https://en.wikipedia.org/wiki/Wind_wave
http://www.infojeffreysbay.com
http://i.cdn-surfline.com/surfnews/images/2011/07_july/mechanics_jbay/full/12a_GB_DSC_0967.jpg
http://bc.outcrop.org/images/shorelines/press4e/figure-17-13-1.jpg
http://image.slidesharecdn.com/thecoastsigcse-100308104414-phpapp01/95/the-coasts-igcse-31-728.jpg?cb=1268066726
http://www.zigzag.co.za/wp-content/gallery/hour-ago-2013/j-bay_hourago.jpg
https://swelllinesmagdotcom.files.wordpress.com/2014/05/breakers.gif