The surf is often roughest close to shore. The wave breaking closest is labeled by surfers as the “inside break”. The inside wave breaks close to shore and then forms a foam wave to the beach.
On sand bar beaches, there is often a second wave a little further out from the shore break. Then on a good day, there is an outside break that usually provides the best shaped waves for the intermediate and advanced surfers. Which waves are available are also functions of the swell arriving and the status of low or high tide not to mention the bathymetry of the bottom.
The shore is where the ocean floor rises to meet dry land. The bathymetry is the structure and substance of the bottom at the shore where the wave energy finally meets an obstacle like a reef or rock on the shallow bottom, or shifting sands like on a sand bar beach.
Waves don’t break when they are in deep water. Even a tsunami can travel at 500 miles an hour and only be a ripple until it hits a shallow bottom or obstacle. The shore stalls the circular motion of the wave energy and causes them to take an elliptical shape. When the elliptical shape becomes unstable, it breaks into a wave.
Water doesn’t move. Water particles revolve in a circle as the energy passes through them. The energy is commonly caused by wind blowing over a wide surface of the ocean called a “fetch”. The larger the surface catching the wind energy, the more energy there is in the wave.
As the energy moves, it is not interrupted until the circulating energy hits a reef or ocean bottom. The reason tides affect waves is that a high tide requires a bigger wave to reach the bottom far out where you would like them to break. A lower tide allows the wave to hit the bottom sooner. The transition which is frequently the best, is the period between high and low tides.
Because there may be twenty factors plus some unknowns that cause any one surf condition, the surf reports are not always accurate. Even scientists say they do not know all there is to know about what causes waves.
Some beaches have reputations for being best at high tides or low tides or during transitions from one to the other. I find that the good times vary on a sand bar beach from week to week. Sometimes high tide is best, sometimes low tide, and sometimes in transition. One thing I have found is that there is usually a best 45 minute window every day and I try to estimate when that will occur. It is usually in the morning when the winds are favorable.
Waves are dispersed out of swells. A swell may contain many waves. The interval of the swell determines how deep the energy is circulating in the water. When the north shore of Oahu in Hawaii gets a swell with 20 second intervals, you are looking at deep waves that cause big surf.
There are mathematics that determining how big a wave will be given the swell interval and how deep the water will be where a certain size wave breaks. For a terrific story and great explanation of the science I recommend “The Wave” by Susan Casey.
It takes wind to generate waves and when the winds are up over a vast area of ocean, the distant surfing spots are going to benefit with big waves. Sometimes swells can be coming from different directions at the same time. There may be a dominant swell.
Swells meeting from different directions cause peaks. These peaks and dominant swells along with the bathymetry of a beach can cause different kinds of breaks. On a reef, the break looks pretty similar most of the time.
On a sand bar beach, the different elements combine to create different results. When the North Swell and the Southern Swell combine in Southern California, we often get the perfect break that then breaks right or left.
As a wave peaks and then rolls right or left, the surfer rides the unfolding pocket and “maneuvers” with his bottom turns and shots off the lip. He harnesses the natural process for his own fun and amusement.
Depending on the original force of the swell, the wave and foam can hit hard or barely cause a ripple. Some days the surfers sit on their boards as the waves roll under them with not enough power to cause a peak or a break. With more energy, the waves hit bottom and rise up with power to allow a surf board to get propelled.
Depending on the tide, the swell energy, and the bathymetry of the beach, the wave can be perfectly formed for great riding or just a “walled off close out” that cannot be ridden. Some beaches have characteristics that cause waves to get walled off or closed out when they reach a certain height.
What beginners don’t realize sometimes when they have a bad day is that the waves were not rideable. The beauty of the beaches that are famous is that they handle the biggest swells and allow the perfect waves to be formed. This is where we see the ASP contests and where the modern surf legends are born.
Sand Bar Vs Reef
A reef is a location where the wave energy hits a barrier that causes the circulating energy to become unstable and break. Most of the best wave beaches in the world are reefs because they are exposed to large fast moving swells that become unstable and form some amazing results.
In Sand Bars, the breaks can occur differently every night as the bottom is shifted around by waves and currents. The beauty of the reef is that the wave occurs in the same place each time and during a specific swell, the waves will look very similar. When they hit reefs such as in Hawaii or Tahiti that are exposed to long distance swells that have tremendous energy, the waves can vary and look spectacular. In local Southern California beaches where the wave energy is generally dissipated by the time it hits, the waves are nicely formed and fairly uniform creating some great breaks.
Sand bar beaches are bottoms that shift every night. The waves breaking tend to look the same over a period of a few days but different each week. Waves also break in different spots from the shore outward. You might take an outside wave that has a gradual face and then the next wave is a close out at the same spot.
You might ride an outside wave moving at a fast speed on one ride and go for a more inside wave that is moving slower on the next ride. The beaches offer variety which can also be seen as a challenge. If you like to paddle you can be moving between breaks and also from outside breaks to inside breaks. Whereas a reef might create one wave that breaks to the shore, a sand bar beach might create an outside, middle and inside break.
Learning About Waves from my book Surf Instructions Beginner to Advanced on Amazon
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