What Makes The Waves Good At Your Local?
First Understand How Waves Break
In simplest terms:
As swell moves into the coastal zone the water gets shallower. The energy of the swell will begin to drag along the bottom of the ocean floor (shoaling) causing the wave to slow down and its energy to be pushed up. Eventually the top of the wave becomes unstable and will break.
So why are the waves good or bad?
There are a number of determining factors that will make the waves good/big/slow/hollow /surfable at your local surf spot.
Thing to Remember:
Wavelength-The distance between waves passing a certain stationary object.
Swell Period-The time it takes for each wave to pass a certain stationary object.
Swell Angle– The Direction the swell is traveling
As mentioned in How Waves Form Swell Period, Swell Height and Swell Angle play a huge part on whether or not there will be waves at your spot.
But these factors also interact with the local variables-Reefs, Headlands, Underwater Canyons, Rock Shelves, Sand Banks, Jetties, Piers, Tides, and Local Winds.
One section of your local coastline might pick up more swell than another section due to a underwater canyon, Or the waves might be better on a lower tide at certain spots.
So understanding what swell period and direction plus what tides, winds is essential if you want to know when your spot will be good.
The best way to know what spot works best on a particular swell, tide, etc.. is plain old observation.
Notice how your local surf spot reacts to certain swell angles or periods, tides, winds etc….
You have to put in the time to understand a surf spot. Checking a surf cam and being spoon fed swell forecasts then rocking up to the beach is hardly putting in the time, get yourself down on the beach.
Some Common Terms To Understand When Thinking About How & Why Waves Break.
Shoaling: When a wave approaches shallower water near shore, its bottom energy begins to drag across the ocean floor, and slows down. The wave energy below the surface of the ocean is pushed upward, causing the waves to increase in wave height while the wavelength decreases.
Shoaling will effect how a wave breaks dramatically, say for instance a wave traveling form deep water suddenly hits a rock shelf or coral reef (Think Mavericks or Teahupoo) the wave height increase dramatically.
While A wave traveling over a gradual sloping ocean floor could become a mushy, slow breaking wave depending on the sea floor or Bathymetry.
Bathymetry: This is the underwater topography or characteristics of the ocean floor.
The ocean bottom is an uneven landscape and waves will react to the bottom contours by slowing down over shallow areas.
When a part of a wave/swell encounters a shallow area its speed will decrease while the same wave/swell in deeper water will maintain its, speed refracting the wave.
Refraction: This is when one part of a wave crest travels slower than another, making the wave bend towards that part which is travelling slower.
So think of a shallow rock slab sticking out form shore and on either side is deep water.
The wave will refract along that shelf, that is, the shallower area will slow down the wave while on either deep side the wave travels at the same speed. This in turn focuses the waves energy on the shallow slab area.
This is why its also important to know what the tide is going to be, a high tide will sometimes “bury” a spot by becoming to deep while a low tide might kill it by exposing a reef and becoming unsurfable.