Big storms and the action of waves moving sand create sand bars which alter the depth of the beach at certain points. The sea floor needs to have different depths at different points of the wave so waves will peel along their length. The waves constantly close out, and you can't get a decent ride. Surfing a flat beach can be a boring experience. Sea floor features are especially important when surfing beach breaks. Reef breaks such as Pipeline in Hawaii are examples of this type of break. Rapid depth change creates steep pitching waves (Often taking the inexperienced surfer with it.) The waves created by the rapid change in depth are much steeper and hollower, and - thus the tube is born! The top of the wave quickly overtakes the bottom and pitches forward. The breaking depth is reached much later that on the gently sloped bottom. From the diagram below it can be seen that the wave "jacks up" due to the rapid change in depth creating a higher wave. The swell approaches the beach / reef at a greater speed. The contrast to the gently sloping sea floor is a steep slope or a reef. WAVE BREAK HOW TOIf you're learning how to surf, then these waves are ideally what you are after.Įxamples of this type of slope can be seen at average beach breaks all over the place. These crumbling waves won't be steep and will lack punch. A gently sloping approach causes the bottom of the wave to drag and will result in the top of the wave prematurely overtaking the bottom resulting in the wave breaking in deeper water. If you've read everything we have written up to this point, you know that it's the action of the sea bed slowing the bottom part of the wave that causes the wave to break. Waves tend to be lumpier and fail to reach their optimum peak. The onshore wind pushes the top of the wave forward causing the wave to break before the normal breaking depth is reached. When you watch waves or see them in surfing magazines with huge plumes of spray blowing back over the top of the wave, you're looking at offshore surf.Īn onshore wind will have the opposite effect. This results in the waves breaking later than they normally would in calm conditions. The wind blows against the top part of the wave and helps delay the top part from overtaking the bottom part. Offshore wind is most desirable for creating good waves. Wind swell will tend to break in deeper water and will not pack such a punch. The breaking waves will be steeper and faster. The longer wavelength waves will move quickly and get into shallow water before starting to break. Groundswell is best for creating good waves. The type of wave that is produced is dependent on different factors. We're surfing! In general a wave will start to break when it reaches a water depth of 1.3 times the wave height. There comes a point where the top of the wave overtakes it and starts to spill forward - the wave starts to break. The increase in wave height begins to occur at depths of around one half of the wavelength.Īs the wave moves into increasingly shallow water, the bottom of the wave decreases speed. The steeper the sea floor gradient the more pronounced the wave height will increase. they shorten their wave period.) This process is called shoaling and results in increasing wave height. As they slow down they have to squash together. The shallower the water becomes the slower they move. Some of the waves' energy is lost through contact with the sea floor. As a swell approaches the coastline and comes into contact with the sea floor the waves will start to slow down.
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