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UNDERSTANDING WAVES

UNDERSTANDING WAVES PEMBROKESHIRE | OUTER REEF SURF SCHOOL

SURFING LESSON ON UNDERSTANDING DIFFERENT TYPES OF WAVES

Hey surfers! Today, we're going to talk about waves and how they are made, which is crucial for understanding the sport of surfing. Waves are the life force of surfing, so let's dive in and learn how they come to be! Here in Pembrokeshire, we are so lucky to have different types of waves right on our doorstep. When the open ocean swell reaches shallower water it becomes steeper and finally breaks into surf. Several factors influence the amount of growth that occurs from a deep water swell to a breaking wave. These include the angle of approach the swell makes with the shore, the configuration of shallow water bottom contours, the slope of the beach, and the deep water steepness of the wave (the ratio of wave height to wavelength).

First off, waves in the ocean are mainly created by wind. When strong winds blow across the surface of the water, they transfer their energy to the water, creating ripples. These ripples then develop into waves as they travel and interact with other waves. The size and quality of waves depend on several factors. One key factor is the speed and duration of the wind. Strong and consistent winds blowing over a long distance generate larger, more powerful waves. This is why you often find great waves in places with strong coastal winds or during storms. Another important factor is the "fetch," which refers to the distance of open water over which the wind blows. The longer the fetch, the more time the wind has to transfer its energy to the water, resulting in larger waves. For example, waves in the open ocean tend to be bigger than those near the shore because they have a longer fetch.

The shape and size of the ocean floor also play a significant role in wave formation. As waves approach shallow water near the shore, they interact with the seabed. This interaction causes the wave to slow down and compress, leading to an increase in wave height. It's this process that allows us to ride waves while surfing. Additionally, waves can be influenced by tides, underwater topography, and other environmental factors. For instance, reefs and sandbars can cause waves to break in specific ways, creating surfable conditions.

Now, as surfers, it's important to understand how to read and anticipate waves. Learning to observe the conditions, such as wind direction, wave height, and period (the time between two successive wave crests), helps us choose the right spot and time to catch the best waves. Remember, waves are dynamic and ever-changing, so learning how they are made and understanding their behavior is fundamental to becoming skilled surfers. So, let's continue our journey, riding those waves and experiencing the exhilaration of surfing!

PLUNGING OR DUMPING WAVES

The greater growth occurs when swells having little steepness and long period approach a strongly sloping beach or reef resulting in Plunging waves.

An example would be Winter waves frequently found on the reef breaks of the North Shore of Oahu in the Hawaiian Islands.

SPILLING WAVES

In areas of gently sloping bottom contours, waves of average steepness break at a water depth of about 1.3 times their height and are known as Spilling waves. These waves are ideal for beginners.

An example would be beach breaks with gently sloping bottom contours found in areas where the continental shelf extends a long way from land.

SURGING WAVES

This is where a swell hits a very steep obstruction and does not break in a rideable form.

An example would be waves that hit breakwaters, piers, or very steep banks.

FACTORS AFFECTING WAVES

TYPES OF SHALLOW WATER BOTTOM MATERIALS

As previously noted, the type of breaker produced depends largely upon the slope of bottom contours near shore.  Shallow water coral and rock bottoms are firmly anchored and quite often have steep slopes resulting in hard breading waves.

Sand bottoms consistently move due to currents and surf. From one day to the next the best place to surf may change drastically. The seaward edge of sandbars usually slopes gradually. This often results in less violent spilling breakers that may tend to become "mushy".

TIDES

Most surf sports seem to break best at a preferred water depth that varies according to surf height. In some areas of small tidal range, such as Hawaii, the 2 foot variation in water level is not too important. In some sections of Europe which have 30 feet (9 metres) tides, the time of tide is very important. It can mean the difference between unbroken swells hitting a steep beach, closed out conditions over low tide continuous sandbars, or good surf at a tide stage in between.

LOCAL WINDS AND CURRENTS

The effect of local wind direction on waves in Pembrokeshire is well known by any regular surfer. Offshore winds prevent a wave from breaking until it is steep and hollow. Onshore wind causes a breaker to collapse early, producing a spilling, mushy wave. Furthermore, the wave faces will be marred by wind chop produced by the onshore wind.

If you happen to surf at a place exposed to a seaward moving current or a rip, the waves will steepen and break in unusually deep water. Shoreward moving currents reduce wave height much as an onshore wind does. In either case, a strong current will cause choppy, bumpy waves. Currents near shore can be produced by tides, winds, or fluctuations in sea level due to surges of white water.

PRESENCE OF MORE THAN ONE SWELL

At times, especially during the winter storm season, two or more major swell trains may be present simultaneously at a point. This is particularly true for islands in the mid-ocean. If two or more swells arrive simultaneously that produce surf, complex interactions can occur. To determine the resulting wave height, one must account for the size, direction, and period of each of the contributing swells.

SET WAVES

Whenever the wave trains of the swells are in phase with each other (the wave crests of both swells arrive at the same time), the resulting wave height is the same as the sum of contributing wave heights. These are called set waves.

LULLS IN THE WAVES

When they are out of phase (the wave crests of one swell arrive at the same time as the trough of the other swell), the final wave height is the difference between the individual heights. The surfer will recognise this phase as a 'lull' between sets. It is important to recognise the pattern of sets and lulls on any given day. Good surfers will use lulls to paddle out in whereas beginners may find themselves paddling out too far and then being caught by the sets. Or paddling out in the sets.

TYPES OF SURFING WAVES

There are 3 main types of surfing waves of which only the first is generally suitable for teaching beginners.

BEACH BREAK

Surfer rebounding of the white water on a beach break wave.  The “mushy” nature of this wave is partly the result of an on-shore wind and a shallow sloping beach.

BEACH BREAKS - SOME COMMON CHARACTERISTICS

Offshore winds and steeply sloping sand banks can give rise to good hollow waves. Water surging towards the beach often causes strong cross currents leading into rip currents as it returns seaward.

Gently sloping contours and a large continental shelf often gives rise to slow beach break waves. Shifting sand banks often create a series of breaking waves and deeper water channels separating them. Beach break waves generally break over sand bottoms and various factors will determine their suitability for the beginner. Ideally the beach will have a gently sloping bottom producing gently sloping spilling waves with several lines of soup.

DUMPING WAVES

These are often found on beaches at high tide where a steep bank may cause the waves to break almost onto the sand. The waves rise up quite suddenly, break top to bottom and close out. They are unsuitable for beginners or experts.  Other factors e.g. a strong rip current can give rise to dumpers.

Waimea Bay Shore Break - A spectacular and very photogenic Dumping wave

REEF BREAKS

A reef may be of rock or coral and may be covered with sand. Because the slope of the reef is generally fairly steep the waves travel fast and break with great power. Reefs can produce excellent waves for more experienced surfers but are unsuitable for beginners.

The Pipeline on Oahu’s North Shore. One of the best known and most challenging Reef breaks in the World.

REEF BREAKS - COMMON CHARACTERISTICS

Offshore winds may contribute to the hollowness of these waves. In many areas, the lack of a continental shelf means that the waves do not lose much of their power prior to breaking. If the reef is at an angle to the approaching swells they will "peel off" along the reef edge. The waves often break hard in shallow water and the hard and often uneven nature of the bottom makes a reef break a more dangerous and challenging surfing location. Definitely not a beginner's wave!.

POINT BREAKS

In certain places a point of land, projecting into the sea will allow waves to break along its length giving long, good quality waves. Although these waves may break quite gently there is often a strong current running along the point requiring surfers to be able to paddle hard in order to reach to initial take off point. Point break waves often break over and in front of rocks and are frequently fast and challenging waves.  They are often unsuitable for beginners.

A classic Point Break - Jefferies Bay, South Africa

POINT BREAKS - COMMON CHARACTERISTICS

Underwater the point stretches out to sea causing the approaching swells to slow down and refract around it (the swells in deeper water will continue to move faster). The waves will then peel along the line of the point as they break. The lines of swell radiate out into deeper water and the current created by the breaking waves moves parallel to the shore into deeper water.

TRAVEL TIME OF SWELL

Offshore winds and steeply sloping sand banks can give rise to good hollow waves. Water surging towards the beach often causes strong cross currents leading into rip currents as it returns seaward.

Gently sloping contours and a large continental shelf often gives rise to slow beach break waves. Shifting sand banks often create a series of breaking waves and deeper water channels separating them. Beach break waves generally break over sand bottoms and various factors will determine their suitability for the beginner. Ideally the beach will have a gently sloping bottom producing gently sloping spilling waves with several lines of soup.

SURFING LESSON IN PEMBROKESHIRE FOR ALL AGES & ABILITIES

SURF LESSONS | UNDERSTANDING THE WAVES IN PEMBROKESHIRE

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