How & Why Do Waves Break: For Surfers!

We all know what a wave break looks like, but do we know how or why waves break?

As surfers, knowing why do waves break is very important to expand your knowledge of the world's oceans.

This article will cover everything you need to know on how and why do waves break!

Why Do Waves Break?

Waves break when they reach shallow waters, causing the lowest part of the wave to slow down due to friction with the ocean floor.

This steepening process results in the wave breaking, releasing energy and creating the familiar crashing sound on the shore.

How Do Waves Break? 

Waves break as they approach shallow coastal areas.

The lower part of the wave slows down due to interaction with the ocean floor, causing the wave to steepen and ultimately break, releasing energy and creating the crashing effect.

Science of How & Why Do Waves Break

Scientists reveal that waves break when their amplitude reaches a critical level near coastlines, converting wave energy into turbulent kinetic energy. 

Why do waves break sounds fairly simple when stated like this, howver it is not the case.

This transformation is guided by the Law of Gravitation and the science of wave shoaling, emphasising the significance of the ratio of wave height to wavelength, typically exceeding 1/7. 

Wind direction further influences the breaking process, with offshore winds impeding and onshore winds accelerating. 

Cyril J. Galvin's 1968 classifications (surging, plunging, and spilling), offer insights into the dynamics of breaking waves, revealing a spectrum of intensities and shapes surfers navigate.

Breaking Waves

What Is a Wave Break 

A wave break, also known as wave breaking or surf, occurs when a wave transitions from deep to shallow water across the world's oceans. This causes the wave's crest to become unstable and spill forward. 

This phenomenon is a result of the wave's energy becoming compressed as it enters shallower depths, leading to the characteristic curling and crashing of the wave. 

Types of Breaking Waves

Breaking waves come in various forms, each with its distinct characteristics important to know when learning why do waves break.

Spilling Waves

These waves break gradually and smoothly, creating a cascading effect as the wave spills gently over. Spilling waves are common on gradually sloping coastlines and are often favoured by beginner surfers due to their milder nature.

Plunging Waves

Plunging waves are renowned for their barrel-shaped tube as the wave crest curls and crashes forward. These waves are favoured by experienced surfers seeking an exhilarating ride within the hollow section of the wave.

Surging Waves

Characterised by a powerful surge of water rushing to the towards the shore, surging waves lack the distinct crest seen in other types. These waves are common in steep, shore-break environments and can pose challenges for swimmers due to their forceful impact.

What Happens When a Wave Breaks 

When a wave breaks, it undergoes a transformative process, transitioning from a smoothly undulating form to a dynamic and energy-releasing event. As a wave approaches shallow waters, the base of the wave begins to interact with the seafloor. 

The increasing friction and decreasing depth cause the wave's energy to compress, leading to the following key stages:

Crest Formation: The top of the wave, known as the crest, becomes steeper as it enters shallower waters.

Curling and Overhang: The wave's crest starts to curl over the base, creating the iconic tube or curl. This process is more pronounced in plunging or tubing waves.

Breaking: The wave reaches a critical point where the crest can no longer support its own weight. This results in the wave breaking, releasing energy forward in a visually striking display.

Whitecap Formation: The breaking wave generates a mass of foamy water known as a whitecap. This frothy mixture of air and water is a visual indicator of the wave's energy dissipation.

These key stages all happen within the space of a few seconds, however each is important to know when looking at why do waves break especially for us surfers.

What Happens When a Wave Breaks on the Beach

As the wave encounters shallower waters near the coast, the friction with the seafloor causes the wave's base to slow down. 

Meanwhile, the top of the wave, the crest, continues moving at its original speed. 

This disparity in speed leads to the wave becoming steeper, eventually reaching a critical point where the crest can no longer support its own weight. The wave then collapses, creating the visual spectacle of a breaking wave.

Why Do Waves Break on the Beach

Waves break on the beach due to the interaction between the wave and the ocean floor. 

When waves enter shallow waters near the coast, their energy is compressed. The reduced depth causes the wave's base to slow down, leading to the steepening of the wave. 

Ultimately, the wave breaks as the crest curls over and collapses.

How Do Waves Form

Waves form through the transfer of energy from the wind to the water's surface as previously mentioned when defining why do waves break.

The process begins when the wind blows across the ocean, creating friction with the surface of the water. As the wind interacts with the water, it transfers energy, generating ripples. 

These ripples then evolve into waves as the wind continues to exert force.

The size and energy of the waves depend on various factors, including wind speed, duration, and the fetch. With sustained wind, waves organise into sets, forming a wave train. 

Factors Affecting Waves Breaking

Understanding the dynamics of why do waves break involves considering several key factors that influence this natural phenomenon.

Type of Swell

The type of swell, whether it's a groundswell originating from distant storms or a windswell caused by local winds, significantly impacts how waves break. Groundswells often lead to more organised and powerful breaks, while windswells can result in choppier and less uniform wave patterns.

Wind Direction Impact on Waves Breaking

Wind direction plays a crucial role in wave formation and breaking. Onshore winds, blowing toward the shore, can create steeper and more powerful waves that are prone to breaking, enhancing the surfing experience. Offshore winds, blowing from the land to the sea, may delay or inhibit the breaking process.

Impact of Tides on Wave Breaks

Tidal variations affect the depth of the water, influencing the behaviour of waves. During high tide, waves encounter shallower waters closer to the shore, potentially leading to more pronounced breaks. Conversely, low tide may cause waves to break farther offshore.

Surfers often use a riptides to make it outback, but it's important to understand the dangers of these currents.

Slope of Sea Floor

The slope of the sea floor as waves approach the shore plays a crucial role in wave breaking. Gradual slopes tend to produce gentler breaks, while steeper slopes can result in more powerful and abrupt wave breaks.

Sea Floor Features

Underwater features, such as sandbars, reefs, or rocky formations, significantly impact wave breaking patterns. These features can focus or disperse wave energy, leading to unique and varied breaking characteristics such as square waves.

Summing It Up: What To Do Now

Nice! Now you are well read on how ad why do waves break! Now get out there and enjoy your local break!

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