Coral Reefs and Wave Energy Dissipation

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Coral Reefs and Wave Energy Dissipation

Energy Dissipation

Wave Principles

Frequency

Long waves need larger reefs for substantial dissipation, whereas high-frequency waves lose energy more quickly across complex reef surfaces.

Reefs react differently to long, low-frequency waves than they do to short, high-frequency waves.

Wave types

Low-energy waves: smaller waves can be efficiently handled by reefs with denser, finer coral forms

High-energy waves: large waves are better dispersed by reefs with stronger, taller structures

Energy Conversion

Potential energy

Friction causes a wave's kinetic energy to decrease, and part of that energy helps to raise the water level above the reef. The reason for this is that the delayed wave lifts the water behind vertically rather than quickly dispersing its energy ahead (there's a brief rise in altitude as the energy of the wave is directed upward)

Kinetic energy

According to the law of conservation of energy, the energy that is "lost" in this process is actually transformed into heat via friction rather than being destroyed.

Hard coral skeletons and live polyps combine to form the rough, asymmetrical structures known as coral reefs. There is a lot of resistance or drag when waves travel across the reef's surface because of the irregular textures and fissures. The water particles' velocity is slowed down and dissipated by this resistance.

Turbulence

The force of waves that reach the coast is lessened by turbulence, which distributes energy throughout the reef.

Turbulence is produced by wave breaking and scattering, which transforms organized wave energy into chaotic motion.

Transformation

Energy conservation controls the change because energy lost to the reef can no longer be used to erode the shore.

The energy loss from friction, drag, and wave breaking causes waves to get lower as they pass over a reef.

Reef Structure

Health

Living corals preserve the structural integrity of the reef, which significantly helps  energy dissipation. Reefs that are dead or damaged can no longer effectively absorb wave energy.

Density

The best widths for dissipating wave energy are coral flats that are 100–300 meters wide, according to studies.

A wider reef plain gives waves more space to dissipate energy before hitting the beach.

Width

Branching corals and other dense coral forms are better at distributing energy and retaining water than smooth surfaces. They offer a large surface area, which is great for reducing drag and energy.

The complexity of a reef's surface is referred to as rugosity. Greater rugosity improves energy dissipation by increasing drag and friction.

Height

Near the surface, taller reefs interact with bigger sections of incoming waves, which results in more efficient energy reduction

Waves break more significantly on steeper (higher) reefs, which increases their ability to dissipate energy

Atolls: by evenly distributing wave energy throughout their perimeter, these reefs can efficiently dissipate icoming wave energy

Fringing Reefs: located nearer the coast, these reefs also significantly reduce wave energy, but they are more susceptible to direct human activity

Barrier Reefs: due to their vastness and shallow areas, these reefs (which run parallel to the shore), are very good at absorbing wave energy

When waves encounter obstacles like coral reefs, sandy beaches, or man-made boundaries, they release energy.

Water levels: by gradually raising the water levels above their structures, reefs lessen the energy that hits the shoreline and the steepness of the waves.

Boundary behaviour: the intricate forms of coral reefs reduce the itensity and impact of wave energy by diffracting (spreading) and refracting (bending)

Forces: the drag force produced by the reef structure interacts with the wave's force, resulting in a decrease of the wave's energy and velocity

Some wave energy is converted to heat as water passes over the reef due to friction between the water and the coral, further reducing the wave's energy

Energy: by creating turbulence and wave breaking, coral reefs absorb the kinetic and potential energy of the wave

Propogation: Ocean waves are mechanical waves that travel through the water and carry energy. Corals disturb the transmission of these waves when they come in contact

Human Activity

Consequences

Twenty-five percent of marine species live on coral reefs. The whole marine food web is upset when they disappear.

Each year, coral reefs provide $375 billion in services related to tourism, fisheries, and coastal protection.

Communities are left vulnerable to storms and sea level rise as a result of increased coastal erosion and floods caused by the loss of coral reefs.

Pollution

Coral ecosystems are disturbed by dredging and construction, which also increases sedimentation and restricts sunlight that is necessary for coral photosynthesis.

Too many nutrients enter the environment by agricultural runoff, causing algal blooms that choke corals.

Overfishing

Blast fishing involves using explosives, such as dynamite, to capture fish, which destroys coral structures.

For instance, in many regions of Southeast Asia, blast fishing has destroyed more than 80% of the coral reefs.

Reduces the number of important species that keep coral reefs in balance, like herbivorous fish that stop algae from growing too much.

Climate Change

The ability of bleached corals to preserve coastlines and sustain marine life is diminished because they are more susceptible to illness and death

Between 1985 and 2012, the Great Barrier Reef's coral cover decreased by 50%, mostly as a result of bleaching occurrences.

Seventy to ninety percent of coral reefs could disappear if global warming increases by 1.5°C over pre-industrial levels.

Corals are under stress from rising water temperatures brought on by climate change, which leads them to expel symbiotic algae called zooxanthellae (bleaching), which provide energy through photosynthesis. As a result, they lose colour and essential nutrients.

Real-World Applications

Innovation

To lessen erosion and wave energy, engineers are creating structures modelled after coral reefs.For example,textured seawalls that encourage the growth of marine life andbreakwaters that are submerged and shaped like coral reefs.

These structures improve climate change resilience while lessening the ecological imprint of conventional coastal defences.

Eco-friendly materials like concrete, steel, or limestone are used to create artificial reefs that resemble the substrates used by corals. Artificial reefs offer marine life habitats and shoreline protection

Artificial reefs are being implementedin Florida to repair damaged reef habitats.

Energy Usage

Systems modelled after coral reefs may capture wave energy, which helps with renewable energy sources. This reduces dependency on fossil fuels, supporting climate change mitgating efforts.

Environmental Education

As carbon sinks, coral reefs lower CO₂ levels in the atmosphere. By absorbing wave energy, reefs lessen the effects of increasing sea levels.

According to studies, protecting reefs may stop $10 billion in flood damage per year worldwide.

Coastal Protection

Storm surges and coastal damage are lessened by coral reefs, which disperse 97% of wave energy.Every year, millions of dollars are saved by preventing land loss and property damage.

Countries like the Maldives depend on coral reefs to defend against flooding, which lessens the harm caused by monsoons and sea level rise.

Secondary Research

Research docs

https://docs.google.com/document/d/1GGbxraCmdbRjIXI_a0YoAVPBH5rYdHPPdoC7dowo7Rc/edit?usp=sharing

Experiment analysis (physics concepts)

Hydrodynamic drag

The wide, sturdy structure of a complex reef increases hydrodynamic drag on the water flow. Drag forces slow down the wave's movement, reducing its ability to displace the sand. In comparison, a simple reef generates less drag, leading to more erosion but still less than in the absence of a reef.

The drag on watercraft that opposes the direction of motion. Describes any circumstance in which a body travels in a fluid and the drag force that results opposes the motion.

Wave boundary behavior

These effects collectively reduce the energy that reaches the shoreline, protecting the sand behind the reef.

Diffraction occurs when waves pass through gaps in the reef or interact with its edges, further scattering the wave energy.

The process of wave refraction bends the wave fronts around the reef, concentrating or dispersing energy in certain areas.

Energy transfer

FROM EXPERIMENTAL DATA: In the absence of a reef (Zone 1), the wave energy reaches the sand uninterrupted, causing significant erosion by displacing the particles and carrying them away. In Zones 2A and 2B, the reefs act as barriers, slowing down the water and reducing its ability to dislodge and displace the sand particles.

As waves interact with the reef, part of their energy is reflected back toward the water body, while another part is absorbed or redirected by the reef structure. This results in a reduction of forward momentum.

Energy disspation

Additionally, reefs create turbulence, where water flow becomes chaotic. Turbulence scatters the wave energy in different directions, further weakening the wave's force as it moves past the reef. The simple reef, while less effective than the complex reef, also contributes to energy dissipation but to a lesser extent due to its reduced surface area.

Complex reefs, with their tall, branching structures, provide a larger surface area and more points of contact for the waves, increasing friction. This friction converts the wave's kinetic energy into heat and sound energy, effectively reducing the energy that reaches the shoreline.

When waves propagate in water, they carry kinetic energy. When encountering a structure like a coral reef, the reef disrupts the wave's motion.

Energy Dynamics

Wave impact

As natural barriers, coral reefs lower the height and force of waves before they hit the coast.

High-energy waves have the potential to cause significant erosion, floods, and habitat damage on exposed coastlines.

Boundary behaviours

Reflection: when a wave changes direction after bouncing off of a hard surface. Reflection has no effect on a wave's energy, period, speed, or frequency.

Diffraction: When waves go through a small opening or around obstacles, they disperse (change direction), spreading energy over a larger region.

Refraction: When waves pass through media with different properties, their direction changes. Refraction happens when waves travel from deep water to shallow water.

Wave breaking

Thus, the sea floor has a significant impact on how rapidly the waves are affected as they approach the coast and how they break.

The wave's bottom contacts the ocean floor as it gets closer to the coast. Wavelength is decreased and front waves slow down as they drag across the bottom. Behind the slower waves, the subsequent ones begin to accumulate, and as their wavelengths get shorter, the wave energy is transmitted upward, raising the wave height. The water at the surface of the wave flows ahead, but the base of the wave is slowed down by the friction along the bottom. Wave instability and breakage occur when the wave steepness, or the ratio of wave height to wavelength, surpasses 1:7.

Wave energy

Thus, higher waves produced by storms frequently cause more erosion or energy dissipation when they come into contact with barriers like coral reefs.

Main factor determining a wave's energy is its height. Ex. A wave that is twice as tall as another has four times the energy.

Potential energy: energy that is stored as a result of the water in the wave's crest being raised above its equilibrium level.

Kinetic energy: isproportional to the water particles' motion. Particles with greater kinetic energy move more quickly.

The energy carried by ocean waves comes from the source that creates them, such as wind.

Ocean Waves

Particle motion

Water particles create crests and troughs by moving perpendicular to the direction of the waves.

Wave Properties

Wave speed (v): the pace at which a wave moves through a medium is its wave speed (v). The formula is v=f×λ.

Strong winds accelerate waves, which have greater velocity and energy.

Wave Period (T): the amount of time it takes for two consecutive crests of the same wavelength to cross a given spot.

Frequency (f): the number of waves per second is a wave's frequency, which is expressed in Hertz (Hz).

Waves with higher frequencies transmit energy more quickly.

Wavelength (λ): the separation of two successive crests or troughs.

Energy is carried by longer wavelengths.

Amplitude: the wave's height, as measured from its equilibrium point to the peak or trough.

The wave's energy is determined by its amplitude.

When wind energy is transferred to the ocean's surface, it creates ocean waves, which are mechanical surface waves.

Wind Duration and Speed: Larger waves are produced by winds that are stronger and remain longer.

Fetch: The unbroken distance that the wind blows. Waves are larger when the fetch is larger.

Wind: The main factor causing the majority of ocean waves. Through friction, wind brings energy to the water's surface.

General

A wave is an oscillation or recurring disturbance that moves energy through space or a medium without permanently shifting the medium's particles. From sound and light to ocean currents and earthquakes, waves are essential to many aspects of nature.

Mechanical waves: need a medium to pass through, such as solids, water, or air.

Surface waves: a mix of longitudinal and transverse waves that are frequently observed in water, where particles travel in elliptical or circular patterns.

Longitudinal Waves: The disruption runs parallel to the direction of the wave, such as sound waves.

Transverse waves: the disruption is perpendicular to the direction in which the waves are propagating.

Coral Reefs

Current State

Increased coastal flooding and a fall in biodiversity could arise from the destruction of coral reefs if this trend persists.

When stressed corals lose their main source of energy and expel their algae, bleaching takes place. Nearly 91% of the Great Barrier Reef was destroyed by events like the coral bleaching that occurred in 2016–2017.

Around 50% of coral reefs have been lost since the 1950s as a result of pollution, overfishing, and climate change.

Role

Economy

An estimated $375 billion is contributed to the economy each year by coral reefs, which sustain the fishing and tourism sectors. Furthermore, reefs are essential for protecting coastlines from storms and tsunamis since they may reduce wave energy by up to 97%. Coastal erosion would destroy infrastructure, houses, and habitats in the absence of this natural barrier. Coral reefs are essential to ecological equilibrium and human livelihoods because of their diverse functions.

Biodiersity

Coral reefs serve as the base of marine food webs, making them essential to biodiversity. Reefs are essential to the survival of more than 25% of marine organisms, ranging from larger fish and predators to tiny invertebrates.

Ex: by consuming algae that would otherwise suffocate corals, parrotfish contribute significantly to reef preservation.

Types

Atoll

These spherical reefs, which frequently occur around underwater volcanic islands, enclose lagoons. For instance, Bikini Atoll offers both wave protection and habitat for marine life.

Barrier Reefs

These reefs, like the Great Barrier Reef, are isolated from the shore by deeper lagoons. They serve as a buffer for Australia's coastal ecosystems against ocean waves.

Fringing Reefs

For example, the Australian Ningaloo Reef prevents erosion on neighbouring beaches.

The most prevalent kind of reef, found along coastlines, serve as direct barriers against the energy of coastal waves.

Habitat

A number of variables, including water temperature, salinity, and light availability, affect how quickly reefs build. Coral reefs can be found in the Caribbean, Southeast Asia, and the Pacific, primarily between latitudes 30°N and 30°S. The study subject of how they dissipate wave energy is closely related to their strategic locations close to coastlines, which emphasize their function in coastal security.

Formation

Coral reefs are especially susceptible to variations in water temperature and clarity because coral polyps depend on zooxanthellae algae for energy through photosynthesis. Their fragility is highlighted by the fact that the calcium carbonate structure is strong but needs stable environmental conditions.

Coral polyps, tiny marine invertebrates, create complex ecosystems called coral reefs by secreting calcium carbonate to construct tough, protective skeletons. These bones build up to create enormous reef structures over many decades. Numerous species depend on coral reefs for food, shelter, and breeding grounds, making them vital to marine life. They flourish in shallow, warm, nutrient-poor environments where sunlight sustains the zooxanthellae, which are symbiotic algae that live inside coral polyps.