WA learning goals

Identify where and how the maximum surge occurs in a hurricane

A storm surge is an abrupt bulge of water driven ashore by a hurricane.Most disastrous during HIGH TIDE, because mass and height of tide adds on to the surge.The surge moves in front of and to the right of the eye of the storm.

Identify key properties of waves

Crest: highest point of the wave Trough: the lowest point of the wave Wavelength (L/λ): distance between 2 successive crests or 2 successive troughs of a wave (meters) Amplitude (a): Height + 2 (meters) Period (T): time for one wavelength to pass a point (mins or secs) Frequency (f): number of waves passing a point per unit of time (per minute or seconds) Celerity/Speed (s): distance travelled per unit time (meters/sec) Steepness: a measure of the peaking wave, the ratio of height (H) to wavelength (L) -> H/L

Describe how coastlines affect waves, and how waves affect coastlines

Describe how coastlines affect waves, and how waves affect coastlines Coastlines can significantly influence the characteristics of waves. Refraction: When waves approach the shore at an angle, they bend or refract. This is due to the decrease in wave speed as they encounter shallower water. The part of the wave in deeper water moves faster than the part in shallow water, causing the wave to bend. Reflection: Waves can also be reflected off steep or rocky coastlines. This can cause interference patterns with incoming waves, leading to complex wave patterns. Diffraction: When waves encounter a barrier such as a breakwater or a pier, they can bend around the obstacle. This bending, or diffraction, can cause waves to spread out into areas of calm water. Waves can have a significant impact on coastlines. Erosion: Waves can erode coastlines, particularly during storms or high tide. This can lead to cliff collapse and the loss of land. Deposition: Waves can also deposit material, such as sand or pebbles, on the coastline. This can lead to the formation of features such as beaches, spits, and bars. Shaping: The constant action of waves can shape the coastline over time. For example, headlands can be eroded into sea arches and eventually stacks, while bays can be filled in with deposited material As waves move from the deep ocean toward the coastline and then into shallower water, the waves change: Waves slow down, wavelength shortens, orbital flatten, energy is conserved, periods stay the same, wave height increases, and waves steepenWaves can also change the shape of a coastline by erosion and the movement of sediment, as well as the uplift and subsidence

Describe the risks from a tsunami for the coast of British Columbia, especially one resulting from a megathrust earthquake

For British Columbia, where the threat of a megathrust type of earthquake is a reality, one of the greatest hazards after such a large earthquake is a tsunami. Residents in high-risk areas must be aware that a strong near-shore earthquake may generate a local tsunami. This means that the tsunami may arrive on shore within 10 minutes of a subduction earthquake. Therefore, it is highly recommended that those in these areas move inland or to high ground immediately as soon as they feel strong ground shaking. Emergency officials may not have time to issue a warning. After a megathrust earthquake, a large tsunami is very likely with the highest risk being to the west coast of Vancouver Island. Medium threat to the north coast and central coast. With low risk to Juan de Fuca Strait and the Strait of Georgia.

Compare and contrast groins

Groins are structures built perpendicular to the shoreline to trap sand moving along the beach. Pros: They can effectively slow down the process of longshore drift and help in beach nourishment. Cons: They can cause erosion on the down-drift side, leading to a need for more groins or other structures.

How to respond to the signs

Move to higher ground immediately: Tsunamis can hit the coast within minutes. The safest place is as high above sea level as you can get. If you can see the wave, you are too close to escape it. Evacuate on foot if possible: Tsunamis can cause roads to become impassable. If it's safe to do so, evacuate on foot. Follow instructions from local authorities: Pay attention to emergency alerts and follow the instructions provided by local authorities. Stay away until it's safe: A tsunami is a series of waves that can continue for hours. Do not return to the affected areas until authorities say it is safeStrong near shore earthquakes may generate a local tsunami. Move inland or to high ground as soon as you feel the ground shaking. Receding water is also a warning sign, and you must stay out of the way until an "all clear" is received.

Explain how a tsunami compares with other ocean waves

Origin: While regular waves are generated by wind, tsunamis are caused by geological disturbances.Wave Length: Tsunamis have a much longer wavelength than regular waves. This means they can travel across entire oceans without losing much energy. Speed: Tsunamis travel at high speeds in deep water, up to 500-600 miles per hour.Approaches shallow water as a fast-rising tide rather than a wind-driven oceanic wave. And is also caused by a displacement of water. Wave isn't confined to the beach like normal nearshore breaks, it can move inland and therefore cause monumental damage. Windblown waves have short periods and small wavelengths. Whereas, tsunami waves have very long periods and very long wavelengths (hundreds of km in wavelength of a tsunami, compared to mere meters for common waves).

Compare and contrast other structures

Other structures like breakwaters and jetties also have their pros and cons. Pros: They can protect harbours and marinas from wave action, and can also help in beach nourishment. Cons: They can disrupt longshore drift and cause erosion or sedimentation in other areas. Groins: elongate a structure that protrudes perpendicular to the shoreline, helps control beach erosion but deposition occurs elsewhere Seawall: reduces the effects of strong waves and defends the coast around a town or harbour - they reflect wave power, but promote increased erosion/destruction of beaches Jetty: protects an inlet or harbour, limits longshore drift Breakwater: defend against wave action and erosion. Also dissipates wave energy, and is usually built away from the coast Tethered Breakwater: removes energy from waves without interrupting sediment transport

Describe wave refraction, seiche (standing waves in enclosed or semi-enclosed bodies), and resonance; how do these affect the coast and people?

Refraction: waves approach a shore at an angle and it's because waves slow down as depth becomes shallow and segment closest to the shore... will "feel the bottom"- which results in the refraction/bending of the wave allowing it to be nearly parallel to the shore as it approaches- causes shore straightening, straightens out a ragged and irregular coast and causes erosion Seiche: resonant wave in a body of water caused by a disturbance by wind or seismic activity. Usually forms in lakes, landlocked seas, and semi-enclosed seas- can have the same effect as a storm surge and can oscillate back and forth, can form from the tsunami in a semi-enclosed body (Can cause drowning) Resonance: every enclosed wave has resonance, a resonant wave is a body of water caused by a disturbance by wind or seismic activity (Seiches)

Compare and contrast seawalls

Seawalls are structures built parallel to the shoreline to protect the land from wave action. Pros: They provide a strong defence against coastal flooding and erosion. Cons: They can accelerate beach erosion by reflecting wave energy onto the beach, and they can also disrupt natural coastal processes.

Use these properties to determine wave speed and behaviour in either shallow or deep water

Shallow-water waves are waves that are travelling in shallow water relative to their wavelengths, that is, where the water depth d is equal to or shallower than L ÷ 20. These waves are said to "feel the bottom" as the water particles near the wave base are dragging on the bottom as they move. Deep-water waves are waves that are travelling in ocean depths d equal to or deeper than L ÷ 2. These waves do not "feel the bottom" because their wave bases are shallower than the depth of the ocean they are passing through. Shallow Water Waves: Where water depth is equal or shallower than L/20- Can "feel the bottom" as the water particles are dragging on the bottom as they move- Move horizontally back and forth Deep Water Waves: Going deeper into the water column, the orbits decrease- Depths (d) equal or deeper than L/2 - Don't "feel the bottom" because their wave bases are shallower than the ocean bottom

Describe how storm surges are generated

Storm Surges are generated by a bulge of water driven ashore by a hurricane, where the hurricane winds are pushing water into a large or tal mound (wind-driven surge) and the rising of ocean water because of low air pressure at the ocean's surface. Generated by 2 processes occurring at the same time:- Wind-driven Surge: when hurricane winds push water into a large and tall mound- Pressure Surge: when ocean water is raised, suctioned upwards, underneath the eye of the storm because of the low air pressure created at the ocean surface A storm surge is NOT a wave as it is only a crest, but it does behave like a shallow water wave.

the three different breakers

Surging Plunging Spilling

Relate these changes to risks for coastal communities

The changes caused by these artificial barriers can pose significant risks for coastal communities. Erosion: The disruption of natural coastal processes can lead to increased erosion, which can threaten homes and infrastructure. Flooding: While structures like seawalls can protect against flooding, they can also increase the risk in other areas by disrupting natural flood defences. Environmental Impact: These structures can have negative impacts on coastal ecosystems, affecting wildlife and potentially disrupting local fisheries. Economic Impact: The cost of building and maintaining these structures can be high, and there can also be economic impacts from lost tourism if beaches are eroded.Vancouver Seawall: The beach has been eroded away, waves will eventually erode the wall and have it collapse

Explain the factors that determine the roughness of the sea

The factors that determine the roughness of the sea are looking at the wind strength/ speed, fetch and the wind duration, and the length that the wind has been blowing over the fetch. Wind strength and speed can transform capillary waves to ripples to chop (short waves)Wind duration, how long it blows over a FETCH (the area over which wind can blow uninterrupted) Longer duration and strong wind speed can create a rough sea, over a long fetch. Energy IN from the wind = energy OUT from breaking

Explain how waves move matter and energy

The ocean surface is intimately linked with the atmosphere. Winds drive the surface circulation of oceanic water. When wind blows over the ocean, it drags on the surface and transfers energy from the atmosphere to the water, thus creating waves and currents. Large-scale, permanent winds that blow over the ocean produce surface currents, which transport both matter (water) and energy. Winds that blow occasionally or over smaller areas produce waves, which transport energy in the direction of the wind. Technically, we define waves as the mechanical expression of energy.Energy is transported by waves and is related to the wave height (H) only in deep water waves.Waves with great heights transport more energy, and even those with long wavelengths.large scale, permanent winds that blow over the ocean produce surface currents which transport both matter and energy

Identify tsunami warning signs

Tsunamis are a series of ocean waves with very long wavelengths (typically hundreds of kilometres) caused by large-scale disturbances of the ocean, such as earthquakes, volcanic eruptions, glacier calvings, and meteorite impacts in the ocean. Recognizing the warning signs of a tsunami and knowing how to respond can save lives. Earthquakes: Since most tsunamis are caused by underwater earthquakes, feeling an earthquake might be the first warning sign of a potential tsunami.Rapid and unexpected ocean withdrawal: If you see the ocean receding unusually quickly or an exposed ocean floor, this is a very clear sign of a coming tsunami.Roaring ocean sound: A loud, roaring ocean sound (like an airplane or a train) coming from the sea is another sign of a tsunami.Abnormal ocean behaviour: Other unusual ocean behaviour, such as sudden sea-level rise or fall, can also indicate a tsunami. How to respond to the signs

Describe how tsunamis form and how they are detected

Tsunamis are formed primarily due to disturbances in the ocean floor. Earthquakes: Most tsunamis are caused by underwater earthquakes. When tectonic plates shift, they displace a large volume of water, creating waves that spread out across the ocean. Volcanic Eruptions: Underwater volcanic eruptions can also displace water and generate tsunamis.Landslides: Landslides, either underwater or on the coast, can displace water and create tsunamis. Tsunamis are detected using a system of buoys and sensors known as the DART (Deep-ocean Assessment and Reporting of Tsunamis) system. These sensors can detect changes in sea level and relay this information to monitoring stations. Tsunami: a wave or a series of waves generated by the rapid displacement of large amounts of ocean water by earthquakes, eruptions, landslides into the ocean, and iceberg falls. meteor impact can be detected by the PACIFIC TSUNAMI WARNING AND MITIGATION SYSTEM (PTWS) which measures and detects earthquakes and tides and sends alerts to the appropriate stationsThe DEEP-OCEAN ASSESSMENT AND REPORTING OF TSUNAMIS (DART) uses tsunameters and can detect small changes in ocean

Discuss why tsunamis come ashore so violently

Wave Height Increase: As a tsunami approaches the shore, the shallowing sea floor compresses the wave, causing it to significantly increase in height. Energy: Tsunamis carry a large amount of energy from the open ocean. This energy is released when the tsunami hits the shore, causing massive destruction. Multiple Waves: A tsunami is not a single wave but a series of waves (wave train). The first wave is often not the largest, and subsequent waves may arrive minutes or hours later, causing additional destruction As tsunamis approach the shore, they slow down to ~60 km/hr, and height increases by> 30 meters Wavelength decreases, waves pile up due to increased friction Destruction from a tsunami comes with the advance and retreat of subsequent waves- Destruction is due to the momentum (speed and mass) of the water and long wavelength and period.

Relate wave interference and resonance to marine hazards

Wave interference (Constructive) can create rogue monster waves that are large and spontaneous and can sing larger ships and ocean liners.

Describe how waves interact; explain constructive and destructive interference

Waves don't usually reflect (bounce back) when they strike other waves. Instead, they combine or are superpositioned, either constructively or destructively. Constructive interference occurs when the wave amplitudes (half the vertical distance between a trough and a crest) reinforce each other, building a wave of even greater amplitude, i.e. bigger waves. Destructive interference occurs when the wave amplitudes oppose each other, resulting in waves of reduced amplitude, namely smaller waves. Constructive: wave amplitude reinforces each other, and builds a wave of greater amplitude (crest + crest) Destructive: occurs when the wave amplitudes oppose each other, resulting in waves of reduced amplitudes (crest + trough)

Describe the forces that generate waves, eliminate waves, and return the ocean to a flat, undisturbed surface

Waves in the ocean are primarily generated by three forces:Wind: The friction between the wind and the ocean surface generates waves. The strength, duration, and fetch (distance over which the wind blows) of the wind determine the size and energy of the waves. Earthquakes: Underwater earthquakes, landslides, or volcanic eruptions can displace a large amount of water, generating waves known as tsunamis.The gravitational pull of the moon and the sun: These forces cause the regular rise and fall of the ocean's surface, known as tides, which can also be considered as very long waves. Waves are eliminated or dissipated by several forces: Friction and Turbulence: As waves move towards the shore, the bottom of the wave experiences friction with the seafloor, causing the wave to slow down, increase in height, and eventually break. Wave Interference: When waves of different sizes and frequencies collide, they can cancel each other out, a phenomenon known as destructive interference. Energy Dissipation: Waves lose energy as they travel, especially during stormy conditions. This energy is converted into heat and sound. Generating Forces and Wave Types:- Wind over the ocean: wind waves at 60-150 m (most common)- Atmospheric pressure, storm surge, tsunami: seiche (episodically)- Faulting, eruption, landslide: tsunami (episodically)- Gravitational attraction, rotation of the earth: Tide Restoring Forces:- Surface tension: capillary waves- Gravity: surface gravity waves (calm wind, seiche, tsunami, and tideWater has high surface tension, therefore ocean surfaces can remain relatively calm with only fine ripples where there is no wind

Define wave breaking and determine when a wave will break

When a wave breaks, its energy is dissipated in the surf zone and transformed into kinetic energy, affecting both the water and land, including the ocean bottom and the shore. The shape, size, and behaviour of the breaking wave are controlled by the slope of the ocean bottom when a wave reaches beyond the following critical points when the ratio of Height (H)/Wavelength (L) ~ (1/7)- when the ratio of height (H)/ depth (d) ~ (3/4)The wave crest becomes unstable and the wave then breaks. Whitecaps (froth) begin to form as the wave turns to SURF. When a wave breaks, its energy is dissipated in the SURF ZONE and is transformed into KE which affects both water and land

What is surging

ocean bottom is VERY STEEP, makes them potentially dangerous

What is plunging

ocean bottoms are MODERATELY STEEP, only for expert surfers

What is Spilling breakers?

the ocean bottom is FLAT and GENTLE, good for surfing

Predict the type of breaking wave that will be found on a given beach

the type of breaking waves expected at a specific beach does not change, surf varies daily. This variation is dictated by the parameters of the waves that arrive on shore, mainly wavelength, wave height, and wave energy. swell from distant storms local wind that may interfere with the waves generated much farther offshore constructive or destructive interference from other swells A gentle slope is spilling/flat/gentle which will create small, gentle SPILLING breakers- wave energy is released over a wide area- not hazardous but good for swimming The same can be said for other types of beach/ocean bottoms.