2.3 Coasts

a swash is the movement of material up teh beach in the direction of the prevailing wind.

the backwash is the movement of water back down teh beach due to the effect of gravity.

the fetch is the distance of open water over which wind can blow to create waves. the greater the fetch the more power the waves have when they hit the coast.

the wave height is the vertical distance between teh wave crest and wave trough.

the wavelength is the distance between two wave crests.

the wave crest is the top of the wave

the wave trough is the bottom of the wave.

destructive waves have a high energy level and they use deposition. there is a high frequency of them (10-14 per minute) and they have a bigger swash than backwash. the wave length is low and the wave height is high. the beach gradient is wide and flat. destructive waves are caused by swells at sea by the wind.

constructive waves have a low energy level and they erode. there is a low frequency of them (6-8 per minute). there is a greater backwash than swash and the wave length is high. the wave height is low and the beach gradient is steep and narrow. they are caused by strong wind storms.

hydraulic action is the force of the waves compressing air in cracks, when it releases teh air in the crack rapidly expands causing the cracks to widen leading to erosion.

solution is when salts and other acids in seawater slowly dissolve the cliff.

attrition is when waves cause rocks and boulders on the beach to bump into each other and to break up into smaller particles

abrasion is caused by large waves hurling beach material against a cliff and causing it to break down.

mechanical weathering includes two main processes called frost cracking and freeze thaw weathering and salt cracking or biological weathering.

biological weathering is when roots and trees grow on the rocks and overtime they can cause cracks to expand.

chemical weathering involves the solution and chemical break down of rock minerals helped by the fact that rain water and spray from the sea is slightly acidic.

a form of hard engineering are groynes. they are wood barriers that are built at right angles to the shore to reduce LSD. they protect the coast from wave energy and encourages deposition. the only last 20 years and they cost a lot to replace. gabions are wire cages filled with stones. they are cheap to build but they have a short lifespan and they can be dangerous. a riprap are large blocks of rock or concrete that are places as a ramp in front of a cliff. they dissipate wave energy effectively but they are hard to transport.

a form of soft engineering is beach nourishment. it is an artificial addition of beach material from another location. it builds up the beach making it buffer wave energy but it requires consistent maintenance especially of LSD is strong. cliff drainage is when pipes are put into a cliff face. there are no direct costs but is very disruptive when in construction. sand dunes are ecosystems that provide areas with protection from erosion and flooding. they work with nature and they enhance the natural protection that dunes provide however the costs are high and some areas of damages dunes may be fenced off, denying public access

a mass movement is a consequence of sub aerial weathering. it occurs when the rock becomes so weak that it collapses. landslides typically occur following heavy rainfall. teh ground becomes saturates and there are very high water pressures that forces fragments of the rocks and soil apart.

A disconcordant coastline has alternating bands of hard and soft rock at right angles to teh sea. because the soft rock is exposed to the sea it is eroded faster than the hard rock. this causes differential erosion.

a concordant coastline has alternating bands of hard and soft rock parallel to the sea. the hard rock acts as a protective barrier to the softer rock behind preventing erosion. if the hard rock is breached, the softer rock is exposed and vulnerable.

long shore drift is teh movement of material along the shore. as waves interact with a beach sediment waves approach the beach at an angle determined by the wind. the swash carries material up along the beach. the backwash transports material at a right able due to gravity.

when swash is greater than the backwash the wave loses energy and drops any material.

the beach is the area between the lowest spring tide level and teh point reached by the storm waves in the highest tides. every beach is different but they are usually made up of material on a wave cut platform. beaches are formed from sand, shingle or pebbles or a combination of all three. they can also be formed from mud and salt. sandy beaches are usually formed in sheltered bays where low energy waves transport material onto the shore. the swash is stronger than the backwash so the material is moved up the beach.

a typical beach has four zones, offshore, nearshore, foreshore and backshore

a spit is a long narrow accumulation of sand or shingle formed by the process of long shore drift. one end is attached to the land and the other end projects out to sea or across a river estuary.

a bar forms when a spit totally crosses over a river estuary. if there is some freshwater behind the bar this is known as a lagoon.

a tombolo occurs when a spit connects to the mainland of an island.

coastal management is the defence against flooding and erosion.

hard engineering is when we control natural processes and soft engineering is when we work with nature

west wittering is a village in west sussex, england.

sand dunes form when windward coasts with prevailing winds from off the sea. large low tide expanse of sand and low lying land behind the beach area. a steady supply of sand to beach area from LSD.

a pioneer species is able to grow in a harsh environment and as it dies it changes conditions. these new conditions are suitable for a new invading specie that succeeds the former specie. this process of invasion and succession continues until the climatic climax is reached. as each dune is changed in plant characteristics a new dune is deposited on the seaward side.

sand dunes are not static - they move.

saltation, surface creep and suspension is needed for sand dunes to form.

coral reefs form at depths not exceeding 25 metres, and need warm water between 20 and 28 degrees Celsius . reefs grow faster in clear water that allows sunlight to penetrate which enables photosynthesis of algae and plankton from which coral feed on. the shallow depth of water also allows the penetration of sunlight for photosynthesis. A coral reef is made up of millions of coral polyps. these are tiny animals but they contain certain plants called algae. the algae convert sunlight into energy for the reef itself. the coral polyps make hard calcium carbonate which builds up over thousands of years to form reefs.

the three types of coral reef are fringing reefs, barrier reefs and atoll reefs.

a fringing reef grow around newly formed islands where the sea level has risen. right next to tropical islands

barrier reefs form around islands that is eroding and the reef is further out to sea. the sea level has risen creating a lagoon between the reef and the island.

an Atoll is a reef that grows around where an island used to be. the island has eroded whilst the sea level has risen.

an underwater volcano creates a seamount that created an island as it grows above sea level. a coral reef forms around the circumference of an active volcanic island. the volcanic island becomes dormant and it starts to become eroded and sinks, the coral continues to grow vertically upwards as it needs to be near the surface to feed on algae that needs sunlight to photosynthesise. this is called a fringing reef. the extinct volcano continues to erode and sink beneath teh surface of teh water. a wide band of water forms between the fringing reed and the island. this is called a barrier reef. sometimes material gets stuck on the reef and enables land to form above sea level. this is called an atoll reef.

coral reefs are important because they protect coastal homes from storms and they support promising medical treatment. they also provide homes for millions of aquatic species.

coral reefs are often describes as the rainforests of teh sea on account of their rich biodiversity. some coral is believed to be up to 2 million years old. coral reefs contain nearly 2 million species of plants and animals and about 25% of the worlds sea water fish breed, grow and evade predators in reefs. Countries such as Barbados rely on tourism based on their reefs. Florida’s reefs attract tourism worth $1.6 billion annually. the global value of coral reefs in terms of fisheries, tourism and coastal protection is worth $375 billion.

global warming leading to coral bleaching due to rapid rise in ocean level - too fast for polyps to keep building up to be in shallow water. ocean temperature increase of 1-2 degrees - algae within the polyps become active and are expelled, killing the coral. ocean acidity rises - polyps are made out of calcium and so will be susceptible to carbonic acid.

blast fishing or coral blasting is a threat to coral reefs because people use dynamite to stun and float the fish damaging the coral reef beds. tourist travel to coral reefs. just walking on them damages them. divers break bits off, locals sell souvenirs of coral and sometimes hotels and houses will need the limestone for building purposes. large shipping lanes such as the Persian gulf and areas around ports will discharge large amounts of oil which will smother and kill coral.

COTS are starfish that harm coral reefs. they rapid economic growth leads to agricultural pollutants such as fertilisers washing into oceans. this encourages phytoplankton growth which in turn feed increased number of crown of thorns star fish which swarm onto reefs eating coral.

we can protect reefs by combating global warming by reducing emissions to reduce sea level rise, acidity and ocean warming. reducing local threats such as trampling, mining and coral blasting by providing local people with jobs that do not involve damaging the coral. designating coral reefs as marine protected areas.

we can coral garden, keep water clean to avoid COTS, reduce carbon emissions.

mangroves are a group of small trees and shrubs numbering some 80 species. they grow in coastal salt water zones in tropical and subtropical latitudes around the globe. they are the only trees in the world that can tolerate sea water, excreting the excess salt through their leaves. mangroves tent to grow numerous long roots which form nest like structures. some mangrove species grow roots that grow upwards, absorbing oxygen which the tide has submerged the lower portion of the mangrove.

mangroves grow in exposed coast lines in warm tropical ocean water. they only grow within a tidal zone right on the shoreline.

mangroves are important because they are a natural coastal defence, they are carbon sinks, they provide livelihoods, they encourage ecotourism and they are rich in biodiversity.

the main threats to mangroves are aquaculture, coastal development, rice and palm oil farming and industrial activity.

a tropical storm is a rotating spiral of high winds and low pressure. a hurricane is when a tropical storm has wind speeds in excess of 74mph, a diameter of up to 800km, a low pressure of 880mb and is centred around an eye. the Saffir-Simpson scale is used to measure the size.

tropical storm occur near the equator. they occur when warm water evaporates and winds push them along and they turn into clouds with high winds pushing them water it condenses. hurricanes cause loss of life, infrastructure destruction and places of work destroyed. they can be monitored and predicted using satellite systems.

warm water heats the air above it. warm, moist air rises quickly creating low pressure at the surface. more air sweeps in, then starts spiralling upwards (caused by the earths rotations). the rising air cools and condenses and it goes higher into the sky. huge spinning thunderclouds are created which are carried across the sea by trade winds. the eye of the storm is in the middle of the hurricane and is an area of high pressure with no winds. the strongest winds are found in the eye wall and can cause extensive damage.

the Philippines is a series of islands in the south China sea, east of Vietnam and north of Indonesia. there are 1.15 doctors per 1000 people in the Philippines. typhoon haiyan happened because there were temperatures of over 27 degrees and there were high winds. it was made worse by climate change and sea levels rising.

the social impacts of the typhoon were that it killed 7500 people and diseases spread in the country due the sewer breakages. the economic impacts were that the country lost $2.9 billion and 120,000 tons of sugar was lost. the environmental impacts were that there were oil and sewage leaks and coconut plantations were destroyed. the political impacts were that a state of natural calamity was announced and the city of Tacloban's city government was decimated.