Constructive waves have strong swash and weak backwash . They break about 6-9 times a minute, and are long in relation to their height . They need calm conditions.
Destructive waves have a weak swash and strong backwash . This erodes pebbles and shingle. High in proportion to their length .
Fetch- the distance a wave has travelled.
Things that affect the size and energy of a wave:
Length of time the wind is or has been blowing
Strength of the wind
Destructive waves happen in Autumn or Winter
TYPES OF EROSION:
Hydraulic Action- water continually hits the rocks and compresses air into cracks, when the wave goes out the air rushes out and rock breaks away. The cracks thus get bigger.
TYPES OF EROSION CONT’D:
Abrasion (or corrasion)- waves break and hurl rocks and debris at the rocks to erode.
Corrosion/ Solution- Chemicals within the water wear away rock. Sea water and weak acids dissolve the rock and minerals.
Attrition- When rocks hit one another and get smaller and break up.
Weathering- the breakdown and decay of rock by natural processes , without the involvement of any moving forces.
Salt crystal growth- The spray from sea water lands on rock, the water evaporates, leaving salt behind . The salt crystals grow and create stress on rock, causing it to break down into smaller fragments.
Acid Rain- all rain is acidic and if air is polluted, can be very strong . When rain falls on rock it can react with weak minerals causing them to dissolve and the rock to decay .
Biological Weathering - Roots of vegetation can grow into cracks in a rock and split the rock apart.
Mass Movement- the downslope movement of material due to gravity.
Rock fall- one of the most sudden forms of mass movement. Rock fall occurs when fragments of rock weathered from a cliff face fall under gravity and collect at the base.
Slumping- Often happens when the bottom of a cliff is eroded by waves. The slope becomes steeper and the cliff can slide downwards in a rotational manner. Usually triggered by saturation due to rain, which lubricates the rock and makes it heavier. It’s visible how the weight added by rainwater and erosion by waves combine to cause the rotational slump.
Rotational Slumping in a cliff face
Wave cut platforms are fairly flat, rocky areas at the bottom of cliffs. Waves erode coastline causing undercutting at the base of the slope. The notch gradually gets bigger, the rock above then looses its support and collapses, debris is washed away by waves and this is repeated; making the cliff slow retreat and get steeper. Diagram on next page.
Saturation by Rainfall Rotational Slump Erosion by waves
Wave cut platform:
Headlands and Bays- always found together, a headland separates bays along a coastline. Their formation is affected by geology, Coastlines are made of different types of rock, the areas of weak, less-resistant rock erode quicker to become bays, resistant rock becomes headlands. Causing an indented coastline.
Wave undercut notch Wave-cut platform Waves Collapse happens Over time
Stack- isolated column of rock standing off the coast, once attached to land.
Stump- a collapsed stack.
Formation of erosional landforms:
Headlands gradually become eroded despite being made from resistant or hard rock. Waves bend around the coastline and erode both sides.
Joints or cracks or weak points erode quicker and small caves form both sides, as erosion occurs they join to make an arch.
More erosion with weathering makes the roof collapse and leaves an isolated stack- which slowly becomes undercut by wave erosion and collapses into a stump, visible only at low tide sometimes. In Dyroholaey, there’s an example of this (SE Iceland)
Erosion- the wearing away of land or soil by action of wind, water or ice.
Transportation- the eroded material is transported by waves, currents, tides and longshore drift.
Deposition- the material e.g. mud, sand, shingle and pebble is dumped or deposited to form a beach.
Headland Cave Arch Stack Stump
Longshore drift- material movement along a coastline.
Waves move towards the coast at an angle, as they break, swash carries material up and along the beach at the same angle. As the swash dies away, backwash and material fall at 90° because of gravity. Material goes in a zig-zag pattern. The prevailing wind is South Westerly and the backwash continues at 90°.
Longshore drift is continuous and can take a lot of a beach.
backwash swash Waves
Groynes cause less material to be transported further along the coast, meaning places along the coast suffer increased erosion.
Transportation- the movement of material by rivers, glaciers, waves and the wind.
Deposition- the laying down or depositing of material previously transported by rivers, glaciers, waves and the wind.
Solution- Chemicals break down rock, and tiny particles go into the sea. Chemical breakdown of carboniferous rock.
Saltation- Rock is rolled or hopped along the sea bed, these are normally smaller particles.
Suspension- Rock particles are held or suspended in the body of water.
Traction- where bigger pebbles are hit by waves and rolled along the beach.
Beach- a gently sloping area of land between the high and lower water marks.
Spit- a long ridge one end band shingle, attached to the land at one end but in the open sea at the other end.
Wave refraction- waves curl around and loose strength.
Spurn Head is an example of a spit in Kingston-upon-Hull. It is migrating.
Waves deposit material as they lose energy. Waves hit the headland and lose energy as they curve Around it. Low Energy
Fresh water and sea water are trapped behind the ridge as it forms.
Dunes could form at the back, hooked end or run along parallel to the coast. Strong winds and sea currents lead to a curved spit end.
Deposition begins at the bend Original coastline Cliffs Spit Bend in coastline Direction of Longshore Drift Mud and marsh in sheltered water Standing water colonised by Marsh plants. Eroded materials picked up by the waves Sediment accumulates as a ridge is built out to sea.
Bar- a barrier of and or pebble deposited offshore.
Longshore drift sometimes continues extending the length of the spit and it may join back up with the other side of the coastline, such as a bay. This is a bar, with a lagoon in the middle.
There is a bar at Slapton On Devon.
Cliff Recession- The process of a cliff getting small and falling apart.
Causes of Cliff Recession-
Erosion- Hydraulic Action, Abrasion
Geology- Soft rock, Resistant Rock
Fetch- Destructive Waves, Constructive Waves
Impermeable rock- can’t absorb water
Permeable rock- takes in water
Erosion- the more erosion, the quicker the recession. Hydraulic action pull rock away from the cliff and abrasion hurls rock at the cliff face causing it to retreat.
Geology- Soft rock erodes quicker than resistant rock, the rock softer recedes faster.
Fetch- the further a wave travels, the more energy and thus the more destructive.
Coastal Management- groynes and breakwaters or boulders dissipate the energy of a wave and prevent recession.
1.8 metres of land a year in part of Holderness, East Yorkshire is lost.
The South West is largely granite.
Effects of Cliff Collapse Include:
Ruined pipes- loss of electricity and water.
Less room for housing. (loss of housing and villages)
Injuries and death.
Loss of transport links (roads, walkways).
Loss of trade (tourists) and farmland.
Holderness- eroding at 1.8 metres a year because of soft rock. It’s located in the North East of the UK in East Riding, Yorkshire. Surrounded by Grimsby, Leeds, Hull and York.
Durlston Bay near Swanage receded 12 metres between 1968 and 1988 ending up 25 metres from an apartment block called Purleck Heights. In 2000/01 severe storms and high energy waves led to a further 12 metres recession and put the building at rock.
In the UK, loss of property to cliff recession isn’t covered by insurance. In the USA, $80m per year is paid out by a national insurance programme.
High recession rates threaten the environment. Durlston Country Park also lies on the cliff top and is home to over 250 bird species. Puffins & Falcons rest on the cliff. Their habitats are threatened by recession of the cliff, which affects the rare species.
Property- is built on cliffs to utilise sea view. Cliff recession in coastal areas means they’re prone to collapse.
Insurance- policies don’t cover coastal erosion, but in the USA they do.
Environment- the recession threatens habitats and the breeding of rare species like puffins and falcons.
Due to global warming sea levels will rise by 1 meter by 2100. The South West will therefore go under water. Tides will be higher, and land will be lost.
Bangladesh, the Maldives and the Netherlands will loose land, making a denser population.
Flooding is predicted to be 8 to 12 times worse by 2100. The Thames Barrier was installed along with the Thames Estuary in 2010 which will see new flood walls added.
Open space will be left to prevent building damage.
The flooding will cause economic problems and high death rates.
The Environmental Agency predicts floods and monitors the weather.
Thames Estuary Case Study- on January 31st 1953 the worst natural disaster in living occurred. A tidal wave built up in the Atlantic coincided with the high spring tide. 307 people died and 40,000 people were displaced. Worst affected was Canvey Island where 58 people died and 160,000 acres were flooded.
As a result a new sea wall was repaired and replaced plus millions of pounds were spent on the Thames Estuary Barrier- the most expensive tidal barrier ever.
The Barrier will only work until 2030, but it’s hoped to be able to extend this to 2100.
In Bangladesh, the coastal embankment project has led to the building of several flood walls, 500 flood shelters were built although 10,000 were needed. Locals are learning about this and flood warning systems have been installed. In 1997, the Cox’s Bazaar area allowed 300,000 people to be evacuated. Only around 100 people died which was lower than before. Buildings now have to have flat roofs and an exterior stairway for people to escape.
Reasons to Protect the Coast:
Population Density- how many people could be displaced.
Trade- how much money lost.
History- risk of ruination of historic landmarks.
Tourism- economic loss; Agriculture- damage of land
SMP- shoreline management plan (Seaford-1974)
1974 Seaford SMP- groyne, sea wall and rip rap all installed.
Soft Engineering- using ecological methods to defend e.g. Vegetate the slope- buffers the wave, absorbs water and energy.
Hard Engineering- man-made materials which stick out from an area e.g. offshore barrier
Rip-rap is the cheapest coastal defence.
Wood Defences can rot.
Different Sea Defences-
Sea Wall- a long concrete barrier built at a cliff base.
Groynes- wooden, rock or concrete ‘fences’ built across a beach, perpendicular to a coast.
Rip Rap- large boulders of resistant rock.
Revetments- slatted wooden or concrete structures built at a cliff base.
Offshore Resets- rock or concrete barriers built on the sea bed or a short distance from a coastline.
Beach Replenishment- adding sand taken from somewhere else, often offshore.
Managed retreat- people and activities are gradually moved back from the vulnerable areas.
Cliff regrading- making the cliff face longer so it’s less steep.
2 2,000 Beach Replenishment 5 4,500 Offshore Reef 10 2,000 Groynes 20 4,000 Sea Wall 5 2,000 Revetments 5 1,100 Rip Rap Maintenance Cost (£ per metre per year) Construction Cost (£ per metre per year) Method
Destructive waves have a weak swash and strong backwash, and are short in relation to their height. They’re also high in relation to length. Erosional and less that 1 metre in height.
Y- Wave cut platform
4. The geology of rock often affects how a coastline erodes; the softer or less resistant the rock, the quicker it erodes. The soft rock (clay etc.) erodes faster than the hard rock (granite etc.) and so a bay is slowly created as the soft rock recedes, the hard rock still remains sticking out, and so becomes a headland. The resistance of rock affects formation.
Groynes- a groyne prevents longshore drift and so allows a beach to form, however, a nearby coast would no longer have any sand deposited and so would recede instead.
Fetch- the greater the distance a wave has travelled, the more energy it has and therefore the more destructive, causing cliffs to recede more. A wave with a low fetch would build up a coast, but one with a high would do the opposite.
Rip Rap- absorb energy and look natural. They restrict access and can be expensive.
Sea wall- protects the base of a cliff, it can reflect wave energy; however, it can be expensive and looks unnatural and horrible.
Coastal flooding can be reduced by the creation of a barrier such as the Thames Estuary Barrier in London, which controls the amount of water in the river at any time. In Bangladesh, mangrove swamps have been created to buffer waves before the reach land and dissipates their energy and sea walls in Seaford (long concrete walls which reflect wave energy) can be used to stop the waves hitting the cliff face and eroding further.
Rip rap can also be used to absorb wave energy and make the impact lessen greatly, a collection of rocks looks natural and provides a barrier against wave erosion. Along Holderness’ coast, a groyne has been installed which lessened the cliff face land but protected many villages. Vegetating a slope also acts as a soft-engineering option to buffer the waves.
A WATERY WORLD
The 3 main uses of water are :
Average water consumption per person is found by dividing the total water usage in a country by the population.
HIC water consumption is high.
Irrigation- artificial watering of crops (sprinklers/ hoses)
3 Sources of water are reservoirs, aquifers and rivers.
Reservoirs are artificial lakes as a source of water supply by building a dam across the valley and allowing it to flood.
Kileder Water Reservoir in Northumberland carries 200bn litres and is surrounded by Kielder Forest. It was built between 1975 and 1981 and was opened in 1982. It’s the largest artificial lake in the UK and the largest artificial forest.
It took 2 years to flood and supploes Newcastle, Sunderland and Middlesborough. Tourists come to the reservoir to enjoy the wide range of leisure opportunities such as waterside parks.
Aquifers are deep layers of rock that hold water, this is extracted by drilling down to the rocks and pumping the water out.
The rocks of the North and South Downs store water like this, they get 750mm of rain and half goes in to the chalk. 400 bn litres of water is stored.
The water soaks through
It is stored.
Dip slope- gentle water slopes in upper chalk means greater cracks and holes and water soaks more.
Dry Valley- water passes own large cracks and holes more quickly.
Scarp Slope- steeper water table slopes in the lower and the middle chalk means less cracks and water flows through less easily.
Aquifers provide most water from wells and boreholes.
The pores in chalk don’t let water flow easily but the fissures allow them to run.
Water extraction from the chalk under London caused levels to drop to 65m, in the 1960s about 480 million litres were extracted per day.
In the 90s, industrial activity decline and the number dropped 100 million to 380 million litres and began to lower this decade.
Because less was extracted, the water levels rose and deep basements and tunnels flooded, the land beneath London around the foundations for tall buildings could soften, leaving buildings unsupported.
Extraction has been increased to control water levels, towards the late nineties water level depression filled up but have since stabilised.
Water can come from rivers too. Since 1980, water has been taken from the Peace River in Florida. This is so that the growing population of over 750,000 people have enough water.
On average, 70 million litres is takes from there and given to people daily, the water is treated near Fort Ogden and can treat 90 million litres.
The water is then stored into aquifers, which are used as natural storage and can be recovered when necessary.
This is called aquifer storage and recovery and is ideal for seasonal water demand.
Water can therefore be withdrawn during wetter months and stored for dry periods when rivers are very low.
Work has been started for a 24bn litre storage reservoir and the capacity of the treatment plant is being doubled, this is to meet the demand for water in the area.
Water surplus and water deficit are dependant on how much water a place receives due to rainfall and how much it looses due to evaporation.
Places in the North are balanced, whilst places along the Equator receive less.
Some places receive more water than that lost which causes a surplus.
Some places have high rates of evaporation and transpiration that they loose more than they receive making a deficit. Some places have a lot of rainfall and high temperature and have no surplus, this is the cause with Africa.
According to the UN, by 2020 water usage should have increased by 40% to support food requirements of the population, something that’s growing from 6.7 bn to 7.5.
1.8billion people will be living in water deficit areas.
70% of the globe is water but only 2% is freshwater.
Desalinisation is a process to convert seawater to freshwater but it’s only useful for coastlines and is 15x more expensive.
By 2050, the population could be 10 billion.
Quality- water isn’t always fit for drinking, it could be saltwater or not clean.
Spatial Variability- where rainfall is distributed in relation to the population, rain falls more in the north though the south has more people. Where the rain falls.
Seasonal Variability- rainfall in relation to the seasons.
Loss through broken pipes- leakages etc. mean water distribution is less efficient. Old pipes break and pollute drinking water.
Quality of water in the UK is monitored by the drinking water inspectorate. 1.7% of tests find water below quality according to the EUs ‘Water Framework Directives’
Nitrogen fertilisers can cause high levels of nitrogen to be poisonous.
Nuclear power plants pump waste water back into the environment.
The EU try to reduce fertilises which are nitrogen-based as they can lead to high nitrate levels, in 2007 the EU reported the chemical quality of water was good or very good in 76% of cases. In 2007, 0.4% were below.
Agriculture- fertilisers, pesticides and herbicides.
Domestic- waste, flushed things.
Industrial- nuclear waste
Others- litter, sports, swimming, dogs urine.
Birmingham is supplied by 3 pipelines from 3 reservoirs in the Elan and Claerwen valleys of mid-Wales more than 100km away. This is because of spatial variability. Most rain falls in the North and West of England but the most demand is in the S & E, water is transported to these places.
Costa Del Sol- places with a lot of seasonal variation suffer supply problems, rainfall in Costa Del Sol, Spain is low- in July and August it’s almost nil.
It’s in these months the demand increases, swimming pools and over 70 golf courses need watering.
In the places around the Mediterranean sea, water tends to fall in the winter season and the summer is a dry time.
There’s no new water to collect.
Dehydration and agriculture suffer.
No food for livestock.
Lack of hygiene.
Resorts lose business.
6 major reservoirs have been created including La Concepción with a capacity of 65 million metres cubed, a desalinisation plant was built in Marbella to 20 million m3. Another desalinisation plant in Mijas was opened in 2009.
Loss of water in the UK from the distribution centre is about 20%.
In London, the water distribution system was mostly constructed in the 1830s and 40s, and many of these have been in use since.
As demand has increased, water pressure has had to be increased to move water quickly through the system, many pipes can’t take the pressure and burst, the burst water mains are responsible for about 20% of London’s water.
Old pipes also rust and decay.
In the ‘90s a new ring main was built 40 metres below the surface and 80 kilometres of 2.5m diameter pipeline. £250 million were spent and leakage losses has been reduced.
1830s and 40s saws the London Water distribution constructed.
Pressure was increased to meet the demand.
This lead to pipes bursting and water being lost.
The new ring main was built in the ’90s.
1.3 bn litres are supplied by it.
LICs face different and more serious problems including the availability.
Russia, the UK, Australia and the USA have the greatest amount of safe water access with over 90%.
Afghanistan and Ethiopia have the lowest safe water.
In Mozambique, most domestic water is accessed by House connection, yard tap with 36%, and neighbour’s houses having 30%. Only 1/3 of the population has piped water.
About 900 million people suffer from water borne diseases, responsible diseases include Bilharzias, Cholera and typhoid. Over 300 million are supposed to have Bilharzias in LICs. Cholera is caught by faeces in water due to inadequate sewage and typhoid is caught by drinking infected water.
In HICs water is managed by:
Water meters in homes, 30% of homes have these and all new homes must have them. Owners pay for the amount of water they use in cubic metres.
It encourages people to be careful with how much water they use, in 2008 the cost was £1.60 per cubic metre.
Single flush toilets use 13 litres of water, now dual-flush toilets use only 6 for a full flush and 4 for a reduced flush.
A hippo bag added to a single flush toilet also saves one litre a time.
Industrial Water Management by:
Using new techniques
Agricultural Water Management by:
More modern, efficient systems.
Drip-feed and sprinklers use less water than irrigation channels and ditches. It’s estimated that drip systems are 90% efficient, with only 10% water being lost to evaporation. Sprinklers are 70% efficient, channels are 50%
Using appropriate technology like boreholes in Mozambique.
The Rural Water Supply Network aims to provide cost-effective boreholes (CEBs) that are appropriate to meet the needs of local communities. CEBs cost around $5k to $6k to install and are funded by the Dutch gvt.
In Kolkata, India, Sewage water is recycled for fish farming and agriculture. Sewage is piped into shallow lagoons which allow sunlight to reach the bottom to help algae and photosynthetic oxygen to grow.
Waste is also being used for farming.
Sewage is piped, sunlight promotes algae growth, aquatic plants use sunlight.
The Colorado River basin is subject to dispute. It’s over 630,000 km2 in area, and it’s source is about 4,000m high in the Rocky Mountains of Colorado.
It flows SW for 2,300 km to the Gulf of California in Mexico.
It and it’s tributaries drain south western Wyoming and Western Colorado.
It used to be very wild with many floods, in the 30s the US gvt. Built a series of dams including the Hoover Dam to stabilise it, provide electricity and water for its cities.
First, LA and California were provided for first but other cities like Vegas and Phoenix grew.
HEP- hydroelectric power to make energy
Other states now want water and power.
California uses the most of the water
After several treaties in ‘22 and ’48, water was allocated to different states.
Wyoming- climate change is bring drier condition to the area and the original agreement didn’t consider drought.
Utah- Drought means less water.
California- population has grown a lot, there’s not enough storage for the water offered.
New Mexico- Seven US sates and Mexico share, is that fair
Arizona- Want to use water conservatively, water levels have reduced, nature would be affected.
SYDNEY OLYMPIC WATER PARK
Developed to enable the city to host the 2000 Olympics.
The Water reclamation and Management Scheme was set up to provide:
A water reclamation plant removes water from sewage at a rate of up to 3 million litres a day.
A brickpit- a water reservoir holding 300 million litres.
A water treatment plant to filter and disinfect water from the water reclamation plant and storage reservoirs at a rate up to 7.5 million litres daily.
A dedicated pipe system to get water from the treatment plant through Sydney Olympic Park and Newington.
Stormwater- runoff passes through treatment ponds to get rid of nutrients and pollutants, sewage is recycled.
The brickpit acts as a storage reservoir to store the stormwater which gets cleaned at the plant.
Dual Supply Network- separate pipelines which carry drinking and recycled water are installed throughout the park.
Not suitable for drinking water but helps recycle and save.
CHALLENGES FOR THE PLANET
Last ice age was 18,000 years ago.
There was a little ice age from 1300-1870.
Natural Causes of Climate Change (Milankovitch):
Eccentricity- Earth’s orbit oscillates very slightly between nearly circular and more elongated every 100,000 years. This is evident in the glacial/interglacial cycles of the same period. When more elongated, the earth is colder.
Tilt- earth spins around on an axis that is tilted from perpendicular to the plane in which the Earth orbits the sun. This causes seasons.
When the angle is high, the polar regions receive less solar radiation than normal in winter and more in summer. High tilt angle= glacial.
Wobble- slow wobble in Earth’s spin axis. Causes peak of winter to occur at different points along Earth’s elliptical orbital path. The season variation occurs every 23,000 in a cycle.
Solar Output- sun’s output is changing and thus the energy affects the temperature.
Sunspots- huge magnetic storms which appear as cool areas of the sun and block energy.
Volcanic eruptions- block sunlight from getting in or trap heat in by the energy reflecting of the particles.
Meteorite Impact- Dust envelopes earth and blocks solar output, killing herbivores and carnivores as plants die.
Laki Volcanic Eruption- no light for 8 weeks. 1783. Fissure eruption split the mountain, 13km3 of material produced, spread over 500km3 over Iceland.
Sustainable development means meeting the needs of today without compromising the needs of tomorrow.