Management

Date: 2015-10-07; view: 534.

Highest points

Mount Logan ( about 5,959 m) is the highest mountain in Canada and the second-highest peak in North America (about 5,959 m). The mountain was named after Sir William Edmond Logan, a Canadian geologist and founder of the Geological Survey of Canada. Mount Logan is located within.

Mount Saint Eliasis the second highest mountain in both Canada and the United States, being situated on the Yukon and Alaska border (at about 5489 m). Its name means “mountain behind Icy Bay”.

Mount Lucania is the third highest mountain located entirely in Canada (at about 5226 m). Lucania was named by the Duke of Abruzzi, as he stood on the summit of Mount Saint Elias in 1897, having just completed the first accent.

· A 450m clay flood embankment was built in Weedon across the river valley upstream of Northampton in 2002. This raised the level of the land by 6.8m.

Will create a flood storage area behind the embankment. Cost £2 million. When floods, water can be stored here, preventing flooding downstream in Northampton.

The river flow is regulated by a culvert through the embankment. The embankment has been landscaped to minimise visual impact and the storage area has been developed as a habitat for aquatic flora and fauna.

· A new housing estate called Upton Square has been built just above the level of the floodplain. This housing has become possible due to the management of the area which has made the area safe from flooding.

· The warning system was upgraded in 2003. Flood risk areas are covered by Environment Agency Flood Warning service where they aim to give 2 hours' notice of the possible onset if flooding.

Testing in the Far Cotton and St James areas and a Flood Season Awareness Campaign was put into operation.

· A flood retention reservoir has been built at Billing, near the aquadrome.

· At Food Meadow, close to the railway station 4m high floodwalls have been installed to protect housing, industry and the Castle Inn. Created an open area of land which the river can flood onto giving protection to the railway station which is on the other side of the river.

Debris was cleared from here so the river velocity would increase and rainwater would be taken away more quickly. Gabion boxes were also added which protect the river banks from erosion giving added security to the new housing beside the river.

· In 2008- defences are built around Upton, near Sixfields. Cost £8 million. The aim of the works is to create an area, called a washland, where water can be diverted from the River Nene in a controlled manner in order to reduce the risk of flooding downstream.

Major roads in this area such as Upton Way (A45) are on embankments up to 6m high. The embankments join up with specially built floodgates to create an area of open land where up to 1,2 million cubic metres of flood water can be stored during times of heavy rain.

The water can be stored harmlessly in open grassland. When the rain had passed, the gates will be opened to allow the water to flow steadily back into the River Nene.

The road is also protected by a 2m high floodwall which is made of concrete sections.

· The river channel capacity at Upton has been increased by building earth embankments set back 10m from the river which have footpaths along the tops. The area has been visually improved by planting trees.

Coasts

What types of waves are there?

Destructive waves- mainly responsible for coastal erosion and for taking sediment away from coastlines. They have number of characteristics:

· The backwash is much stronger than the swash and is therefore able to carry sand and pebbles away from the shore.

· They break frequently; there are between ten and fifteen every minute.

· They are high in proportion to their length.

· They are generally found on steep beaches.

Constructive waves- responsible for deposition in coastal areas. They have number of characteristics:

· The swash is more powerful than the backwash and therefore deposits sediment on beaches.

· They break infrequently at a rate of ten or fewer per minute.

· They are long in relation to their height.

· They are usually found on gently sloping beaches.

How are coasts eroded?

Main types of weathering

Physical, chemical and biological.

-Physical weathering- Freeze-thaw weathering or frost action is when water gets into cracks in rocks.

The temperature falls below freezing the water expands as it turns into ice. This expansion puts pressure on the rock around it and fragments of rock may break off.

Common- in highland areas where the temperature is above freezing during the day and below freezing during the night.

-Chemical weathering- Rainwater contains weak acids that can react with certain rock types. The carbonates in limestone are dissolved by these weak acids and this causes the rock to break up or disintegrate. This can be seen on limestone statues or limestone pavements.

-Biological weathering- The action of plants and animals on the land. Seeds that fall into cracks in rocks will start to grow when moisture is present. The roots the young plant puts out, force their way into cracks and, in time, can break up rocks. Burrowing animals, such as rabbits, can also be responsible for the further break-up of rocks.

What is mass movement?

When material moves down a slope due to the pull of gravity.

Soil Creep

This is the slowest downhill movement of soil. Gravity will pull the water that is contained in the soil down a slope. The soil will move downhill with the water. As this happens very slowly, it's not possible to see it happening, although it does move more quickly after heavy rainfall. The slope may appear rippled (like sheep paths around the hill) - terracettes.

Landforms created by coastal erosion

Formed by destructive waves .

Headlands and bays

On coastlines where rocks of varying resistance lie at right angles to the sea, the bays are the softer rock and are indentations (углубления) in the land. The headlands are the more resistant tock and protrude (торчат) into the sea.

As the bays are made from less-resistant rock type, the erosion rates are greatest at first. In time, as the sea cuts the bays back, the waves reaching the coast are less powerful because they have to travel over a longer expanse of beach. At this point the headlands, which are further out to sea, start to experience the more powerful waves and are eroded at a faster rate than before.

Cliffs and wave-cut platforms

Headlands are usually formed from cliffs. When the sea moves against the base of the cliffs using corrosion and hydraulic action ( and if the rock type is limestone or chalk, corrosion), it undercuts the cliff and forms a wave-cut notch. Over time, it will fall into the sea as a result of pressure of its own weight and the pull of gravity.

The sea will continue to attack the cliff and form another notch. In this way, the cliff will retreat, becoming higher and steeper. The remains of the cliff rock, now below the sea at high tide, form a rocky, wave-cut platform. As the width of the platform increases, so the power of the waves decreases, as they have further to travel to reach the cliff.

Caves, arches, stacks and stumps

Formed in rocks that have a fault or line of weakness. The action of the sea will exploit the fault, through erosional processes such as hydraulic action. In time the fault will widen to form a cave. If the fault is in a headland, caves are likely to form on both sides. When the backs of the caves meet, an arch is formed. The sea will continue to erode the bottom of the arch. Weathering will also take place on the bare rock faces. As the sea undercuts the bottom of the arch, a wave –cut notch will form. It will collapse in time, as it is pulled down by the pressure of its own weight and gravity. This leaves behind a column of rock not attached to the cliff, known as a stack. Continued erosion and weathering will lead to the formation of a stump that is visible only at low tide.

Landforms created by coastal deposition

Formed by constructive waves which build rather than destroys the coastal environment. It deposits sand and pebbles that form beaches.

Beaches

An area between the low tide and storm tide marks and is made up of sand, pebbles and, in some places, mud and silt. They are formed by constructive waves, often in bays where the waves have less energy due to the gently sloping land and, as a result, deposit material. They can also be found along straight stretches of coastline where longshore drift occurs. Seaside resorts often build groynes to keep beaches in place and to reduce the effects of longshore dirft.

Spits

Long, narrow stretch of pebbles and sand which is attached to the land at one end, with the other end tapering into the sea. It forms when longshore drift occurs on a coastline. When the coastline ends, the sea deposits the material it is transporting because the change in depth affects its ability to transport the material further.

If there is a river estuary, then the meeting of the waves and the river causes a change in speed which results in both the waves and the river dropping their sediment. In time, the material builds up to form a ridge of shingle and sand known as spit. On the land slide, silt and alluvium are deposited and salt marshes form. The wind and sea currents may curve the end of the spit around. Spits are very dynamic, which means that their shape and form continually change. If spits are present on a coastline, it should be possible to determine the direction of longshore drift.

Bars

If a spit develops in a bay, it may build across it, linking two headlands to form a bar. Only possible when there is a gently sloping beach and no river entering the sea. In this way, bars can straighten coastlines.

An example is Slapton Ley in Devon which also has the characteristic lagoon formed behind the bar where any run-off water is trapped and slowly seeps through the bar to the sea.

What affects the rate of coastal erosion?

ü Waves- their power is determined by 2 factors: wind speed and the distance over which the wind blows over open water, known as fetch. The longer the fetch=the stronger the wind=the more powerful the wave.

Waves are created by a transfer of energy from the wind to the sea. As the wave approaches the coast, it begins to lose energy due to the friction with the beach. The more gentle the beach's incline= the more energy the sea will lose. On steep beaches, the wave retains (удерживает) much of its energy until it reaches the beach and consequently forms a destructive wave.

ü The type of rock- if the cliffs are made from resistant rock (granite), they will erode more slowly than the cliffs made from less resistant rock(clay).

ü The rock's structure- rocks that are well jointed or with many faults (limestone) , will erode more quickly as the waves exploit (используют) these lines of weakness. Cliffs that are gentle and well vegetated will be more resistant to mass movement and weathering than cliffs of bare rock. This will also affect the rate at which they can be eroded by the sea.

Effects of coastal recession (падение) on people and environment

The amount of effect is determined by the land use. If the area suffering from cliff recession is used for settlement = the effect is greater than, if the cliff recession is affecting farmland, which is seen to be less important as it's not worth as much money. The effects of coastal recession can be seen all around the coast of the UK.

North Norfolk coast

The North Norfolk coast's new Shoreline Management Plan which adapts a managed retreat will mean that nearly 1,000 homes, 1,400 caravan and chalet parks, 6 hotels and guest houses, 7 historic buildings, 3.5km of road, 7 golf course holes and 3 community halls will be lost to the sea over next 100 years.

The government will save £41 million by not building coastal defences but the human and environmental costs will be great. The estimated economic cost is £100 million with another £357 million lost in tourist income.

3 golf courses are suffering from the effects of coastal recession- there is no coastal protection in this area and no plans to build any.

One village under threat from this policy is the village of Happisburgh which has a population appx 850. It is one of the fastest eroding areas in the world.

The area was defended in 1958 with revetments which reduced the amount of erosion about 50cm a year.

In 1995, the council stopped repairing the coastal defences which caused the rate of erosion to accelerate.

Since this time, 25 properties and the village's lifeboat launching station have been washed away. The main area of concern is Beach Road which terminates in the sea.

The houses were worth £80,000 when the coast was defended but are now valued at £1, even though their sea view improves each year.

The government has refused to protect Happisburgh because it's not cost effective. The village is less valuable than the cost of the defences to protect it although it contains 18 listed buildings including a Grade 1 church which is only 60m from the cliff and estimated to be in the sea by 2020.

The cost of sea defences is appx £4 million for 500m.

The district council did defend the area in 2007 with 5,000 tonnes of granite rip-rap at a cost of £200,000; the local villagers raised a further £40,000 on a website which bought another 1,000 tonnes of rock.

This is slowing down the rate of erosion but there is no hope for the residents of Beach Road whose homes will soon be in the sea.

Hard engineering	Description	Advantages	Disadvantages
Rip-rap	Large rocks placed in front of the cliff.- protect the sand dunes   COST-£300 per metre	· Dissipates wave energy. · Can be very cheap, depending on rock type. · Effective for many years.	· Can make the beach inaccessible to tourists. · Unattractive · Not effective in storm conditions.
Recurved seawall	Walls usually made of concrete. The modern ones have a recurved face.   COST-£3,000 per linear metre	· Reflects and absorbs wave energy. · Very visible- makes residents feel safe. · Effective for many years.	· Ugly- puts tourists off. · Expensive to build. · Can cause wave scouring if not positioned correctly.