COASTS CASE STUDIES Flashcards
What is happening in kiribati?
In 2014 president purchased 20km2 of land of fijian islands . Nation of kiribati 33 widely spaced islands in pacific consisting of low lying sand and mangrove atolls- only 1 metre of less above sea level. Predicted that many of the islands could dissapear in the next 50 years. In places SL rising by 1.2cm a year.
Why are sea levels rising?
Global warming, average global temps rose by 0.85 degrees from 1880 to 2012. During a similar period, 1870 to 2010 average SL rose by 21cm. Sea levels are rising because of polar ice sheets are melting and because of thermal expansion. Scientist best guess is that SL will rise 40cm by 2100.
WHat is next for kiribati?
Land purchased by Kiribati will be used in the immediate future for agriculture and aquaculture to secure countries food security rising SL in kribati is contaminatinf ground water sources and affecting its ability to grow crops. In the future, if neccessary people could move from kiribati to fiji. Gov launced migration with dignity poilicy ti apple fpr jobs in neighbour countries such as NZ if lislands are submerged pop will become enviromental refugees.
What 2 isostatic changes are occurring in the UK currently?
Land in the north and west was covered by ice sheets during the last ice age- is still rising as a result of isostatic recovery by 1.5mm a year in what is known as post-glacial rebound.
> However land in the south and east which the ice sheets never covered is sinking 1mm per year. Rivers pour water and sediment into the Thames eustary. The weight of the sediment causes the crust to sink there and for relative sea levels rise. Therefore, south-east england faces increased flood-risks as a result of the land sinking due to isostatic change, as well as a rising sea level caused by global warming.
How can sea level change due to tectonic activity?
On boxing day 2004, an earthquake between 9.0-9.3 on the Richter scale caused a tsunami in the Indian ocean that killed aprox. 300,000 people. Sumatra was worst hit as closest to the epicentre. City of banda aceh was hit by a 15m high wave and flooded just 15 mins after initial earthquake. But devastation was made even worse, because the earthquake caused the Earths crust at Banda Aceh to sink- permanetly flooding parts of the city. Caused by estimated 1600km of fault line slipping baout 15metres along the subduction zone where indian plate slides under the Burma plate. Seabed rose meters displacing 30km3 of water and triggering a tsunami. Not only that, but the raising of the seabed reduced capacity of the entire indian ocean- producing a permanent rise in sea level of an estimated 0.1mm
Past tectonic activity also had an effect on coasts around the globe.
<caused uplift of mountain ranges and coastal land at destructive and collision plate margins
<Local tilting of land eg. some ancient mediterranean ports have been submerged and others have been stranded above the current sea level.
Why is erosion such a problem at holderness?
On average holderness loses 2m of coastline each year. Since roman times the holderness coast has retreated by 4km - at least 29 villages have been lost to sea.
3 main reasons why the coastline at Holderness is retreating so rapidly.
>Geology
>Fetch
>LSD and beach material
How does the geology of holderness affect the rate of erosion?
> Most of Holderness coast consists of weak boulder clay which is structually weak and has little resistance to erosion producing shallow sloping cliffs between 5 to 20 meters high.
> chalk band that surrounds the boulder clay has created a headland at Flamborough head. Erosion along fault lines and bedding planes has created features such as cliffs, arches and stacks.
How does fetch infuence erosion at holderness?
Effects wave energy holderness is exposed to winds and waves from the North-east with a small fetch of about 500-800km across the north sea but also infuenced by
> currents that circulate around the UK from the Alantic ocean into the North Sea. The Atlantics fetch is 5000km or more, so its currents add energy to the waves in the north sea. Therefore, there are often powerful destructive waves at work along this coastline.
> low-pressure weather systems and winter storms passing over the north sea are often intense- producing locally strong winds and waves. Low-pressure air weighs less, raising sea levels which in turn produce higher tides.
> Small enclosed seas such as the north sea often generate huge waves during storms as waves move within the sea, but cannot disperse their energy.
> sea floor is relatively deep along holderness so waves reach cliff without being weakened by friction.
How do sub-aerial processes affect coastal erosion?
Cliffs at holderness are affected by both mass movement and weathering.
>chemical weathering is relatively ineffective at holderness except for chalk flamborough head. Mechanical and biological weathering are far more significant. The main types of weathering experienced at holderness a freeze-thaw and wetting and drying of boulder clay.
Slumping main form of mass movement on the boulder clay of holderness the alternate wetting and drying of the clay causes expansion and shrinkage-producing cracks during long,dry periods. Subsequent rains then enter the cracked clay and percolate into the cliff, which becomes lubricated and much heavier, clay slides downslope under gravity and then slumped material collects at the cliff base and is then rmoved by the sea- causing cliff line retreat.
How does LSD affect coastal erosion at holderness?
Beches at holderness are the main problem does to the sediemnt produced form bolder clay being fine and easily traspoted they don’t accumulate as beach sand ans as a result the beaches are narrow and offer little friction to absorb wave energy as a result not enough snad t stop waves from reaching the cliff base. Tides flow southwards transporting sand south by LSD leving cliffs poorly protected. Beaches south of horsea have reduced in width due to backwash exceeding swash sediment.
WHo are the key players in holderness?
1.central gov agencies-The Env agency is resposible fot coastal management but budget cut since 2012.
2.Local gov- Locl authorites are jointly resposibe for coastal management but in 2010, local-gov funding was cut by cen gov which restricted local councils to minimal increases in council tax.
3.stakeholders in the local economy
>tourist industry wants greater spending on coastal protection
>Farmers want money spent to protect their farmland which is of lower value than urban places
>residents at mappleton and horsea want garenteed prot for homes and businesses.
>insurance companies are increasingly refusing to insure vunerable properties.
4.envi stakeholders
>English nauture and RSPB want to protect spurn head so a continuing flow of sand southward by LSD is essential. Gives protection fot mudflats on Humber eustary ( one of UKs most important birdlife reserves)
How has coastal management impacted coastal erosion?
sea walls,groynes and rock armour at Horsea protect part of the coast but also interrupt the flow of beach material by LSD beach downdrift of horsea at mappleton is then starved of material and cliffs are exposed to wave attack. This is known as terminal groyne syndrome.
> first sea wall was built in Horsea in 1870 lasting for 6 years in 1906 stronger one was built and extended 5X at the southern end defences were reconfigured in 1977. The T-shaped rock armour designed to let beach sediement accuklate and pass beneath it, groynes built at horsea starved mappleton of sediement. By 1990s 4metres of cliff were eroded at mappleton each year.
What economic and social losses have inccured as a result of erosion at holderness?
It is predicted that 200 roads and several homes will fall into the sea between falmborough head and spurn point by 2100. Nationally, envriomental agency suggests that 7000 homes will be lost due to coastal erosion by the same date.
Individuals lose out socially and finacially as a result of coastal erosion and very little financial help is available for them. NO compensation is paid out for the loss of private propert or land caused by coastal erosion.
Between 2010-2012 east riding of yorkshire used 1.2 mil of direct oney form Defra to trial different ways of helping people adapt to living on erosing coastline giving finacial support to 36 households on the coast,supported by 16 relocations and 43 property demolitions, remainder of money was used to help with relocation and adaption packages.
What were the adapation and relocation packages?
Relocation package involved
>demolition costs for a property
>relocation costs up to a maximum of 1000£
>expenses caused by relocating to a new homw up to max of £200
Adaption package involved
>Rollback- expenses incurred as a result of an individuals decision to replace a threatened coastal propert with a new home inland. But it only covers things like planning application fees. Rollback was introduced particularly to adress the risk of caravan parks,farms and homes in areas where coastal defences not visable.
>assistance grants- to adapt to properties which may be at risk from coastal erosion in the future (eg.relocating septic tanks/waste pipes and changing access routes for some properties)
Why is Bangladesh at risk?
Worlds most densely populated country with estimated pop of 169million in 2015. 46% of pop lives less than 10m above sea lecvel and lies of the floodplain of 3 major rivers with 54 tributaries and huge amounts of himilayan snow melt adds to monsoon rains every year. Coastal flooding is a major problem with voilet thunderstoms with winds of 160km/h creating 6 meter high waves
