Coasts Flashcards
When will a wave break?
when the ratio of wave height to wavelength = 1:7
Example of long fetch
Southern Atlantic 40-60 S, waves average 5m in height as westerly winds blow continuously.
Vertical cliff example
White Cliffs of Dover - Chalk - Kent
Undercliff profile example
E.g Isle of wight
Cave arches stack stumps example
E.g Old harry Rocks, Dorset.
made of chalk
Tombolo example
Chesil Beach, Dorset
Off shore bar example
E.g coast of the Carolinas, SE USA.
barrier beaches example
E.g 300 islands along the east and south coast of the USA. e.g Fire Island
Ria example
A drowned river valley, created by a rise in sea levels. E.g Milford Saud, Wales
Raised beach example
Beaches that are well above the present day sea level, due to fall in the sea level over the last 10mn years. Can get relict beaches e.g caves. E.G Kings Caves in isle of Arran, Scotland
Fjord example
A drowned glaciated valley, created by a rise in the sea level. E.g Sognefjord, Norway. The largest and deepest fjord in Norway
Costal plain example
Found in areas with wide, shallow continental shelf, created by a fall in the sea level. May be backed by relict line of cliff which represents the old coastline. E.g Alaska’s Arctic National Wildlife Refuge
Dalmatian coast example
Coastal mountain chains, formerly with river valleys between the mountains are flooded and turned into islands, from a rise in the sea level. E.g Dalmatian Coast in South Croatia
Fjard example
An inlet formed by the marine submergence of formerly glaciated valleys and depressions within a rocky glaciated terrain of low relief. Fjards are characterized by a profile that is shorter, shallower, and broader than the profile of a fjord. E.g Strangford lough, Northern Ireland
optimal temperature for coral reefs
between 23 - 25 C
water depth for coral reefs
less than 25m
Salinity for coral reefs
intolerant to levels below 32psu
Climate change threat to coral fact
increases of 1-2C can cause bleaching
Ocean acidification threat to coral fact
Oceans have absorbed about 1/3 of the carbon dioxide produced from human activities since 1800.
Moving the ocean’s pH from 8.179 to a current pH of 8.06, which means the ocean is about 30% more acidic now than it was in 1751.
Education and responsible reef practices example
Great barrier Reef : Responsible Reef Practices, that encourages tourists/locals to minimise their damage to the reef.
E.g disposal of litter, reduction of fertiliser use, following zoning rules, ‘Look Don’t Touch’, reducing carbon footprint and not anchor away from corals.
Sighting network: alerting authorities of damage, bad practise….
Land zoning for coral reefs
The Great Barrier Reef Marine Park Zoning Plan 2003 provides for a range of ecologically sustainable recreational, commercial and research opportunities and for the continuation of traditional activities. Each zone has different rules for the activities that are allowed, the activities that are prohibited, and the activities that require a permit.
Solution to crown of thrones starfish
Outbreak of starfish since 1962, current outbreak began in 2010 due to leaching of fertilisers= decline of coral by 50% over last 30 years, half of which is due to starfish as they prey on Coral Polyps.
SOLUTION: since 2011; 300,000 starfish have been culled in 80 reefs by a team of 10 divers. Use of injection cull method which causes starfish to break apart and die within 24 hours. More effective that previous method in which divers had to extract the starfish from its location and inject it more than 20 times to get the same effect.
Threats to Holderness coast
Fast rate of erosion (up to 2m per year) due to:
- Geology: boulder clay is made up of unconsolidated sands and gravels which is very easily eroded by waves, causing rotational slumping.
- Waves: Destructive waves with long fetch because current circulate around the UK meaning the fetch comes from the atlantic (>5000km)
- Weather: winter storms causes storm surges due to low pressure system in North Sea. Bring very heavy rain which increases subaerial erosion and mass movements.
- Coastal flooding at Spurn head due to low lying land which means there is a risk of inundation at high tides. Made worse by global warming and sea level rise.
Hold the line advantages on holderness coast
At BRIDLINGTON 3.6km of concrete sea walls, timber groynes and rock armour have protected a town of 33,000 people and a major economic area from tourism and fishing. (tourism contributes £500mn to east ridings economy annually)
AT EASINGTON: 1km of rock armour protects a gas terminal that accounts for 25% of the UK’s gas supply.
Hold the line disadvantages on holderness coast
At BRIDLINGTON: sea walls were originally makeshift and unregulated hence v expensive to maintain. E.g part of the wall needs upgrading as its unsupported foundations threaten its stability due to a lowering of the foreshore.
Long term cost will rise as frequency of storm surges increases e.g £65,000 on maintenance after 1990s storm.
At MAPPLETON: 0.45km of rock armour groynes and revetments to protect only 50 homes. Cost of compensation less than £2mn cost in 1991 and continued maintenance. Also at time paid for by EU hence unsustainable after brexit?
Do nothing on holderness coast advantages
At very small towns and hamlets along the coast. Very cheap. Allows natural process to occur.
Do nothing on holderness coast disadvantages
At GREAT COWDEN: Suffers from terminal groyne syndrome due to sea defences (rock armour groynes) at mappleton. Rate of erosion increased from 2.5 m in 19991 to 3.8 in 2007. = Loss of farms and 100 chalets from golden sands holiday park.
Managed retreat on holderness coast advantages
At SPURN HEAD historically defended by hard engineering due to its environmental value (salt marsh is breeding and feeding ground for birds) BUT managed retreat reduces economic strain. Also area now a nature reserve, with boardwalks and information signs about conservation of saltmarsh and dunes. = 100, 000 migrating birds in 2017.
Managed retreat on holderness coast disadvantages
At SPURN HEAD terminal groyne syndrome has caused increased erosion rate. 20m narrowing in some place from 2003 to 2008. Whilst other area frozen solid. Hence natural evolution of peninsula is affected.
Sea level rise of 1m by 2100 = extreme risk of flooding = reduced biodiversity.
Thames barrier flood prevention
Thames Barrier: Built to prevent the flooding of greater London by high tides and storm surges moving up from the North Sea. It is a barrier that spans 520m across the Thames with 10 steel gates, that when raises stand 5 storeys high.
+ve: protects 1.5mn people and £200bn of assets. London did not flood in 2007 during a storm surge of the same scale to 1953 (when a flood occured)
-ve: construction cost £534mn and v expensive to maintain especially as being used twice as often since construction. Does not protect easternmost boroughs of Greater London.
coastal erosion on dubai
Under threat from a fast rate of coastal erosion.
Dubai’s beaches eroding at 25m per year. Erosion rate increased since construction of world islands in 2003, caused prevailing wave direction to change, hence increasing erosion from diffraction effects.
Beach replenishment e.g Umm Suqeim beach in 2007 with 500, 000m3.
+ve visually pleasing so good for tourism, fairly cheap.
-ve groynes from sandbags also needed to be made, increasing management cost. Theses are mitigating measures that slow the impact of erosion. Not a sustainable long term solution. Most beaches were man made and will always need constant maintenance as did not develop naturally.
Coral reefs threat in Dubai
Under threat from damage to coral reefs:
High level of construction and land reclamation, algal blooms from nutrient rich dischare and leacking of crude oil.
Fasht al Adham reef had 50% cover in 1985 => 0% in 2008.
Emirates marine Environmental group established in 1996. => translocated 12, 000 coral colonies from palm jebel Ali site, with 90% success rate. BUT very small scale, less biodiversity.
Erosion rates
Erosion rate of granite = less than 0.001m per year.
Erosion rate of Chalk = 0.1 - 1m per year
Erosion rate of glacial till/boulder clay = 0.1-10m per year
Mangroves adaptations
ultrafiltration of salt system: salt glands in surface in leaves to secrete salt. Salt accumulates in old leaves before they fall. Root membranes prevent salt entering. Pneumatophores arise from roots above ground to let O2 in. Prop roots descend from trunk to give support.
Mangroves value fact
Value: natural protection from tsunamis, cyclones, storm surges… important habitat; birds in canopy, fish nurseries, insects, crabs…Logging. Traps sediments from rivers to act as filter to allows coral reefs to develop in sediment free areas. Carbon sink.
E.g 0.5mn bangladeshis come to sundarbans (largest mangroves) each year to harvest its products.
Mangroves threats facts
Threats:
coastal development. E.g st thomas race track built on mangroves in US virgin islands.
Shrimp farming. E.g shrimp has overtakes tuna to become USA’s favourite seafood.
Unsustainable logging. Sea level rise.
Oil spills e.g sundarbans oil spill in 2014.
Size of sand and cobbles and beach angle
sand (0.02mm diameter = beach angle of 3
cobble (32mm diameter = beach angle of 24
Dunes example and vegetation
vegetation e.g marram and sea couch.
e.g sand dunes at Saunton Sands, North Devon
atoll reef
Atolls: these rise from submerged volcanic foundations and often support small islands of wave borne detritus. E.g Christmas island, indian ocean
barrier reef
Barrier reefs: occur at greater distances from the shore than fringing reefs and are commonly separated from it by a wide, deep lagoon. Barrier reefs tend to be broader, older and more continuous that fringing reefs. E.g Great barrier reef, Australia. 1200 miles long.
Fringing reed
Fringing reef: grows around an island. Characterised by an outer reef edge capped by an algal ridge, a broad reef flat and a sand-floored ‘boat channel’ close to the shore. Many fringing reefs grow along shores that are protected by barrier reefs, hence there are low wave conditions. The largest fringing reef in the world is near Msambweni, Kenya.
Salt marsh example
E.g Tamar Estuary near Plymouth,Devon or Keyhaven marshes formed behind Hurst Castle Spit, Southern hampshire
