Unit 7 Mini Case Studies Flashcards
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Tidal ranges
There are almost no tides in the Mediterranean but in the Bay of Fundy the tidal range is 15m
Microtidal examples
South Australia
Japan
Mesotidal examples
Oman
Yemen
Macrotidal examples
UK
West Madagascar
Tidal bores
The Severn Bore is a tidal surge. It is caused by a combination of rising tide and the physical shape of the Severn Estuary. As the tide rises it forces water into a channel that continually reduces in width and depth. This wave can be up to 1m high and travels up to 30kmph
Hurricane Katrina
2005
Gulf Coast of the USA
Up to 28 feet in some areas storm surge
Over 1800 killed
Thousands injured
Hundreds of thousands made homeless
Extensive damage to New Orleans and surrounding areas
$125 billion in damage
Typhoon Haiyan Yolanda
2013
Philippines
Up to 23 feet storm surge
Over 6300 killed
Thousands injured
4.1 million people displaced
Major destruction in Tacloban City and other coastal regions
$2.98 billion in damage
North Sea Flood
1953
Netherlands, UK, Belgium
Up to 18 feet storm surge
2551 killed (1836 Netherlands, 307 UK, 28 Belgium)
Thousands of homes destroyed
Tens of thousands displaced
Prompted major improvements in sea defenses like the Delta Works in the Netherlands
Cyclone Nargis
2008
Myanmar Burma
Up to 15 feet storm surge
Over 138000 killed
Hundreds of thousands injured or displaced with extensive damage to the Irrawaddy Delta region
$10 billion in damage
Erosion in Southern Nigeria
Logos is a break in coast and the city developed rapidly in the 19th and 20th century. Dredging began in 1907. Breakwaters and a jetty provide a channel for large ships. These developments interrupted the W/E longshore drift on the W African coast. There has been more deposition on Lighthouse Beach on the W updrift side of the jetty at Tarkwa Bay which traps sediment and increase erosion on the E downdrift side of the jetty and shipping channel. Victoria Beach erodes by 70m/y and over 2km of beach has been lost. Used for recreation so beach replenishment has been used since 1976. When marine currents change direction material is deposited in the harbour channel which has to be dredged. Deposition on Lighthouse Beach will cause deposition beyond Tarkwa Bay cutting off the Lagos Harbour channel
Inputs in Southern California Littoral cell
River deposits
Sediment from cliffs
Materials for beach replenishment
N/S longshore drift
Southern California Littoral cell
Irregular and variable river supplies have fallen by 33% by dam construction. Most material supplied for beach replenishment is fine silt and sand. Each year rip currents and offshore currents move 100000m^3 of sediment into La Jolla submarine canyon and 200000m^3 of material drifts. Seasonal variations in in constructive/destructive waves redistribute coastal sediment and sea levels are rising 6-15mm/year
Human impacts on Southern California Littoral cell
Dams reduce sediment supply by 33%
Buildings, houses, pools, boats and roads are destabilising cliffs
Oceanside Harbour in the N is blocking S movements of sediment and most is diverted to offshore currents and to the La Jolla submarine canyon
Ocean currents in West Africa
Ocean currents have removed a lot of beach material along the Ghana and Nigeria coast. This affects settlements, tourism and industry. Rise in coastal retreat was blamed on construction of Akosombo Dam on Volta River in Ghana. The Guinea current is one of the strongest removing 1.5 million m^3 of sand per year between Ivory Coast and Nigeria
Causes of coastal erosion in West Africa
Traced to Akosombo Dam in 1967. It is 110km from the coasts and disrupts sediment from River Volta preventing 40% reaching the coast. Less sand to replace what is washed away so coastline retreats due to erosion by coastal protection. Keta, 30km E of Volta estuary have been destroyed as the protective beach is removed. Other towns in Togo are threatened with destruction
Togo human activity (west Africa)
Problem is worsened by artificial breakwaters. In 1960s a port opened at Lome to improve trade with neighbours like Mali and Niger. Lome is protected by 1300m breakwaters obstructing the natural Guinea current flow. Sand collects on the W of the breakwater. The E is open to erosion. Result is erosion of beach and infrastructure. In 1984 a 100m stretch of the Ghana Benin highway destroyed in 24h. Erosion by Tropicana cause advance of sea by 100m. Uncovered resistant sandstone which is protective by not attractive. Kpeme, 18km E is a port for most of Togo phosphate exports. The jetty was threatened. Engineers have reinforced erosion foundations. The boulders trap sand and stop it moving down the coast. E towns erosion 6-30m/y cosint 1-2m pounds to protect every km of coastline. If Togo protects its coastline it could increase erosion in Benin
Simple and compound spits examples
Presque Isle, Lake Ene
Sandy Hook in New Jersey
Examples of bars
Low Bar in Cornwall, UK composed of shingle
The nehrung of the Baltic coast which pond Black Lagoon called haff
Example of cuspate forelands
Dungeness near Dover, UK. The foreland forms the seaward edge of Romney Marsh. In 900CE the marsh was a bay. WIthin the last 1000 years it has silted with mudflats and marshes due to the growth of the cuspate foreland. The shingle was deposited by longshore drift curling west from the North Sea and by the longshore drift following eastwards up the English Channel. Deposition from Rye Bay, wave refraction and colonisation by vegetation also contributed to the formation
Example of offshore bars
Off the coast of the Carolinas in South-East USA
Example of barrier beaches
The longest series is the 300 islands along the east and south coasts of the USA. The distance between barrier beaches and the shore is variable. Islands are generally 200-400m wide. Some Florida islands are so close to the shore that residents don’t realise they are on an island. Parts of Hatteras Island in North Carolina are 20km offshore. The island in Chatham Harbour has migrated south over 140 years
Chesil beach overview (tombolo)
Chesil beach on the south coast of England is 25km long connecting the Isle of Portland with the Dorset coast at Burton Bradstock. At the east end it is 13m above sea level composed of flinty pebbles. At the west end it is 7m above sea level and built of smaller flinty material. The height and size of material suggests dominant wave action from east to west. The largest material is at the east and being the hardest to transport. Smaller material is further west. Dominant wave action comes from SW up the Channel from Atlantic Ocean. Morphology of the ridge should be the opposite
Theory of Chesil beach (tombolo)
One theory is that Chesil is young so is unstable in the present environment. 18000-20000 years ago in Pleistocene period, sea level fell to 100m below the present position. Much of the English Channel was dry. During the Ice Age a lot of debris was produced on the nearby land by glacial and periglacial action. This could have been carried into the dry channel by meltwater at the close. As sea level rose in post-glacial times, the material could have been pushed onshore and trapped by the Isle of Portland and Lume Bay. Present wave action is sorting the material
Saltmarshes example
Scolt Head Island on the North Norfolk coast is home to saltmarshes. It is exposed to cold winds from the east and at high tide, it is cut off from the sea and at low tide it joins to the mainland. There is a large sand and shingle foreshore. Wave action sorted the shingle, forming ridges near the HWM. As they became more stable, dunes developed and moved the island west. Most of the shingle came from glacial deposits
Tamar Estuary in Tasmania
The longest navigable estuary in Australia at 70km. It is a drowned river valley which was formed by rising sea levels flooding an existing river valley. The Australian coastline includes more than 1000 estuaries
Chesapeake Bay
The largest estuary in the USA. About half of the water volume is sourced from the Atlantic Oceans saltwater while the other half drains from the 64000 mile squared watershed
Rio de la Plata
A muddy estuary formed by the confluence of the Uruguay river and the Parana river at Punta Gora. It forms part of the border between Argentina and Uruguay
Mangroves example
There are 2 groups: Eastern group in East Africa, India, Southeast Asia and Australasia with 40 species of trees
Western group in West Africa, South America and the Caribbean with only 8 species
Ria example
Falmouth, UK
Fjord example
Sogne fjord, Norway
Fjard example
In Scandinavia, fjors dominate along the North Sea coast while fjards dominate the Baltic Sea coast
Great Barrier Reef formation
The 2600km reef off Eastern Australia was formed over 5 million years ago
Salinity levels example
Some corals can tolerate high salinity levels such as in the Red Sea or Persian Gulf
Barrier reefs examples
The Beqa barrier reef off Fiji stretches unbroken for over 37km
That off Mayotte in the Indian Ocean for about 18km
The largest barrier reef system in the world is the Great Barrier Reef which extends 2600km along the east Australian coast usually tens of km offshore
Another long barrier reef is in the Caribbean off the coast of Belize between Mexico and Guatemala
Atoll reefs examples
There are over 300 atolls in the Indian and Pacific Oceans but only 10 are found in the Western Atlantic
Charles Darwin places
Supporters have shown that submergence has taken place as in the case of drowned valleys along parts of Indonesia and along the Queensland coast of Australia. In other areas such as the Caribbean there is little evidence of submergence
Economic importance of reefs examples
Countries like Barbados, the Seychelles and the Maldives rely on tourism. Tourists attracted to Floridas reefs bring in $1bn annually, and the global value of coral reefs in terms of fisheries, tourism and coastal protection is estimated to be $375bn
Natural threats to coral reefs
Dust storms from the Sahara have introduced bacteria into Caribbean coral. Many areas of coral in the Indian Ocean were destroyed by the 2004 tsunami
1998 coral bleaching
There were major effects in the Arabia/Persian Gulf, East Africa, throughout the Indian Ocean, in South East Asia, parts of the western Pacific and the Caribbean and Atlantic region. It was estimated that 16% of the worlds area of coral was severely damaged
In 1998 there was bleaching that affected the majority of coral reefs around Puerto Rico and the northern Caribbean. In the south west a large number of coral colonies bleached completely
In Barbados about 20% of bleached corals did not survive but most are showing signs of recovery from hurricanes
2004 coral assessment examples
The most damaged reefs are in the Persian Gulf where 65% have been destroyed, followed by reefs in South and South East Asia where 45 and 38% are considered destroyed. There are more recent reports that many reefs in the wider Caribbean have lost 80% of their corals
Most of the recovered reefs are in the Indian Ocean, part of the Great Barrier Reef off the coast of Australia and in the western Pacific especially in Palau. In 2004 Australia increased protection from 4% to 33% and 34% of Ningaloo Reef Marine Park was made off limits from fishing
Evidence of climate change damage to coral reefs
Mass bleaching is in the long history of countries like the Maldives and Palau before they were devastated in 1998. About 16% of the worlds coral bleached and died in 1998. 500-1000 year old coral died in Vietnam, Indian Ocean and western Pacific
The major bleaching years for the Caribbean were in 1998 and 2005. Records for hurricanes were broken in 2005. The bottom cover of corals has dropped by over 80% since 1977
Between 50 and 905 of corals died from bleaching on many reefs in the Indian Ocean
The first major bleaching event on the Great Barrier Reef was in 1998 and since then 2002 and 2006. Growth of species has declined by 14% since 1990
Coral management examples
The damage and probable sea level rise of 0.8-1.2 metres will seriously affect communities on Kiribati, the Marshall Islands, the Maldives and Tuvalu and many communities will cease to exist
