Unit 7 Mini Case Studies

Question 1

Tidal ranges

Answer 1

There are almost no tides in the Mediterranean but in the Bay of Fundy the tidal range is 15m

Question 2

Microtidal examples

Answer 2

South Australia
Japan

Question 3

Mesotidal examples

Answer 3

Oman
Yemen

Question 4

Macrotidal examples

Answer 4

UK
West Madagascar

Question 5

Tidal bores

Answer 5

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

Question 6

Hurricane Katrina

Answer 6

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

Question 7

Typhoon Haiyan Yolanda

Answer 7

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

Question 8

North Sea Flood

Answer 8

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

Question 9

Cyclone Nargis

Answer 9

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

Question 10

Erosion in Southern Nigeria

Answer 10

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

Question 11

Inputs in Southern California Littoral cell

Answer 11

River deposits
Sediment from cliffs
Materials for beach replenishment
N/S longshore drift

Question 12

Southern California Littoral cell

Answer 12

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

Question 13

Human impacts on Southern California Littoral cell

Answer 13

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

Question 14

Ocean currents in West Africa

Answer 14

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

Question 15

Causes of coastal erosion in West Africa

Answer 15

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

Question 16

Togo human activity (west Africa)

Answer 16

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