coasts case studies

Dam - example of human actions that interfere with the natural flow of sediment?

Aswan Dam, Egypt: the River Nile is the source of sediment and the Nile Delta is the sink. The Dam traps water and sediment reducing sediment volume transported to the Delta, before the dam 130 million tones of sediment was deposited annually now only 15 million tonnes. this starvation of sediment increases recession rates from 20 M/YR to over 100.

Removal of sediment - example of human actions that interfere with the natural flow of sediment?

Hall sands, Devon: in 1897 the removal of material from the inter-tidal zone at the beach to extend the royal dockland at Devon Port. this took 1600 tonnes of gravel/sand a day. by 1904 the beach level lowered 6 meters, as 97% of the beaches volume was removed this reduced wave dissipation. in 1917 a storm in spring tides, 12m waves, destroyed the village.

Groynes - example of human actions that interfere with the natural flow of sediment?

Great Cowden, Holderness: the groynes distrupt the longshore drift of sediment, trapping it in the transfer zone to build the beach and protect the village of Mappleton. Down drift at Great Cowden there is a starvation of sediment increasing recession rates to 4M/YR loss of farmland. (terminal groyne effect)

example of local factors influencing flooding - height above sea level

1. Maldives: 2.3m is the highest point above sea level, a 50cm sea level rise would inudate 77% of the land. in response they built Hulhmalie an island 4M above sea level.

2. Bangladesh: 60% less than 3M above sea level, very susceptible to storm surges and monsoons. By 2050 17% of the land could be submerged displacing 18 million people as parts of the Delta experience subsidence. salt water intrusion is reducing food security causing increased displacement.

example of local factors influencing flooding - vegetation removal

30 to 50 % of all mangroves have been removed, in Sunderland's 40% has been removed since 1900s

short term impacts of storm surges

Bangladesh (India): 40% of all storm surges occur here killing 1.3 million since 1700. As the cost line by the Bay of Bengal is shaped like a funnel which increases the height of storm surges e.g. Cyclone Sadir 2007, category 4, had an 8M storm surge.

Cyclone Amphan 2020 the air pressure fell to 920mb causing. category 2 storm; social impacts - 26 died in 2020, 3000 died in 2007. economic impacts - $1.5 billion in 2020. environmental - Sunder bands mangroves uprooted.

North Norfolk storm surge

January 1953 in the night, in England it killed 300 people and 2100 in the Netherlands. Flooding occurred along the east coast from Yorkshire to Kent as sea levels rose by 3M. 65,00 hectare of farmland and 20,000 homes flooded as 32,000 people evacuated.

Typhoon Haiyan, Philipines, 2013

category 5 with winds of 315km and hour. 6200 dead and 28,000 injured. 90% of Tacloban was destroyed by a 7M storm surge as it is a low lying area, flooding occurred 1km inland as 14.1 million people where affected.

Fairborn North Wales - vulnerable to flooding

GDP per capita of £24,400, HIC

Has a population of around 750 with 450 houses, by 2054 the government plans to relocate the population due to the threat of flooding.

It is located on a low-lying floodplain so as sea levels rise it faces increased risks of inundation, especially in storm surges. If the sea rises by 0.5m the currents sea defences would be inadequate, increasing flooding.

Because of uncertainties in relation to sea level rise projections, including the effectiveness of sea defences and the impact of climate change on weather patterns, there are debates between the authorities and residents about the severity of the threat and what responses should take place.

After an announcement of the potential relocation of the village the property prices have dropped leaving the homeowners with assets that are difficult to sell creating an economic loss for residents.

Netherlands - places vulnerable to flooding

GDP per capita is €54,000 making it the fourth highest in European union, HIC.

Currently has a population around 18million, it is projected to reach 19 million by 2037. This growth is from increased migration and life expectancy. However, most of the population is older as by 2040 it is predicted that 60% of the population will be over 65.

Highly susceptible to sea level rise with 26% below the sea level currently. If there was a rise of 0.5m some major cities e.g. Amsterdam could be flooded depending on the effectiveness of the sea defences.

Uncertainty in different projections of sea-level rise stem from unclear climate models and future effectiveness of currents defences.

Severe flooding could cause their GDP to decline by 3% within the year of the flood. This is due to the potential 30% housing price decrease and a one-month standstill in economic activity.

Socially, the flooding could lead to displacement of homes and a change to daily life. It could also effect the community's cohesion as people compete for safe property.

Tuvalu - places vulnerable to flooding

GDP per capita of $7,714, LIC

Population of 11,500, it has an annual growth rate of 0.76% which is expected to continue.

Highly vulnerable to sea level rise as it is a low-lying atoll (island). By 2050 half of the main atoll Funafuti could be submerged by daily tides. By 2100 95% of the land could have routine flooding. This threats infrastructure, freshwater supplies and habitability.

Uncertainties are in different predictions from climate models, the changing pattern of Tropical Cyclones and the effectiveness of potential migration measures. Local factors contributing to this include land subsidence and coral reefs health.

They have already had economic impacts e.g. 2015 Cyclone Pam caused damages costing 25% of their GDP.

Sea-level causes loss of arable land and contamination to freshwater supplies.

Communities face displation leading to the potential loss of heritage and social cohesion.

Management case study - hold the line and managed retreat

Holderness - coast on unconsolidated boulder clay:

a high energy coast line due to the large fetch across the North Sea with Scandinavia over 1,000km away.

1. Bridlington sea wall

2. Mappleton - pressure from residents; rock armour and 2 rock groynes protect it

3. Easington - £4.5 million on Rock armour to protect gas terminal that supplies 25% of North Sea gas

this distruption to flow of sediment is destroying the mudflats at Humber estuary

Management case study - Sustainable / strategic management

East Head Chichester Harbour - Sand dune habitat with a spit infant that provides protection from storm waters. the spit is being eroded due to sea level rise (climate change) and increased storms. this causes less protection to the Harbour and settlements of West Wittering.

approaches:

1. Managed realignment - removal of some defences

2. soft engineering - Beach nourishment

3. Hard engineering - Groynes in strategic locations

Management case study - No active intervention

Undercliff Isle of Wight - due to technical feasibility the cost of prevention would be too high as it requires extensive engineering solutions. it has a complex cliff profile of weak permeable clays, sands and chalk that sit on impermeable clay and marl. this results in it being prone to landslides and landslides (2014 had a huge one) as rain water infiltration and marine erosion occur at the cliff base.

Management case study - LIC, Sustainable soft engineering in Kenya

Kenya, Gasi Bay: 3,000 residents stopped logging mangroves as international clients pay for the restoration of mangrove forests through a community led project 'Mikoko Pamela'. it is an area with limited job opportunities because of low education levels, this project helped shift community focus to conservation. By 2020 they made $25,000 in carbon credits sold, this money is used to insure the basic needs of locals is met.

despite the success of it there is still deforestation due to the absence of official boundaries and the volatility of the carbon market causing prices to fluctuate.

Integrated Coastal Zone Management

Bangladesh, Chittogram. it is responsible for 90% of Bangladesh's maritime trade. its threats: Cyclones, erosion (recession), sea level rise and riverine sedimentation from river Kamapholi. to solve this there are; storm shelters on stilts, embankments to prevent salt water inundating low lying areas to protect agricultural land from salinisation; Mangrove restoration and wetland conservation and periodically dredging the river.

cost benefit analysis for Happinsburgh

hold the line for 600m stretch of coastline: seawall £1.8m, rip-rap £0.8-3.6m, groynes £0.1-1.5 million

costs of erosion: £160,000 to Manor caravan park to assist relocation, affected residents could get £2000 each in relocation, grade 1 St Marys church and 2-listed Manor House could be lost.

benefits of protection:

by 2105 20 - 35 houses costing £4 to 7 million would be saved from erosion, 45 hectare of farm at £945,000 would be saved.

costs £6million in sea defences, higher than the compensation costs payable to local residents supporting decision to not defend village.

Blackwater Estuary in Essex

attitudes to coastal management between players depend on a wide range of factors and therefore is unlikely to please all players.

Area of tidal salt marsh and low-lying farmland prone to flooding and coastal erosion. was protected by flood embankments and revetments.in 2000 Essex Wildlife trust purchased Abbotts Hall Farm which was threatened by flooding / erosion. they implemented a 4000hectare managed realignment scheme by creating 5 breaches in the sea wall in 2002. allowed new salt marshes to form inland.

positives:

- Abbotts hall farm owners received the market price for their threatened farm

- high costs of 'hold the line' policies where avoided

- water quality of estuary improved as reed beds expanded

- imported bird and fish nurseries where enhanced.