Coasts Case Studies

Contemporaty Sea Level Change

Kiribati

Contemporaty Sea Level Change

Kiribati

Located in the South Pacific ocean

• Very low lying islands (average of 1m or less about sea level, max 3 metres)

• Sea level is rising by 1.2cm a year (4x faster than global average)

• In 2014 the president of Kiribati purchased 20km² land in one of the Fijian islands, allowing a place of eventual climate refuge (currently used for agriculture and fish-farming projects)

• Salt water inundation occuring, contaminating water supplies and rendering ability to grow crops

• South Tarawa (capitol) has a population of 50,000 and a similar population density to Tokyo (6,100 per km²)

• No current coastal protection around Tarawa

• Shifting weather patterns could push Tarawa into hurricane belt

• Government launched a ‘migration with dignity’ scheme to allow people to apply for jobs in neighbouring countries

Sea Level Change due to Tectonic Activity

Boxing Day Tsunami 2004

• 9.3 magnitude earthquake triggered a tsunami in the Indian ocean

• Killed 230,000

• 1600 km long fault line slipped 15 metres along the sybduction zone between the India and Burma plates

• 30km² water was displaced, tirggering the tsunami and causing a permanent sea level rise of 0.1mm

• The earthquake also caused the Earth’s crust at Banda Aceh (capitol of Indonesia) to sink, permanently flooding some parts of the city

Storm surge in developing country

Bangladesh and Cyclone Sidr 2007

Why Bangladesh is vulnerable

• 46% population live less than 10m about sea level

• One of world’s most densly populated countries

• Lies in the floodplain of 3 major rivers sourcing from the Himalayas (Himalayan glaciers melting 65% faster since 2010)

• 80% country classified as a floodplain

• High population causing land to sink (land subsidence) as built on silt deposited by rivers

• Deforestation of coastal mangrove forests has removed vegetation tht once stabalised coastal swamps and dissipated wave energy during cyclones

• Poor infrastructure increases impermeable surfaces

Subsidence

• Bangladesh’s estuarine islands have sunk by 1.5m in the last 50 years due to isostatic reajustment

• Islands have been cleared of mangrove forests to make space for agriculture, however saltwater inundation has been affecting the ability to do so. Large earth embankments have been built around the islands to help protect against storm surges, however they prevent the natural deposition of sediement to maintain the height of these islands, thus are subsequently sinking

Cyclone Sidr 2007

• 6m storm surge

• Category 4 storm

• Broke many coast / river embankments

• $1.7billion in damages

• Sanitation centre destroyed

• Electricity knocked out

• 3300 deaths

Cyclones - for every drop in air pressure of 10mb, sea level rises by 10cm

Storm surge in developed country

Netherlands 1953 and 2013

Netherlands 1953

• 5m storm surge

• 10% dutch farmland flooded

• 40,000 buildings damaged / flooded

• 1800 deaths

Netherlands 2013

Built a series of Delta works in response to 1953 storm

• Shortened coastline by 700km

• Coast $5billion

• Provide flood defence

• Provides fresh drinking water

• Traffic improvement between islands

• Generated employment

• Shipping / transport improvements

• Irreversible environmental impacts

• Polluted rivers

• Dissapearing tides

• Harsh transition from salt to fresh water - affecting flora and fauna

Netherlands North Sea storm 2013

• 2 metre storm surge

• No deaths

Storm surge in developed country

UK 2013

UK 2013

Extreme low pressure cause ocean to expand and swell

• Strong winds of 200km/h

• Coastal flooding of 1400 homes

• 2 deaths

• £100million in damages

• Storm surge reached heights of 5m in Hull

• All rail services cancelled in Scotland

• 40,000 homes lost power

Holderness Coast

Factors affecting erosion and Key Players

From Flamborough Head to Spurn Point

• Fastest eroding coastline in Europe (2m annually)

• Retreated 4km since Roman times, and lost 29 villages

• Mainly consists of boulder clay / glacier till

• Relatively small fetch (in comparison to Cornwall for example) however currents circulate around the UK from the Atlantic into the North Sea, adding energy

• Deep ocean floor along the coast so waves reach cliffs without being slowed by friction of shallow beaches

• Boulder clay erodes to produce fine clay particles that are easily transported by suspension, rather than accumilating on shore

Key Players

• Farmers want money spent to protect agricultural land

• Residents an increased budget for coastal protection for homes and businesses

• English nature and RPPB want to protect Spurnhead (UK’s largest coastal spit) therfore a continuation of sediment by longshore drift to maintain the spit is vital

Holderness Coast

Mappleton and Great Cowden

Mappleton

• Boulder clay cliffs have been eroding 7-10 metres a year here

• Served by the B1242, connecting it to villages along the coast. Erosion means the coastline is only 50m from the road at points

• Cheaper to protect Mappleton than constructing a new route

• A £2million project introduced 2 rock groynes intended to trap sediment transported by longshore drift

• Revetment constructed, working by absorbing wave energy using large air spaces between boulders and a broad surface area

• Cliff stabalisation implimented (planting vegetation) to protect cliffs from undercutting, reducing the gradient of the cliff, which has managed mass movement and slumping

• As a result of these management stratergies, no properties have been lost to the sea and the road remains safe

Great Cowden

• South of Mappleton, Great Cowden has experienced sediment starvation due to the groynes implimented in Mappleton (terminal groyne syndrome), leading to increased erosion and slumping rates

• Has led to farms destroyed (Cowden Farm) and loss of 100 chalets at the Golden Sands holiday park

Coastal Realignement

Essex Blackwater Estuary

Managed retreat at the Blackwater Estuary

• Essex Wildlife trust converted over 84 hectares of farmland to saltmarshes

• Cost benifit analysis concluded it was not worth maintaining the embankments as soil quality and land value were low

• Cost £645,000

• Provides sustainable sea defence as mudflats and slatmarshes absorb incoming high seas and storm surges, reducing volume of water travelling up Essex estuaries that could otherwise flood settlements

• Saltmarshes create new intertidal habitats

Stakeholder concerns

• Oyster fishing concerned sediments could choke and kill oysters, and remove habitats

• RSPB concerned of changing bird habitats