Coasts : Flooding Coasts / Causes and Consequences of Rising Sea Levels

1. Coasts : Flooding Coasts / Causes and Consequences of Rising Sea Levels 52 • Sea levels are rising around the world as a result of : • Increased global temperatures resulting in polar ice caps melting • Melting of glaciers in high mountains areas (Alps, Andes, Himalayas) • Thermal expansion of the sea – as sea-water gets warmer, it expands to occupy more area. • Increased storm surges as low pressure systems allow the sea level to rise – Hurricanes and more frequent & more intense resulting in higher tides & waves. Key Terms : Sea level rise Sea level refugees Polar melting Storm surge Low pressure Example / Case-Study : New Orleans, USA Carteret Islands, Pacific Ocean Possible Questions : Why are global sea levels rising? With reference to examples you have studied, how are people being affected by global changes in sea level? Sea Level Rise Refugees The 2,400 inhabitants of the Carteret Islands are being forced to abandon their islands and move to the neighbouring islands of Bougainville. The islanders who are just off the coast of Papua New Guinea have been forced to flee as rising sea levels have caused salt sea water to flood their fields and contaminate their fresh water. The infant mortality rate is growing due to malaria with mosquitoes breeding in stagnant pools of surface water. Is this how it is going to be for others? • Consequences of rising sea levels & warmer oceans : • Sea Levels are likely to rise for the next 100 years • Storm Surges will be more frequent • High tides will be higher than existing coastal defences are built for • Coastal Erosion will be more rapid on ‘Soft’ coasts • Coastal Vegetation may be destroyed • Sea-water will penetrate further inland, destroying farmland and contaminating supplies of fresh water in wells • Coastal communities will suffer more frequent flood alerts- and more frequent flood events, eg. New Orleans • More people will demand extra spending on coastal flood protection Weblinks http://www.bbc.co.uk/programmes/b00kj9z1(listen to radio programme or read summary) http://www.solomontimes.com/news.aspx?nwID=3622 http://www.global-greenhouse-warming.com/Carteret-Atoll.html

2. Coasts : Flooding Coasts / Strategies for dealing with rising sea levels 54 • Management options for protecting coasts from rising sea levels consist of : • Do nothing – let the sea flood onto land • Move entire communities inland onto higher land • Build higher defences with sea walls & embankments • Plan for Managed Retreat (coastal realignment) Key Terms : Managed retreat Coastal realignment Coastal estuary Example / Case-Study : Humber estuary Canvey Island, Thames Estuary Possible Questions : Wjhat do you understand by Managed Retreat of the coastline What options are open to those responsible for managing the response to rising sea levels? • The issues facing the Humber estuary • sea levels are expected to rise in the next 50 years by 50cm. • the Humber estuary is one of the longest estuaries in the country needing flood defences • the land is low-lying (much below 5m) – so any flooding will penetrate a long way inland • existing flood embankments are in need of repair and sometimes breached by very high tides • the government is not providing enough money to upgrade all the existing embankments for future higher seas – or for any new ones. • higher sea levels are covering major bird feeding mudflats along the Humber depriving them of food • expanding chemical industries on the south Humber bank are building on feeding mudflats. • relatively few people live in the flood danger area apart from a few scattered farms. Weblinks BBC video clip on how rising sea levels have affected the Maldives BBC video clip – the flooding of Canvey Island in 1953 BBC video clip on Managed Retreat in Somerset versus higher sea walls http://www.hull.ac.uk/coastalobs/media/pdf/humberestuarysmp.pdf (full Humber Shoreline Management Plan)

3. Coasts : Flooding Coasts / Managed Retreat - north Humber Estuary near Hedon 55 • Paull Holme Strays Managed Retreat (coastal realignment) near Hedon. Reasons for the Plan: • The existing embankment was breached by a storm surge in 2003. The engineers had to decide whether to repair the breach, or put in a longer term solution. • Sea level rises along the Humber estuary are forecast to continue over the next century • Mudbanks are being lost to feeding birds by sea level rise and expanding industries along the estuary Key Terms : Managed retreat Coastal realignment Coastal estuary 2000 Example / Case-Study : Humber estuary Paull Holme Strays – next to Fort Paull, near Hedon, Humber North Bank 2006 • The advantages of the Humber managed retreat plan • The existing coastal embankment breach was left unrepaired. Two new breaches were created. • When high tides and storm surges flow up the Humber estuary, the surplus water is able to flood into the land that was previously farmland. • The height of the floodwater is reduced elsewhere in the estuary. • when the floodwaters subside, the deposited mud provides ideal feeding habitats for wading birds • the solution is much cheaper than trying to repair and constantly raise the height of existing embankments. • The disadvantages of the managed retreat plan • farmland is now useless – contaminated with sea salt. • farmers have had to be compensated for lost production • as the planet faces food shortages, farmland is being lost Possible Questions : What are the advantages and disadvantages of managed retreat Using an example you have studied, how can Coastal realignment help reduce the threat from rising sea levels? Weblinks BBC video clip on Managed Retreat along the Humber.