Download to read offline
More Related Content
Coastal landscapes
- 1. Coastal landscapes Our coastlinesare constantly changing, through natural processes that have been occurring since the world has been turning... So what causes the shaping of our coastline? How does it affect us? And what can we do about it?
- 2. Coastal erosion Destructive waves, strongswash/backwash and tidal currents cause: Hydraulic action Abrasion Attrition Solution The sea shapes the coastal landscape. Coastal erosion is the wearing away and breaking up of rock along the coast.
- 3. Birling Gap, EastSussex in 1905 shows the third chimney from the left separated from the sea by four other houses, a garden and large stretch of land The extent of erosion: 1905
- 4. To now: Justin a century! Shows the property with the same chimney now teetering on the cliff-edge after the sea cut its way through all of the other homes
- 5. Coastalisation means the‘the movement of people to coastal areas’. We engineer our coastlines to suit our needs, develop infrastructure and tourism.
- 6. But it cansometimes be very costly. Can we really stop the forces of nature? We certainly try, but how successful are our methods and technology?
- 7. Coastal defences -Hard engineering Porthleven, Cornwall, during a storm. Sea walls: Permanent stone or brick structures built to protect settlements or cliff bases from erosion. Although seemingly effective they do not absorb the waves energy, rather reflects it actually causing beach erosion, sometimes undercutting the structure. Tend to be expensive, short-term options that may also have a high impact on the landscape or environment and considered to be unsustainable.
- 8. Coastal defences -Hard engineering Groynes mitigate the loss of material caused by longshore drift by ‘trapping’ it and helps build up a beach with new imported material. But causes erosion outside of the groynes as beach maretial is no longer deposited there. Gabions, rock armour and revetments all absorb the energy of the waves to mitigate further erosion of the base of the cliff or beach. But all are short- term solutions. Groynes Rock armour Gabions Revetments
- 9. Coastal defences –Soft engineering Beach nourishment Beach profiling Cliff stabilisation Sand dune restoration Managed retreat, creation of salt marshes Often much less expensive than hard engineering options, and usually more long-term and sustainable, with less impact on the environment.
- 10. Managed retreats –Most sustainable Advantages Land becomes a marsh, slowing waves and reducing erosion Creates new habitats and promotes biodiversity Good for recreation, walking and bird watching Disadvantages Arable/development land is lost Can be costly depending on scale of human resettlement Managed realignment involves altering the location of the line of defence, to provide a more sustainable position to manage flood and erosion risks.
- 11. Contrasting coastal landscapes JurrasicCoast, Dorset Happisburgh coastline, Norfolk
- 12.
- 13. Contrasting coastal landscapes JurrasicCoast, Dorset Happisburgh coastline, Norfolk Triassic, Jurassic and Cretaceous period resistant sedimentary rock of red sandstone, limestone, clay and shale cliffs 71 layers rich in fossils documenting 185 million years of plant and animal fossilisation Tall, vertical cliffs with highest point 191 m above sea level making it highest point along South west coast 18 mile barrier beach with intertidal lagoon important to biodiversity https://en.wikipedia.org/wiki/Jurassic_Coast Very low lying coastline approximately only 10 m tall cliffs to sea level. Cliffs are composed of glacial drift deposited from a retreating ice sheet 425,000 years ago. The beds below the glacial till comprise muds, sands and gravel. The cliffs are unconsolidated material therefore non-resistant and easily eroded. http://www.northfolk.org.uk/geology/happisburg h.html
- 14. Case study: Happisburgh Inless than a decade it is clear from these aerial photos that the rate of erosion along this part of the coastline has been extensive. Various hard engineering strategies have been constructed to mitigate the effects of coastal erosion and although they may have seemingly slowed down the process, it certainly did not stop the forces of nature and erosion continued regardless. The red line in the 1998 photo indicates the actual coastline in the 2007 photo. Many metres of land have been lost, as well as the houses that were once situated on it. Erosion continued... https://www.pinterest.com/pin/545920786062323545/
- 15. Case study: Happisburgh Happisburgh.26 Feb 2014. Photo: Mike Page http://www.edp24.co.uk/news/environment/aerial-photos-of-happisburgh- spanning-13-years-show-ravages-of-coastal-erosion-1-3370564 Extract: Relentless coastal erosion has seen many metres of land lost to the North Sea’s ravages... Vulnerable homes have been demolished ahead of their inevitable tumble down the crumbling cliffs, and their occupants have retreated inland... Happisburgh suffered because it was the “soft underbelly,” sandwiched between two sets of hard sea defences. But he added: “Hard defences only reduce risk. In the end you cannot stop the sea. We have to learn how to manage our way through the whole problem of climate change.”
- 16. Case study: Happisburgh Happisburghin 1996, 2006 and 2012 during which time it has lost a number of sea front properties (copyright Mike Page) https://blog.geographydirections.com/2013/11/01/adapting-to-coastal-change-understanding-different-points-of-view-in-coastal-erosion-management/
- 17. Possible solution toHappisburgh As the continuation of coastal erosion is inevitable, the most important factor in the land management decision is the protection of the town and surrounding settlements. It has been proven that hard engineering strategies are short- term and expensive therefore a more holistic approach is vital to provide any long-term solution to this area. Although seemingly counter productive in the eye of local residents, a managed realignment of the coast is necessary, allowing the tidal energy to enter and be absorbed by a purpose built wetlands or salt marsh.
- 18. Case study: Medmerry,Sussex https://www.ice.org.uk/knowledge-and-resources/case- studies/managed-realignment-at-medmerry-sussex ⃝ Previous coastal defence wall costing £300,000 PA to maintain ⃝ Breach of sea defence in 2008 cost £5 million in damage ⃝ Sustainable coastal realignment project cost £28 million ⃝ Generated 300 ha wildlife refuge including mudflats, reed beds, saline lagoons and grassland includes 183ha of intertidal habitat mitigates effect of ‘coastal squeeze’ ⃝ A total of 348 properties, plus sewage works, caravan parks and Selsey's main road route are now protected ⃝ Around £90m of direct economic benefit is expected from the scheme.
- 19. Possible solution toHappisburgh ⃝ Eroding cliffs only 7 m tall ⃝ Settlement only 10 m above sea level ⃝ Extensive agricultural land suitable wetlands site similar to Medmerry ⃝ Excavated material ideal for large wetland perimeter providing a viable sea defence for settlement
- 20. Conclusion ⃝ Coastal landscapesare diverse, formed of a variety of rock types with variable resistance to erosion. ⃝ We create human settlements in vulnerable areas along the coast, therefore require engineering strategies to protect our towns from storm surge and coastal erosion. ⃝ Hard engineering strategies are expensive to build and need regular maintenance which is costly and only short-term solutions ⃝ Low laying coastal areas prone to erosion or flooding are ideal sites to create salt marshes and wetlands, creating protected areas to promote biodiversity. ⃝ A managed realignment of the coastline is a holistic approach to safeguarding settlements, working ‘with’ the forces of nature. ⃝ Agricultural land more viable to realign coastline minimising costs of relocating local residents. ⃝ Created wildlife habitats also good for recreation activities and tourism as well as boosting the local economy.