Coasts : Coastal Protection / Hard and Soft Engineering Strategies 17 There are many different ways to reduce the rate of coastal erosion. Some are more expensive than others, some last longer, some are less of an eye-sore ..etc. There are 2 main categories of coastal protection: HARD Engineering Strategies : Building or creating something which will interfere with coastal processes – usually to reduce the power of breaking waves against cliffs. SOFT Engineering Strategies : Working with the natural processes of sea and sand in a more environmentally sustainable way. Using the natural processes to bring about an intended effect. Key Terms : Coastal protection Coastal management Protection strategies Hard engineering solutions Soft engineering solutions Sustainable protection strategies Choosing which methods of coastal protection is most appropriate for an area of coastline may take into account the following: COST : concrete sea wall is expensive. Wood revetments are cheaper LIFETIME : rock groynes may last decades. Beach rebuilding will have to be carried out every few months ENVIRONMENTAL IMPACT : offshore reefs will not affect the look of the beach but concrete tetrapods will look awful and put tourists off using the coastline SUSTAINABILITY : using hardwood from tropical rainforests for timber groynes is not sustainable – they will deteriorate and need replacing faster than new hardwood trees grow. Beach rebuilding is sustainable as you are moving sand from where it has been deposited, to where it has been eroded from. Example / Case-Study : Holderness coast Easington Gas Terminal Withernsea Hornsea Mappleton Possible Questions : Why might certain coastal protection methods be selected instead of others? What is the difference between Hard and Soft coastal protection techniques? Weblinks http://www.bbc.co.uk/schools/gcsebitesize/geography/coastal/coastalmanagementrev2.shtml
Coasts : Coastal Protection / Hard Engineering Strategies 18 Key Terms : Hard engineering Concrete Sea wall Revetment Gabions Rock Armour / Rip-Rap Example / Case-Study : Holderness coast Easington Gas Terminal Withernsea Hornsea Mappleton Possible Questions : Which coastal protection would you suggest for a coastal resort – and which would you reject – and why? Which of these hard engineering techniques is most effective? Weblinks http://www.bbc.co.uk/schools/gcsebitesize/geography/coastal/coastalmanagementrev2.shtml
Coasts : Coastal Protection / More Hard Engineering Strategies 19 Key Terms : Hard engineering Tetrapods Groynes / Breakwater Cliff Drainage Example / Case-Study : Holderness coast Easington Gas Terminal Withernsea Hornsea Mappleton Possible Questions : Which coastal protection technique is most appropriate for a section of cliff which has a history of slumping – and why? Which coastal defence technique would be best for a coastal industry – and why? Surface Water Drainage Pipe Weblinks http://www.s-cool.co.uk/alevel/geography/deltas-and-estuaries-and-changes-to-coastal-areas/human-influences-at-the-coast.html
Coasts : Coastal Protection / Soft Engineering Strategies 20 Key Terms : Soft Engineering strategies Offshore Reef Beach Re-cycling Beach Re-building Example / Case-Study : East Anglia Pevensey Bay, East Sussex Possible Questions : Why are soft engineering strategies more sustainable? What are the advantages of soft engineering coastal defences over hard engineering defences? Weblinks http://www.s-cool.co.uk/alevel/geography/deltas-and-estuaries-and-changes-to-coastal-areas/human-influences-at-the-coast.html
Coasts : Coastal Protection / Hard Engineering Case-Study : Mappleton Location 21 Mappleton was given a £3m coastal defence scheme in 1992 due to the danger to the main north-south coast road being lost if erosion continued. This would have severely affected trade and emergency transport in the region. Why have they built 2 rock groynes? Why is one larger than the other ? Are they working ? How can you tell?
Coasts : Coastal Protection / Hard Engineering Case-Study : Mappleton Strategies 22
Coasts : Coastal Protection / Hard Engineering Case-Study : Mappleton Evaluation 23 Key Terms : Longshore Drift Active cliff Accumulation Beach-robbing Precedent Evaluation • Successful Outcomes of the Mappleton Defences • Erosion has been effectively stopped behind the defences. The grass growing on the landscaped cliffs shows they are no longer ‘active’ – in contrast to the cliffs downcoast. • The road has been ‘saved’ – along with the village. • Tourism in the area has increased as a result of the wider beach and the interest in the scheme. Example / Case-Study : Mappleton, East Yorkshire • Less Successful Outcomes of the Mappleton Defences • Erosion has increased downcoast. Material moved by Longshore Drift is successfully ‘trapped’ at Mappleton by the rock groynes – but this means it is not moving down the coast to accumulate on beaches there. As a result beaches south of Mappleton are robbed of sand, becoming narrower and erosion is faster than it used to be before the scheme • Other villages under threat of coastal erosion say that a precedent has been set – and their villages should now be protected like Mappleton – otherwise it is unfair. • Erosion is still taking place north of Mappleton, so in the future the protected area is likely to become a peninsula as the coast to the north and south retreats westward. So more money will have to be spent protecting the sides of it. Possible Questions : Why are there sometimes negative consequences of protecting some parts of the coast and not others? What conflicts of interest might arise as a result of coastal protection measures? Weblinks View this BBC video clip And this one BBC video clip
Coasts : Coastal Protection / Easington Gas Terminal – A Controversial Issue 24 • 20% of Britain’s gas comes onshore at the Easington Gas terminal from the undersea gas pipeline stretching from Norway. Protecting this piece of coastline is therefore vital. The following issues occur though: • Which form of coastal protection should be selected? What criteria would you select for your basis of choosing (cost?, effectiveness?, environmental impact? Sustainability?... • Who should pay for any coastal protection here? (The government? East Yorkshire Council? British Gas? Gas customers?) • Who could be negatively affected by protecting this area of coastline? (look further along the coast beyond the gas terminal) • Should there be any compensation for anyone negatively affected? If so – who should pay it?
Coasts : Coastal Protection / Soft Engineering Case-Study – Pevensey Bay 25 The Pevensey Bay Beach Replenishment Project Suffolk CoastSouth England Using Soft Engineering Coastal Protection techniques to Hold the Line on a coast under threat.
26 Reasons behind the Beach Replenishment scheme at Pevensey Reason 1 : Almost all of the 150 wooden Groynes had deteriorated and either needed repair or replacement. Both would be very expensive and use a lot of hardwood – which isn’t a sustainable solution. They were removed in 2007. Reason 2 : The beach environment has many valuable plant species and these needed to be protected and encouraged to thrive. Reason 3 : There are many coastal homes looking out over the beach – and their protection, but also their views needed preserving. Removing the old groynes
Technique 1 : Beach Replenishment Sand and gravel is hoovered up by a dredger ship off the coast, and sprayed onto the lower beach at high tide. At low tide, bulldozers push the material up the beach to raise the height of the beach This takes place 3 times a year – in early Autumn after the holiday season, in January before the main winter storms, and at Easter just before the holidayseason and to correct winter storm damage to the beach. 27
Technique 2 : Beach Recycling There is strong Longshore Drift from West to East along the bay Bulldozers dig up the accumulated sand at the eastern end of the bay and transfer it to trucks. Trucks take the beach material back along the beach to the western end – so that Longshore Drift can distribute it along the length of the beach over the year. 28
Re-profiling After Technique 3 : Beach Re-profiling This means changing the gradient of the beach to the best one for absorbing the wave energy. Winter storms remove lots of the lower beach with their strong backwash. Bulldozers spread the sand evenly across the beach in Spring to create a more even profile – which is better at absorbing wave energy. 29 Before