New Unit: Managing Coasts We are moving onto a new unit called ‘Managing Coasts’. This topic will cover processes and features of the UK coastline. L1: Features of different types of wave. L2 & 3: Different erosion processes and associated features. L4 & 5: Different depositional processes and associated features. L6: Coastal defences L7: UK Case study How can we protect our coastline? Learning Objectives: - To know about the different coastal management strategies Why do we need to protect our coastline? As Britain is an island we are extremely vulnerable to coastal erosion. The coastline needs to be managed in order to maintain a balance between the forces of nature and the demands of people. Our coastline is under threat from cliff collapse, erosion, weathering, flooding and future sea level rise. Many of our coastal towns are also tourist destinations, e.g. Blackpool, Brighton and Great Yarmouth. These locations are of high value to our economy. Many people also live on the coastline therefore how these areas are managed is incredibly important. Coastal management strategies. • There are 2 categories of coastal management – (1) hard engineering and (2) soft engineering. I think the difference between hard and soft engineering is: Task: Using the photographs below, write down what you think is the difference between hard and soft engineering. An example of a hard An example of a soft engineering strategy engineering strategy Coastal management strategies. Hard engineering: Soft engineering: Uses artificial (man-made) structures Works with the natural coastal processes, to control the forces of nature. and uses very little man-made interference. Task: Using the correct definitions above and the photographs on the next slide, complete the table below – write H (hard) or S (soft) Management strategy H/S managed retreat gabions beach replenishment groynes sea wall dune regeneration revetments rip-rap breakwater Coastal management strategies. gabions sea wall revetment groynes rip rap beach replenishment dune replenishment managed retreat offshore breakwater Coastal management strategies Task • Using the information on slides 10 – 17 to complete the table on the next slide. • Remember you don’t have to write everything that is on the slide! Write in your own words so that you understand it! Name What it does Cost Advantages Disadvantages Sletch Name What it does Cost Advantages Disadvantages Sketch Coastal management strategies - GABIONS These are rock-filled wire cages often stacked or built up as a wall. They absorb wave energy as they are permeable and so reduce erosion. Although not pretty, they are cheap and effective. A disadvantage is that they are not very strong. • Sometimes gabions are made from reclaimed material such as old railway lines and rock boulders. This could be seen as environmentally friendly as no new materials are being used. • Although they are cheap and absorb wave energy well, they look un-natural and could deter tourists. • In some locations, local rock is used to reduce the visual impacts. • Some people are worried about the risks of gabions, particularly if the mesh breaks, as the rocks could fall out. Coastal gabions defence Cost £100 / m Lifespan 30 – 40 years Coastal management strategies – DUNE REGENERATION Dune regeneration involves creating or restoring sand dunes. Marram grass is planted on sand dunes, which helps to stabilise them and trap sand to further build the sand dunes. The dunes then provide a barrier and absorb wave energy. • During dune regeneration the land needs to be carefully managed so that any new vegetation that is planted is protected from trampling by humans. This could involve temporarily fencing off the dunes or by providing wooden walkways. • This is a relatively cheap process and it helps to maintain a natural looking coastline. Some people do not like areas of sand dunes being fenced off. Coastal dune regeneration defence Cost £30 / m Lifespan 30 – 40 years Coastal management strategies – SEA WALL A permanent concrete wall built to reflect wave energy back out to sea, preventing erosion. Very expensive to build and requires costly maintenance. They can create a strong backwash which can erode and damage the wall. They also limit access to the beach for visitors and tourists. • Some sea walls are curved and some are straight walls. In some coastal locations they have steps at the bottom to further break up the wave energy. • They are effective at protecting the base of a cliff. They usually have a walk way along the top of them. • Sea walls don’t always look very nice which can impact on tourism. • Although they are costly, the benefits should outweigh the costs protecting people, property and conservation areas amongst other things. Coastal sea wall defence Cost £7000/m £1000 – 2000 for repair work Lifespan up to 100 years Coastal management strategies – GROYNES These are usually wooden (or concrete) fences built at right angles to the coast. They trap material being transported by longshore drift thereby allowing beaches to develop. • They are cheap to build however they prevent the movement of sediment and starve beaches further along the coast of sand and so can cause erosion problems elsewhere along the same coastline. • Relatively easy to build and are inexpensive in comparison to other coastal management strategies. • Easily broken especially in stormy conditions. • Some people don’t like the look of groynes and get frustrated having to climb over them. Coastal groynes defence Cost £1500/m Lifespan 30 – 40 years Coastal management strategies – BEACH NOURISHMENT Sand is taken from elsewhere and pumped onto the beach to increase its size. It tries to replace material lost to longshore drift. Large, wide beaches are very effective at reducing the energy of waves. • Creating beaches can generate tourism and it is fairly cheap. It does however need to be maintained regularly. • Beach nourishment can only be carried out when wave energy is low, otherwise the sand is transported away from the beach by the waves. • Beach nourishment could have a short lifespan (may have to be re-done every few months) if there is strong longshore drift removing sediment from the beaches. Coastal beach nourishment defence Cost £50/m Lifespan 6 – 12 months Coastal management strategies – RIP RAP (or rock armour) This defence comprises of boulders or concrete blocks. It is placed at the foot of cliffs or back of beaches. It works by absorbing wave energy and so reduces erosion. Although not pretty, they are cheap and effective. • The rocks / blocks are piled up along the shoreline to form a type of sea wall. • They are placed on top of each other and gaps are left between them which help to break up the wave energy. • Rocks such as granite and basalt are often used. • Tourists may be put off by the look of rock armour / rip-rap. It is visually not very attractive. In some locations they have tried to use rocks which are the same colour as nearby cliffs to look more environmentally sympathetic. Coastal rip rap defence Cost £1000/m Lifespan 100 – 500 years Coastal management strategies – REVETMENTS These are wooden or concrete slanted barriers built parallel to the coast. They are designed to absorb wave energy. They are cheaper than sea walls but are often viewed as ugly. They also make it difficult for visitors and tourists to access the beach and need periodic repairs. • Revetments are often permeable and have natural stones or concrete blocks inside. They break up and absorb wave energy. • In very stormy conditions the wooden slats can be broken therefore repairs would be needed. • Tourists may not like to see the revetments and some people see them as visually obtrusive. • Revetments can also make access more difficult depending on where they are built. Coastal revetments defence Cost £2000/m Lifespan 30 – 40 years Coastal management strategies – MANAGED RETREAT The controlled flooding of low-lying coastal areas. If an area is at high risk of erosion, managed retreat could be an option. It usually occurs where the land is of low value, for example farm land. • This is a cheap option compared to paying for sea defences. • Creates a salt marsh which can provide habitats for wildlife and a natural defence against erosion and flooding. • Salt marshes are diverse ecosystems supporting many species. • Land is lost as it is reclaimed by the sea. • Landowners need to be compensated - this can cost between £5,000 - £10,000 per hectare. Coastal managed retreat defence Cost varies Lifespan permanent Diamond nine Which methods do you think are effective at Most effective protecting the coastline? • Seawall • Revetments • Gabions • Rip rap • Groynes • Sand dunes • Beach replenishment • Managed retreat Least effective • Do nothing.