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Coastal Landscapes in the UK Knowledge Organiser

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Coastal Landscapes in the UK Knowledge Organiser Coastal Landscapes in the UK Knowledge Organiser The Coast is Shaped by a Number of Physical Processes Coastal Processes Mass Movement Weathering Processes Erosion Transportation Deposition (Sub-Aerial Processes) Mechanical weathering – The shifting of loose Hydraulic power – Destructive waves carry Longshore drift – material Constructive waves deposit rain and sea water expands material down a cliff. as the powerful waves out erosional processes. is moved along the coast: more material than they when it freezes and turns There are three main types: smash into the cliff face, • waves travel in the erode. Key characteristics: to ice, then as temperatures air is compressed in the same direction as the Sliding – • steep and high waves; Key characteristics: rise again, the ice melts. small cracks in the rock. prevailing wind and hit material shifts down a slope • waves have a high • low and long waves; This continual expansion Tiny fragments of rock get the coast at an angle in a straight line. Image frequency (10-14 waves • low frequency waves and contraction can put blasted away as the process (swash); requested through RCP per minute); (6-8 waves a minute); pressure on rocks and is repeated many times. • material is carried back • the backwash is • the wash is more break them apart. It is also Slumping – down the beach at a Attrition – more powerful than powerful than the known as frost shattering saturated soil and rock right angle (backwash); eroded material in the sea the swash, removing backwash, depositing or freeze-thaw weathering. move down the slope (with • material zig-zags along bumps into each other material from the coast. material on the coast. rotation) over impermeable and eventually wear each the coast. rock. other down. Over time, the Material carried by material becomes smaller seawater is deposited and more rounded. on the coast when the water loses energy. More Abrasion – material will be deposited Chemical weathering – Rock falls – during storms, the strong when there is lots of this is when water reacts the base of the cliff is waves pick up rocks, pebbles erosion (e.g. after a storm) with minerals in rocks and eroded, leaving the rock and sand. The material is or when there is lots of the structure of the rock is above unsupported. This then smashed into the cliff transportation. changed. The best example breaks up and collapses. face. This can break off is solution. pieces of the cliff face. material slides straight down Page 1 of 3 visit twinkl.com Coastal Landscapes in the UK Knowledge Organiser Distinctive Coastal Landforms – are the result of rock type, structure and physical processes. Erosional Landforms Depositional Landforms Example of UK Coastline Headlands and bays – when a Beaches Chesil Beach coastline is made up of different • In sheltered bays, deposition of sediment often leads to The Dorset coast has many types of rock, they are called the formation of sandy beaches with a gentle slope. features of coastal erosion: discordant coastlines. The rocks • If cliffs are being eroded and there are high energy A 30km tombolo (a type of bar bay will erode at different speeds. The waves, this could lead to the formation of a pebble which connects an island to the beach with a steep gradient. less resistant rock is eroded faster, mainland) which encloses Fleet forming a bay. The more resistant • The profile of a beach is unlikely to be smooth. headland Lagoon. rock is eroded slowly, forming discordant coastline • At the top end of the beach you may find a storm beach headlands at either side of the bay. where boulders and shingle have been deposited by the Headlands and Bays strongest waves in a storm. There may also be a line of Formed along a discordant Cliffs and wave-cut platforms shingle and sand below this called a berm – this marks coastline, where resistant – waves cause most erosion at the usual high tide. rock forms headlands (Ballard the foot of cliffs creating a wave- Sand dunes – wind carries sand deposited by longshore Point and Durlston Head) and cut notch. The rock above will drift up the beach to create sand dunes. softer rock erodes to form bays eventually collapse and the cliff (Studland Bay and will retreat, leaving a wave-cut Incipent Dune - grass covered and changing Swanage Bay). platform in front of the cliff. Foredune - larger vegetation Old Harry Rocks and more stable Headlands are normally made of resistant rock which do not erode A cave and a stack (Old Harry easily, but cracks can develop into caves, arches and stacks. Hind Dunes - established soils, Rock) has been eroded from the large vegetation, little affect Caves – hydraulic power and abrasion enlarge cracks in headlands chalk headland. from ocean spray/winds creating caves. Photo courtesy of JOHN SIMPSON (via wikimedia commons) - granted under creative Spits – form at sharp bends in the coastline. Longshore commons licence – attribution Arches – caves continue to erode until they break through the headland creating arches. drift doesn’t turn the corner so it takes the sediment out to sea forming a long, sandy ridge known as a spit. As Stacks – erosion will continue to the ridge extends into more open water, it is affected by weaken the rock supporting the waves and wind. This leads to the tip of the spit curving. arch until it collapses forming Eventually, the sheltered area behind the spit can become a stack. a mudflat or salt marsh. Stumps – continuing erosion will Bars – sometimes the ridge of sand can go all the way lead to the collapse of the stack, across the bay or river mouth; this is called a bar. A leaving a stump. lagoon can develop behind the bar. Page 2 of 3 visit twinkl.com Coastal Landscapes in the UK Knowledge Organiser Different Management Strategies Can Be Used to Protect Coastlines from the Effects of Physical Processes The Costs and Benefits of Management Strategies An Example of a Coastal Management Scheme in the UK: The Holderness Coast Hard Engineering The Reasons for Management 1. Sea Walls • The Holderness Coast is made of soft boulder clay Scarborough Made out of hard material (e.g. concrete) to reflect waves back out to sea. which is eroding at an average rate of 1.5-2.5 Pros – prevents coastal erosion and flooding. metres a year. The cliffs at Golden Sands Chalet Cons – expensive to build and maintain. Can cause greater erosion downdrift due to waves reflecting off seawall. Park, Hollym near Withernsea, have retreated by Spurn Head Holderness more than 122m in 25 years! In some places Coast 2. Rock Armour erosion has been even more dramatic. Large rocks dumped to absorb and reflect wave energy. • 26 villages mentioned in the Domesday Book have been lost to the sea along the Pros – allows material to be deposited. Holderness Coast. Cons – expensive. Boulders need to be transported long distances (e.g. from Norway). • Prevailing winds and longshore drift in the North Sea erode and transport material 3. Gabions downdrift, exposing cliffs for further erosion. Wire cages filled with rocks to form a wall. • To protect settlements (e.g. Withernsea with over 6,000 inhabitants) and Pros – cheaper and easier than many other management strategies. infrastructure (e.g. B1242 road near Mappleton). Cons – the wire cages corrode over time. Can be considered to be ugly structures. The Management Strategy 4. Groynes Wooden/stone fences built at right-angles to the coast. 1. Withernsea is a popular tourist town. Various sea defences have been built at Withernsea over the last 100 years: a sea wall (which cost over £6.3 million) and Pros – traps material transported by longshore drift. rock armour to protect the promenade. Wooden groynes that were over one century Cons – can be costly. Can cause greater erosion downdrift. old have been replaced. Soft Engineering 2. In 1991, a £2 million scheme at Mappleton dumped blocks of granite (rock amour) 1. Beach Nourishment and Reprofiling at the base of the cliffs, protecting them from erosion. Also, two rock groynes were Sand/shingle/pebbles shifted up the beach profile. built on the beach to trap sediment creating a wider beach which prevents the Pros – creates wider beaches which reduces erosion and flooding. waves from reaching the cliff. Cons – constant maintenance needed, especially after extreme weather/high tides. The Resulting Effects and Conflicts 2. Dune Regeneration 1. Withernsea has been protected from erosion. However, the groynes trap sediment Creating/restoring sand dunes through beach nourishment or planting vegetation to stabilise sand. on Withernsea’s beach and as a result this sediment no longer is transported south Pros – provides a barrier between land and sea. causing increased erosion downdrift (e.g. the loss of land at the Golden Sands Chalet Cons – often limited to small areas as nourishment is expensive. Park which is south of Withernsea). Managed Retreat – Coastal Realignment 2. Mappleton village and the B1242 have both been protected. However, the area to the Removal of sea defences to allow the formation of salt marshes. south of the sea defences have faced increased erosion (from an average of 1.7m a Pros – cheap and easy. No maintenance. Prevents erosion and flooding elsewhere. year to 3.3m a year). Farmland to the south of Mappleton has been lost, including Cons – salt can alter ecosystems. Land and buildings will be lost – compensation cost could be high. the complete loss of Cowden Farm and Grange Farm. Page 3 of 3 visit twinkl.com.
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