Discordant Coastline: Waves Waves are caused by friction that is generated when wind Headlands and Bays Caves, Arches and Stacks What other processes change our coastlines? blows across the surface of the sea! Bands of differing rock strengths (resistant and Headland Sub-aerial As a wave reaches the beach: less resistant) run The water running up the beach is called the swash. As the wave loses perpendicular (in the Caves, arches and stacks Water enters cracks, and in cold climates, freezes, energy, the water begins to run back down the beach to the sea, and is opposite direction) to the often form at headlands, expanding by around 10%. This increased pressure called the backwash. If you’ve ever been to the beach, you will have felt this coastline. Along this should make sure you Mechanical weakens the cliff face. This process repeats, until motion under your feet when paddling in the shallow waters! coastline, a mixture of clay remember how headlands (freeze thaw) the rock is weak enough to fragment. In warmer initially form! Two types of waves! (less resistant), chalk and climates, the salt crystals of the sea expand when they dry, resulting in a similar process. limestone (resistant) run Akraberg Headland, Scotland Destructive Waves: Strong winds, perpendicular to the Rain water contains a chemical called carbonic powerful waves and cause coastal erosion. coastline. Cave They are tall and steep. The backwash is acid, which when comes into contact with certain Concordant Coastline: Bands of rock run parallel to the coastline. Along Chemical stronger than the swash, so material is Destructive waves break rocks such as limestone, can react and weaken the this coastline, limestone (resistant rock) runs along the entire length of carried out to sea. against the cliff face, rock as it dissolves. the coast. weaknesses in the rock are Constructive Waves: Light winds, not The roots of plants and trees, burrowing animals attacked. Through hydraulic Biological powerful and cause deposition, rather So what does this have to do with headlands and bays? and nesting birds can all help to weaken the rock. than erosion. Stronger swash, so material action, the crack widens, Headland eventually widening the crack is carried up the beach and deposited. Mass Movement enough to form a cave. Along a discordant coastline, the rocks Erosion is a term used to describe a wave removing This term refers to the downwards movement of rocks and soil under Erosion of higher resistance erode at a slower Merlin’s Cave, Cornwall, England material from the coastline the influence of gravity. It can occur in three different forms! rate to the rock of lower resistance. As a Attrition result, the high resistant rocks protrude Arch Slumping: After a period of rainfall, the out from the coastline, producing Small rocks that the waves are carrying, Waves erode the cave, via the permeable rock (absorbs rainfall) becomes headlands. collide in to one another. The rocks break process of hydraulic action, heavy, and can slip at the point where it and abrasion, with rocks and meets an impermeable rock (doesn’t absorb up, becoming smaller and rounder. This Peveril Point, South Coast of England continues to occur until the rock becomes pebbles swirling within the rainfall), often in a rotational manner. sand. Bays cave. If the cave sits in a narrow headland, waves Rock falls: Sudden fall of rocks, often due to Abrasion Along a discordant coastline, the rocks erode through the cave, weathering from above, or a growing wave of lower resistance erode at a faster rate Rocks that the wave is carrying are thrown creating an arch. cut notch that has resulted in an unstable than the rocks of higher resistance. This cliff face. against the coastline. This wears away at results in the rock eroding back more Green Bridge, Wales the coastline overtime. quickly to produce bays. Constructive Sliding: Similar to slumping, but occurs along a flat surface, usually a Stack bedding plane. Hydraulic Action ways often bring sediment to form a beach. Continued erosion of the base Weather Large waves break against the cliff. The cliff Swanage Bay, South Coast of England of the arch weakens the will often have faults/cracks in. The water structure, until a point where In the UK, we often experience winter storms is forced into these faults/cracks in the cliff, Cliffs the roof collapses due to (such as Storm Brian, Dylan etc.), which can which causes immense pressure. When this instability, leaving a stack, bring torrential rain and winds in excess of Cliffs are produced through the process of hydraulic action and pressure is released, it produces a force separated from the mainland, 100mph. These storms bring very large waves abrasion, where destructive waves erode the cliff between the high and that makes the crack larger. as shown above and to the and tidal surges, increasing erosion rates. low tide marks to create a wave cut notch. As this notch is eroded, the right. Solution cliff above becomes unstable, collapses and is removed by waves. Sea water has lots of different chemicals in, Wave Cut Platform Merlin’s Cave, Cornwall, England and these can sometimes react with the So where is the coastline eroding fastest in the UK? rock, causing the rock to dissolve. This Below the wave cut notch, an occurs most frequently with limestone. area of exposed rock is left, which is visible during low Happisburgh, Norfolk: tide. The surface is not This area has eroded smooth, as erosional by almost 90m over processes such as abrasion, the last 10 years, due and weathering, continue to to a failure in coastal erode the rock face. defences. Longshore Drift How do humans affect the coastline? What challenges do coastal landscapes present? Can we protect our coastline? Waves approach the beach at an Over 20 million people in the UK live near to Many people choose to live near the coastline in the UK due Planners must try to find sustainable ways of managing the angle equal to the prevailing wind. Settlement the coast. Along the Holderness coast, 29 to the economic (jobs), environemental (QOL) and social coastline, and do this using a process called Integrated Coastal Material is moved up the beach at an villages have been lost due to coastal erosion. (ommunities) benefits it brings. Coastal erosion removes Zone Management (ICZM). This involves Shoreline angle (swash), returning material from the coastline, with many areas in the UK at risk Management Plans (SMPs) being drawn up, which recommend perpendicular to the coast. Along the Coastal tourism is BIG business! 13% of jobs at of this. Dawlish in South Devon is a great example of this, to do one of the following things: Dawlish are in tourism. Coasts are often south coast of the UK, the prevailing Tourism with roads, railways and homes damaged in recent years due wind is from the South West, moving managed for tourists, such as building groynes to storms. material from west to east. to trap sediment for beaches. No Intervention No investment in flood defences. Roads, railways, shipping ports and oil Beaches refineries are just some of the infrastructure Dawlish railway found at the coast. The Esso oil refinery at damaged. Maintain the existing coastline with Formed when eroded material is transported by Infrastructure Hold The Line longshore drift and deposited by constructive Southampton sees 2000 ships dock each year. defences. waves. Sandy beaches are found in sheltered bays Hard engineering features are often built to Winter Storms 2014. (bay head beaches), and have shallow gradients harness infrastructure. Dredging the sea to construct ports can have Rising Sea Level Allow the shoreline to change adverse effects to wildlife. It can also impact Managed Construction naturally, but manage this process areas further down the coastline, due to Sea level in the English Channel is expected to rise by 15cm Realignment by 2030 due to global warming. A warmer climate causes and the impacts. Erosion altering the sediment budget and cell. water to expand, and ice sheets and glaciers to melt. Sea level rise and increased coastal erosion will impact farmland due to it being of a low Pebble beaches are found in areas where cliffs have been eroded by high Agriculture Build new defences on the seaward economic value, and therefore low priority in Advance The Line energy waves, and have a steep gradient. management. side. Could we see Spit London looking What are the advantages and disadvantages of coastal like this in the defences? A spit is a narrow ridge of sand or shingle, that stretches out from the Bournemouth Beach. future? coastline, into a gap in the coastline. A spit forms due to longshore drift. Sediment moves along the coastline until a change in coastline occurs. This Tourism, settlement and Defence Advantages Disadvantages results in material being deposited. This builds up overtime until the spit infrastructure. System extends out further into the gap. Saltmarshes begin to form being the spit due to it being enclosed. A spit may begin to curve due to wind and waves Storms and Storm Surges Protects base of from other directions. A storm surge is a large increase in sea level due to a storm. cliff. Made of Expensive and Southampton Port. Strong winds drive the waves, whilst low pressure allows the Sea Wall resistant unattractive. sea level to rise up to 3m above normal in the UK. These concrete that Restricts access. Settlement, infrastructure events can last for days, and can cause significant harm, and deflects energy. Dawlish Warren and construction. loss of life. Sand Spit, Devon. High cost of Winter UK 2014 Storms Maintains a wide maintenance.