Coastal Processes Coasts are shaped by the sea and the action of waves. The processes that take place are erosion, transportation and deposition. The power of waves is one of the most significant forces of coastal change. Waves are created by wind blowing over the surface of the sea. As the wind blows over the sea, friction is created - producing a swell in the water. The energy of the wind causes water particles to rotate inside the swell and this moves the wave forward. The size and energy of a wave is influenced by: ● ● ● Label the diagram below with long fetch and short fetch: Types of waves Waves can be destructive or constructive. When a wave breaks, water is washed up the beach - this is called the swash. Then the water runs back down the beach - this is called the backwash. With a constructive wave, the swash is stronger than the backwash. With a destructive wave, the backwash is stronger than the swash. Label the diagram below with swash and backwash: Constructive and Destructive Waves Summary Points on Destructive Waves: ● ● ● ● ● Summary Points on Constructive Waves: ● ● ● ● Coastal erosion The sea shapes the coastal landscape. Coastal erosion is the wearing away and breaking up of rock along the coast. Destructive waves erode the coastline in a number of ways: 1. Hydraulic action: __________________________________________________________________ __________________________________________________________________ 2. Abrasion. __________________________________________________________________ __________________________________________________________________ 3. Attrition. __________________________________________________________________ __________________________________________________________________ 4. Solution. __________________________________________________________________ __________________________________________________________________ Illustrate the four types of erosion on the four diagrams below Coastal Transport Waves can approach the coast at an angle because of the direction of the prevailing wind. The swash of the waves carries material up the beach at an angle. The backwash then flows back to the sea in a straight line at 90°. This movement of material is called transportation. Continual swash and backwash transports material sideways along the coast. This movement of material is called longshore drift and occurs in a zigzag. Illustrate longshore drift on the diagram below: Deposition When the sea loses energy, it drops the sand, rock particles and pebbles it has been carrying. This is called deposition. Deposition happens when the swash is stronger than the backwash and is associated with constructive waves. Deposition is likely to occur when: ● ● ● Coastal Processes: Questions Erosional landforms Along a coastline there are features created by erosion. These include cliffs, wave-cut platforms and wave-cut notches. There are also headlands and bays, caves, arches, stacks and stumps. Cliffs, wave-cut platforms and notches One of the most common features of a coastline is a cliff. Cliffs are shaped through a combination of erosion and weathering - the breakdown of rocks caused by weather conditions. Soft rock, e.g. sand and clay, erodes easily to create gently sloping cliffs. Hard rock, e.g. chalk, is more resistant and erodes slowly to create steep cliffs. The process of cliff erosion: 1 2 3 4 5 Headlands and bays Headlands are formed when the sea attacks a section of coast with alternating bands of hard and soft rock. The bands of soft rock, such as sand and clay, erode more quickly than those of more resistant rock, such as chalk. This leaves a section of land jutting out into the sea called a headland. The areas where the soft rock has eroded away, next to the headland, are called bays. Geology is the study of the types of rocks that make up the Earth's crust. Coastlines where the geology alternates between strata (or bands) of hard rock and soft rock are called discordant coastlines. A concordant coastline has the same type of rock along its length. Concordant coastlines tend to have fewer bays and headlands. Caves, arches, stacks and stumps Describe the formation of the following: Cave: __________________________________________________________________ __________________________________________________________________ Arch: __________________________________________________________________ __________________________________________________________________ Stack: __________________________________________________________________ __________________________________________________________________ Stump: __________________________________________________________________ __________________________________________________________________ Depositional landforms Beaches are a common feature of a coastline. Beaches are made up of eroded material that has been transported from elsewhere and deposited by the sea. Constructive waves help to build up beaches. The material found on a beach (i.e. sand or shingle) depends on the geology of the area and wave energy. The material found on a beach varies in size and type as you move further away from the shoreline. The smallest material is deposited near the water and larger material is found nearer to the cliffs at the back of the beach. Large material is deposited at the back of the beach in times of high energy, for example during a storm. Most waves break near the shoreline, so sediment near the water is more effectively broken down by attrition. Sandy beaches have gently sloping profiles and shingle and pebble beaches are steeper. Spits Spits are also created by deposition. A spit is an extended stretch of beach material that projects out to sea and is joined to the mainland at one end. Spits are formed where the prevailing wind blows at an angle to the coastline, resulting in longshore drift. An example of a spit is Spurn Head, found along the Holderness coast in Humberside. Describe the development of a spit: Spurn Head Coastal Management Successful management of coastal areas depends on understanding the different uses of coastal land and the physical processes impacting on the coast, such as erosion and longshore drift. Techniques for managing these physical processes can be divided into hard engineering options (such as building sea walls) and soft engineering options (such as beach nourishment and managed retreat). Conflicts of interest Land uses in coastal areas include tourism, industry, fishing, trade and transport. There are many different groups of people who have an interest in how coastal areas are managed. These include: ● ● ● Reasons why groups of people might be concerned about the coast ● ● ● Management strategies Physical management of the coast attempts to control natural processes such as erosion and longshore drift. Hard engineering Hard engineering options tend to be expensive, short-term options. They may also have a high impact on the landscape or environment and be unsustainable Soft engineering options Soft engineering options are often less expensive than hard engineering options. They are usually more long-term and sustainable, with less impact on the environment. There are two main types of soft engineering. 1. Beach management ● ● ● 2. Managed retreat ● ● ● Case Study: Coastal Management Use this space to create a mind-map of your coastal management case study .