COASTAL PROCESSES COASTAL PROCESSES COASTAL EROSION COASTAL TRANSPORTATION COASTAL DEPOSITION COASTAL DEPOSITION It refers to processes that results in the addition of materials to the coasts. COASTAL TRANSPORTATION This refers to the movement of materials along the coast. COASTAL EROSION This refers to the processes that results in the removal of materials from the coasts. COASTAL EROSION COASTAL EROSIONAL PROCESSES HYDRAULIC ACTION FACTORS AFFECTING EROSION WAVE SIZE ABRASION/ ROCK COMPOSITION/ CORRASION STRUCTURE ATTRITION POSITION OF COAST SOLUTION/ CORROSION CLIMATE COASTAL EROSIONAL PROCESSES HYDRAULIC ACTION I Waves repeatedly hits against soil and rocks along a coast. Over time, the repeated wave action loosens these soil and rocks and sweeps them away. This process is known as hydraulic action. HYDRAULIC ACTION II As the waves pound against the coast, the air within these cracks is compressed. When the waves recede, the compressed air suddenly expands. Over time the repeated compression and expansion widens and weakens cracks and ultimately breaks the rocks. ABRASION Waves carry rock fragments such as pebbles and gravel. These fragments act as chiselling tools when they are hurled against the coast, and breaks the rocks. This process is known as abrasion. ATTRITION Rock fragments carried by the waves are thrown against one another. This gradually break up the rocks into smaller, smoother and rounded pieces. This process is known as attrition. SOLUTION Soluble minerals in coastal rocks are dissolved in and removed by the seawater. For example, calcium carbonate reacts chemically with the carbonic acid and changes into soluble hydrogen carbonate. When solution occurs, the rocks are weakened and ultimately disintegrates. FACTORS AFFECTING COASTAL EROSION WAVE SIZE The bigger the waves, the more energy they have to erode the coast. This is because larger waves have more powerful backwash than the smaller waves that plunges over when breaking. This erodes the coast faster. ROCK COMPOSITION I Soft rocks such as shale and clay will be eroded faster than hard rocks such as granite and basalt. This is because, such rocks being weaker are unable to withstand the force of the strong waves. ROCK COMPOSITION II Similarly, rocks with mineral composition that that or chemically react with water to form new chemicals are more prone to erosion. This is because, such rocks are gradually weaken under the constant attack of sea water and break down. ROCK STRUCTURE The presence of lines of weaknesses such as joints and bedding planes will result in a faster rate of erosion. This is because such weaknesses makes the rocks more susceptible to the strong force of waves. POSITION OF COAST A coast that is exposed to strong prevailing onshore winds will be more susceptible to erosion. This is because it is exposed to the full force of wave action while sheltered coast is protected. CLIMATE Strong prevailing onshore winds such as monsoon period will intensify coastal erosion. This is because wave action is much more stronger during this period. HUMAN INTERFERNCE Coastal defences such as seawalls and breakwaters slows down the rate of coastal erosion. COASTAL TRANSPORT COASTAL TRANSPORT One of the ways in which waves transport sediments along a coast is by longshore drift. Definition: This refers to the movement of materials along a coast by the action of waves. Draw: Longshore Drift LONGSHORE DRIFT Waves approach coast at an angle. Swash carries the materials up the coast at an oblique angle. Backwash carries the materials perpendicularly down the beach due to gravity. This results in a zig-zag movement of materials along a coast known as the longshore drift. COASTAL DEPOSITION WHEN? SHELTERED COAST: Deposition occurs when the coast is sheltered from prevailing winds as wave erosion is minimal in these areas. GENTLE COASTAL SLOPE: On a gentle slope, depositional materials are brought by constructive waves as swash is more powerful than backwash in this area. WHEN? EXCESSIVE LOAD During a storm, large amounts of materials are eroded from the coast. These materials are deposited when the storm subsidies as the retreating waves are unable to carry them. SHALLOW WATERS When the coastal waters are shallow, the advancing waves break off and leave eroded materials on the coast and deposition occurs.