What Factors Influence Coastal Erosion Rates? (IB Geography)
Coastal erosion rates vary greatly between locations and over time, making this topic central to IB Geography, particularly within Option B: Oceans and Coastal Margins. Coastal erosion refers to the wearing away of land by waves, tides, and currents. The rate at which erosion occurs depends on a combination of physical factors and human influences.
One of the most important physical factors affecting erosion rates is wave energy. High-energy coastlines experience powerful waves generated by strong winds and long fetch distances. These waves have greater erosive force, increasing rates of hydraulic action and abrasion. In contrast, low-energy coastlines are more sheltered and experience slower erosion. Storm events can dramatically increase erosion over short periods by producing unusually powerful waves.
Geology and rock type strongly influence erosion rates. Hard, resistant rocks such as granite erode slowly, while softer rocks like clay and sandstone erode much more quickly. Coastlines made of alternating hard and soft rock experience differential erosion, forming bays and headlands. Rock structure, including faults, joints, and bedding planes, also affects erosion by creating weaknesses that waves can exploit.
The shape and orientation of the coastline play a role in erosion rates. Headlands are exposed to wave refraction, which concentrates wave energy and increases erosion. Bays receive lower wave energy, encouraging deposition rather than erosion. Steep cliffs are more vulnerable to mass movement, while gently sloping coasts tend to erode more slowly.
Weather and climate influence erosion over both short and long timescales. Increased rainfall can saturate cliffs, increasing the likelihood of slumping and landslides. Freeze–thaw weathering weakens rock structures, making them more vulnerable to wave erosion. Climate change may increase erosion rates by raising sea levels and increasing storm frequency and intensity.
In IB Geography, human activity is also recognised as a major factor influencing erosion. Coastal management structures such as groynes, sea walls, and breakwaters alter sediment movement and wave energy. While these structures may reduce erosion locally, they often increase erosion further along the coast by disrupting longshore drift.
Human land use affects erosion rates as well. Coastal development can increase pressure on cliffs through excavation and added weight. Removal of vegetation reduces slope stability, increasing erosion and mass movement. Dredging and offshore construction can also alter wave patterns and sediment supply.
Overall, coastal erosion rates are influenced by a complex interaction of wave energy, geology, coastal shape, climate, and human intervention. In IB Geography, strong answers recognise that erosion is dynamic and spatially variable rather than uniform along coastlines.
RevisionDojo helps IB Geography students understand coastal erosion clearly by linking physical and human factors into structured, exam-ready explanations.
