Geography – Coastal environments | e-Consult

A coastal cliff is primarily formed through wave erosion. The process begins with wave attack, where waves directly impact the cliff face, causing hydraulic action (force of water entering cracks) and abrasion (waves carrying sediment that grind against the rock). This weakens the cliff face over time. Undercutting occurs as waves erode the base of the cliff, creating an overhang. Eventually, the overhang becomes unstable and collapses, leading to cliff retreat. The eroded material is then transported by waves and currents, forming a wave-cut platform at the base of the cliff.

Human activities significantly accelerate coastal erosion. Coastal development, such as the construction of buildings, roads, and sea walls, can disrupt natural sediment transport processes. Sea walls, while intended to protect, can reflect wave energy back onto the cliff face, increasing erosion in adjacent areas. Dredging for ports and navigation channels removes sediment from the seabed, depriving the coastline of a natural sediment supply. Coastal quarrying can also destabilise cliffs. Climate change, leading to rising sea levels and increased storm frequency, exacerbates erosion by increasing wave energy and inundation.

Examples:

• Coastal development in Miami, USA: Sea walls have increased erosion in some areas.
• Dredging in the Thames Estuary, UK: Reduced sediment supply leading to increased cliff retreat.
• Coastal quarrying in Cornwall, UK: Instability of cliffs and increased erosion.