Wave Attack & Cliff Undercutting
Coastal cliffs retreat primarily through wave action at their base. Breaking waves exert enormous pressures — up to 100 kPa during storms — that exploit joints, bedding planes, and weaknesses in the rock. Hydraulic action forces water into cracks at high pressure, abrasion grinds the rock with wave-carried sediment, and repeated wetting-drying and salt crystallization weaken the rock matrix. The result is an erosional notch that undercuts the cliff face.
Cliff Collapse & Mass Failure
Once the notch extends deep enough, the overhanging cliff becomes gravitationally unstable and collapses. The failure mode depends on rock structure: toppling in horizontally bedded rocks, planar sliding along inclined joints, and rotational slumping in weak clays. The collapsed debris temporarily protects the cliff base from wave attack, creating cycles of rapid erosion (notch growth) and quiescence (debris protection) that make retreat highly episodic.
Shore Platform Development
As the cliff retreats, it leaves behind a wave-cut platform — a gently seaward-sloping rock surface. The platform acts as a natural breakwater: as it widens, waves must travel further across shallow water, losing energy to friction and breaking. This negative feedback means retreat rate decreases over time as the platform grows, establishing a self-regulating equilibrium between wave energy delivery and cliff resistance.
Climate Change & Accelerating Retreat
Rising sea levels threaten to reset the equilibrium by drowning shore platforms, allowing larger waves to reach cliff bases. Combined with more intense storms and changing precipitation patterns that affect cliff stability, coastal erosion rates are projected to accelerate significantly. Managing this risk requires understanding the coupled dynamics of waves, cliffs, platforms, and sediment transport that this simulation explores.