Processes by which wave action, currents, tides, and storm surge remove beach, cliff, or shore sediments and rock, producing landward retreat of the coastline and modification of shore morphology.

Principle

Coastal erosion results from the transfer of hydrodynamic energy to the shore; wave impact, overtopping, hydraulic pressure, abrasion by transported clasts, and seabed/currents‑driven scour act together with sediment supply and shore material strength to determine net erosion rates.

Demonstration

Following a high‑energy storm, a sandy beach loses its berm and a nearby cliff shows a measurable retreat of several metres; longshore currents under persistent oblique waves progressively remove sand down‑drift, leading to beach narrowing over seasons.

Misapplication

Attributing all shoreline retreat to coastal erosion without separating contributions from relative sea‑level rise, subsidence, or human excavation; or applying a steady‑state shoreline model to an episodically driven system.

Consequence

Accurate identification of coastal erosion mechanisms allows targeted interventions (setbacks, managed retreat, soft engineering, sediment nourishment) and improves hazard assessments for infrastructure, ecosystems, and communities.

Reversal

Reversal is coastal accretion: where depositional processes dominate (sediment supply exceeds removal), the shore advances seaward rather than retreats.

Boundary

Refers to natural and storm‑driven removal of shore materials at the land‑sea interface; excludes inland fluvial or glacial erosion, engineered excavation that is not hydrodynamically induced, and chemical dissolution of bedrock without mechanical removal.

Semantic Tension

Differs from the broader term 'shoreline change' which includes both erosion and accretion and contributions from vertical land movements; 'coastal erosion' emphasizes removal by hydrodynamic processes.

Synthesis

Coastal erosion is the hydrodynamically driven loss of shore materials by waves, currents and surge, modulated by sediment supply, material resistance, and sea‑level/geomorphic context, producing shoreline retreat and morphological change.