Coastal boulder deposits consist of megagravel, with 100+ tonne blocks close to sea level, as well as boulders of many 10s of tonnes mass emplaced at elevations 10s of metres above high water and up to 250m inland. The largest boulders can be moved by several metres during storm events. Understanding the mechanisms of boulder generation and transport gives a unique insight to the powerful events that occur along high-energy coastlines.
We present a model of boulder generation via a hydraulic press-like action on exposed beams on platforms. The stress generated in the rock can propagate cracks to full fracture. Hydrodynamics, mechanics, and fracture models are discussed in relation to the problem, alongside field evidence.
The subsequent transport of large boulders by overtopping waves and surges has been actively modelled for the last 20+ years. We discuss some fundamentals in the models, and show improvements in determining the forces involved in a number of situations. We use complex variable techniques, treating the boulder as an obstacle in the flow.