Helmholtz-Zentrum Deutsches Geoforschungszentrum

Fatigue, Rock Damage, and Erosion on Rocky Coasts

Though they comprise about 80% of global coastlines, rocky coasts with persistent sea cliffs are significantly understudied in comparison to depositional coastlines. However, the patterns and processes of sea cliff retreat are of significant importance for the resilience and management of coastal communities and infrastructure. While long-term cliff retreat rates scale with energy delivery to the coast, the mechanical processes by which sea cliff erosion occurs at the event-scale represents a fundamental knowledge gap in coastal geomorphology. Specifically, the observed contrast between the applied force of individual waves and the strength of most rocks suggests that a significant reduction in rock strength must occur to drive cliff failure and retreat.

Currently, the overall susceptibility to, extent of, and geomorphic role of accumulated rock damage on rocky coasts remains almost entirely unconstrained. This project will address three main research questions:

  1. How is wave energy integrated across sea cliffs and transformed into mechanical work?
  2. How sensitive is cliff rock strength to cyclic wave action?
  3. Can transient changes in rock strength explain episodic cliff failure over short timescales?

We seek to address these questions through a combination of passive seismic monitoring, active seismic experiments, and other near-surface geophysical methods to ascertain the temporal and spatial variation in rock strength properties. These measurements will be paired with change detection methods to better quantify the links between cliff erosion and rock damage accumulation. We are currently installing networks of broadband seismometers on the Orkney Islands, Scotland, UK, and Perranporth, England, UK.

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