We discuss various situations where the formation of rocky coast morphologycan be attributed to the retro-action of the coast morphology itself on theerosive power of the sea. Destroying the weaker elements of the coast, erosioncan creates irregular seashores. In turn, the geometrical irregularityparticipates in the damping of sea-waves, decreasing their erosive power. Theremay then exist a mutual self-stabilization of the wave amplitude together withthe irregular morphology of the coast. A simple model of this type ofstabilization is discussed. The resulting coastline morphologies are diverse,depending mainly on the morphology/damping coupling. In the limit case of weakcoupling, the process spontaneously builds fractal morphologies with adimension close to 4/3. This provides a direct connection between the coastalerosion problem and the theory of percolation. For strong coupling, rugged butnon-fractal coasts may emerge during the erosion process, and we investigate ageometrical characterization in these cases. The model is minimal, but can beextended to take into account heterogeneity in the rock lithology and variousinitial conditions. This allows to mimic coastline complexity, well beyondsimple fractality. Our results suggest that the irregular morphology ofcoastlines as well as the stochastic nature of erosion are deeply connectedwith the critical aspects of percolation phenomena.
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