Mesoscale coastal behavior related to morphological self-adjustment

High-energy events (extratropical storms, tsunamis, and hurricanes), sediment supply variability, and sea-level rise are regarded as major drivers of coastal geomorphic behavior. In this paper we document a 170 yr record of cyclic coastal changes that occur independently of such external drivers. In a geologically constrained situation with no external sediment input, two end-member morphological configurations (attractors) are identified between which the system alternates. Although neither configuration is stable, the system as a whole exhibits century-scale equilibrium. Our findings present a hitherto unreported form of decadal scale self-adjustment in a coastal system that has occurred under a stable sea level with a consistent wave and tidal regime.