Developing a modular and multi-process modeling framework for rocky-coast evolution

Rocky coasts evolve under the combined actions of rock uplift and erosive processes. These processes are mostly related to the sea-land interface but have varied mechanisms, ranging from wave-driven rock fatigue and cliff collapse to efficient salt weathering in the intertidal zone. The relative importance of these processes remains poorly quantified and is rarely addressed directly in modeling efforts. In particular, widely used coastal-erosion models are rarely subjected to systematic, field-informed testing that explicitly separates the contributing processes, limiting confidence in their transferability across sites.

Here we present a modelling framework that evaluates and extends wave-driven cliff–platform models by separating process regimes and representing coastal erosion as a modular combination of mechanisms. We implement the framework in xarray-simlab (Xsimlab) which facilitates modular model construction and systematic comparison of process combinations. We implement and compare formulations for (i) talus production and removal at cliffs, (ii) intertidal weathering that drives vertical downwearing of the intertidal platform, and (iii) subaqueous wave-driven horizontal backwearing with nearshore energy dissipation.

Our results show that different combinations of these processes—and their relative contributions—produce markedly different styles of erosional topographic evolution, leading to divergent long-term trajectories and contrasting marine-terrace preservation. This highlights the need to reconsider which model components are appropriate for different geomorphic settings. By exploring combinations of these modules across representative wave and tectonic, and lithological scenarios on the Noto Peninsula and Sado Island (Japan), we assess how shifts in process dominance generate distinct modern shoreline configurations and, ultimately, different coastal morphologies.