This paper describes the development, behaviour, and application of a mesoscale numerical geomorphological model of eroding soft rock and beach shores. The model, SCAPE (Soft-Cliff and Platform Erosion), describes coastal processes and engineering interventions and is a suitable tool for testing management strategies. The mesoscale capability of SCAPE arises because it includes a broad system: its principal modules describe wave transformation, platform erosion, and a (one-line) beach. Feedback within and between the modules regulates their behaviour, brings long-term (dynamic) stability, and allows quantified representation of qualitatively different shore behaviours. SCAPE is demonstrated through the construction of a model of more than 30 km of the North Norfolk coast. A precalibration initialisation phase is required to allow dynamic equilibrium to emerge. Once initialised, calibrated, and validated against an 87-year record, the model is used to explore the development of the North Norfolk coast from 2003 to 2053 under six management scenarios. The model is also used to demonstrate the losses and benefits of erosion under these scenarios and to reveal two qualitatively different modes of behaviour, termed rock strength limited erosion and sediment transport limited erosion. Some generic implications of these different modes are discussed.