Modeling the role of weathering in shore platform development

Abstract

A mathematical, wave-erosional model was modified to study the additional effect of weathering by wetting and drying and salt weathering on the development of shore platforms in macro- to mesotidal environments. Model rates of downwearing by these processes, at different tidal elevations, were based on data obtained from a series of laboratory experiments on sandstones from eastern Canada. Backwearing by mechanical wave erosion was calculated using basic wave equations. There were several types of run which were designed to determine the effect of: weathering and the production of fine-grained sediment; the periodic accumulation of debris on weathering in the upper intertidal zone; and weathering in reducing rock resistance and facilitating wave quarrying. The results implied that, compared to mechanical wave erosion, the direct effect of weathering and fine-grained sediment production makes only a small contribution to the long-term development of shore platforms. The relationship between cliff-foot debris occurrence and platform development and morphology was inconsistent because of the negative feedback relationship between erosion rates, surface gradients, and rates of wave attenuation. The model suggested that weathering can play an important, indirect role in assisting wave quarrying of joint blocks and other rock fragments.