A composite fall-slippage model for cliff recession in the sedimentary coastal cliffs

A composite fall-slippage model is proposed in this study for the Tertiary sedimentary coastal cliffs of Varkala in the western coastal tract of Peninsular India which are retreating landwards due to the combination of several factors. The fall model in the present study accounts both spring seepage and wave action, resulting in undercutting and this fall affects only the topmost laterite and the just below sandstone in the cliff. Slippage in this area affects all the litho-units and hence the geologic characteristics of all the litho-units are considered for developing the slippage model. This mathematically derived model can be used in other cliffs exhibiting the same morphology as well as the one controlled by the same influencing factors. This model differs from other models in incorporating multi-lithounits as well as multi-notches. Varkala cliffs form a part of the aspiring geopark in the Global Geopark Network and hence a study on the cliff recession is a pressing requirement.