Modèle d'évolution de paysages, application aux karsts en cockpit de Jamaïque

Abstract

Landscape evolution model, example of cockpit karst terrains, Jamaica A model of cockpit karst landscape evolution is presented. After explaining implementation of dissolution processes of limestone in the landscape evolution model CHILD, we develop a model of limestone denudation based on epi karst theory processes. The model takes into account an anisotropic dissolution in space and time according to what is observed in reality or described by scenarios of cockpit karst landscape evolution. This model requires a fracture's network to take into account subsurface flow. Then, dissolution and thus fractures widening are computed and show a positive feedback between dissolution and flow. The relation between subcutaneous dissolution of fractures and denudation of the topography is introduced by means of an empirical equation associated with epikarst processes : the denudation is taken to be proportional to the dissolution in the subcutaneous zone. Simulated cockpit karst terrains are compared with real landscapes by means of morphometric criteria. Results of the model are very dose to reality which hence confirms the importance of anisotropic dissolution processes and above all could be a numerical validation of the epikarst processes to describe cockpit karst genesis.