Simplified Comprehensive Scour Model compared to Erodibility Index Method

This paper presents a simplified application of the Comprehensive Scour Model (CSM) developed by Bollaert (2002, 2004). The CSM is a physics-based theoretical method used to estimate the scour potential in fractured rock. It allows the user to determine the time evolution of scour formation as well as the ultimate scour depth and the shape of the scour hole in a semi-3D manner. Despite its successful application to many dams worldwide over the last 15 years, one of the drawbacks of the method is its relative complexity of application and the wide range of values that can be used for basic input parameters. Hence, without any experience, sound application of the method may rapidly become challenging. Based on advanced modelling experiences acquired during the last 15 years with the CSM, this paper proposes a less complex and more straightforward application of the model. This Simplified Comprehensive Scour Model (SCSM) allows estimating the ultimate scour depth and its time evolution in a simple but theoretically still defendable manner. SCSM is compared with the popular and easily applicable semi-empirical Erodibility Index Method. Guidelines are provided for sound application of the method in practice.