BEYOND THE “SHOCK AND AWE”- A CRITICAL REVIEW OF THE SBEACH MODEL

The SBEACH (Storm-induced BEAch CHange) model of beach profile response is routinely used for the design and justification of coastal engineering projects, especially beach nourishment. Yet, a critical review of the fundamental assumptions and processes of the model has not been done. A review of the model assumptions and verification tests, along with an analysis of field applications of the SBEACH model is conducted. This review indicates that the use of SBEACH for predictive purposes is not warranted either by laboratory or field tests of the model. Furthermore, SBEACH has limited usefulness even as a simple heuristic model. The empirical relationships upon which the model is based are not clear, nor have they been subjected to extensive peer review. Numerous site and scale-specific empirical coefficients or “fudge factors” are introduced and adjusted throughout the model development in order to more closely match limited wave-tank observations. Such unique fitting parameters do not improve the physical basis for the model formulation and preclude the application of the model to natural settings. A recent attempt to include non-erodible hard-bottoms to the model simply introduces a host of new coefficients that require unique adjustment of the model. Despite the claims of model developers, the introduction of new empirical coefficients with every new or previously ignored set of real world phenomena does nothing to improve the appropriateness of the governing equations of the model. On the contrary, such efforts merely point to the glaring shortcomings inherent in the governing equations while at the same time increasing the degrees of freedom and the uncertainty in the model results. It is time to look beyond the smoke and mirrors of the SBEACH model and recognize the faulty assumptions and inappropriate model development practices that make it an unacceptable tool for beach project design and evaluation. The development and application of the SBEACH model is a clear case of the “bad and the ugly” that occasionally exists within environmental modeling.