Pilkey, O.H. and Cooper, J.A.G., 2007. Lifting up the flap or why quantitative beach behaviour predictive modelling can't work. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 585 – 587. Gold Coast, Australia, ISSN 0749.0208

Quantitative mathematical modelling of beach behaviour with sufficient accuracy for engineering purposes is not possible. Success in “prediction” by hindcasting does not indicate a model works. Probabilistic modelling of beach processes is not possible either because accurate determinations of error bars is impossible. One measure of the problem with quantitative modelling is the nature of model simplifications. In qualitative models where the how, why and what if answers sought are directional, or order of magnitude, simplifications are often quite useful and valid. But a quantitative model can have no simplifications of important processes. All important processes along with their interactions and feedbacks must be represented in the models. Even if all parameters in the models are perfectly understood, one never knows their intensity, frequency, direction or duration. Some widely used models such as the Bruun Rule use virtually none of the critical processes in the model (except sea level rise) that cause shoreline retreat. The CERC equation and its many variants uses only a few of what are likely to be the important parameters effecting sand transport.