Numerical models become attractive means of study, when considering the limited knowledge and guidance on functional design of coastal groins. In the present article, a process-based 3D numerical model (Delft3D) is verified against two different datasets. For application on design of straight open (normal) groins, Badiei et. al. 1994 laboratory measurements, and in case of T-Head groins Ozolcer et. al. 2004 field measurements are considered. In case of normal groins, the model showed good agreement with the observations, hence, a design exercise and method has been developed. In case of T-Head groins, the model showed sensitivity to the numerical representation of the structure, while still satisfactory resemblance was perceived. Comparing to the present design rules, application of a numerical study is of crucial importance.