where (x, y) is a complex wave potential function. The solution of this equation is highly complex and beyond the scope of this text. However, the interested reader is directed to Dingemans (1997) for a review of the subject. This type of model is also discussed further in Section 3.9. One of the more recent developments in solving the mild slope equation is that due to Li (1994a). This version of the mild slope equation allows the simultaneous solution of refraction, diffraction and reflection. It has also been the subject of a field validation study. Initial results may be found in Ilic and Chadwick (1995). They tested this model at the site of the Elmer offshore breakwater scheme (shown in Figure 2.14(b)) where refraction and reflection are the main