Beach Planshape Modelling summarises the theory, solution methods, and applications of what has become known as the 1‑line beach model, whereby changes in the planform shape of a beach can be described by the movement of a single height contour. This effectively describes shoreline response to interventions such as the construction of groynes and beach nourishment. This book covers the underlying theory; analytical solutions to the equations for restricted cases; semi‑analytical methods for less restricted cases; computational methods for more general situations; applications to specific sites, with a focus on the ‘tricks of the trade’ that allow complicated cases to be modelled; extensions of the 1‑line method to find parameters from observations; and a discussion of uncertainties in the results of predictions. It provides real‑life applications and guidance for creating a realistic and effective model for use in line with the commercial GENESIS/GENCADE beach modelling package.