A simple model is used to predict shoreline changes and uses the coast of Rio Grande do Sul (Brazil) as a case study. A continuity model is used to calculate changes in shoreline position attributable to longshore sediment transport (LST). The model is based on calculations of net LST using WAM hindcaste data in the CERC formula from 1997 to 2002. The model was able to reproduce most of the observed oscillations in shoreline during this period. The simulation demonstrated that reversals in shoreline displacements from erosion to accretion or vice-versa could be explained at first order by changes in the wave climate. The results demonstrate that relatively small changes in the wave climate can significantly affect coastal position and that these changes are broadly predictable over short to medium-term periods.