An integrated method for the determination of set-back lines for coastal erosion hazards on sandy shores

Coastal hazards affect the majority of sandy shores worldwide, and are responsible for damage to, and destruction of, property and infrastructure. The research reported here presents an integrated method for defining set-back lines associated with coastal hazards on sandy shores for a 50-year period of interest. The method is based on a worst-case scenario approach, the shoreline evolutionary trend being the basis for the initial set-back line determination. Set-back lines are afterwards adjusted by incorporating changes associated with the acceleration of sea-level rise and the evaluation of the consequences (instantaneous shoreline retreat and overwash) of an extreme storm. The method considers different approaches depending on the shoreline behaviour (erosion, dynamic stability or accretion). The set-back lines as determined are plotted over rectified aerial photographs, allowing for a straight-forward interpretation of results. The method was applied to a test case within a barrier island system (Ancão Peninsula, Ria Formosa, Algarve, Portugal). This study area was chosen because it exhibits the three different types of shoreline evolution. The method easily shows the differences in erosion-related coastal hazards along the study area, being an important tool for coastal management. However, the method should be able to be refined at every 5–10 years, for a new 50-year period, by integrating new formulations based on advances in coastal science, and by including updated information and data about the areas to which the method is applied.