Dealing with natural dunes in coastal hazard management

Coastal dunes can provide a protective role against coastal hazards. Moderating the coastal erosion hazard, they can also affect the coastal flooding hazard, ensuring one level of protection when their massiveness enables them to contain the hydraulic stresses, or sometimes increasing the hazard by greater speeds when breaching. From the literature, this article presents the characteristics of these natural structures with regard to management principles applied to hard coastal structures and provides technical criteria to take into account their specific aspects in coastal risk management tools: "coastal risk prevention plans" and safety assessment of hard hydraulic structures. In particular, coastal dune types were defined to identify structures that may play a role in the characterization of the coastal flooding hazard. A database of historical breaches made by Cerema (ex-Cetmef) assesses the adaptation of hard structure criteria to coastal dunes. A framework for coastal dunes management is finally proposed to reconcile as far as possible protecting people and preserving biodiversity.