This study suggests the analysis of scoastal flood prone zone (PPR-SM) at Guissény (Finistère, France), where an increase of the stakes is taking place in a strong hazard area. The PPR flood prone zone in this commune shows some insufficiencies and can be improved by using a more accurate Digital Elevation Model and by considering the wave setup in 100-year water level calculation. The Analysis of the shoreline kinematic and the water level elevation expected for 2100 are taken into account too. The comparison between the building expansion, the flood prone zone and the land use plan shows that the PPR flood prone zone does not stop the increase of the stakes in the hazard area in this commune.