Natural morphologies, such as sand dunes, river mouth bars and wetlands around a river mouth, are formed by dynamic processes of waves, river currents and wind, and are dynamically stable unless a large-scale anthropogenic effect is induced. Their coastal protection and ecosystem functions for maintaining habitats of many organisms were re-evaluated. The sand dune and wetland in front of an earth dike were maintained as they were, and the overall morphology was regarded as a shore protection facility against storm surges. The setting back of the protection line for maintaining a sand bar and a salt marsh was planned for the first time in Japan with the participation of local citizens and stakeholders, and the construction was completed in 2005. These conservation activities are effective not only for enhancing the safety of the area but also for keeping the sustainability of fishery.