Sediment related disaster triggered by various factors, e.g., heavy rainfall, earthquake, or volcanic eruption causes serious damage to the society and human. In our research field, we have conducted researches elucidating mechanisms of sediment transport phenomena which lead to the disaster, for the purpose of disaster prevention and mitigation. We have also investigated forest environment changed by natural or artificial impacts, and tried to restore it properly in terms of disaster prevention and mitigation. We aim that outputs from those researches can be practically used in the societies in Japan and overseas to mitigate damages by sediment related disasters.