Northern Kyusyu was hit by the record heavy rain between July 5th and 6th, 2017. The fishing industry has been negatively impacted by a large amount of driftwood flowing into the Sea of Ariake and Suonada. It was reported that fishing vessels are damaged by contact with the driftwood. Therefore, it is imperative to characterize the danger that driftwood presents to fishermen to ensure their occupational safety. In this study, we aim to calculate the impact force when a fishing boat collides with driftwood using the equation of motion and considering the contact stiffness. Moreover, we created the poster to convey the obtained information and promote safety and displayed it in the Usuki branch office of the Oita prefecture fisheries cooperative.