Ryouta Nagai

Characteristics of Water Accidents Caused by Rip Currents Based on Analysis of Accident Information in the Waters Surrounding Niigata City

Naoyuki Inukai

This study statistically examines water accidents in the coastal area surrounding Niigata City, focusing particularly on the characteristics and causes of incidents related to rip currents. Across Japan, approximately 450 water-related accidents occur each summer, with more than half taking place at sea, and this trend is also observed in Niigata Prefecture.
Analysis of data from 2018 to 2024 shows that accidents around Niigata City are concentrated in July and August, corresponding to a seasonal rise in beach attendance. The increase in accidents closely parallels the growth in the number of beach users. Adults account for the largest share of incidents, mainly during marine leisure activities. However, accident patterns vary by age group: suicides and fishing-related falls are more common among the elderly, while minors are primarily involved in summer swimming accidents.
Long-term data from 2001 to 2024 reveal similar trends. Of 181 marine leisure accidents, 134 occurred during swimming, and about 44% were attributed to rip currents. Approximately 70% of swimming accidents were strongly associated with natural factors such as wind waves and sudden depth changes. Importantly, rip current accidents were not limited to high-wave conditions. Many occurred when wave heights were between 0 and 0.6 meters, a range generally regarded as safe for swimming. Previous research indicates that rip current velocities can reach 0.2–0.4 m/s even under moderate wave heights (0.3–0.6 m), making them difficult to resist, especially when swimmers lose stable footing in chest-deep water.
These findings suggest that accident risk depends less on wave height alone and more on the interaction between sea conditions and swimmers’ physical capabilities. Effective prevention requires comprehensive risk assessment and clearer public information about rip current hazards and local coastal conditions.