The Terror Lurking in the Silver Snowfields

Working to prevent and mitigate snow and ice disasters occurring near us.

Faculty's Column (Early-Career) September 24, 2025

NIIYA Hirofumi Associate Professor, Research Institute for Natural Hazards and Disaster Recovery

Japan is a small island nation, yet it experiences an unusually high number of natural disasters compared to most countries worldwide. While the types of disasters prone to occur in each country vary due to geographical conditions, Japan's Act on Support for Reconstructing Livelihoods of Disaster Victims defines natural disasters as follows: “damage caused by a storm, heavy rain, heavy snow, flood, storm surge, earthquake, tsunami, volcanic eruption, and any other abnormal natural phenomenon.” This definition, including “heavy snow,” means that disasters caused by snow and ice are firmly recognized under the law. In the research world, such phenomena are collectively referred to as “Seppyo” in the Japanese research community.

When you hear the word “heavy snow,” what scene comes to mind? You might picture a world of silver white, or villages buried deep under heavy snowfall. However, according to data from the Ministry of Land, Infrastructure, Transport and Tourism, approximately half of Japan's land area—from the San'in region through Kinki, Hokuriku, Tohoku, and Hokkaido—is designated as a “heavy snowfall area.” Furthermore, in recent years, heavy snowfall events, thought to be influenced by climate change, have become more localized and extreme. Consequently, snow and ice disasters occur almost every year, not just in heavy snowfall areas, but across the entire country.

Snow and ice disasters in Japan are categorized into six types: heavy snowfall, roof snow, snow accretion, snow avalanches, blowing snow, and road snow and ice. My research primarily focuses on blowing snow and snow avalanches. Blowing snow causes poor visibility where one cannot see ahead, creates snowdrifts along roadsides, and causes snow to accumulate on power lines and traffic signals, leading to power outages and traffic accidents. Snow avalanches, on the other hand, cause accidents involving climbers and skiers, damage roads and bridges, and lead to fallen trees in forests. The risk level of these disasters is determined by a combination of factors: the scale and intensity of the natural phenomenon, the density of people and buildings, and the level of disaster preparedness awareness and structural strength of buildings. Within this, I focus my efforts on “accurately reproducing and predicting natural phenomena.”

In recent years, the term “hazard map” has become a term everyone has heard. To summarize my research goal in one sentence: “To create as accurate a hazard map as possible for blowing snow and snow avalanches.” In other words, I aim to map out when, where, and on what scale blowing snow and snow avalanches occur. To achieve this, I travel all over Japan during winter—observing blowing snow on Hokkaido's Pacific and Sea of Japan coasts, conducting artificial avalanche experiments in Niseko, and investigating avalanches in Niigata Prefecture.

Taking blowing-snow research as an example, the key factors are “wind strength” and “the amount of transported snow.” Since these vary significantly with height above the snow surface, we use instruments such as ultrasonic anemometers to measure wind in detail and devices to count snow particles. However, field observations alone have limitations. For instance, while blowing snow can be predicted to some extent by wind speed and temperature, it also depends on snow-surface conditions. Freshly fallen snow is powdery and easily carried by the wind, whereas over time, snow particles stick together and harden, making blowing snow less likely.

In addition to observations, I also conduct experiments using the “Low-Temperature Wind Tunnel” at the National Research Institute for Earth Science and Disaster Resilience in Shinjo City, Yamagata Prefecture. This facility allows year-round use of artificial snow and enables us to freely adjust wind strength and snow surface conditions, making it possible to investigate detailed processes that are difficult to observe. We then formulate the insights gained from these experiments into mathematical equations and incorporate them into our blowing-snow model, thereby improving the accuracy of numerical simulations. We then verify that the results match actual blowing snow using observational data, thereby creating more accurate hazard maps. However, advancing the model also presents a challenge: sometimes there is no observational data available for comparison. Therefore, we have also begun working on introducing new observational technologies. By advancing our research through this back-and-forth among observation, experimentation, and theory, we aim to minimize the damage caused by snow and ice disasters and contribute to people's safety.

Observations of snowdrifts formed by snow fences in eastern Hokkaido: We are testing new observation instruments and establishing a unique observation system that transcends existing frameworks in snow and ice science.

Avalanche investigation in Niigata Prefecture: By March, avalanche traces mixed with sediment are visible everywhere, with deposits consisting of hard snow blocks exceeding several tens of centimeters in thickness.

Profile

NIIYA Hirofumi

Associate Professor, Research Institute for Natural Hazards and Disaster Recovery

Ph.D. (Science). Specializes in geophysics and snow and ice studies. Conducts research on natural disasters associated with the movement of granular materials (such as snow and sand), including blizzards and sandstorms. After completing his doctoral program at Hiroshima University, he served as a Japan Society for the Promotion of Science (JSPS) Postdoctoral Fellow (PD) and a Specially Appointed Assistant Professor at Nagoya University. In 2018, he became a Specially Appointed Assistant Professor at the Interdisciplinary Research Institute of the Research Promotion Organization at Niigata University. Then, in 2020, he was promoted to Assistant Professor, and since 2022, he has been an Associate Professor at the Niigata University Research Institute for Natural Hazards and Disaster Recovery.

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*Article content and profile information are current as of September 2025.