Papers

1.	Tadamichi Sato, Yoh Katsuki & `Yasuhiro Shuin, Evaluation of influences of forest cover change on landslides by comparing rainfall‑induced landslides in Japanese artificial forests with different ages, Scientific report, https://doi.org/10.1038/s41598-023-41539-x, 2023.08, In this study, we evaluated the influence of forest cover changes on rainfall-induced shallow landslides by comparing two shallow landslides and debris flows that occurred on plantation forests of different ages in Japan: the Kake disaster in 1988 and the Asakura disaster in 2017. At Kake, the trees ranged in age from 10 to 30 years, whereas at Asakura the trees were over 40 years old. The rainfall characteristics that triggered each landslide were estimated using a three-layer tank model, and the results, as well as the volume of driftwood produced by the landslides, were then compared. Both landslides occurred when the first tank storage layer value, corresponding to the temporal variation in groundwater level in the shallow soil layer, exceeded its previous maximum. The return period of this value at the time of the landslides was 3.0-fold higher in the more mature forests of Asakura than in the young forests of Kake. The upper limit of driftwood volume was 30-fold higher in Asakura than in Kake. Our findings indicated that shallow landslides and debris flows become increasingly rare as forests mature; however, the large volume of driftwood produced by landslides in mature forests may cause substantial damage when extreme rainfall events exceed the landslide resistance of those forests. These insights may be applied to effective landslide risk management..
2.	Tadamichi SATO, Yasuhiro Shuin, Impact of national-scale changes in forest cover on floods and rainfall-induced sediment-related disasters in Japan, Journal of Forest Research, https://doi.org/10.1080/13416979.2022.2131221, 28, 2, 106-110, 2023.04, Changes in forest cover influence floods and sediment-related disasters. In Japan, forest cover has changed substantially at the national scale, and floods and rainfall-induced sediment-related disasters have subsequently decreased. In this study, we determined the quantitative impact of national-scale changes in forest cover on floods and rainfall-induced sediment-related disasters. The growing stock of forests and the flooded area were obtained from the Forestry Agency and the Ministry of Land, Infrastructure, Transport and Tourism, and were used as indices to examine the relationship between forest cover and floods and rainfall-induced sediment-related disasters. The flooded area decreased exponentially until the growing stock of forests reached 3.13 billion m3 (124.5 m3/ha), but was not reduced more as the growing stock further increased. Our findings agree with a previous study that investigated the growing stock of forest needed to prevent landslides. The two indices used in this study were suitable because they have corresponded with forest cover, floods, and rainfall-induced sediment-related disasters since the 1960s. The results of this study can be a guide to determining the volume of logging without increasing floods or sediment-related disasters..
3.	Tadamichi SATO, Yasuhiro SHUIN, Relationship between landslides and long-term rainfall trends, Arabian Journal of Geosciences, https://doi.org/10.1007/s12517-022-10532-5 , 2022.07, Evaluating how the changes in rainfall caused landslides is important to prevent sediment disasters. Using the soil water index (SWI) and a three-layer tank model, this study examined the relationship between the occurrence of landslides and long-term changes in rainfall in Miyagawa Village, Mie Prefecture, Japan, where shallow and deep-seated landslides have occurred at different times. The three-layer tank model detected the effects of long-term changes in rainfall on landslides. We educated that the change in the first storage tank layer indicates the potential risk of shallow landslides, while that in the second and third storage tanks indicates the potential risk of deep-seated landslides. Our method could be used to examine the effects of long-term changes in rainfall on landslides in the same region at different times, or over a wider area. Besides, these results are valid because the three-layer tank model used to calculate the SWI is applied throughout Japan, and its effectiveness has been verified..
4.	Kazuhiro Aruga, Tasisei Sekiguchi, Tadamichi Sato, Yasuhiro Shuin, Evaluation of Forest Road damages using return periods caused by heavy rains in Kanuma and Nikko cities of Tochigi prefecture, Japan, Forestist, 10.5152/forestist.2021.21013, 2021.06.

Presentations

With the basic goal of elucidating the causes of landslides from mountainous areas to coastal areas and establishing methods to predict and prevent disasters, my educational activities focus on the natural disaster mitigation function of forests, improvement through forest conservation, and civil engineering technologies for forest disaster prevention in harmony with the environment. Recently, I have been studying the effects of climate change over several decades on rainfall and the impact of long-term changes in forest vegetation on the occurrence of landslides.