Faculty of Agriculture, University of Miyazaki, Miyazaki 889-2192, Japan.
Shiiba Research Forest, Kyushu University, Shiiba, Miyazaki 883-0402, Japan.
Sci Total Environ. 2022 Jun 25;827:154392. doi: 10.1016/j.scitotenv.2022.154392. Epub 2022 Mar 8.
Landslides are natural hazards that cause severe damage and human losses. Japan has succeeded in reducing the number of landslide fatalities and is one of the few countries with long-term databases of landslide fatalities. In this study, we identified the factors that contributed to the decrease in fatalities associated with rainfall-triggered landslides in Japan between 1945 and 2019. We examined trends in landslide fatalities and six factors for Periods I, II, III, IV, and V-each period spans 15 years of the study period-and for Periods I-II, II-III, III-IV, and IV-V. We examined the trends in the number of landslides (N) and in the ratio between the number of fatalities (N) and the number of landslides (N/N), and considered fatalities as the product of the number of landslides and the probability of fatalities. The number of fatalities decreased continuously between Periods I and IV; the rate of the decrease declined over time. During Period I-II, N/N decreased, whereas N remained unchanged. Decreases in the average number of household members, changes in building structure, and increases in the number of people evacuated may have contributed to the decrease in N/N. During Periods II-III and III-IV, N also decreased. During Period II-III, the area of mature forests increased slowly. During Period III-IV, the implementation of structural measures (i.e., hard measures) was aggressively pursued. The factors that contributed to the decrease in landslide fatalities changed with time, suggesting that measures for reducing landslide fatalities changed according to the degree of maturity of the nation. Furthermore, we identified increases in rainfall and N in Period V, which might indicate a future increase in landslide fatalities.
滑坡是一种自然灾害，会造成严重的破坏和人员伤亡。日本成功地减少了滑坡造成的死亡人数，是少数拥有长期滑坡死亡数据的国家之一。在这项研究中，我们确定了 1945 年至 2019 年期间导致日本降雨诱发滑坡死亡人数减少的因素。我们检查了滑坡死亡人数的趋势以及六个因素在五个时期中的变化：每个时期跨越研究期的 15 年，以及时期 I-II、II-III、III-IV 和 IV-V。我们检查了滑坡数量 (N) 的趋势，以及死亡人数 (N) 与滑坡数量 (N/N) 的比值的趋势，并将死亡人数视为滑坡数量和死亡概率的乘积。时期 I 和 IV 之间，死亡人数持续减少；随着时间的推移，减少的速度有所下降。在时期 I-II 期间，N/N 减少，而 N 保持不变。家庭人口平均数量的减少、建筑结构的变化以及撤离人数的增加可能导致了 N/N 的减少。在时期 II-III 和 III-IV 期间，N 也减少了。在时期 II-III 期间，成熟森林的面积缓慢增加。在时期 III-IV 期间，积极推行了结构措施（即硬措施）。导致滑坡死亡人数减少的因素随时间而变化，这表明减少滑坡死亡人数的措施根据国家的成熟程度而变化。此外，我们在时期 V 中发现了降雨量和 N 的增加，这可能预示着未来滑坡死亡人数的增加。
