斜面の模型を用いた防災教材の検討

－樹木の根の模型による土砂流出防止－

抄録

  In Japan, landslides are one of the most frequent disasters, with approximately 1,500 occurrences in 2023. Therefore, education about landslides is important and is covered across various fields, including science and social studies, from elementary to upper secondary school. Japanese fifth graders learn about the effects of water flow on soil erosion while conducting experiments. Experiments are useful for understanding soil erosion without using special equipment. In this study, a model experiment was conducted by burying a model of tree roots in a soil slope to understand how trees affect soil erosion. Soil slopes were made of decomposed granite soil, culture soil, or andosols, and the slopes were assembled according to a fifth grader’s science textbook. Six models of tree roots made of copper wire were buried in the slope, and 400 mL of water was applied from the top of the slope. The tree root models did not significantly affect slope collapse on decomposed granite soil, but it was observed that the outflow of fine soil was inhibited by the root models. Significant effects were observed on culture soil, indicating that the tree root models inhibited slope collapse and soil outflow. On the andosol slope, the tree models inhibited slope collapse but slightly affected soil outflow. The effects of tree root models may depend on the physical properties of the soil. These results suggest that this experiment may be useful for understanding the role of trees on slopes in disaster prevention.