Measures for enhanced inundation driftwood trapping by inland flood-restraining forest belts were examined in a hydraulic model experiment. The forest model (scale: 1/100) consisted of rods with a diameter of 3.05 mm set in a 3-cm square lattice form. The model driftwood pieces (length: 1 cm) all passed through the initial model forest. Subsequently, parts representing ropes, nets, boards and piles were installed between the trees in the rearmost row at a height of 2.4 cm to represent the situation of actual flood-fighting measures implemented by residents near rivers. The ropes were 0.33 mm in diameter and were set 3 mm apart, the nets were 0.35 mm in diameter and were set 3 mm apart, the boards were 9 mm in width and were set 3 mm apart, and the piles had a rectangular cross section of 1 × 1.2 mm and were set 4 mm apart. Each of the capture ratios was improved to approximately 56, 50, 7 and 49%. These results show the effectiveness of using simple and practical installations in inland flood-restraining forest belts for enhanced trapping.

　堤内水防林の洪水氾濫土砂の捕捉効果について，水理模型実験により検証した．模型は1/100スケールとし，直線開水路内に氾濫域を設け，破堤口地点から直径3.05mm，樹木間隔3cm四方の水防林を幅0.1-0.4mで設置した．土砂は5-8号の混合珪砂（乾燥密度約1.43g/cm³）を自然乾燥状態で用い，4.9×10^-3m³の堤防を越流破堤させ土砂を流入した．水防林区間通過後の流入土砂質量比は，水防林なしの場合で約77%，水防林幅0.1mと0.2mで約62%，幅0.3mで約64%，幅0.4mで約61%であったが，水防林内での土砂捕捉効果よりも，破堤規模緩和による堤内への土砂流入抑制効果が卓越した．また，水防林区間の通過中，中央粒径d50については小さくなる傾向が確認され，d₈₄/d₁₆については一定の傾向が見られなかった．