A Countermeasure against Slope Disaster during Heavy Rain in Citrus Groves on Steep Slope

As a slope disaster countermeasure for citrus groves on steep slopes during heavy rain, the permeability of surface soils may be improved to reduce rainfall infiltration from the ground surface. Accordingly, seepage experiments were conducted in this study using a soil tank that considered various soil materials. The layer of soil 10 cm from the surface in the soil tank was set as the improvement layer, and the tested materials included clay soil, dried Citrus unshiu peels, and peat moss. The time-varying volumetric water content of the soil was measured under 80 mm/h of artificial rainfall in the soil tanks with added material. As a result, when clay was present, the saturated hydraulic conductivity decreased as the clay mixing ratio increased, and when the mixing ratio reached 50%, infiltration to depths below the improvement layer was almost completely inhibited. The absorption of rainfall by Citrus unshiu peels prevented infiltration to depths below the improvement layer. Meanwhile, peat moss suppressed rainfall infiltration owing to its water-repellent effects.