Time domain reflectometry (TDR) was used to monitor soil water conditions and to evaluate infiltration characteristics associated with rainfall into a volcanic-ash soil (Hydric Hapludand) with a low bulk density. Four 1 m TDR probes were installed vertically along a 6 m line in a bare field. Three 30 cm and one 60 cm probes were installed between the 1 m probes. Soil water content was measured every half or every hour throughout the year. TDR enabled prediction of the soil water content precisely even though the empirical equation developed by Topp et al. (1980) underestimated the water content. Field capacity, defined as the amount of water stored to a depth of 1 m on the day following heavy rainfall, was 640 mm. There was approximately 100 mm difference in the amount of water stored between field capacity and the driest period. Infiltration characteristics of rainfall were investigated for 36 rainfall events exceeding 10 mm with a total amount of rain of 969 mm out of an annual rainfall of 1192 mm. In the case of 25 low intensity rainfall events with less than 10 mm h^-1 on to dry soils, the increase in the amount of water stored to a depth of 1 m was equal to the cumulative rainfall. For rain intensity in excess of 10 mm h^-1, non-uniform infiltration occurred. The increase in the amount of water stored at lower elevation locations was 1.4 to 1.6 times larger than at higher elevation locations even though the difference in ground height among the 1 m probes was 6 cm. In the two instances when rainfall exceeded 100 mm, including the amount of rain in a previous rainfall event, the increase in the amount of water stored to a depth of 1 m was 65 mm lower than the total quantity of rain on the two occasions (220 mm); this indicated that 65 mm of water or 5.5% of the annual rainfall had flowed away either by surface runoff or bypass flow. Hence, approximately 95% of the annual rainfall was absorbed by the soil matrix but it is not possible to simulate soil water movement by Darcy's law over a long period at farm level due to the local differences in rainfall intensity.

Damage caused by weather events has increased dramatically across the world in recent years. In the case of Japan, record-breaking rainfall has caused devastating damage almost every year since 2014; many people have been killed in these disasters. To better prepare for future heavy rainfalls, we need to discover how to prepare for disasters and mitigate damage by learning from examples in resilient communities. In 2017, torrential rains hit Toho Village in northern Kyushu, and the people as a whole responded well to avoid disastrous outcomes. We studied the actions and motivations of residents of Toho during this rainfall event by conducting semi-structured interviews in November 2017. The interviewees indicated that their motivation for evacuating was “personal observation of the danger” or “communication with neighbors”. Communication within the community was found to be an important factor that enabled the safe evacuation of community members, even without notice of the disaster risk and/or in the absence of timely information from the government because of a power outage. Knowledge of local landforms would be also helpful to reinforce appropriate actions and precautions needed during a disaster.