In Japan, where mountainous districts occupy 70% of the land, a lot of shallow landslides caused by heavy rain have occurred each year. It is important to identify soil hydraulic parameters in order to simulate rainwater infiltration processes. Recently, much attention has been paid to the inverse analysis based on in-situ measurements, to identify the soil hydraulic parameters. In this study, the particle filter, which is one of the data assimilation methods, was applied as the method of inverse analysis. Firstly, the soil hydraulic parameters, which are used in the water retention curve proposed by van Genuchten, were identified through the inverse analysis of the particle filter. Then, the numerical simulation, in which the identified parameters are used, was performed to verify the reproducibility to soil moisture behavior. As a result, the analytical results, which simulated with time for the condition of heavy rainfall, were in excellent agreement with in-situ measurements. Therefore, the particle filter was available to identify the soil hydraulic parameters based on in-situ measurements.
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