Characteristics of meltwater and/or rainfall regime in a snowy region and its effect on sediment-related disasters.

Meltwater and/or rainfall (MR) were monitored using lysimeters in a mountainous region in the north-central part of Japan, where a seasonal snowpack forms, to collect basic data sets for understanding the MR regime and sediment-related disasters. Statistical analyses of the data over 11 years showed that high hourly MR intensities were mainly observed as rain during the non-snow cover period, but the annual maximum daily MR often occurred during the snow cover period. The longer the time unit, the greater the shift in maximum MR values from the non-snow to snow cover periods. For a time unit of 70 h, almost all maximum values were recorded during snow melting periods. The timing, intensity and duration of MR regulate the characteristics of sediment-related disasters such as debris flows, slope failures and landslides. In the case of deep-seated landslides, if there are no accurate observations of MR during the snow cover period, the degree of risk may be underestimated. Furthermore, when designing groundwater discharge works to prevent deep-seated landslides, the timing, intensity and duration of MR must be accurately evaluated to effectively discharge groundwater during the snow melting period. [ABSTRACT FROM AUTHOR]