Seasonal transition of hydrological processes in a slow‐moving landslide in a snowy region

• DOI: 10.1002/hyp.13212
• Publication Date: 2018-06-25T13:42:25Z
• Authors: Hikaru Osawa; Yuki Matsushi; Sumio Matsuura; Takashi Okamoto; Tatsuya Shibasaki; Hiroyuki Hirashima
• Keywords: Meltwater; Snowmelt; Snowpack; Infiltration (HVAC)

Abstract A comprehensive understanding of seasonal hydrological dynamics is required to describe the influence pore‐water pressure on stability landslides in snowy regions. This study reports results continuous meteorological and observations over 2 years a landslide body comprising Neogene sedimentary rocks northern Japan, where thick (3–5 m) snowpack covers land surface. Monitoring volumetric water content shallow unsaturated zones (<0.8 m depth) saturated bedrock at depths 2.0 5.2 revealed clear seasonality responses rainfall meltwater supply. During snow‐free periods, both soil moisture deep responded rapidly intense rainwater infiltration. In contrast, during snowmelt, pore fluctuated accordance with daily cycle input, without notable changes conditions. occasional foehn events that cause snow melting midwinter, flows preferentially through layered snowpack, converging produce localized supply ground episodically triggers significant rise pressure. The differences were characterized by set newly proposed indices for magnitude quickness increases head near sliding Under snow‐covered conditions, increase tends be suppressed, probably owing reduction infiltration caused decrease permeability surface soils, effective drainage highly conductive colluvial layer. Deep groundwater flow within remained steady upwelling state, enhanced increasing soils under cover, reflecting convergence subsurface from surrounding hillslopes.