An observation of spatial pore water pattern in a mountain hollow

Abstract

The further development of landslide prediction models requires field understanding about soil pore pressure distribution and water table dynamics in steep hillslopes. However, soil pore water pressure dynamics in steep hillslopes is poorly understood, since most of previous observation has been conducted at relatively gentle hillslopes or in a twodimensional line such as vally. Here we present new data about pore water pressure distribution in a steep zero-order hollow in Tanakami Mountains. Forty tensiometers in twenty nests were installed with recording pressure transducers. Pore pressures were recorded at 10-minute intervals throughout the observation period. Tensiometers showed that there were small difference in the timing and magnitude of pore pressure change at 20cm depth during medium size storm, regardless of slope position. While, the temporal pore pressure changes at the soil-bedrock interface were related to the upslope drainage area and the soil depth. At peak rainfall intensity, pore pressures at soil-bedrock interface were mainly influenced by soil depth, indicating that the dominance of downward flux within soil layer. While, after the rainfall peak, pore pressures was more related to upslope drainage area, suggesting that subsurface lateral flow gave impacts on pore pressure distribution.