Monitoring of groundwater flow penetrated by heavy rainfalls at landslide slope areas using a resistivity survey

Abstract

Recently, landslide due to natural disasters such as large-scale typhoons, or local torrential rain as a consequence of climate change, has become a serious problem for effective and detailed management of infrastructure safety. Particularly, slopes at risk of large-scale landslide in the future should be evaluated across the entire slopes for the behavior of groundwater infiltration from heavy rainfall. It is very important to establish monitoring techniques to visualize rainwater infiltration across entire slopes for the long term management of landslide risks. The authors developed a new electrical exploration system for remote-controlled measurement. We conducted a continuous electrical survey over a period of two years at two slope sites in order to monitor rainwater infiltration of landslide slopes. Based on resistivity changes during rainfall events of 50-100 mm, the findings indicate that rainwater rapidly infiltrated shallower sediments to depths of a few meters during rainfalls, and evaporated slowly after rainfall ceased. We also estimate that rainwater penetrated slowly into deeper layers. The sampling period was limited to 50-60 days, due to frequent methodological challenges such as the severing of cables by wild animals and rock falls, and instrument failure caused by the thunderbolts at two sites. Furthermore, we were unable to continue the measurement during heavy rainfall events of more than a few hundred millimeters. The biggest factor is that the instruments were not protected from thunderbolts during storms. It is recommended that future studies should incorporate protective circuits for thunderbolts to double or triple insulation.

A Review of Groundwater Observation Methods for Slow-Moving Landslide

“…[2006] conducted multiple resistivity electrical surveys to assess seasonal variation in groundwater flow. In recent years, a system for the continuous observation of resistivity values has been developed to understand long-term groundwater behavior [Suzuki et al ., 2016].…”