Groundwater flow after heavy rain in landslide‐slope area from 2-D inversion of resistivity monitoring data

Abstract

In the interest of monitoring the flow of groundwater from heavy rains, we conducted surface resistivity tomography through the vadose zone over several days. The measured data were modeled by 2-D inversion. A laboratory experiment was carried out to estimate the difference in geological characteristics. We measured the effects of groundwater fluctuation using two tank models: one using sand and one using bricks, which represent unconsolidated sediments and jointed rocks, respectively. In the sand model, we succeeded in monitoring water‐level fluctuation as the change in resistivity over time. In the brick model, the water level did not appear as a distinct boundary. Field experiments were carried out in an area in which the near‐surface conditions consisted of heavily weathered rocks with an extensive shear zone several tens of meters thick. Measurements were performed over 42 days, during which we observed changes in resistivity associated with heavy rainfall. It became clear that resistivity decreases of up to 8% were present in highly porous zones in heavily weathered layers. This result suggests a connection between a decrease in resistivity and the infiltration of rainwater. In particular, a pronounced zone of minimum resistivity may indicate infiltration of rainwater into the vadose zone. The relationship between resistivity changes and rainfall was inferred to depend on the permeability of geological structure.

Review: Some low-frequency electrical methods for subsurface characterization and monitoring in hydrogeology

“…This includes the monitoring of water flow in the vadose zone and, therefore, the determination of the hydrodynamic properties of the vadose zone (e.g., Daily et al 1992;Suzuki and Higashi 2001;Binley et al 2002;Koestel et al 2009). Legaz et al (2009) showed that the displacement of water by steam in a hydrothermal system can be imaged with time-lapse ERT.…”

Imaging Rainfall Infiltration Processes with the Time-Lapse Electrical Resistivity Imaging Method

“…It can also be used for monitoring the groundwater flow and river water discharge patterns (COSCIA et al 2011(COSCIA et al , 2012HAYLEY et al 2009;SUZUKI and HIGASHI 2001). In the recent years, the time-lapse ERI method has been applied to monitor the preferential flow paths within the rock/soil mass (DRAHOR et al 2011;HERMANS et al 2012b;MAITI et al 2012;MUCHINGAMI et al 2012) and the geological system of CO 2 storage for the real-time purpose (BERGMANN et al 2012;CHRISTENSEN et al 2006;PICOTTI et al 2013).…”

A data-driven approach for landslide susceptibility mapping: a case study of Shennongjia Forestry District, China

“…The types of aquifer determine the migration of groundwater, which is one of the important indicators of lithological character (Stegmann et al 2011;Suzuki & Higashi 2012). The layer of aquifers was directly digitized from the published hydrological map of the Hubei province with a 1:100,000 scale.…”