Recognising hazardous glacial lakes in high-mountain environments
To investigate the subsurface characteristics and processes of glacial moraine dams, electrical resistivity tomography (ERT) was integrated with electrical self-potential (SP) to investigate the structure of, and hydrological processes within, a moraine-dam complex at the Miage glacier, Italy. Differential GPS (dGPS) was used to provide a 3-D location for each of the survey points and to create a digital elevation model (DEM) to aid the interpretation of the SP signal measured at the ground surface. ERT data revealed a continuous free surface within the complex; the morphology reflects the topography of the moraine complex akin to unconfined groundwater aquifers. SP data were corrected for spatial changes in the thickness of the upper unsaturated layer using principles of electrography. The residual streamingpotential map is consistent with Darcian flow of lake waters through the moraine complex.These electrical signatures are consistent with those generated by water seepage through earth dams in various non-glacial settings.
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