Electrical Resistivity Survey of Peat Layers in the Toushe Basin
Background
Located in Yuchi Township, Nantou County, the Toushe Basin is known for its peat geology and ground subsidence issues. To advance nature-based solutions and enhance flood resilience, this survey aimed to delineate the spatial distribution and thickness of the peat layers, providing scientific data for future mitigation engineering.
The Toushe Basin is a mountain-encircled basin featuring flat central terrain formed by lacustrine or swamp deposits. Stratigraphically, it consists of the Paileng Formation, Shuichangliu Formation, and basin deposits composed of clay, sand, and organic peat. Historical records indicate that peat layers in the central basin can exceed 20 meters in thickness, characterized bysoft soil conditions and high moisture content.
Technical Features
- 2D Electrical Resistivity Tomography (ERT): Selected for its speed and wide coverage, 2D ERT effectively differentiates the electrical resistivity of peat from surrounding sandy layers.
- Survey Deployment: Using an AGI 8-channel resistivity meter (USA), 15 survey lines were deployed. Inverted data revealed that peat layer resistivity is typically below 22.5 Ω‧m, whereas adjacent sand or clay layers exhibit higher values.
- Layer Delineation: Central basin lines (such as L13, L14, and L15) indicated peat thicknesses reaching up to 40 meters, gradually thinning toward the southern edge in alignment with natural depositional patterns.
Application of Results
Combining geophysical line data with topographic elevations, the peat layers were mapped across the flat central region of the basin. Despite uncertainties in areas constrained by man-made structures, ERT successfully validated the distinct electrical signatures of the peat layers.
Geological core drilling is recommended at key line locations to calibrate resistivity profiles against soil strata and refine interpretation precision. These findings offer foundational data for mitigation works while building practical experience for similar geological investigations.