Shallowsubsurface

Shallowsubsurface is a term used in geology and hydrology to describe the near-surface portion of the subsurface, extending from the ground surface downward to depths where soil and regolith transition into deeper rock. It encompasses soils, weathered rock, colluvium, and unconsolidated sediments, and its defined depth range varies by region and purpose, typically from a few meters to tens of meters.

Its properties and processes differ from the deep subsurface. The shallowsubsurface often lies within the vadose zone above the water table, where pore water is only partially saturated. Core processes include infiltration and runoff, evaporation and evapotranspiration, capillary rise, root penetration, weathering, and biogeochemical activity. Moisture, temperature, and texture drive hydraulic conductivity, porosity, and mineralogy, producing strong spatial variability.

Researchers study the shallowsubsurface with boreholes, coring, and shallow monitoring wells, along with trenching and soil profiling. Geophysical methods such as electrical resistivity tomography, ground-penetrating radar, and seismic surveys help map heterogeneity when direct access is limited. In-situ tests (infiltration tests, slug tests, piezometry) and laboratory analyses of collected samples support characterization of hydrologic and geotechnical properties.

Knowledge of the shallowsubsurface informs groundwater recharge assessments, contaminant transport predictions, agricultural planning, and infrastructure design. It is also critical for slope stability analysis, erosion control, and evaluating root-zone depth for vegetation and ecosystem health.

The term is used across disciplines, including civil engineering, environmental remediation, agronomy, and earth science, to emphasize the importance of the near-surface layer in controlling hydrological, geotechnical, and ecological processes.