Using ground-penetrating radar to delineate subsurface features along a wetland catena

Continuous descriptions of the spatial variability of subsurface materials are desirable in many hydrogeological studies. However, traditional point-measurement techniques, such as soil coring and pit excavation, are destructive and provide an incomplete characterization of the subsurface. In this study, ground-penetrating radar (GPR) was used to continuously and nondestructively map shallow subsurface features along a small wetland catena in southeastern Newfoundland. Detailed profiles of soil dielectric constant and common midpoint velocity surveys were used to determine radar pulse velocities through subsurface features. Major reflectors Identified in the study included: (i) organic soil-mineral soil contact, (i) placic horizons (saturated mineral soil-unsaturated mineral soil contacts), (iii) water tables (unsaturated mineral soil-saturated mineral soil contact), and (iv) mineral soil-bedrock contact. Thicknesses of major soil features were estimated from radar profiles and compared with thicknesses determined from soil core-anger data. The relationship between estimated and observed thicknesses is strong (r = 0.99). Spatial relationships between placic horizons and wetland community types were also identified.