USING GROUND-PENETRATING RADAR TO DELINEATE SUBSURFACE FEATURES ALONGA WETLAND CATENA

Continuous descriptions of the spatial variability of subsurface mater ials are desirable in many hydrogeological studies. However, tradition al point-measurement techniques, such as soil coring and pit excavatio n, are destructive and provide an incomplete characterization of the s ubsurface. In this study, ground-penetrating radar (GPR) was used to c ontinuously and nondestructively map shallow subsurface features along a small wetland catena in southeastern Newfoundland. Detailed profile s of soil dielectric constant and common midpoint velocity surveys wer e 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-unsa turated mineral soil contacts), (iii) water tables (unsaturated minera l 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 w etland community types were also identified.