Analysis of fluvial, lacustrine and anthropogenic landforms by means of ground-penetrating radar (GPR): field experiment

摘要

A field experiment aiming to study the influence of measurement conditions on depths of penetration and resolution of GPR surveys was conducted in the middle Obra valley (western Poland). The tests were carried out along five profile lines in three sites representing fluvial, lacustrine and anthropogenic landforms. The GPR surveys were conducted at various hydrogeological conditions: high and low groundwater levels, and in winter conditions when the ground was under snow/ice cover and frozen. The best measurement conditions for imaging the internal structure of fluvial landforms were found during a period of low groundwater levels. At high groundwater levels the bottom parts of radar profiles were obscured by reverberations originating from the differences in the water content between unsaturated and saturated parts of the studied sections. Some sedimentary structures within lacustrine landforms were better seen at high levels when all the deposits were saturated. In winter conditions, high quality radar profiles were obtained only when measurements were conducted on an elevated, anthropogenic landform, unaffected by dispersion and attenuation of the radar signal in the other landforms due to a water layer situated between the ice cover and land surface. It was also shown that it is possible to image sedimentary structures of landforms built of deposits with significant admixtures of silts, although the depths of penetration are reduced in such cases.