Microgravimetric and GPR surveys for detection of unconsolidated zones in a levee Monika Łój, Sławomir Porzucek, Tomisław Gołębiowski and Mark E. Everett E3S Web Conf., 66 (2018) 01022 Published online: 26 November 2018 DOI: 10.1051/e3sconf/20186601022