Combination of Airborne Geophysical Surveys at the Estuaries of the Weser and Elbe Rivers in Northern Germany

The German Federal Institute for Geosciences and Natural Resources (BGR) carried out six airborne geophysical surveys in Northern Germany close to the estuaries of the Weser and Elbe rivers. Two of them were conducted in coopera-tion with the Leibniz Institute for Applied Geophysics (LIAG). The common aim was the acquisition of a reference data set for monitoring climate or man-made induced changes of the salt-water/fresh-water interface at the German North Sea coast and to build up a data base containing all airborne geophysical data sets. Airborne frequency-domain electromagnetic, magnetic, and radiometric data were collected simultaneously using BGR’s helicopter-borne geophysical system. The airborne geophysical results show geological and hydrogeological structures down to about 100 m depth. The elec-tromagnetic data, converted to resistivity, reveal several hydrogeological important features such as the distribution of sandy or clayey sediments, the extension of salt-water intrusion, and buried valleys. The electromagnetic results are supported by magnetic and radiometric data indicating lateral changes of weakly magnetized sediments or mineral compositions of the top soil. The combination of airborne geophysical data sets provides a data base of a huge area serving as base-line data for a variety of applications and particularly for groundwater modelling and monitoring.