Repeated geophysical measurement: the basic principle of the GMS methodology used to inspect the condition of flood control dikes

Abstract

Geophysical Monitoring System GMS is a modern and complex methodology of investigation serving as a complement to the classical techniques of inspecting the condition of flood control dikes. It is based on a combination of fast and cheap techniques for the basic description of long dike segments with more sophisticated methods serving for detailed description of problematic dike segments. Especially a combination of suitable geoelectrical methods – dipole electromagnetic profiling (DEMP) and resistivity tomography (RT) is applied and, where appropriate, complemented by another independent method (mostly some of the seismic methods or microgravimetry). One of the innovations of the GMS methodology is the execution of repeated geophysical measurements at various levels of dike saturation with water. The interpretation of such measurements may detect the existence of anomalous seepage zones in the dikes. When performing the analysis of repeated measurements, it is important to eliminate the effect of “natural” (seasonal, climatic) changes in the measured parameters. In the case of the DEMP method which serves for the basic description of long dike segments it is calculation of the so-called residual resistivity anomaly and mutual correlation of these anomalies in a series of repeated (monitoring) measurements.