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EN
A series of catastrophic floods that have occurred over the last twenty years in Poland brought an urgent need for taking preventive steps to monitor river embankment conditions. The main problem seems to be the development of efficient (i.e. fast and economical) measurements for controlling the condition of river embankments, because the execution of the full range of geotechnical measurements is both lengthy and costly. In this situation, a cheap and quick geophysical survey has been proposed to undertake this purpose. In this article the results of geophysical surveys are described which were performed using geoelectric and electromagnetic methods along a section of the Vistula embankment, located near the Maniów area in the Małopolska province. According to the archival data, this region is situated in a high-risk flooding zone. Three geophysical methods were used to recognize conditions of the levee: (i) Electrical Resistivity Tomography (ERT), (ii) Induced Polarization (IP) and (iii) Electromagnetic Conductivity (EMC). Geoelectrical measurement results were presented in the form of resistivity and polarization cross-sections. Results of conductivity measurement were presented in the form of plots. These parameters effectively supplement geotechnical testing, providing spatial information about the changes within the embankment and its substrate. It allows the prediction of potentially vulnerable areas to water percolation during flooding.
EN
The need to continuously monitor the flood embankment is necessary to introduce the measurement methods which give quick results in crisis situations. The protection of embankments as well as the prevention from floods are not only associated with the examination of the body river levee. Experience suggests that one of the problems involves the unknown geotechnical conditions of the levee base. Unfortunately, point geotechnical surveys carried out with a big measurement step were not able to fully identify the lithology variation over larger areas. This is caused by the high cost of drilling shallow wells. The application of non-invasive geophysical methods allows the completion of geotechnical research, and supplies additional information about the variability of geological medium. The structure in the area of the former river beds creates favorable conditions for carrying out geophysical surveys dependent on the variability of geoelectrical properties of rocks. This problem is solved by the use of conductivity method on the 100 m long part of the flood bank. This is recommended for quick and non-invasive measurements. A complex interpretation of geotechnical, hydrogeological and geophysical data provided information about the variability of geoelectrical parameters over this area and therefore made it possible to identify areas prone for greater filtration during high water levels.
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