DIAA E. HAMED–SÁNDOR KOVÁCS–ENAS MUHAMMED–TIBOR BORZA–KÁROLY FIALA–GERGŐ GÁL–TÍMEA KISS–GYÖRGY SIPOS: Mapping the condition of artificial levees using different methods along the Lower Tisza River, Hungary
szeptember 24.
2021
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Lóczy Dénes
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Artificial levees along alluvial rivers are major components of flood risk mitigation. This is especially true in the case of Hungary, where more than one-third of the country is threatened by floods and protected by an over 4200 km long levee system.
Most of the levees were built in the 19th century, and since then several natural and anthropogenic processes, such as compaction, erosion, etc. could contribute to the slow, but steady deformation of these earth structures. Meanwhile, as construction works were scarcely documented the structure and composition of artificial levees is not well known. The aim of the present analysis was therefore to map structural differences, possible compositional deficiencies, and sections where elevation decrease is significant along a 40 km section of the Lower Tisza River. Investigations were conducted by RTK-GPS, Ground Penetrating Radar (GPR), and Electrical Resistivity tomography (ERT). GPR data have shown that levee structure can significantly vary even in a few km on sections with the same construction history. GPR profiles showed many anomalies including subsidence zones, contraction cracks and animal burrows that could be considered the main causes of flood risk. Penetration depth varied between 3 and 4 m but showed an increasing trend going upstream, referring to an increase of grain size concerning levee material. Based on elevation results, the mean height of the levee crown had 14 cm general decrease. However, at some locations elevation decrease could reach up to 30 cm. Sections affected both by structural anomalies and increased subsidence are considered to be especially sensitive to floods.