Mapping and evaluating the condition of artificial levees

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 2940-km-long levee system. Most of the levees were built in the 19th century. Since then, several natural and anthropogenic processes, such as compaction, erosion, Etc., could contribute to these earth structures' slow but steady deformation. Meanwhile, as construction works were scarcely documented, the structure and composition of artificial levees are not well known. Therefore, the present analysis aimed to use different geophysical techniques to validate their efficiency in mapping structural differences, possible compositional deficiencies, potential defects and sections where elevation decrease and compare the compositional and structural variations of two very different levee sections along a 24 km section of the River Tisza and a 24 km section of the River Maros. Investigations were conducted by real-time kinematic GPS (RTK-GPS), Ground penetrating radar (GPR), Electrical Resistivity Tomography (ERT) and drillings. Onsite data acquisition was complemented with an analysis using a Persistent Scatterer Synthetic Aperture Radar (PSI) to assess general surface deformation. The higher frequency 200 MHz GPR data have shown that levee structures can significantly vary even in a few km on sections with the same construction history. Based on electrical resistivity tomography results with a precise analysis of grain size and their related physical parameters used for monitoring the materials of two different levee sections along the Tisza and Maros rivers, we noticed that the main components of investigated Tisza levee section are medium and fine silts, however, the situation of the investigated Maros levee section shows more variation of different materials which are fine, medium, and coarse silt, moreover, fine, medium, and coarse sand. The investigated section of the Tisza levee showed low resistivity values, indicating the fine-grained materials' conductivity. In contrast, the investigated section of the Maros levee showed high resistivity values, indicating the resistivity nature of higher grain size sediments forming this section, especially noticed on the protected side of the levee. It was possible to capture structural changes and resolving the thin layers by 1 m electrode spacing ERT profile. In turn, at a larger spacing it was possible to get information on the sedimentary base below the levee body. The selected levee section could be assessed in terms of its structure and composition and major units within the levee body and their composition could be resolved by the applied methods. In general, there is a similarity in the materials and their resistivity range which form the core of Tisza and Maros levees, however, the situation on their both sides is not the same. Regarding the analysis of different physical properties of the two levee systems like resistivity, porosity, density, water content, grain size, and saturated hydraulic conductivity, the materials of the Maros levee could be distinguished well and showed more variation when it is compared to the materials of Tisza levee. It means that the physical properties of levee materials are very important, and they are recommended when carrying out further levee investigations. From the physical properties mentioned above, it was found that some of them show a connection with resistivity except hydraulic conductivity parameter that did not show a direct connection, however the latter could exhibit the aquitard nature of Tisza levee materials and the non-aquitard nature of Maros levee materials which illustrates the difference in levee composition in terms of flood risk or flood safety. Based on height measurements, the mean elevation of the levee crown decreased by 8 cm in a 40-year time span. However, elevation decrease could reach up to 30 cm at some locations. Sections affected by structural anomalies, compositional changes, and increased surface subsidence are especially sensitive to floods when measurement results are compared to flood phenomena archives. GPR profiles showed several anomalies, including structural and compositional discontinuities and local features. They were classified into six types regarding to the flood risk; tensile cracks (enables piping, leading to levee breach or mass failure, cracks might close when the levee gets wet), remarkable changes in dielectric permittivity (enables seepage, leading to mass failure), animal burrows (enables piping, leading to levee breach or mass failure), layer deformation (results in height decrease, overtopping), paleo river channel (enables seepage below the levee, leading to water upwelling and the development of sand boils), sudden change in stratification or dipping layers (enables contour line seepage, leading to mass failure). The penetration dept

Comparative evaluation of the material of the artificial levees : A case study along the Tisza and Maros Rivers, Hungary

Artificial levees have major importance in protecting human livesand infrastructure as they are essential elements of the flood protectionmeasures. Nevertheless, the lack of the necessary information about theirstructure and internal composition might cause high risks. To monitor theirstability, integrated surveys are needed, including geophysical andgeotechnical methods. Levees along the rivers in Hungary were constructedmore than 150 years ago, and they were heightened several times; therefore,investigations are required to assure their performance in flood riskmitigation. Our investigation aimed to utilise non-invasive geophysicaltechniques, primarily electrical resistivity imaging, with the validationof geotechnical investigations to map and compare the compositional andstructural variations of two very different levee sections along RiverTisza and River Maros. Integrating the analysed drilling data with ERTprofiles showed that the main composition of the investigated Tisza leveesection is fine and medium silt with an average resistivity 30 Ωm, however,the investigated section of Maros levee was built of not only of fine andmedium silt but also of medium and coarse sand exhibiting higherresistivity values reaching up to 2200 Ωm. Several physical parameters weremeasured to study the nature of constituting levee materials like moisturecontent, grain-size, porosity, bulk-density, saturated hydraulicconductivity, and resistivity. It was found that most of them show aconnection with resistivity, but the hydraulic conductivity did not show adirect connection, however the latter could exhibit the aquitard nature ofTisza levee materials and the non-aquitard nature of Maros levee materials

A dombói vár tégláinak kormeghatározása termolumineszcens módszerrel

A dombói vár Dombóvár városától délre, egy a Kapos folyó árteréből kiemelkedő dombon helyezkedik el. Az egykori várból ma mindössze három vegyes tégla-kő alapanyagú faltömb és egy téglaépítésű pillér maradványa látható. A lelőhely szisztematikus régészeti kutatása 2014-ben kezdődött, és azóta is folyamatosan tart. Az eddigi ásatások eredményei alapján a vár építésétől az 1702. évi fennállásáig öt nagyobb építési periódust lehet elkülöníteni. A hagyományos régészeti módszerekkel történő keltezés azonban több szempontból is megerősítésre szorul, ugyanis a datáló értékkel bíró leletek, a lelőhely nagyfokú pusztulása és a közelmúltig tartó bolygatások miatt, nem eredeti helyükről kerültek elő, hanem másodlagos vagy harmadlagos feltöltésekből. A vár keltezésének problematikájából kifolyólag, illetve figyelembe véve, hogy az erősség legnagyobb része téglából épült, a termoluminsezcens (TL) kormeghatározás tűnt a leginkább alkalmazható abszolút kormeghatározási módszernek. Kutatásunk célja az egyes építési fázisok kronológiájának meghatározása TL kormeghatározás segítségével, illetve a meglévő, régészeti alapon felállított periodizáció pontosítása, esetleges felülvizsgálata. A TL kormeghatározás segítségével kerámiák, cseréptárgyak, terrakotta műalkotások, valamint téglák és egyéb iparrégészeti vonatkozású objektumok kiégetési ideje állapítható meg. Vizsgálatainkhoz 13 téglamintát gyűjtöttünk a vár különböző pontjairól. A TL mérések során az additív módszert alkalmaztuk, a mérésekhez a legoptimálisabb beállításokat pedig plató tesztekkel állapítottuk meg. Az eredmények pontosítása érdekében fakulási teszteket és az α-hatásfokra vonatkozó vizsgálatokat is végeztünk. Az építési periódusokra vonatkozó eredményeinket igyekeztünk több minta átlaga alapján megadni. A TL mérés által kapott koradatok többsége megfelelően igazodott a régészeti módszerekkel meghatározott korokhoz, két építési fázis esetében viszont további elemzések elvégzésére van szükség, mivel csak egy-egy minta alapján történt az értékelés. Vizsgálataink mindemellett rámutattak arra is, hogy elengedhetetlenül fontos az α-hatásfok közvetlen mérése, valamint hogy lehetőség szerint egy jelenségből több minta gyűjtésével a mérési eredmények pontosíthatók