Search
Search Results
-
Morphological grouping of fossil floodplain forms in the northeastern part of the Pannonian plain
21-33Views:62The Bereg Plain is located in the northeastern part of the Pannonian Plain, close to the Carpathian Mountains. Clarification of the evolution of its topography is essential for the development of the whole area. The former single alluvial cone has been fragmented, some parts of it subsiding and others rising. The displacements of the subsided parts of the area were dominated by erosion processes, as in the Bereg Plain. As a consequence, a significant part of the sand in the area has been degraded and only traces of it remain in the Bereg Plain. The existing sand patches have been identified and classified using DEM. In the area identified 10 floodplain islands not yet mentioned in the scientific literature. The investigation of the numerous islands – hitherto unknown and be-longing to different morphological types – enabled us a reconstruction of the surface development of the Bereg Plain that is more differentiated and precise than ever before. Based on their morphogenetic properties, these floodplain islands can be divided into three main types: (1) erosion islands, (2) point-bars, (3) coastal dunes. In the area, I could recognize no pattern or re-gularity in the position of the individual forms of any type. In many cases, the direction of the longitudinal trends is perpendicular to one another, which excludes their Aeolian origin. The sediment of the floodplain islands mainly consists of medium-, small- and fine-sized sand, but the settlement of loess-mantled and loess-like layers among the sandy sediment of certain forms can also be observed. The layer with 15 % lime content and 53–60 % loess fraction (0.05–0.01 mm) – found in the 110–50 cm high section of the erosion island called the Homok-tanya in Mátyus – can be considered a typical loess, based on the detailed parameters. Its formation in all probability took place at the same time and under similar conditions than that of the more than 2 m thick aeolian loess mantle found in the Nyírség area, some 10 km west from there, which had accumulated before the Bölling period. In case of an erosion island 2.5 km to the south and lying some 2 m lower, such a loess mantle cannot be found anymore, despite the fact that the sandy layers of the two sediment series are almost completely identical. The background of this phenomenon is the more active and frequent, mainly erosional fluvial processes – because of the lower position –, which eroded the loess mantle. The composition of the surface sediments is de-termined by the absolute altitude as well. The cover sediment of the lower-lying islands is identical to the finishing silt-clay deposits found at the alluvial parts of the Bereg Plain, whereas the surface of higher-lying forms that have not seen flood for ages, is covered by sand or loessy sand.
-
Studying the development of fluvial landforms in the Berettyó-Körös Region using geoinformatic methods
137-144Views:181Development of fluvial landforms from 1980 till nowadays was studied based on digital elevation maps (DEM) composed from contour lines of topographic maps, field data obtained by RTK GPS and aerial photos taken by a drone. Greatest denudation of 6-9 metres was measured in the eastern side of the erosional valley at Pocsaj caused by piping and mass movements. As a result, the valley widened and slightly deepened. Since 1980 around 1-2 metres of accumulation and erosion of similar rate have been measured in the secured floodplain environment dissected by abandoned beds, point-bars and swales at Kismarja. These values, however, rather reflect the geometric uncertainties and deficiencies of the contours of topographic maps than real land changes. Therefore topographic maps can give reliable basis for studying the development of lowland landforms only if they depict adequately large sized (minimum 100 x 100 m) positive or negative forms with great height difference as well (minimum 8-10 m). Accuracy of DEMs composed from aerial photos using photogrammetric methods – taking off height faults caused by vegetation – is around the same as that of the models created on the basis of RTK GPS measurements.
-
Flood model for the Bódva catchment
12-26Views:184In term of floods the current area of Hungary has extensively been endangered. Modelling of flood processes – mainly following the hydrological events in the riverbed – has recently been developed. As far as protection dykes provide protection of the inhabited and agricultural areas, the flood models can run with acceptable preciseness. However, when dykes cannot withstand against the increasing load and a dyke burst occurs, fast and efficient protection measures shall be taken in the protected areas. The dynamic 4D Flood model presented in this paper makes possible a fast modelling of dyke burst occurring in the protected side and spreading of water mass, based on real parameters. For this reason the features of protected area shall be recognised, for example topology of creeks, features of agricultural and inhabited areas, parameters of roads, railways, rainwater drainage, buildings, natural conditions (soil parameters, meteorological characteristics, etc.). The results satisfy the comprehensive demands of the Directorate General for Disaster Prevention of Borsod-Abaúj-Zemplén County. In case of dyke burst, the completed Flood Model can run the expected events of the next hour in a few minutes. This time is enough for the specialists to bring operative decisions to protect the inhabitants and avoid material losses.
-
Morphometric characteristics of a tropical river basin, central Kerala, India using geospatial techniques
1-14Views:251The Thutapuzha watershed (TW) is one among the major tributaries of Bharathapuzha – the largest west flowing river in Kerala, India. Morphometric analysis was carried out to determine the spatial variations in the drainage characteristics and to understand the prevailing geologic variation, topographic information and structural setup of TW using Survey of India topographic maps and ASTER-DEM. Geoprocessing techniques has been used for the delineation and calculation of the morphometric parameters of the watershed. The TW sprawled over 1107Km2 and the study revealed that the watershed includes a sixth order stream and lower order streams mostly dominate the basin with a drianage density of 1.36 m/Km2 exhibiting highly resistant subsoil, dense vegetation, and low relief of surface nature . The study indicate that rainfall has a significant role in the drainage development whereas the drainage pattern is controlled by structure and relief. The watershed of TW is moderate to well-drained and exhibited a geomorphic maturity in its physiographic development. The shape parameters revealed the elongated nature of TW having less prone to flood, lower erosion and sediment transport capacities and drainage network development in the watershed. This study strongly brings to light that the drainage morphometric parameters have the enormou spotentiality to unveil the hydro-morphologicalcharacteristics of the river basins. Integrating hydro-morphological characteristics with conventional watershed assessment methods would have a beneficial effect on judicious watershed management, which helped to formulate a comprehensive watershed management plan.
-
Remnant surfaces in the Tárkány Basin
20-30Views:215The terraces of the Tárkány Basin, located in the SW part of the Bükk Mountains are known since the beginning of the 20th century. Based on field surveys, six morphological levels were delineated and described in 1936. During the later geological mapping surveys, three gravel terraces had been mapped in the basin. Since then, no comprehensive morphological mapping has been made in the Tárkány Basin. Our study aimed to validate the results of these early studies using a digital elevation model. We delineated the remnant surfaces of the basin by morphometric and GIS techniques. Then, based on field surveys and former geological maps; we characterised these remnant surfaces, and their area was measured as well. The results of this study contribute to a better understanding of the surface evolution of the basin and its surroundings.