Search
Search Results
-
Accumulation studies at specific sampling areas of the active floodplain in the Upper-Tisza region
14-22Views:170In this paper the rate of accumulation was studied along four VO floodplain cross sections of the UpperTisza region between 1974 and 2014. VO floodplain cross sections are based on a mapping base-point grid (established in 1890), and they are located a few kilometers from each other. Furthermore, the roughness changes of different surface types, crossed by the VO floodplain cross-sections, were also determined between 1965 and 2015. The accumulation studies were extended to include the accumulation rates of the cut off meanders located along and/or close to the VO cross-sections. The roughness values increased in all four floodplain VO cross-sections since 1965; in two of them it reached or approximated 100 %. The average accumulation along the VO cross-sections was between 28 and 47 cm (0.73–1.23 cm/year) during the 38-year period. However, its areal distribution showed large differences. The highest values (169–309 cm, i.e. 4.44–8.13 cm/year) were found at the lowest points of the cut off meanders and swales in every case. The accumulation rate of the examined three cut off meanders near the floodplain cross-sections (140 and 1570 meters from the river bed) was lower (0.84–2.5 cm/year), but the study period was significantly longer (154 and 161 years, respectively). Comparing the values of the two periods, it is obvious that the accumulation of the active floodplain accelerates, presumably due to the significant increase of surface roughness.
-
Land use changes and their effect on floodplain aggradation along the Middle-Tisza River, Hungary
1-10Views:65Land-use changes and their effect on overbank sediment accumulation were investigated on the floodplain of Middle-Tisza River. Military survey maps (1783, 1860, 1883 and 1890) and aerial photos (1950, 1965, 1980 and 2000) were used to evaluate land-use changes and to calculate the vegetational roughness of the area. To determinate the rate of overbank sedimentation sediment samples were collected from a pit, the grain-size, content of organic matter, heavy metal content (Pb, Cu, Zn, Ni and Cd) and pH were measured. Until 1950 meadows and pastures were typical on the floodplain, gallery-forest was along the river, the oxbow-lake and the artificial levee. Notable landuse changes were detected in the second half of the 20th century, as the aerial photo taken in 1965 shows extensive forestry in the area. These land-use changes affected the average vegetational roughness, as it has been doubled since the disappearance of grasslands. Land-use changes highly affect the aggradation, as the increased roughness decreases the flood velocity on the floodplain, causing accelerated aggradation. Using Pb marker horizons and grain-size changes the studied sediment profile was compared to dated profiles (Braun et al. 2003), thus, the sediment accumulation rate could be determined for the periods of 1858-1965 and 1965-2005. According to our measurements the accumulation rate was doubled since 1965, very likely in connection with the doubled vegetational roughness.
-
Studying the development of fluvial landforms in the Berettyó-Körös Region using geoinformatic methods
137-144Views:158Development 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.
-
Studying floodplain roughness in an Upper Tisza study area
85-90Views:180Floods slowing down due to the significant decrease of the gradient have considerable sediment accumulation capacity in the floodplain. The grade of accumulation is further increased if the width of the floodplain is not uniform as water flowing out of the narrow sections diverge and its speed is decreased. Surface roughness in a study area of 492 hectares in the Upper Tisza region was analysed based on CIR (color-infrared) orthophotos from 2007. An NDVI index layer was created first on which object-based image segmentation and threshold-based image classification were performed. The study area is dominated by land cover / land use types (grassland-shrubs, forest) with high roughness values. It was concluded that vegetation activity based analyses on their own are not enough for determining floodplain roughness.
-
Elemental concentration in deposited dust on urban tree leaves depending applied washing method
45-52Views:200In our study, the concentrations of elements were determined in leaves and deposited dust of Quercus robur and Celtis occidentalis which were washed with distilled water, rainwater and tap water. According to our results, each washing solutions had a significant effect on the elemental concentrations in the foliage dust. The highest concentrations of aluminum, chromium, copper, iron, manganese and zinc were detected in the foliage dust which was washed down with rainwater. The highest strontium and barium concentrations were found in the foliage dust which was washed down with tap water. We observed chromium and manganese accumulation in Q. robur leaves, while the concentrations of barium, copper and strontium were the highest in C. occidentalis leaves. Our results demonstrated the effect of rainwater on tree leaves which phenomenon occurs naturally. Rainwater may wash down the dry deposited foliage dust from the leaf surface, but it also delivers a certain concentration of elements through wet deposition.
-
Assessment of the vulnerability of zemmouri bay to coastal erosion, diachronic study between 1957 and 2017
15-30Views:151The analysis and understanding of coastline variability and coastal erosion trends, and accretion are essential to scientists and local decision-makers to guide shoreline management regulations and decisions. This study focuses on detecting and analyzing historical changes in the Zemmouri (Central Algeria) shoreline position between 1957 and 2017. We collected all the necessary data related to the Zemmouri bay to achieve our objective, such as satellite images, aerial photos, and topographical surveys carried out by the DGPS, all between 1957 and 2017 DSAS calculation tool. Diachronic analysis of aerial photographs and satellite images of Zemmouri Bay revealed that only 39% of sandy beaches are eroding while 3% have some stability. The maximum erosion at Mazer East beach is -1.25m/year. The maximum accretion rate of +1.40m/year at Blue Waves beach, mainly due to the implantation of breakwaters at this beach which created tombolos favoring sand accumulation and beach widening.
-
Statistical Indices of Land Use Changes and Nutrients Balance of Tomatoes and Peppers Production in Jordan Valley and Highlands (1999-2019)
65-76Views:199Climate change has caused pressure on water resources in Jordan. This was accompanied by the Syrian refugee crisis during the period 2009 to 2019. This descriptive study was conducted in the University of Debrecen, during the years 2020 and 2021 within the course of sustainable land use by collecting official statistical data from reliable sources in Jordan on the production of tomato, pepper, and paprika during five years 1999, 2004, 2009, 2014 and 2019 to compare the change in land use, crop sown structure, country production, unit area average yield and estimation of unit area pollution with major nutrients. The study showed an increased land used for the production of vegetables by (+ 37.84%) during the period from 2004 to 2014, high productivity per hectare for three crops from 2014 to 2019. Jordan had the highest tomato and paprika crop yields in 2014. The reason is due to the increase in the local and global demand for these crops along with other reasons, which have promoted the use of mass production agricultural techniques, the most important of which is chemical fertilization. Which caused the accumulation of phosphorus and potassium in soils.