Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Mechanical Erosion in a Tropical River Basin in Southeastern Brazil: Chemical Characteristics and Annual Fluvial Transport Mechanisms  [PDF]
Alexandre Martins Fernandes,Murilo Basso Nolasco,Christophe Hissler,Jefferson Mortatti
Journal of Geological Research , 2012, DOI: 10.1155/2012/127109
Abstract: This study aims to evaluate the mechanical erosion processes that occur in a tropical river basin, located in the S?o Paulo state, southeastern Brazil, through the chemical characterization of fine suspended sediments and the transport mechanisms near the river mouth, from March 2009 to September 2010. The chemical characterization indicated the predominance of SiO2, Al2O3, and Fe2O3 and showed no significant seasonal influences on the major element concentrations, expressed as oxides. The concentration variations observed were related to the mobility of chemical species. The evaluation of the rock-alteration degree indicated that the physical weathering was intense in the drainage basin. The fine suspended sediments charge was influenced by the variation discharges throughout the study period. The solid charge estimate of the surface runoff discharge was four times higher in the rainy season than the dry season. The transport of fine suspended sediments at the Sorocaba River mouth was 55.70?t?km?2?a?1, corresponding to a specific physical degradation of 37.88?m?Ma?1, a value associated with the mechanical erosion rate that corresponds to the soil thickness reduction in the drainage basin. 1. Introduction The mechanical erosion processes that occur in a drainage basin tend to reduce the thickness of the soils and the volume of the bedrock, by which dislocated and degraded particles are exported by the rivers to the sedimentation areas (lakes and oceans). The sediment production, transport, and deposition at the drainage basin scale are principally controlled by natural processes that may be intensified due to human activities, mainly agriculture and urbanization [1]. It is now recognized that in areas where urbanization grew drastically during the last century, the contribution of urban-originated sediments to the suspended particulate matter of water bodies is significant [2]. Soil erosion and its impacts on agricultural productivity, water quality, and siltation in rivers and reservoirs have been frequently discussed with regard to sustainable management of the services that these ecosystems deliver to the population [3]. In this context, the knowledge of mechanical erosion processes that occur in a tropical river basin is of outmost importance. It is now essential to reduce the loss of surface soil layers in agricultural areas and to anticipate the accumulation of deposited sediments at the industrial/urbanized areas. The intensity of mechanical erosion in a drainage basin can be assessed by monitoring the fine suspended sediments (FSS) dynamic in a
The scale relationship of sediment discharge, erosion amount and sediment delivery ratio in drainage basin: A case study in the Ganjiang River Basin
输沙量 、侵蚀量与泥沙输移比的流域尺度关系——以赣江流域为例

JING Ke,JIAO Ju-ying,LI Lin-yu,ZHANG Shi-jie,

地理研究 , 2010,
Abstract: The research of sediment discharge, erosion amount and sediment delivery ratio is known as frontier topics in the field of soil erosion and sediment yield in a drainage basin, with the hope that the research results of slope or runoff plot could be transformed into much larger areas according to the theory of scale transformation. Based on the measured sediment discharge, calculated erosion amounts and sediment delivery ratio in the Ganjiang River Basin, this paper discusss the relationships of the three variables at a basin scale, and analyzs the possibilities of scale transformation of the three variables. Both the scatter diagrams and correlation equations of the three variables and drainage areas reflected the fact that the three variables are not correlative with the drainage area and against the conclusion that the three variables have inverse relations with the drainage area presented by some scholars. It also describs the connotation of basin area and its relationship with the influencing factors of sediment discharge, erosion amount and sediment delivery ratio. The result reveals that there is no scaling effect between the influencing factors of the three variables and basin areas. Therefore, there is little possibility for scale transformation in sediment discharge, erosion amount and sediment delivery ratio in the Ganjiang River Basin. Further research work should be done to find out if this conclusion could be reliable and have a universal meaning.
The silt carrying in Jerma river basin
Manojlovi? Predrag A.,Mustafi? Sanja,Dragi?evi? Slavoljub
Glasnik Srpskog Geografskog Dru?tva , 2003, DOI: 10.2298/gsgd0302003m
Abstract: The silt carrying in the upper part of Jerma river basin in amount of 82.3 t/km/year is relatively high, considering the situation in all Serbia. The specific silt carrying in the upper part of Crnica river basin is 23.9 t/km/year (Manojlovi P.), while it is even lower in the basin of Crni Timok river (3.5 t/km/year; Manojlovi P, Gavrilovi Lj. 1991.). In the Kolubara river basin, the specific mechanical water erosion is between 4.6 t/km/year (Gradac) and 73.2 t/km/year in Tamnava basin (Dragicevic S. 2002). Greater erosion in the upper part of Jerma river basin is result of great part of metamorphic stones that intensively disintegrates and significant anthropogenic influence in Znepolje. The great slopes at the left side of the basin, under the Ruj mountain, should be considered, too. That doesn't mean that the erosion is strong, because, for example in the basin of Beli Timok, between Knja evac and Zaje ar, it is 186 t/km/year. Following regression, base on flow and silt concentration values can calculate the silt carrying very precisely: t/day=6251+26875 - C+1058 - Q Based on beta coefficients (0.73 for silt and 0.31 for flow) it could be concluded that concentration of silt has greater influence on erosion, than flow. More interesting is the influence of seasonal factor on the carrying of suspended silt. Months with the highest amount of carried suspended material are March, April and May. During these months 50.5 % of average yearly value is evacuated from a basin. Similar excessivity has been noticed in the other basins (Dragicevic S. 2002), only in other months.
Dillip K. Ghose,,Dr. Prakash C. Swain
International Journal of Engineering Science and Technology , 2011,
Abstract: River erosion by the Mahanadi river is evaluated in terms of basin geology, hydrology, dissolved and suspended load characteristics. Bulk of suspended sediment is carried in fine fraction. Its mineralogy is characterized by clay minerals illite, kaolinite, smectite and chlorite in addition to quartz and felspar. The river annually transports a cumulative load of 33.59 million tons into the Bay of Bengal. The dissolved load constitutes less than 25% of the total. Present study reveals that Mechanical load is strongly correlated with discharge, elevation and area while a weak correlation exists between bed slope and mechanical load. The ratio of mechanical to chemical erosion rate an index of erodibility of the basin, seems to be related to rock type in the catchment area.Higher values of erodibility index correspond to higher elevations, lesser area and hard silicate rocks of subbasins. On the other hand, sub-basins with low to moderate elevation and chemically active sedimentary rocks, are characterized by low values. The river has registered 14% decrease in sediment load transport over a decadedue to anthropogenic activities.
Bank erosion events and processes in the Upper Severn basin
D. M. Lawler,J. Couperthwaite,L. J. Bull,N. M. Harris
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 1997,
Abstract: This paper examines river bank retreat rates, individual erosion events, and the processes that drive them in the Upper Severn basin, mid-Wales, UK. Traditional erosion pin networks were used to deliver information on patterns of downstream change in erosion rates. In addition, the novel automatic Photo-Electronic Erosion Pin (PEEP) monitoring system was deployed to generate near-continuous data on the temporal distribution of bank erosion and accretion: this allowed focus on the magnitude and timing of individual erosional and depositional events in relation to specific flow episodes. Erosion dynamics data from throughout the Upper Severn basin are combined with detailed information on bank material properties and spatial change in channel hydraulics derived from direct field survey, to assess the relationships between flow properties and bank erosion rates. Results show that bank erosion rates generally increase downstream, but relate more strongly to discharge than to reach-mean shear stress, which peaks near the basin head. Downstream changes in erosion mechanisms and boundary materials, across the upland/lowland transition (especially the degree of development of composite bank material profiles), are especially significant. Examples of sequences of bank erosion events show how the PEEP system can (a) quantify the impact of individual, rather than aggregated, forcing events, (b) reveal the full complexity of bank response to given driving agents, including delayed erosion events, and (c) establish hypotheses of process-control in bank erosion systems. These findings have important implications for the way in which bank erosion problems are researched and managed. The complex responses demonstrated have special significance for the way in which bank processes and channel-margin sediment injections should be handled in river dynamics models.
CliFEM – Climate Forcing and Erosion Modelling in the Sele River Basin (Southern Italy)
N. Diodato, M. Fagnano,I. Alberico
Natural Hazards and Earth System Sciences (NHESS) & Discussions (NHESSD) , 2009,
Abstract: This study presents a revised and scale-adapted Foster-Meyer-Onstad model (Foster et al., 1977) for the transport of soil erosion sediments under scarce input data, with the acronym CliFEM (Climate Forcing and Erosion Modelling). This new idea was addressed to develop a monthly time scale invariant Net Erosion model (NER), with the aim to consider the different erosion processes operating at different time scales in the Sele River Basin (South Italy), during 1973–2007 period. The sediment delivery ratio approach was applied to obtain an indirect estimate of the gross erosion too. The examined period was affected by a changeable weather regime, where extreme events may have contributed to exacerbate soil losses, although only the 19% of eroded sediment was delivered at outlet of the basin. The long-term average soil erosion was very high (73 Mg ha 1 per year ± 58 Mg ha 1). The estimate of monthly erosion showed catastrophic soil losses during the soil tillage season (August–October), with consequent land degradation of the hilly areas of the Sele River Basin.
Changes of the intensity of Ljig river basin erosion: Influence of anthropogenic factor  [PDF]
Dragi?evi? Slavoljub,Stepi? Milomir
Glasnik Srpskog Geografskog Dru?tva , 2006, DOI: 10.2298/gsgd0602037d
Abstract: According to new field investigations as well as mapping of erosion in Ljig river basin we have found out that its intensity has changed in regard to period of 40 years ago. The most expressive changes were noticed in Ljig river basin. As we have not noticed changes in physical-geographical factors the cause of the intensity decrease might be only influenced by indirect anthropogenic factor. Processes of growing old and decrease of rural population, migration village-town, marginalization of agriculture and decrease of cattle reserves caused the changes of land utilization. Agriculture areas were becoming overgrown with growing wild vegetation which restrained gradually considerable expressed processes of erosion in the past.
Erosion Vulnerability Assessment of Sperchios River Basin, in East Central Greece—A GIS Based Analysis  [PDF]
Nikolaos Stathopoulos, Evdoxia Lykoudi, Eleni Vasileiou, Dimitrios Rozos, Dimitrios Dimitrakopoulos
Open Journal of Geology (OJG) , 2017, DOI: 10.4236/ojg.2017.75043
Abstract: One of the most important natural processes, with significant environmental impacts, is soil erosion. The aim of this paper is to evaluate and assess the erosion vulnerability of the geological formations constituting Sperchios River basin, in Eastern Central Greece, as well as to distinguish and locate the areas of such risk and estimate it. The developed methodology in this paper is based on Multi-Criteria Evaluation (MCE), with the implementation of Weighted Cartographic Overlay (WCO) technique in Geographic Information Systems (GIS) environment. By applying this method, an attempt was made to combine a set of factors, such as geological-hydrogeological characteristics, morphological slopes and hydrographic texture (causative factors of the phenomenon) along with rainfall (triggering factor) and land cover/use (competitive factor). The weighted combination of these factors defines the vulnerability of the formations in the area of interest. The main results of the methodology are two thematic maps of erosion vulnerability of Sperchios basin’s formations, one that does not include land use/cover factor and one with current existing conditions of the basin (co-evaluating land use/cover). In the first case, 36% of the basin surface undergoes high erosion vulnerability, while 53% present medium vulnerability. These percentages reduced significantly in the second case (3% is the high erosion vulnerability category and 38% the medium one), fact that proves the importance of vegetation in erosion restriction and protection of the geological formations consisting the Sperchios River basin.
The study of the natural characteristics of the basin as a function of forecasting erosion and deposition processes on the example of the selected basin  [PDF]
Nikoli? Jugoslav,Nikoli? Milena,Nikoli? ?or?e
Journal of the Geographical Institute Jovan Cvijic, SASA , 2012, DOI: 10.2298/ijgi1202015n
Abstract: For an integral perception of the possibility of forecasting erosion-deposition processes and their consequences it is essential to analyze the factors of erosion and deposition. The attempt was made in the paper to analyze quantitative and qualitative impact of some of the most important factors of erosion-deposition processes. The analysis was performed through a multidisciplinary approach, on the example of the Zapadna Morava River upper basin. The methodology of research encompasses an application of the adequate knowledge from the areas of meteorology, geomorphology, hydrogeology, spatial planning, economic geography, forestry, hydrology and environmental protection. The analysis encompasses meteorological factors, terrain characteristics and anthropogenic factors. The importance of the analysis and forecasts of the investigated processes for the industry, economy, spatial planning and environmental protection was emphasized.
Soil loss prediction in Guaraíra river experimental basin, Paraíba, Brazil based on two erosion simulation models  [cached]
Richarde Marques Silva,Celso Augusto Guimar?es Santos,Leonardo Pereira Silva,Jorge Flávio Cazé. B. da Costa Silva
Ambiente e água : An Interdisciplinary Journal of Applied Science , 2007,
Abstract: In this study, two hydrological models to estimate soil losses and sediment yield due to sheet and channel erosion, at the basin outlet, are applied to Guaraíra River Experimental Basin, located in Paraíba State, northeastern Brazil. The soil erosion models are (a) the classical Universal Soil Loss Equation (USLE), which is used to simulate annual and monthly soil losses; and (b) Kineros model, which is used to simulate the sediment yield within the basin. Kineros model is a physically-based distributed model that uses a cascade of planes and channels to represent the basin and to describe the processes of interception, infiltration, surface runoff and erosion within the basin. The USLE is computed using land use, soil erodibility, topographic digital maps, as well as observed rainfall data. It was found that Guaraíra river experimental basin has a low potential for soil losses; however, specific areas which are susceptible to the erosion process in the basin could be detected by the modeling techniques coupled to a GIS (Geographic Information System).
Page 1 /100
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.