Browsing by Subject "erosion"

Now showing 1 - 7 of 7
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    Erosión y desertificación.-Combating erosion as the main effective factor in land degradation in arid and semi-arid regions of Iran
    Feiznia, S.; Kouhpeima, A.; Ahmadi, H.; Hashemi, S.A.A.; Universidad de Murcia
    ABSTRACT Soil erosion is one of the most important environmental problems in the world including Iran. For decreasing the impacts of soil erosion, soil conservation measures are required. For successful soil conservation measures, obtaining information about the relative importance of sediment source and their shares in sediment production is required. There are different methods for determining the relative importance of sediment sources, among which tracing or source studies are emphasized in recent years due to their privileges. In this research, sediment sources were identified in Amrovan Drainage Basin, Semnan Province, Iran, using tracing method. A small earth dam is constructed at the outlet of Amrovan Drainage Basin in 1993. Sediments are accumulated in the reservoir of dam. In this study, sediments were sampled from dam reservoir, different sources were also sampled. Fifteen tracers were first selected for tracing which are: the amounts of N, Carbon, Cr, Co, Mg, K, Na, smectite, cholorite, illite, kaolinite, PH and two magnetic properties consisting of XLF and XFD. The samples were analyzed in the laboratory for these parameters and different statistical methods were applied to the data including Nonparametric Kruskal Walis Test, Stepwise Differentiation Function Analysis. The results have shown that the main sediment source is Upper Red formation consisting of evaporitic marls. Keywords: Erosion, Sedimentation, Small dams, Semnan Province, Iran, Tracing, Fingerprinting, Source studies.
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    Erosión y desertificación.-How development and disturbance of biological soil crust do affect runoff and erosion in drylands? PDF
    Chamizo, S.; Cantón, Y.; Afana, A.; Lázaro, R.; Domingo, F.; Solé-Benet, A.; Universidad de Murcia
    ABSTRACT Deserts and semiarid ecosystems (shrublands and grasslands) are the largest terrestrial biome, covering more than 40% of the Earth's terrestrial surface and Biological Soil Crusts (BSCs) are the predominant surface type in most of those ecosystems covering up to 70% of its surface. BSCs have been demonstrated to be very vulnerable to disturbance due to human activities and their loss has been implicated as a factor leading to accelerate soil erosion and other forms of land degradation. Incorporation of the response of different type of soil crusts and the effects of their disturbance is likely to improve the prediction of runoff and water erosion models in arid and semi-arid catchments. The aim of this work is to analyse the influence of BSC development and the impact of crust disturbance on infiltration and erosion. Extreme rainfall simulations at microplots scale were performed in two semiarid ecosystems with different lithology and conditions of occurrence of BSCs: El Cautivo and Amoladeras. Moreover, open plots were set in the field to examine the response under natural rainfall, and contributing area was estimated from a 1 centimetre resolution DEM built from laser scan height records. Our results demonstrated that the stage of development of the undisturbed BSCs affects infiltration and erosion with an increase in the infiltration rate and a decrease in erosion as crust development is higher. Crust disturbance affected infiltration and erosion: trampling caused the highest runoff rates and crust removal the highest erosion, nevertheless, the effects of crust disturbance on erosion were lower for Amoladeras, an area with a flat topography and a coarser soil texture. At both sites, under extreme rainfalls, although crust removal enhanced infiltration at the beginning of the rain, the early development of a new physical crust increases runoff until reaching similar runoff rates as undisturbed crusts. The responses of BSCs to extreme simulated rainfall and to natural rains were compared to evaluate when the differences among BSCs in different degree of development are more accentuated in order to identify critical thresholds to incorporate in runoff and erosion models.
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    Erosión y desertificación.-Land degradation of Taleghan drainage basin, Iran from saline and alkaline marly formations
    Feiznia, S.; Hosseini, S.H.; Universidad de Murcia
    ABSTRACT In Iran fine – grained, saline, alkaline and erodible Tertiary marly formations are exposed in many geological zones and play important role in the formation of present landforms. They also play important role in degradation of water resources and soils as diffuse sources, they are the main sources of suspension loads of many rivers and are endless sources of sediments for sand dunes. These marly formations are present in Zagros, Central Iran, Alborz and Kopeh – Dagh Geological Zones and consists of different geological formations such as Gachsaran, Mishan and Razak Formations(in Zagros), Lower Red and Upper Red Formations(in Central Iran) and Neogene Red Beds(in Albors and Kopeh-Dagh). In this research, Neogene marly formations of Taleghan Drainage Basin, located in Alborz Geological Zone are investigated for chemical, physical and mechanical characteristics and erosion and sediment yield potential. The studied area is located about 100 kilometers west of Tehran and is one of the subdrainages of sefid-Rood Dam. Runoff and sediment yield were measured using field rainfall simulator. According to their physical and chemical characteristics, Neogens fine grained Formations of Taleghan Drainage Basin were classified into six subunits: Siltstone (NgSi), Claystone (gy1C), marl(gy1M), haliferous siltstone (NgSiH), haliferous claystone (gy2CH) and gypsiferous claystone (gy1CG). From the view point of salinity and alkalinity, NgSi unit is alkaline and NgsiH, gy2CH, gy1C and gy1CC units are saline and alkaline. The order of the units in respect to sediment and runoff production is as follows: NgsiH>Ngsi>gy2Ch>gy1CC > gy1C.
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    El impacto de la ganadería y la agricultura en los ecosistemas terrestres.-Degradación física del suelo por actividades antrópicas en la zona II de la cuenca de burgos, Tamaulipas, México.
    Arias Miño, F.; Espinosa Ramírez, M.; Andrade Limas, E.; Castro Meza, B.; Romero Díaz, A.; Universidad de Murcia
    ABSTRACT The objective of this work was to characterize the physical degradation of the soil for antropic activities during the years 2007 and 2008 in the II zone of the Burgos Basin in Tamaulipas, México. In this region, human action manifests itself due to activities such as agriculture, livestock and industry. The conventional farming, based mainly on the cultivation of sorghum, is characterized by greater mechanization and tilling the soil which has contributed in large measure to aggravate erosion processes. There is also some logging, mainly for charcoal production and, recently, has joined the exploration and exploitation of natural gas. We used the methodology for Assessment of Soil Degradation (ASSOD) to identify, locate and define the types of soil degradation within physiographic units. Results showed that nearly 74% of the study area presents some kind of degradation. The main process was water erosion, followed by compaction and wind erosion. The main factors are essentially overgrazing and inadequate farming practices. Approximately 60% of the units evaluated presented a moderate level of degradation, but the speed of this process indicates that maintenance works are needed to reverse.
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    El impacto de la ganadería y la agricultura en los ecosistemas terrestres.-Modelos de distribución espacial de la erosión en laderas cultivadas con viñedos
    Arnáez, J.; Ortigosa, L.; Ruiz-Flaño, P.; Llorente, J. A.; Lasanta, T.; Universidad de Murcia
    RESUMEN Soils cultivated with vineyards have high rates of erosion. In the Mediterranean area, this is related to the environmental characteristics and the management of cultivation techniques. Indeed, in this region the rainfall intensity and the location of vineyards on slopes favour the erosive activity of runoff. The total area of vineyard in La Rioja (Spain) is currently almost 40,000 ha. Vineyards are located on hillsides between 400 and 600 m a.s.l. Of the vineyards of La Rioja, 81.7% are planted on slopes with a gradient between 3º and 9º. The aim of this paper is to present the behaviour and spatial organization of soil erosion in vineyards after high intensity rainfall and to identify the factors that influence in this organization. From erosion processes cartography, geographic information systems and multivariate statistical analysis, the distribution of erosion on a hillside cultivated with vineyards is modelling and predicted. The results are validated and compared with WATEM, a spatially distributed soil erosion and sediment delivery model. The use of spatial models of erosion can be very useful for agriculture, since they predict areas vulnerable to erosion and assist in planning of soil conservation techniques.
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    Modelización en Geografía Física.-Landscape Evolution Modelling - LAPSUS
    Baartman, J.E.M.; Temme, A.J.A.M.; Schoorl, J.M.; Claessens, L.; Viveen, W.; van Gorp, W.; Veldkamp, A.
    ABSTRACT Landscape evolution modeling can make the consequences of landscape evolution hypotheses explicit and theoretically allows for their falsification and improvement. Ideally, landscape evolution models (LEMs) combine the results of all relevant landscape forming processes into an ever-adapting digital landscape (e.g. DEM). These processes may act on different spatial and temporal scales. LAPSUS is such a LEM. Processes that have in different studies been included in LAPSUS are water erosion and deposition, landslide activity, creep, solifluction, weathering, tectonics and tillage. Process descriptions are as simple and generic as possible, ensuring wide applicability. Vegetation-effects can be included. Interactions between processes are turn-based: volumes of one process are calculated and used to update the DEM before another process starts. LAPSUS uses multiple flow techniques to model flows of water and sediment over the landscape. Though computationally costly, this gives a more natural result than steepest descent methods. In addition, the combination of different processes may create sinks during modelling. Since these sinks are not spurious, the model has been adapted to deal with them in natural ways. This is crucial for several purposes, for instance when studying damming of valleys by landslides, and subsequent infilling of the resulting lake with sediments from upstream.
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    Morfología Fluvial.-Erosion, water availability and plant characteristics control plant colonisation on semiarid eroded slopes
    Bochet, Esther; García-Fayos, P.; Poesen, Jean; Universidad de Murcia
    ABSTRACT The objective of this study was to understand the mechanisms that control spontaneous plant colonisation on severely eroded slopes in a semiarid badland area of East Spain. More specifically, we aimed at (1) determining topographic thresholds for plant colonisation, (2) identifying the soil properties that limit plant establishment and (3) identifying plant traits that enable colonising species to cope with these limitations. We used slope angle and aspect as surrogates of erosion rate and water availability respectively. Since soil erosion and water availability can limit plant establishment and both interact in the landscape, we analysed variations in colonisation success with slope angle and aspect. Vegetation success was measured in terms of total vegetation cover on 156 different slopes. After determining slope angle thresholds for plant colonisation, soil was sampled on slopes just above and just below the threshold values for soil analysis in order to test for differences in soil properties related to plant establishment and development. Plant traits related to plant colonising capacity were analysed in two different groups of species: the group of species colonising the steep slopes near the threshold and the group of noncolonising species present on more gentle slopes but unable to colonise the slopes just below the threshold. The identified slope angle threshold values for plant colonisation clearly decreased from North to South. No differences were found in soil properties neither among slope aspects at the slope angle threshold values nor between slope positions (just below and above the threshold) within slope aspect classes. Long-distance dispersal mechanisms and ability of seeds to segregate mucilage in contact with water were more frequent characteristics in colonising species than in non-colonising ones. It is concluded that water availability for plants which, in turn, is controlled by the solar radiation can explain the differences in the slope angle threshold values for plant colonisation among slope aspect classes. Some important implications of these results in the context of ecological restoration of these severely eroded areas are also discussed.�L /