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  • 1
    Electronic Resource
    Electronic Resource
    Impact of land use changes on the hydrological properties of volcanic ash soils in South Ecuador (2002)
    Oxford, UK : Blackwell Publishing Ltd
    Soil use and management 18 (2002), S. 0 
    Details
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. The effect of land use on the water retention capacity of Umbric Andosols in south Ecuador was studied. The objective was to acquire a better insight into the hydrological processes of the ecosystem and the role of the soil, in order to assess the impact of changing soil properties due to land use change on the hydrology of the high Andes region. Field data on the water retention capacity at wilting point of Umbric Andosols were collected for both cultivated field conditions and original bush vegetation. The pH in water and in NaF, texture, organic matter content and dry bulk density were measured to show which physicochemical soil characteristics are responsible for the water retention of the Umbric Andosols and for the irreversible loss in water retention due to air drying. Organic matter content appears to be very important and certainly more important than allophane clay content. Water retention of the organic litter layer was calculated to be 16 mm, this would be lost when vegetation was cleared and the land cultivated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1475-2743.2002.tb00226.x
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  • 2
    Electronic Resource
    Electronic Resource
    Effectiveness of stone bunds in controlling soil erosion on cropland in the Tigray Highlands, northern Ethiopia (2005)
    Oxford, UK : Blackwell Publishing Ltd
    Soil use and management 21 (2005), S. 0 
    Details
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Use of stone bunds to enhance soil and water conservation was first introduced to Tigray, northern Ethiopia in 1981. This study was designed to examine the factors that control the effectiveness of bunds installed on cropland. Qualitative and quantitative assessments of soil loss and sediment accumulation were conducted on 202 plots at 12 representative sites in Dogu'a Tembien district. Mean annual soil loss from the foot of the bunds due to tillage erosion was estimated at 39kgm−1yr−1 or 20tha−1yr−1, a rate which decreased with increasing age of bund. The assessed mean annual soil loss rate by sheet and rill erosion in the absence of stone bunds is 57tha−1yr−1. The mean measured annual rate of sediment accumulation behind the stone bunds is 119kgm−1yr−1/sp or 59tha−1yr−1. The measurements show that the introduction of stone bunds to the region has led to a 68% reduction in annual soil loss due to water erosion. This reduction is due to the accumulation of sediment behind the stone bunds, which occurs faster in the early years after construction and decreases as the depression behind the bunds becomes filled with sediment. New stone bunds are particularly effective in trapping sediment in transport, but regular maintenance and increase in height of the bunds is necessary to maintain their effectiveness. The average USLE P factor for stone bunds in the study area is estimated to be 0.32.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1475-2743.2005.tb00401.x
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  • 3
    Electronic Resource
    Electronic Resource
    The effectiveness of loose rock check dams for gully control in Tigray, northern Ethiopia (2004)
    Oxford, UK : Blackwell Publishing Ltd
    Soil use and management 20 (2004), S. 0 
    Details
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. Over the last two decades, large gully control programmes have been established in Ethiopia. Based on detailed observations and measurements of 400 check dams in the highlands near Hagere Selam (Tigray, northern Ethiopian Highlands), the effectiveness of the check dam technique was assessed. In this study, catchment area, slope gradient, technical characteristics and the presence of smectite clays are the main factors controlling dam stability. Simple and logistic regression techniques were used to analyse the data. The frequent collapse of dams (39% after two years) is strongly associated with drainage area (A) and slope gradient of the soil surface near the gully (S), the product of these factors (S×A) being a proxy for runoff energy. Good functioning dams have a spillway, apron, concave plan form (when looking downslope) and are built at vertical intervals and with heights that result in a negative slope gradient of the line connecting the spillway and the foot of the upstream dam. Therefore, a reverse slope of this line is recommended. Furthermore, if large cracks are present in smectite-rich soils, the construction of check dams can lead to piping and concentrated flow bypassing the dam. Given that the collapse of some check dams seems inevitable where catchment areas are large or there are steep slopes, it is necessary to repair dams as soon as partial collapse starts and to complement this gully control technique with biological control measures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1475-2743.2004.tb00337.x
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  • 4
    Electronic Resource
    Electronic Resource
    Evaluating an integrated approach to catchment management to reduce soil loss and sediment pollution through modelling (2002)
    Oxford, UK : Blackwell Publishing Ltd
    Soil use and management 18 (2002), S. 0 
    Details
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. Soil erosion and sediment delivery cause many environmental problems posing a substantial financial burden upon society. Policy makers therefore look for a strategy to minimize their impact. The spatial nature of soil erosion and sediment delivery, as well as the variety of possible soil conservation and sediment control measures, requires an integrated approach to catchment management. To evaluate such management, a spatially distributed soil erosion and sediment delivery model is necessary. Such a model (WaTEM/SEDEM) was applied to three agricultural catchments in Flanders (Belgium). The model was first used to identify where the measures to control soil loss should be taken. Secondly, a scenario analysis was used to select the most effective set of techniques. The findings showed that soil conservation measures taken in fields are not only effective in reducing on-site soil loss, but also in drastically reducing sediment yield. Off-site sediment control measures appear to be much less effective in reducing sediment yield than previously thought. The results also suggest that data from field experiments cannot be extrapolated to a catchment scale.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1475-2743.2002.tb00257.x
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  • 5
    Electronic Resource
    Electronic Resource
    Simulation of the redistribution of soil by tillage on complex topographies (2003)
    Oxford, UK : Blackwell Science Ltd
    European journal of soil science 54 (2003), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Tillage redistributes soil and contributes significantly to the within-field soil variation, especially on topographically complex terrain. Although the basic principles of the redistribution are well understood, models for simulating the redistribution are poor predictors. This paper presents a modelling structure that allows a simulation of the redistribution of soil constituents on complex topographies for various tillage implements. The model simulates the redistribution of soil constituents by convoluting the probability distribution of the tillage displacement with the spatial distribution of the soil constituents. The probability distributions in two dimensions are derived from a series of tillage experiments conducted with a mouldboard plough at various positions in the landscape. Furthermore, the effects of topography and tillage direction on the probability distributions were characterized and implemented in the model. A first application showed that the direction of tillage significantly affects the long-term redistribution of soil constituents. The inclusion of other implements in the model was explored, and we found that data in the literature could be used for simulating the long-term effects of tillage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2389.2003.00470.x
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  • 6
    Electronic Resource
    Electronic Resource
    The role of tillage in soil redistribution on hillslopes (1994)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of soil science 45 (1994), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Soil tillage is usually considered as a process having only an indirect influence on soil erosion. This paper describes the results of field experiments carried out with a mouldboard and a chisel plough showing that an important net downslope soil movement can be associated with soil tillage. Available experimental evidence suggests that the soil redistribution by tillage can be described by a diffusion-type equation, which allows the intensity of the process to be characterized by a single number, which may be called the diffusion constant. The experimentally determined values of the diffusion constant vary between 100 and 400 kg m−1 a−1. This implies that erosion and sedimentation rates associated with tillage may be more important than those associated with water erosion on much of the hilly arable land in western Europe. A comparison of recent hillslope evolution with model simulation results corroborates this conclusion. Therefore, tillage should be considered as a soil degradation process per se, rather than a process which makes the soil more sensitive to erosion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2389.1994.tb00532.x
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  • 7
    Electronic Resource
    Electronic Resource
    Initiation of motion in overland flow (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Sedimentology 34 (1987), S. 0 
    Details
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: This article reports the results of an experimental study concerning the initial movement of sediment in overland flow. Experiments were carried out in a small flume using water and quartz materials of various grain sizes.The comparison of our experimental results with classic criteria showed that the Shields-curve and the criterion of Yang can also be used for turbulent overland flow. Generally, higher shear stresses are necessary to provoke bed-instability under laminar flow conditions, especially at higher shear-velocity particle Reynolds numbers. A relative roughness effect also exists in laminar flow. Contrary to the observations by Savat on fixed beds, laminar flow does not show an ‘uncommon selectivity’, when loose, homogeneous beds are considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3091.1987.tb00598.x
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  • 8
    Electronic Resource
    Electronic Resource
    A modified technique to determine the tear energy of impression materials (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of oral rehabilitation 13 (1986), S. 0 
    Details
    ISSN: 1365-2842
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: A modified method to determine tear energy of impression materials is described. Trousers-shaped specimens were prepared between two platens. They are different from those used before in that (1) a V-shaped line is created so as to guide tear growth, and (2) the thickness gradually increases, then remains constant and, ultimately, decreases instantaneously. The specimens were tested at ten different rates between 0.2 and 50cm/min. λ can be computed from the force–time diagram. Six different materials were tested: two condensation silicones, Xantopren regular (Bayer, FRG) and Xantopren light; a polyvinylsiloxane, Reprosil regular (DeTrey, Switzerland); a polysulphide Coeflex regular (Coe, USA); a polyether, Impregum (Espe, FRG); and an alginate, Cavex, Fast Set, Dust Free (Keur & Sneltjes, The Netherlands). Tear strength (in kJ/m2) variations at rates between 0.2 and 50cm/min are as follows: Xantopren regular, 0.37–0.64; Xantopren light, 0.29–0.46; Coeflex, 1.10–5–29; Reprosil, 0.66–1.07; Impregum, 0.62–1.04; Cavex, 0.22–0.37. These values are consistent with those reported before. It might be concluded that the new test method gives reliable tear energy values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2842.1986.tb00666.x
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  • 9
    Electronic Resource
    Electronic Resource
    Rill erosion on arable land in Central Belgium: Rates, controls and predictability
    Amsterdam : Elsevier
    Catena 18 (1991), S. 133-155 
    Details
    ISSN: 0341-8162
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Geography , Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0341-8162(91)90013-N
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  • 10
    Electronic Resource
    Electronic Resource
    Selectivity and transport capacity of thin flows in relation to rill erosion
    Amsterdam : Elsevier
    Catena 12 (1985), S. 35-49 
    Details
    ISSN: 0341-8162
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Geography , Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/S0341-8162(85)80003-5
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