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  • 1
    Language: English
    In: Soil Science Society of America Journal, 2014, Vol.78(4), pp.1168-1176
    Description: Aggregate stability is a key property affecting the movement and storage of water, seedling emergence, and soil sensitivity to erosion. Many studies have shown that aggregate stability changes through time. Field monitor- ing studies performed with a relatively large (monthly) time step showed the seasonal trend of aggregate stability. However, shorter time step monitor- ing is required to explore dynamics of aggregate stability at short term. For now, biological activity was recognized to be the main factor of aggregate stability dynamics, but previous studies were currently based on the external stimulation of aggregate stability. The objectives of this study were to assess variations in aggregate stability at short time steps in the field and to identify the factors controlling these variations of stability. A 6-mo field monitoring was performed at short time step (2-5 d) on a bare field of Luvisol without organic amendment. Aggregate stability was measured for both on surface and subsurface materials by the ISO 10930 (2012) method. Rain amount and intensity, air temperature and humidity, soil temperature, water content and hydric history, and soil water repellency were measured as explanatory fac- tors. The results showed that aggregate stability varied greatly (up to 40%) over a few days for both surface and subsurface. Short term dynamics of aggregate stability were already shown by laboratory experiments, but such dynamics was never observed in the field for a bare soil without external stimulation of biological activity. For the surface, short time step variations of surface aggregate stability were primarily controlled by soil water content (WC0 and WC1/2), hydric history (DWC4 and API), and rain intensity. While large changes in aggregate stability were found for the subsurface, explanatory factors remain to be found.
    Keywords: Sciences of the Universe ; Earth Sciences ; Agriculture
    ISSN: 0361-5995
    E-ISSN: 1435-0661
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  • 2
    Language: English
    In: Journal of Hydrology, 2011, Vol.403(1), pp.141-156
    Description: ► A surface-subsurface flow model with multi-objective global optimization is presented. ► The model performance was evaluated using bench-scale flow experiments. ► Inverse parameter estimation required observations at different spatial positions. ► The Pareto trade-off and model mismatch suggest lateral flow in soil layers. ► The model system is versatile for studying soil water and overland flow. A comprehensive description of water flow in environmental and agricultural systems requires an account of both surface and subsurface pathways. We present a new model which combines a 1D overland flow model and the 2D subsurface flow HYDRUS-2D model, and uses the multi-objective global search method AMALGAM for inverse parameter estimation. Furthermore, we present data from bench-scale flow experiments which were conducted with two 5-m long replicate soil channels. While rainfall was applied, surface runoff was recorded at the downstream end of the soil channel, subsurface drainage waters were sampled at three positions equally spaced along the channels, and pressure heads were recorded at five depths. The experimental observations were used to evaluate the performance of our modeling system. The complexity of the modeling approach was increased in three steps. First, only runoff and total drainage were simulated, then drainage flows from individual compartments were additionally evaluated, and finally a surface crust and immobile soil water were also considered. The results showed that a good match between measured and observed surface runoff and total drainage does not guarantee accurate representation of the flow process. An inspection of the Pareto results of different multiobjective calibration runs revealed a significant trade-off between individual objectives, showing that no single solution existed to match spatial variability in the flow. In spite of the observed crust formation, its consideration in the more complex model structure did not significantly improve the fit between the model and measurements. Accounting for immobile water regions only slightly improved the fit for one of the two replicate soil channels. Discrepancies between relatively complex model simulations and seemingly simple soil channel experiments suggest the presence of additional unknowns, such as heterogeneity of the soil hydraulic properties. Nevertheless, with its versatile subsurface options and powerful inverse method, the model system shows promise for studying hillslope flow problems involving both surface runoff and subsurface flow.
    Keywords: Overland Flow ; Surface Runoff ; Multi-Objective Global Parameter Optimization ; Mobile–Immobile Model ; Simulation ; Flow Channel Experiment ; Geography
    ISSN: 0022-1694
    E-ISSN: 1879-2707
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  • 3
    Language: English
    In: Journal of Hydrologic Engineering, 2015, Vol.20(6)
    Description: The spatial distribution of land management practices (LMPs), such as the use of vegetated filters, may have a strong impact on theirefficiency in trapping sediments and pollutants. Distributed water erosion models help managers, planners, and policymakers optimize theefficiency of these LMPs regarding their location relative to water and sediment pathways. In this work, the authors analyzed the impactof the spatial distribution of LMPs using an existing distributed model and sensitivity analysis procedures. The distributed model that wasused is a distributed single-event physically based water erosion model developed to calculate erosion rates and sediment flow for small (lessthan 10 km2) agricultural catchments. To measure the impact of the spatial distribution of LMPs, the authors developed a stochastic model thatgenerates LMP locations over the entire catchment. The stochastic model has three input parameters: the density of LMPs, their downslope/upslope location probability, and the probability density function shape controller. Because of its ability to account for the cross effects betweenparameters, the variance-based Sobol method was used to calculate the sensitivity of the soil loss ratio of a typical Mediterranean agriculturalcatchment (Roujan, southern France) to the LMP location model parameters. Three measurement points (two subcatchment outlets and the mainoutlet) were used to examine the spatially distributed effects of the LMP locations. The simulation results indicated that 70% of the variation ofthe net erosion is explained by variations in LMP density for the main outlet catchment, making LMP density the most sensitive parameter.However, the total Sobol sensitivity indices indicate a strong interaction among the three parameters when the density values are low (few LMPsare applied). Thus, although the density of the LMPs is the most sensitive parameter, their location may influence their global trapping efficiencyin (real) cases where few LMPs are applied.
    Keywords: Environmental Sciences ; Engineering Sciences ; Civil Engineering ; Spatial Distribution of Land Management Practices ; Erosion Rates ; Distributed Water Erosion Models ; Sediment Flow ; Mhydas-Erosion ; Engineering ; Environmental Sciences ; Geography
    ISSN: 1084-0699
    E-ISSN: 1943-5584
    Source: Hyper Article en Ligne (CCSd)
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  • 4
    Language: English
    In: Hydrological Processes, 05/30/2011, Vol.25(11), pp.1717-1728
    Description: In this paper, we present MHYDAS-Erosion, a dynamic and distributed single-storm water erosion model developed as a module of the existing hydrological MHYDAS model. As with many catchment erosion models, MHYDAS-Erosion is able to simulate sediment transport, erosion and deposition by rill and interrill processes. Its originality stems from its capacity to integrate the impact of land management practices (LMP) as key elements controlling the sedimentological connectivity in agricultural catchments. To this end, the water-sediment pathways are first determined by a specific process-oriented procedure defined and controlled by the user, which makes the integration of LMP easier. The LMP dynamic behaviours are then integrated into the model as a time-dependent function of hydrological variables and LMP characteristics. The first version of the model was implemented for vegetative filters and tested using water and sediment discharge measurements at three nested scales of a densely instrumented catchment (Roujan, OMERE Observatory, southern France). The results of discharge and soil loss for simulated rainfall events have been found to acceptably compare with available data. The average R2 values for water and sediment discharge are 0?82 and 0?83, respectively. The sensitivity of the model to changes in the proportion of LMP was assessed for a single rain event by considering three scenarios of the Roujan catchment management with vegetative filters: 0% (Scenario 1), 18% (Scenario 2, real case) and 100% (Scenario 3). Compared to Scenario 2 (real case), soil losses decreased for Scenario 3 by 65% on the agricultural plot scale, 62% on the sub-catchment scale and 45% at the outlet of the catchment and increased for Scenario 1 by 0% on the plot scale, 26% on the sub-catchment scale and 18% at the outlet of the catchment.
    Keywords: Catchment Area ; Land Management ; Soils ; River Discharge ; Sediment Transport ; Soil Erosion ; River Basin Management ; Agricultural Runoff ; Modelling ; Erosion ; Hydrologic Analysis ; Land Management ; Catchment Basins ; Sediment Transport ; Soil Loss ; Filters ; Soil ; Sensitivity ; Erosion ; Land Management ; Rainfall ; Catchments ; Sediment Transport ; Filters ; Outlets ; Erosion ; Hydrologic Models ; Agricultural Watersheds ; Catchment Areas ; Deposition ; Model Testing ; Sediment Discharge ; Filters ; Outlets ; Erosion ; Hydrologic Models ; Agricultural Watersheds ; Catchment Areas ; Deposition ; Model Testing ; Sediment Discharge ; France ; Freshwater ; Precipitation ; Sewage ; Issues in Sustainable Development ; Surface Water Hydrology (556.5) ; Food & Drugs ; Coastal Zone Management;
    ISSN: Hydrological Processes
    ISSN: 10991085
    E-ISSN: 08856087
    E-ISSN: 10991085
    Source: Wiley (via CrossRef)
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  • 5
    Language: English
    In: Earth Surface Processes and Landforms, August 2004, Vol.29(9), pp.1117-1129
    Description: Aggregate stability is a soil characteristic often linked with soil erodibility, but this relationship is generally empirical. The aggregate size distribution is a recognized factor influencing crust characteristics and transport during interrill erosion events. This parameter was used in this work in order to improve the understanding of the relationship between aggregate stability and erodibility. A second aspect of this study was to investigate the size selectivity of interrill erosion processes, i.e. breakdown, detachment by splash and transport by overland flow. This experimental work was based on rainfall simulations and aggregate stability tests which were performed using two different soils: a clay loam slightly sensitive to erosion, and a more susceptible silt loam. Size distributions of soil fragments either produced by aggregate stability tests or detached by splash or transported by runoff were measured by both wet sieving and laser diffraction sizer analysis. The clay loam is particularly stable and has coarse breakdown products with mean weight diameters larger than 1400 µm. Aggregate breakdown is more efficient for the silt loam and leads to finer soil fragments with mean weight diameters between 229 and 380 mm. For the more stable soil, the clay loam, splash rate and sediment concentration are respectively two and six times lower and less time variable than for the silt loam. For the two soils, detachment by splash and short distance transport are size‐selective interrill erosion processes. This selectivity leads to the enrichment of silt and clay fractions of the eroded aggregates in comparison with the breakdown products. The low erodibility of the more stable soil is in accordance with results of aggregate stability tests. Copyright © 2004 John Wiley & Sons, Ltd.
    Keywords: Interrill Erosion ; Aggregate Stability ; Rainfall Simulation ; Aggregate Size Distribution ; Detachment And Transport Processes
    ISSN: 0197-9337
    E-ISSN: 1096-9837
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  • 6
    Language: English
    In: Journal of Environmental Management, 2012, Vol.96(1), pp.74-85
    Description: To preserve the quality of surface water, official French regulations require farmers to keep a minimum acreage of grassland, especially bordering rivers. These agro-environmental measures do not account for the circulation of water within the catchment. This paper examines whether it is possible to design with the farmers agri-environmental measures at field and catchment scale to prevent soil erosion and surface water pollution. To support this participatory approach, the hydrology and erosion model STREAM was used for assessing the impact of a spring stormy event on surface runoff and sediment yield with various management scenarios. The study was carried out in collaboration with an agricultural committee in an area of south-western France where erosive runoff has a major impact on the quality of surface water. Two sites (A and B) were chosen with farmers to discuss ways of reducing total surface runoff and sediment yield at each site. The STREAM model was used to assess surface runoff and sediment yield under current cropping pattern at each site and to evaluate management scenarios including grass strips implementation or changes in cropping patterns within the catchment. The results of STREAM simulations were analysed jointly by farmers and researchers. Moreover, the farmers discussed each scenario in terms of its technical and economical feasibility. STREAM simulations showed that a 40 mm spring rainfall with current cropping patterns led to 3116 m total water runoff and 335 metric tons of sediment yield at site A, and 3249 m and 241 metric tons at site B. Grass strips implementation could reduce runoff for about 40% and sediment yield for about 50% at site A. At site B, grass strips could reduce runoff and sediment yield for more than 50%, but changes in cropping pattern could reduce it almost totally. The simulations led to three main results: (i) grass strips along rivers and ditches prevented soil sediments from entering the surface water but did not reduce soil losses, (ii) crop redistribution within the catchment was as efficient as planting grass strips, and (iii) efficient management of erosive runoff required coordination between all the farmers using the same watershed. This study shown that STREAM model was a useful support for farmers' discussions about how to manage runoff and sediment yield in their fields. ► Runoff and erosion in cultivated catchment are sources of water pollution. ► Farmers have to implement agro-environmental measures to prevent it. ► We test a participatory approach supported by a hydrological model with farmers. ► Organising cropping pattern and planting grass strips are two management options. ► Efficient management at catchment scale requires coordination between farmers.
    Keywords: Erosion ; Runoff ; Agriculture ; Land Management Options ; Participatory Approach ; Modelling ; Agriculture ; Environmental Sciences ; Economics
    ISSN: 0301-4797
    E-ISSN: 1095-8630
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  • 7
    In: Soil Science Society of America Journal, Nov-Dec, 1992, Vol.56(6), p.1898(6)
    Description: The effects of soil water content and successive rainfalls on soil crusting, subsequent runoff and erosion are discussed. Silty clay loam and silt loam surface samples were subjected to successive one-hour rainfalls as water splash, runoff, soil splash and wash materials were collected every five minutes. The influence of initial surface soil water content on aggregate breakdown mechanisms, crust formation, seal processes and subsequent runoff and erosion was ascertained.
    Keywords: Soil Erosion -- Measurement ; Runoff -- Environmental Aspects ; Rain -- Environmental Aspects
    ISSN: 0361-5995
    Source: Cengage Learning, Inc.
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  • 8
    Language: English
    In: Journal of Hydrology, April 2015, Vol.523, pp.409-426
    Description: Soil erosion is a serious threat for cultivated soils on steep slopes under tropical conditions. In Costa Rica, coffee plantations are widespread on such steep slopes in several basins used for hydroelectric generation, which are affected by soil erosion and sedimentation in dam reservoirs. For this study, surface runoff and soil loss rate were measured during three years on large experimental plots installed within a coffee field on a steep slope (60% average). The time interval for rainfall and runoff measurements was 5 min. A simple infiltration model presented by Diskin and Nazimov (1995) was used to estimate runoff during a rainfall event showing the relevance of initial soil water content in order to estimate runoff base on rainfall intensity variations. Three complementary embedded time scales were analyzed: annual–monthly, event and intra-event. The rainy seasons included 581 rainfall events giving a total depth of 2206, 1778 and 2220 mm in 2011, 2012 and 2013 respectively. Total runoff was 103 ± 55, 54 ± 14 and 33 ± 6.4 mm in 2011, 2012 and 2013 respectively. Annual average sediment concentration was about 1.3 ± 0.3 g l with reduced temporal variations between years or rainfall events. The total soil loss was 1686 ± 784, 914 ± 306 and 575 ± 140 kg ha for 2011, 2012 and 2013 respectively. Around 60% of rainfall and 90% of runoff and soil loss respectively came from the August–October period and more than half of it from October. Total rainfall event and soil water content explained most of surface runoff and soil loss dynamics at three time scales analyzed. Inherited soil water storage from previous year played an important role on the relationship between rainfall and runoff dynamics the following year. Soil and coffee coverage did not have a significant effect on runoff and soil loss variability due to permanently good soil coverage (even in the rainy season). This good coverage over the rainy season prevented crust development. The presence of old micro-terraces helped to reduce runoff and sediment loss. The Diskin and Nazimov model demonstrated that a combination of rainfall intensity and soil water content dynamics on an intra-event scale explained better the differences observed in runoff and soil loss on an inter-event scale. Runoff at intra event scale had high and low runoff moments depending on rainfall intensity and superficial soil layer water status and saturation of deeper layers under long rainfall events.
    Keywords: Steep Slope ; Soil Erosion ; Runoff ; Coffee ; Plot Scale ; Infiltration ; Geography
    ISSN: 0022-1694
    E-ISSN: 1879-2707
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  • 9
    Language: English
    In: Journal of Environmental Management, 01 March 2015, Vol.150, pp.57-68
    Description: Global climate and land use changes could strongly affect soil erosion and the capability of soils to sustain agriculture and in turn impact regional or global food security. The objective of our study was to develop a method to assess soil sustainability to erosion under changes in land use and climate. The method was applied in a typical mixed Mediterranean landscape in a wine-growing watershed (75 km ) within the Languedoc region (La Peyne, France) for two periods: a first period with the current climate and land use and a second period with the climate and land use scenarios at the end of the twenty-first century. The Intergovernmental Panel on Climate Change A1B future rainfall scenarios from the Météo France General circulation model was coupled with four contrasting land use change scenarios that were designed using a spatially-explicit land use change model. Mean annual erosion rate was estimated with an expert-based soil erosion model. Soil life expectancy was assessed using soil depth. Soil erosion rate and soil life expectancy were combined into a sustainability index. The median simulated soil erosion rate for the current period was 3.5 t/ha/year and the soil life expectancy was 273 years, showing a low sustainability of soils. For the future period with the same land use distribution, the median simulated soil erosion rate was 4.2 t/ha/year and the soil life expectancy was 249 years. The results show that soil erosion rate and soil life expectancy are more sensitive to changes in land use than to changes in precipitation. Among the scenarios tested, institution of a mandatory grass cover in vineyards seems to be an efficient means of significantly improving soil sustainability, both in terms of decreased soil erosion rates and increased soil life expectancies.
    Keywords: Climate Change ; Soil Erosion ; Land Use Change ; Modeling ; Soil Sustainability ; Environmental Sciences ; Economics
    ISSN: 0301-4797
    E-ISSN: 1095-8630
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  • 10
    Language: English
    In: Agriculture, Ecosystems and Environment, 2011, Vol.144(1), pp.382-389
    Description: The objective of this study was to compare the effects of repeated field applications of three urban compost amendments and one farmyard manure amendment over a 9-year period on aggregate stability in a silty loam soil initially characterized by low clay and initial organic matter contents and poor aggregate stability. Three different aggregate stability tests with increasing disruptive intensities (fast wetting 〉 mechanical breakdown 〉 slow wetting tests) and different disaggregation mechanisms, were used. All of the amendments, which were applied at approximately 4 Mg C ha(-1) every other year, increased the organic carbon content and improved the stability of the aggregates against the disruptive action of water, as determined by each of the stability tests. However, the year-to-year variations in the aggregate stability that related to factors other than the organic inputs were greater than the cumulative increase in aggregate stability relative to the control. The positive effects of the tested amendments on aggregate stability were linked to their contribution to soil organic C contents (r=0.54 for the fast wetting test and r = 0.41-0.42 for the mechanical breakdown and slow wetting tests; p 〈 0.05). The addition of urban composts had a larger positive effect on aggregate stability than farmyard manure at the majority of sampling dates. The addition of biodegradable immature compost, such as municipal solid waste (MSW), improved the aggregate stability through an enhanced resistance to slaking. The addition of mature composts, such as the co-compost of sewage sludge and green wastes (GWS) or biowaste compost (BW), improved the aggregate stability by increasing interparticular cohesion. The MSW compost was the most efficient in improving aggregate stability during the first 6 years of the experiment (average improvements of +22%, +5% and +28% in the fast wetting, mechanical breakdown and slow wetting tests, respectively, compared to the control treatment); this result was likely due to the larger labile organic pool of the MSW compost that was highly effective at stimulating soil microbial activity. After the first 6 years, the two other composts, GWS and BW, became more efficient (average improvements of +25%, +61% and +33% in the fast wetting, mechanical breakdown and slow wetting tests, respectively, compared to the control treatment), which was probably linked to the greater increase in soil organic C contents. Therefore, the application of urban compost to silty soil that is susceptible to water erosion was effective at improving aggregate stability and thus could be used to enhance the resistance of soil to water erosion.
    Keywords: Life Sciences ; Ecology, Environment ; Compost ; Manure ; Long-Term Field Experiment ; Aggregate Stability ; Carbon Content ; Cohesion  ; Expérimentation de Longue Durée ; Stabilité ; Agriculture ; Environmental Sciences
    ISSN: 0167-8809
    E-ISSN: 1873-2305
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