References of "Degré, Aurore"
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See detailÉVOLUTION DE LA TENEUR EN EAU LE LONG D’UNE TOPOSEQUENCE FORESTIERE ARGILO-LIMONEUSE
Deraedt, Deborah ULiege; Colinet, Gilles ULiege; Degré, Aurore ULiege

in Milieux Poreux et Transferts Hydriques (in press)

For the hydrological modeling of forested watersheds, the understanding of the forest hydrodynamic is essential. This study focusses on the hydrology of a Belgian forested plot with high stoniness and ... [more ▼]

For the hydrological modeling of forested watersheds, the understanding of the forest hydrodynamic is essential. This study focusses on the hydrology of a Belgian forested plot with high stoniness and steep slope. The soil water content is monitored at several positions on the toposequence and at different depth. During rain events, peak in soil water content are observed in different depth depending on the position along the toposequence. [less ▲]

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See detailDynamic of soil drying close to saturation: What can we learn from a comparison between X-ray computed microtomography and the evaporation method?
Parvin, Nargish ULiege; Beckers, Eléonore ULiege; Plougonven, Erwan ULiege et al

in Geoderma (2017), 302

The soil water retention curve (SWRC) is a unique relationship between water content and soil water potential. SWRC in near saturation gives the dimension of soil macroporosity which plays an important ... [more ▼]

The soil water retention curve (SWRC) is a unique relationship between water content and soil water potential. SWRC in near saturation gives the dimension of soil macroporosity which plays an important role in water translocation into soil. Thus, the accurate measurement of SWRC is crucial. The aim of this study is to compare SWRC obtained through two different methods: X-ray computed microtomography (X-ray CT) and evaporation method by HYPROP device. Three different depths (0–10, 25–30 and 45–60 cm) are considered for soil sampling. The results showed significant differences in SWRC between the techniques. The SWRC from X-ray CT showed more volumetric water content at 25–30 cm (0.044) and 45–60 cm (0.024) than evaporation at saturation (0 kPa) in cases where the macroporosity was higher. Macropores may have connections with neighbouring pores of smaller sizes. Hence we assume that these pores can be observed through X-ray CT but cannot be evaluated by evaporation. As macropores with narrow opening do not evaporate at very low tension. These pores therefore got empty at relatively higher tension. Consequently, SWRC near saturation appeared rather flatter with the evaporation method where the X-ray CT presented deviation. Accordingly, interpretation of macro pores from SWRC through evaporation method would give comparatively smaller volume of macropores than they really are. Pore morphology and other hydraulic functions of soil, for example, mean connection surface of pores, hydraulic conductivity, and the efficiency of water conducting macropores also support the X-ray CT findings. [less ▲]

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See detailEffect of different tillage systems on aggregate structure and inner distribution of organic carbon
Gao, Lili ULiege; Beckers, Eléonore ULiege; Liang, Guopeng et al

in Geoderma (2017), 288

Tillage is a common agricultural practice affecting soil structure and biogeochemistry. Pore network geometries are crucial to oxygen concentration, gas diffusivity, water location and water movement ... [more ▼]

Tillage is a common agricultural practice affecting soil structure and biogeochemistry. Pore network geometries are crucial to oxygen concentration, gas diffusivity, water location and water movement. Soil aggregates, 4–6 mm in diameter and collected from silty loam in Belgium and sandy loam in China, were scanned using a micro-computed tomography scanner. Images with a pixel size of 6.9 μm were then processed with ImageJ software for pore network analysis. The treatments were no tillage (C-NT) and conventional tillage (C-CT) in China, and shallow tillage (G-ST) and conventional tillage (G-CT) in Belgium. The results showed that aggregates in conservational tillage (G-ST and C-NT) had numerous connected pores compared with conventional tillage (G-CT and C-CT). The Euler number (Ev) was significantly lower and visible total porosity and surface area (SA) were significantly higher in conservational tillage (G-ST and C-NT) than in conventional tillage (G-CT and C-CT) in both studied locations. The predominant size of pores was significantly higher in conservational tillage (G-ST and C-NT) than in conventional tillage (G-CT and C-CT) (> 150 μm vs 90–120 μm). Pore location within the aggregates also showed differences, with porosity being evenly distributed in the aggregates under conventional tillage (G-CT and C-CT). Under conservational tillage (G-ST and C-NT), the aggregates were heterogeneous, showing higher porosity at the center of the aggregates. There was a higher soil organic carbon (SOC) content in the external layer than in the internal layer in conservational tillage in Belgium (G-ST). In no tillage in China (C-NT), the SOC in the external and internal layers, however, showed similar results. Overall, conventional tillage (G-CT and C-CT) reduced the proportion of the largest pores within soil aggregates, whereas there was no significant relationship between pore morphologies and SOC content. Further investigation is required to measure the active and slow carbon pool distribution in the different layers and under different tillage practices. [less ▲]

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See detailConvention Région wallonne et HGE-ULg Caractérisation complémentaire des masses d’eau dont le bon état dépend d’interactions entre les eaux de surface et les eaux souterraines - Délivrable D1.8 Rapport final
Brouyère, Serge ULiege; Briers, Pierre ULiege; Descy, Jean-Pierre et al

Report (2017)

Mechanisms of interactions between groundwater bodies and rivers whose status and anthropogenic use can be detrimental from a quantitative and qualitative point of view to one or the other of these two ... [more ▼]

Mechanisms of interactions between groundwater bodies and rivers whose status and anthropogenic use can be detrimental from a quantitative and qualitative point of view to one or the other of these two compartments of the water cycle. In addition, contamination of groundwater by nitrate remains relevant. Based on these observations, a study financed by the Public Service of Wallonia was carried out over a period of 39 months to investigate (1) the direction, importance and dynamics of water exchange between groundwater and rivers at the scale of a river section; (2) the impact of these interactions on river baseflows and the river ecological status as a function of groundwater withdrawal and recharge at the catchment scale; (3) mechanisms and timing of transfer and abatement of pollutants (nitrate) between groundwater and surface waters at the watershed scale. The consequences of these mechanisms on the medium- and long-term evolution of groundwater and surface water quality were to be determined. To achieve this, the project relied on the implementation of a series of field investigations essentially focused on the interfaces between surface water and groundwater compartments (soil and unsaturated zone and water-table interface), while acquiring additional information on groundwater. The investigations carried out in the watersheds of the upstream Hoyoux and Triffoy watershed in the Condroz region aimed to provide 6 specific responses to water quantity and quality issued associated with groundwater – surface water interactions in the selected basins and generic responses in the form of new knowledge concerning the mechanisms of recharge and groundwater - river exchanges, concerning the evolution of nitrate concentrations in watersheds, data and measurements for the parameterization of models, and water resources management tools in the form of quantitative and qualitative indicators for groundwater - surface water interactions. [less ▲]

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See detailDétection de l’érosion dans un bassin versant agricole par comparaison d’images multidates acquises par drone
Lisein, Jonahtan; Pineux, Nathalie; Pierrot-Deseilligny, Marc et al

in Revue française de Photogrammétrie et de Télédétection (2017), 213-214(janvier-avril), 133-141

L’émergence des drones comme outils de cartographie rapide, de par leur capacité à répondre à des besoins très spécifiques, offre de nombreuses opportunités aux scientifiques. Par ailleurs, les récentes ... [more ▼]

L’émergence des drones comme outils de cartographie rapide, de par leur capacité à répondre à des besoins très spécifiques, offre de nombreuses opportunités aux scientifiques. Par ailleurs, les récentes évolutions des techniques de photogrammétrie et de vision par ordinateur permettent, à partir de prises de vues aériennes stéréoscopiques, de fournir aux géomorphologues et aux hydrologues des données topographiques à haute résolution (Tarolli, 2014). En effet, les algorithmes d’orientation externe (structure from motion en anglais, Snavely et al. (2008)) permettent la détermination automatique de la position et de l’orientation des prises de vue d’une collection d’images se recouvrant. La corrélation dense automatique permet ensuite, depuis un bloc d’images orientées, de modéliser finement le relief. L’utilisation en géomorphologie de drones pour la modélisation du relief en est encore à ses premiers souffles, mais montre un potentiel très intéressant. La précision des mesures photogrammétriques rivalise en effet avec les relevés LiDAR, pour un coût d’acquisition significativement moins élevé. Cette recherche se focalise sur deux objectifs. Le premier est de déterminer si la précision des mesures photogrammétriques issues d’images acquises avec un mini-drone permet la détection de changement de relief très fin via la comparaison d’acquisitions multi-dates. Le deuxième objectif, plus spécifique, est de déterminer la manière la plus optimale de paramétrer la compensation par faisceaux avec points d’appui au sein de la suite photogrammétrique open-source MICMAC. [less ▲]

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See detailDiachronical soil surveys: a way to quantify long term diffuse erosion?
Pineux, Nathalie ULiege; Michel, Brieuc ULiege; Legrain, Xavier ULiege et al

in Geoderma Regional (2017), (10), 102-114

Because of high inter-annual variability, representative soil erosion measurements are best carried out over time scales of a few decades. In this paper, a novel approach was tested that relies on ... [more ▼]

Because of high inter-annual variability, representative soil erosion measurements are best carried out over time scales of a few decades. In this paper, a novel approach was tested that relies on diachronic, high-resolution soil mapping. For this purpose, a 116-ha, cropland-dominated watershed was selected in central Belgium. A first augering soil survey was carried out in 1956, with a density of 1.8 observation points /ha. A second survey was carried out in 2015 with a density of 4.5 observations/ha. The results were interpreted in terms of changes in depth of transitions between successive horizons. The results indicate that a great proportion of the soils classified as non-eroded in 1956 were strongly eroded in 2015. Strongly eroded soils represented 52% of the watershed area in 2015 but only 8% in 1956. Some colluvial areas have been subjected to erosion and then covered again by colluvium over the last 60 years. Only the flatter areas close to the watershed boundary appear to remain in the “non eroded soils or soil subject to weak erosion” class. A mean net erosion rate of 37 t/ha.yr is computed within the watershed with this method. The diachronic comparison of the pedological maps over a 60-year time interval in a context of intensive farming is a potential source of information for the calibration of landscape evolution spatial modelling. This method joins the few ones allowing a quantitative spatialization of erosion and deposition phenomena at the catchment scale. [less ▲]

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See detailArtificial surfaces characteristics and sediment connectivity explain muddy flood hazard in Wallonia
de Walque, Baptiste; Degré, Aurore ULiege; Maugnard, Alexandre et al

in Catena (2017), 158

Over the last decades, the off-site damages caused by muddy floods have been of growing concern throughout much of Western Europe, and particularly in Wallonia (Belgium). A reliable identification of ... [more ▼]

Over the last decades, the off-site damages caused by muddy floods have been of growing concern throughout much of Western Europe, and particularly in Wallonia (Belgium). A reliable identification of locations with a high muddy flood hazard is thus a key issue in this context. The main objective of this study was therefore to build and evaluate a muddy flood hazard prediction model in order to assess the probability of occurrence of muddy floods at any specific location. A logistic regression approach was used to explain muddy flood occurrence using a database of 442 muddy flood-affected sites and an equal number of homologous non-flooded sites. Explanatory variables were related to geomorphology, land use, sediment production and sediment connectivity in the contributing area. The prediction quality of the model was then validated using an independent dataset composed of 48 pairs of flooded and non-flooded sites. The best muddy flood hazard assessment model required a total of 5 explanatory variables as inputs: the mean slope, a sediment connectivity index, as well as the proportion, spatial aggregation and proximity to the outlet of artificial surfaces. The model resulted in a prediction quality of 76% (calibration dataset) and 81% (validation dataset). Including the characteristics of artificial surfaces substantially improved the model quality (p-values from 10−11 to 10−5). All three variables related to artificial surfaces showed negative correlations with the muddy flood hazard. The proportion of cropland was not included in the final model, but this variable was strongly inversely correlated to the proportion of artificial surfaces. Besides the characteristics of artificial surfaces, sediment connectivity also showed significant explanatory power (p-value of 10−12). A positive correlation between sediment connectivity and muddy flood hazard was found. Future muddy flood hazard models should therefore include both artificial surfaces characteristics and sediment connectivity-related information. Given the good prediction quality, the developed statistical model could be used as a reliable tool to prioritize sites at risk of muddy floods in order to install mitigation measures. [less ▲]

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See detailComparison of soil water potential sensors: a drying experiment
Degré, Aurore ULiege; van der Ploeg, Martine; Caldwell, Todd et al

in Vadose Zone Journal (2017), 16(4),

The soil water retention curve (WRC) plays a major role in soil’s hydrodynamic behaviour. Many measurement techniques are currently available for determining WRC in the laboratory. Direct in situ WRC can ... [more ▼]

The soil water retention curve (WRC) plays a major role in soil’s hydrodynamic behaviour. Many measurement techniques are currently available for determining WRC in the laboratory. Direct in situ WRC can be obtained from simultaneous soil moisture and water potential readings covering a wide tension range, from saturation to wilting point. There are many widely used soil moisture probes. Whereas near-saturation tension can be measured using water-filled tensiometers, wider ranges of water potential require new, more expensive and less widely used probes. This paper reports on a comparison of three types of soil water potential sensors that could allow us to measure water potential in the field, with a range relevant to water uptake by plants. Polymer tensiometers (POTs), MPS-2 probes and pF-meters were compared, in a controlled drying experiment. The study showed that the POTs and MPS-2 probes had good reliability in their respective range. Combined with a soil moisture probe, these two sensors can provide observed WRCs. The pF-meters below -30 kPa were inaccurate and their response was sensitive to measurement interval, with greater estimated suction at shorter measurement intervals. Recommendations are provided for future tests. In situ-WRC can provide supplementary information, particularly with regard to its spatial and temporal variability. It could also improve the results of other measurement techniques, such as geophysical observations. [less ▲]

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See detailEffects of the soil pore network architecture on the soil’s physical functionnalities
Smet, Sarah ULiege; Beckers, Eléonore ULiege; Léonard, Angélique ULiege et al

in Geophysical Research Abstracts (2017), 19

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See detailX-ray µCT: how soil pore space description can be altered by image processing
Smet, Sarah ULiege; Plougonven, Erwan ULiege; Léonard, Angélique ULiege et al

in Vadose Zone Journal (2017)

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See detailCan DEM time series produced by UAV be used to quantify diffuse erosion in an agricultural watershed?
Pineux, Nathalie ULiege; Lisein, Jonathan ULiege; Swerts, Gilles ULiege et al

in Geomorphology (2017), 280

Erosion and deposition modelling should rely on field data. Currently these data are seldom available at large spatial scales and/or at high spatial resolution. In addition, conventional erosion ... [more ▼]

Erosion and deposition modelling should rely on field data. Currently these data are seldom available at large spatial scales and/or at high spatial resolution. In addition, conventional erosion monitoring approaches are labour intensive and costly. This calls for the development of new approaches for field erosion data acquisition. As a result of rapid technological developments and low cost, unmanned aerial vehicles (UAV) have recently become an attractive means of generating high resolution digital elevation models (DEMs). The use of UAV to observe and quantify gully erosion is now widely established. However, in some agro-pedological contexts, soil erosion results from multiple processes, including sheet and rill erosion, tillage erosion and erosion due to harvest of root crops. These diffuse erosion processes often represent a particular challenge because of the limited elevation changes they induce. In this study,we propose to assess the reliability and development perspectives of UAV to locate and quantify erosion and deposition in a context of an agricultural watershed with silt loam soils and a smooth relief. Erosion and deposition rates derived from high resolution DEM time series are compared to field measurements. The UAV technique demonstrates a high level of flexibility and can be used, for instance, after a major erosive event. It delivers a very high resolution DEM(pixel size: 6 cm) which allows us to compute high resolution runoff pathways. This could enable us to precisely locate runoff management practices such as fascines. Furthermore, the DEMs can be used diachronically to extract elevation differences before and after a strongly erosive rainfall and be validated by field measurements. While the analysis for this study was carried out over 2 years, we observed a tendency along the slope from erosion to deposition. Erosion and deposition patterns detected at the watershed scale are also promising. Nevertheless, further development in the processing workflow of UAV data is required in order to make this technique accurate and robust enough for detecting sediment movements in an agricultural watershed affected by diffuse erosion. This area of investigation holdsmuch potential as the images processing is relatively new and expanding. [less ▲]

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See detailTraining engineers to meet the challenges of a changing world: how a competency framework improves teaching programs and team cohesion
Degré, Aurore ULiege; Colaux, Catherine ULiege

in Mazijn, Bernard (Ed.) 8th Conference on Education engineering for sustainable development (2016, September 05)

The competency framework is a complex and time-consuming exercise seen by most teachers as an administrative process. When applied, however, it can be a powerful tool for adapting curricula for engineers ... [more ▼]

The competency framework is a complex and time-consuming exercise seen by most teachers as an administrative process. When applied, however, it can be a powerful tool for adapting curricula for engineers to meet the emerging needs of society, including training in sustainable development. This paper looks at how to use the competency framework to generate a tool for bringing teachers together around shared objectives, helping students build their career paths and improving communication with the ‘outside world’. This approach, largely inspired by the Tardif approach, is being used for the Bioengineering Masters Degree in Environmental Sciences and Technology at the Gembloux Agro-Bio Tech Faculty, University of Liège, Belgium. The approach has allowed the teaching staff to build a common educational project aimed at enabling bioengineers to meet the needs of society [less ▲]

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See detailCharacterization of stony soils' hydraulic conductivity using laboratory and numerical experiments
Beckers, Eléonore ULiege; Pichault, Mathieu; Pansak, Wanwisa et al

in SOIL (2016), 2

Determining soil hydraulic properties is of major concern in various fields of study. Although stony soils are widespread across the globe, most studies deal with gravel-free soils, so that the literature ... [more ▼]

Determining soil hydraulic properties is of major concern in various fields of study. Although stony soils are widespread across the globe, most studies deal with gravel-free soils, so that the literature describing the impact of stones on the hydraulic conductivity of a soil is still rather scarce. Most frequently, models characterizing the saturated hydraulic conductivity of stony soils assume that the only effect of rock fragments is to reduce the volume available for water flow, and therefore they predict a decrease in hydraulic conductivity with an increasing stoniness. The objective of this study is to assess the effect of rock fragments on the saturated and unsaturated hydraulic conductivity. This was done by means of laboratory experiments and numerical simulations involving different amounts and types of coarse fragments. We compared our results with values predicted by the aforementioned predictive models. Our study suggests that it might be ill-founded to consider that stones only reduce the volume available for water flow. We pointed out several factors of the saturated hydraulic conductivity of stony soils that are not considered by these models. On the one hand, the shape and the size of inclusions may substantially affect the hydraulic conductivity. On the other hand, laboratory experiments show that an increasing stone content can counteract and even overcome the effect of a reduced volume in some cases: we observed an increase in saturated hydraulic conductivity with volume of inclusions. These differences are mainly important near to saturation. However, comparison of results from predictive models and our experiments in unsaturated conditions shows that models and data agree on a decrease in hydraulic conductivity with stone content, even though the experimental conditions did not allow testing for stone contents higher than 20 %. [less ▲]

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See detailGiser: Gestion intégrée sol-érosion-ruissellement - Rapport d'activités 2015-2016
Bielders, Charles; Degré, Aurore ULiege; Demarcin, Pierre ULiege et al

Report (2016)

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See detailSoil-specific calibration of capacitance sensors considering clay content and bulk density
Parvin, Nargish ULiege; Degré, Aurore ULiege

in Australian Journal of Soil Research (2016)

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See detailDélivrable D4.2. Modélisation agro-hydrologique
Sohier, Catherine ULiege; Degré, Aurore ULiege

Report (2016)

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