References of "Bielders, Charles"
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See detailGISER - Gestion intégrée Sol Erosion Ruissellement - rapport d'activités année 3
Bielders, Charles; Degré, Aurore ULg; Demarcin, Pierre ULg et al

Report (2014)

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See detailWhich measurement strategies to improve spatial erosion and deposition patterns modelling?
Pineux, Nathalie ULg; Maugnard, Alexandre; Swerts, Gilles ULg et al

in Geophysical Research Abstracts (2014), 16

Validation of the erosion models requires field data. To date, many authors continue to highlight the paucity of accurate field observations and long-term enough studies. The fields observations are often ... [more ▼]

Validation of the erosion models requires field data. To date, many authors continue to highlight the paucity of accurate field observations and long-term enough studies. The fields observations are often put aside because these measures are difficult to obtain: weighty experimental devices, climatic dependence, . . . Hence the models are evolving and propose refined calculation procedures including for instance the calculation of landscape evolution. The need of field data therefore increases and new measuring strategies should arise. In the centre of Belgium we choose an agricultural watershed quite representative of the local context. It covers 124 ha of loamy soil with more than 90% of arable land and a weak proportion of forest and artificial lands. The slope ranges between 0 and 9%. Instrumentation on the watershed includes meteorological observations and discharge measurement coupled with water sampling at different outlets. The weather data (radiation, temperature, wind velocity, relative humidity and rainfall) and discharge measurement (comparison between Doppler and pressure sensors) will allow us to model the hydrological behaviour of the catchment. Rainfall readings (tipping buckets) are completed with erosivity readings (disdrometer). Erosivity, together with soil data, land use and agricultural practices observations on field, will be used as entry in the Landsoil model. The sediment samplings at 3 points in the catchment will give an insight of the sediment delivery of 3 subcatchments. The Landsoil model calculates the evolution of the DTM through time. This cannot be compared to measurements at the outlet and requires further data collection. Older elevation data and/or archaeological data are a possible source of information even if their precision remains scarce in our context. 1950’s soil surveys are on the contrary really informative since they detail the horizons depth in a spatial way and can be compared to new observation across the watershed. Coupled with unmanned aerial system, they should allow us to test the model performances and improve our knowledge of the spatial patterns of erosion and deposition. [less ▲]

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See detailUncertainty assessment of ephemeral gully identification, characteristics and topographic threshold when using aerial photographs in agricultural settings
Maugnard, Alexandre; Cordonnier, Hélène; Degré, Aurore ULg et al

in EARTH SURFACE PROCESSES AND LANDFORMS (2014)

Manual digitizing on aerial photographs is still commonly used for characterizing gully erosion over large areas. Even when automated detection procedures are implemented, manual digitizing is frequently ... [more ▼]

Manual digitizing on aerial photographs is still commonly used for characterizing gully erosion over large areas. Even when automated detection procedures are implemented, manual digitizing is frequently being resorted to in order to constitute reference datasets used for training and validation. In both cases, manual digitizing entails some subjective decisions on behalf of the operator, which introduces uncertainty into the resulting datasets. To assess the magnitude of this uncertainty, 11 experienced operators were asked to digitize and classify ephemeral gullies (EGs) on cropland following a standardized methodology. The resulting 11 datasets were compared in terms of number, type and location of EGs. Furthermore, for EGs located on a welldefined runoff flow concentration axis, the slope versus contributing area topographic thresholds required for initiating gully channels were assessed using four thresholding methods, and compared across the 11 datasets. The operators identified 259 different EGs. However, the number (52–139) and sum total length (8.9–23.7 km) of EGs varied widely across operators. Only 34% of the EGs were digitized by more than half of the operators, and 7% were identified by all. Identification of EGs located on a well-defined flow concentration axis proved least subjective. The longer the EG and the more fields the EG crossed, the larger the number of operators that were able to identify it. EGs were also most easily identified when located in sugar beet fields as compared to other crops. EG classification and topographic threshold lines were also found to be strongly operator-dependent. Quantile regression appeared to be one of the most robust thresholding methods. Operator subjectivity when digitizing EGs on orthophotographs introduces uncertainty that should be taken into account in future remote sensing-based studies of EG erosion whenever they rely, in part or in full, on manual photograph interpretation. [less ▲]

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See detailGISER - Gestion intégrée Sol Erosion Ruissellement - rapport d'activités année 2
Pineux, Nathalie ULg; Maugnard, Alexandre; Demarcin, Pierre ULg et al

Report (2013)

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See detailCartographie du risque d’érosion hydrique à l’échelle parcellaire en soutien à la politique agricole wallonne (Belgique)
Maugnard, Alexandre; Bielders, Charles; Bock, Laurent ULg et al

in Étude et Gestion des Sols (2013), 20(2), 127-141

L’érosion hydrique des sols pose le problème de la protection de la ressource « sol » mais également de la prévention des impacts environnementaux et sociétaux qui y sont associés tels que la dégradation ... [more ▼]

L’érosion hydrique des sols pose le problème de la protection de la ressource « sol » mais également de la prévention des impacts environnementaux et sociétaux qui y sont associés tels que la dégradation de la qualité des eaux de surface, l’envasement des retenues d’eau et des bassins d’orage ou encore les inondations boueuses. Afin de cibler au mieux les mesures de lutte anti-érosives, il convient d’identifier les parcelles agricoles les plus à risque d’érosion. Mettant à profit la disponibilité d’importantes bases de données en matière de climat, sol, topographie, parcellaire et occupation du sol, une procédure automatisée de calcul de l’aléa érosion hydrique potentielle à l’échelle parcellaire, adaptée du modèle RUSLE, a été mise au point pour la Wallonie (Belgique). La carte de l’aléa érosion potentielle montre une sensibilité maximale à l’érosion hydrique en Ardenne et Haute-ardenne, en raison du relief accentué et d’une érosivité plus importante des pluies. Pour les principales zones agro-pédologiques de Wallonie, un suivi des principales cultures (céréales d’hiver, mais, betterave, pomme de terre, colza, lin) a également été réalisé, permettant d’estimer le facteur cultural C des principales successions culturales et ainsi l’érosion effective. La prise en compte de l’occupation du sol fait cette fois ressortir un aléa maximal dans les régions (sablo-)limoneuses et le Condroz, en raison des superficies importantes de grandes cultures industrielles. En Ardenne et Haute Ardenne, l’aléa d’érosion effective est faible en raison d’une couverture végétale dominée par les prairies permanentes. Enfin, sur base de la carte numériques des sols de Wallonie, une classification de la vulnérabilité des sols à l’érosion a été établie à partir du volume de sol pouvant être exploité par les racines. La vulnérabilité apparaît élevée sur une majorité du territoire wallon, à l’exception des Régions (sablo-)limoneuses et de la Région jurassique. Un indice d’érosion, calculé comme le rapport de l’érosion potentielle (aléa) sur l’érosion tolérable (vulnérabilité) permet de calculer le risque d’érosion hydrique et, par conséquent, de cibler au mieux les parcelles pour lesquelles l’érosion constitue une menace majeure pour leur valorisation durable. Une gestion appropriée de ces parcelles par un choix judicieux en termes d’occupation du sol (forêt, prairie, rotations culturales) et de pratiques culturales (p.ex., TCSL, inter-cultures) devrait permettre d’y réduire les risques de dégradation des sols par érosion hydrique. [less ▲]

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See detailGISER - Gestion intégrée Sol Erosion Ruissellement - rapport d'activités année 1
Pineux, Nathalie ULg; Maugnard, Alexandre; Demarcin, Pierre ULg et al

Report (2012)

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See detailConvention de recherche d'intérêt générale Gestion Intégrée Sol Erosion Ruissellement - Rapport final
Colard, François ULg; Cordonnier, Hélène; Feltz, Nicolas et al

Report (2011)

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See detailDune rehabilitation using a mechanical fixation technique : effect on sediment fluxes and on the quantitative and qualitative recovery of the herbaceous groundcover.
Tidjani, Adamou Didier; Bielders, Charles; Ambouta, Karimou et al

in Geophysical Research Abstracts (2011)

This research shows the potentialities of mechanical windbreaks to rapidly stabilize dunes in the north sahelian area (Niger) thanks to the recovery of herbaceous groundcover.

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See detailPerspectives - Quel avenir pour les cuvettes oasiennes dans le Niger oriental ?
Tychon, Bernard ULg; Ambouta, Karimou Jean-Marie; Ozer, André ULg et al

in Geo-Eco-Trop (2009), 33

The oasian interdunal depressions of eastern Niger are areas of life providing refuge to agro-pastoral activities in a generally hostile environment. The inter-university Targeted Program (ITP) funded by ... [more ▼]

The oasian interdunal depressions of eastern Niger are areas of life providing refuge to agro-pastoral activities in a generally hostile environment. The inter-university Targeted Program (ITP) funded by the Coopération Universitaire au Développement (CUD) called "Invasion of circular lowlands (cuvettes) of south-eastern Niger by aeolian deposits: processes, impacts and means of struggle" has studied the problem of silting of these refuge areas and proposed technical means, including physical and biological fixation of dunes that threaten the villages and interdunal depressions. Given the increasing human pressure and the present climate context that seems to move towards dryer conditions, environmental degradation of the study area should be investigated more broadly. Set up of strategies to allow people to adapt their conditions of life to an environment increasingly rough should also be considered. This paper presents some possible options for adaptation and examines the question of the very future of these interdunal depressions. [less ▲]

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