Several methods were employed in the Ardennian rivers (Belgium) to determine the depth of the active layer mobilized during floods and to evaluate the bedload discharge associated with these events. The use of scour chains has shown that the depth of the active layer is systematically less than the b‐axis of the average particle size (D50) of the elements which compose the surface layer of the riffles. This indicates that only a partial transport exists during low magnitude floods. The bedload discharge has been evaluated by combining data obtained using the scour chains technique and the distance covered by tracers. Quantities of sediment transported during frequent floods are relatively low (0·02 t km–2) due to the armour layer which protects the subsurface material. These low values are also related to the fact that the distance calculated for mobilized bedload only applies to tracers fitted with PIT (passive integrated transponder)‐tags (diameter > 20 mm), whereas part of the bedload discharge is composed of sand and fine gravel transported over greater distances than the pebbles. The break‐up of the armour layer was observed only once, for a decennial discharge. During this event, the bedload discharge increased considerably (2 t km–2). The use of sediment traps, data from dredging and a Helley–Smith sampler confirm the low bedload transport in Ardennian rivers in comparison to the bedload transport in other geomorphological contexts. This difference is explained by the presence of an armoured layer but also by the imbricated structures of flat bed elements which increase the resistance to the flow. Finally, the use of the old iron industry wastes allowed to quantify the thickness of the bed reworked over the past centuries. In the Lembrée River, the river‐bed contains slag elements up to a depth of about 50 cm, indicating that exceptional floods may rework the bed to a considerable depth. Copyright © 2012 John Wiley & Sons, Ltd.

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a b s t r a c t a r t i c l e i n f oA good evaluation of the Quaternary uplift of the Rhenish shield is a key element for the understanding of the Cenozoic geodynamics of the western European platform in front of the alpine arc. Previous maps of the massif uplift relied on fluvial incision data since the time of the rivers' Younger Main Terrace to infer a maximum post-0.73 Ma uplift of~290 m in the SE Eifel. Here, we propose a new interpretation of the incision data of the intra-massif streams, where anomalies in the terrace profiles would result from knickpoint retreat in the tributaries of the main rivers rather than from tectonic deformation. We also use additional geomorphological data referring to (1) deformed Tertiary planation surfaces, (2) the history of stream piracy that severely affected the Meuse basin in the last 1 Ma, and (3) incision data outside the Rhenish shield. A new map of the post-0.73 Ma uplift of the Rhenish shield is drawn on the basis of this enlarged dataset. It reduces the maximum amount of tectonic uplift in the SE Eifel to~140 m and modifies the general shape of the uplift, namely straightening its E-W profile. It is also suggested that an uplift wave migrated across the massif, starting from its southern margin in the early Pleistocene and currently showing the highest intensity of uplift in the northern Ardennes and Eifel. These features seem to favour an uplift mechanism chiefly related to lithospheric folding and minimize the impact on the topography of a more local Eifel plume.

Due to its cost-effectiveness and repeatability of observations, high resolution optical satellite remote sensing has become a major technology for land use and land cover mapping. However, inventory compilers for the Land Use, Land Use Change, and Forestry (LULUCF) sector are still mostly relying on annual census and periodic surveys for such inventories. This study proposes a new approach based on per-pixel supervised classification using Sentinel-2 imagery from 2016 for mapping greenhouse gas emissions and removals associated with the LULUCF sector in Wallonia, Belgium. The Land Use/Cover Area frame statistical Survey (LUCAS) of 2015 was used as training data and reference data to validate the map produced. Then, we investigated the performance of four widely used classifiers (maximum likelihood, random forest, k-nearest neighbor, and minimum distance) on different training sample sizes. We also studied the use of the rich spectral information of Sentinel-2 data as well as single-date and multitemporal classification. Our study illustrates how open source data can be effectively used for land use and land cover classification. This classification, based on Sentinel-2 and LUCAS, offers new opportunities for LULUCF inventory of greenhouse gas on a European scale.

RésuméL’analyse du transport de la charge de fond de plusieurs rivières du massif ardennais (Belgique) par différentes techniques de marquage de galets (peinture, charge métallique, émetteurs radio) a permis d’identifier le débit critique où débute le charriage. Pour les rivières les plus importantes (plus de 500 km2), la mise en mouvement se produit à des débits légèrement inférieurs au débit à plein bord (0,7 à 1 Qb), débits qui se présentent en moyenne 5 à 11 jours par an. Pour les rivières de taille intermédiaire (entre 100 et 500 km2), le charriage débute à un débit avoisinant 0,5 fois le débit à plein bord, avec une récurrence de 0,3 an et une durée variant entre 8 et 12 jours par an. Pour les rivières de dimension modeste (moins de 100 km2), la mise en mouvement se produit à des débits compris entre 0,5 et 0,8 Qb, mais leur récurrence est relativement faible et le charriage peut se produire jusqu’à 20 jours par an. Par ailleurs, le transport solide a été évalué à l’aide de pièges à sédiments dans les rivières de petite dimension (moins de 10 km2) ; il est relativement peu important dans les bassins forestiers (0,5 t/km2/an), en raison de la multiplication des embâcles végétaux qui accroissent la rugosité du lit. Pour les rivières plus importantes, le transport solide a été estimé entre 0,4 et 2,5 t/km2/an grâce à l’analyse des quantités curées systématiquement aux mêmes sites et à la réalisation de levés topographiques de contrôle. Nous avons ensuite analysé l’évolution des quantités charriées en fonction de la puissance spécifique à plein bord développée par ces rivières. La relation établie sur la base de ces données a permis de mettre en évidence le déficit en sédiments de certaines rivières ainsi que plusieurs facteurs influençant le charriage.