A fragmentary nerineoid gastropod collected from the Maasvlakte 2 beach may be identified as Ptygmatis cf. bruntrutana (Thurmann, 1832). Probably originating from Upper Jurassic strata in north-eastern France, it must have been transported here by a forerunner of the River Meuse (Maas).

Despite increasing research into changes in the discharge of the River Meuse, estimates of the river’s sediment yield are less forthcoming. Three published studies (in 1883, 1982, and 1987) have estimated suspended sediment yield at the Belgian-Dutch border; the latter two studies surmise that this increased substantially between the late 19th and 20th Centuries. In this paper a more recent and longer time-series of observed discharge and suspended sediment data (1995 – 2005) is used to estimate mean annual suspended sediment yield (ca. 386,000 Mg.a−1), and the results of the previous studies are revisited. New insights suggest that those studies do not in themselves provide evidence of increased sediment yield: the higher estimates in the late 20th Century could equally be due to interannual variability or methodological differences. Furthermore, there has been no significant increase in rainfall erosivity between the late 19th and 20th Centuries, and the effect of land use change over that time would have been to cause a decrease in suspended sediment yield, rather than an increase.

The fluvial history of the northern Lower Rhine Embayment shows interplay of three main river systems: Rhine, Meuse and smaller rivers draining the central and northern part of Belgium.

The Pliocene and Early Pleistocene (pre-)Rhine and Meuse river systems had their conjunction in the southern part of the Roer Valley Graben between Aachen and Jülich. Despite slight differences in the heavy-mineral assemblages the lithological composition of the Pliocene deposits of the three river systems shows close resemblance and therefore they cannot be mapped separately. However, due to a marked change of the petrographical composition the Upper Pliocene and Lower Pleistocene deposits of the Rhine are easily recognised and as a result Rhine and Meuse deposits can be mapped separately upstream of their confluence.

The Lower Pleistocene deposits of Rhine, Meuse and the Belgian rivers show a clear interrelationship. They are bounded by two regional well-mapable unconformities and are preserved in from west to east changing lithostratigraphical sequences. Revision of the lithostratigraphical schemes in Germany and the Netherlands and the better defined lithostratigraphical position of Meuse deposits in Germany now strongly constrain the correlation of the various fluvial deposits. As a result existing reconstructions of the fluvial deposition and tectonic history of the southern Roer Valley Graben can be evaluated and re-adjusted.

It is concluded that the main course of the Meuse was aligned through the so-called East Meuse valley during the larger part of the Early Pleistocene. Available pollen data do not conflict with this conclusion. At the same time the Rhine ceased to enter the southern part of the Roer Valley Graben. Instead, the Meuse accumulated here a series of deposits derived from the East-Meuse valley. Simultaneously, the Belgian rivers filled available accommodation space in the Roer Valley Graben of the southern Netherlands. The conclusions are based primarily on the revised lithostratigraphical framework. In general they simplify the picture of fluvial and tectonic behaviour of the area.

Using marine planation surfaces, fluvial terraces and a digital terrain model, the amount of eroded rock volume versus time for the Meuse catchment has been computed. A comparison of the amount of eroded volume with the volume of sediment preserved in the Roer Valley Rift System shows that 12% of the eroded volume is trapped in this rift. The neotectonic uplift evolution of the Ardennes is inferred from the incision history of the Meuse River system and compared to the subsidence characteristics of the Roer Valley Rift System. Both areas are characterized by an early Middle Pleistocene uplift event.

This paper aims to provide a synthesis and update concerning the fluvial terraces of the rivers flowing from the Vosges Massif (Moselle and palaeo Upper-Moselle-Meuse, Meurthe, Sarre). The terraces of these rivers are especially well-developed in the marly depressions of the Eastern Paris Basin, justifying an extensive field mapping expedition. The main rivers exhibit terrace staircases with 8 to 13 stepped terrace steps within 100m of the present valley floor. The fluvial sediments mainly originate from the Vosges Massif (crystalline basement and Permo-Triassic sandstones and conglomerates). Another peculiarity of the study area is the presence of several palaeovalleys, typically related to fluvial capture events which occurred to the detriment of the River Meuse. Many palaeomeanders have also been recognised in the Paris Basin (Meuse catchment), and the Rhenish Massif (Moselle and Sarre valleys). Despite some similarities, palaeoenvironmental reconstructions provide evidence for the terrace staircases being distinct from one valley / section of valley to another. These differences are related to the morphostructural framework and to the climate forcing (presence/absence of glaciers in the upper catchment of the rivers). The chronological framework suggests that the terrace sequences and the main capture events may be older than previously thought.

La structure et l'évolution temporelle des communautés zooplanctoniques de deux bras morts de la Meuse («noues de Tailfer»et «noue de Waulsort») ont été suivies durant les périodes printanières et estivales 1993 et 1996 et comparées à celles du coursprincipal du fleuve. La composition des communautés zooplanctoniques se caractérise par une abondance plus importante decrustacés à Waulsort que dans la Meuse, alors que la structure et la densité du zooplancton dans les noues de Tailfer sont prochesde celles du cours principal. Dans les noues se remarque une forte hétérogénéité spatiale de la répartition zooplanctonique, nettementinfluencée par les communications avec le fleuve et les facteurs hydrologiques.

Une étude quantitative des peuplements d'invertébrés benthiques en relation avec certains substrats naturels et artificiels, utilisés pour la consolidation des berges, a été réalisée dans 9 stations du bief de Waulsort lors de la mise en chômage technique de la Meuse (Belgique). Les stations à grande hétérogénéité physique sont caractérisées par une richesse et une diversité faunistique importante (33 familles, 15 790 nd./m2, H' = 2,08) de même qu'une colonisation optimale de substrat. Les stations à substrats artificiels, fortement homogènes, restent peu accueillantes pour la faune benthique (17 familles, 1 352 ind./m2, H' = 0,52). Dans la perspective de l'aménagement futur des berges du barrage de Waulsort, la construction de perrés non cimentés à faible pente doit être privilégiée.

This paper presents a comprehensive study of the impact of damming on the spawning migrations of Barbus barbus in the canalized River Meuse (Southern Belgium). A Denil fish pass on the Ampsin-Neuville dam was controlled 251 times in 1989-1993. The most striking feature is the almost complete absence of barbel in 1990-1993 (15 fishes in 4 years). Most captures of barbel in the fish pass in 1989 were clumped within a few days (mid-May) and related with spawning migrations. Stepwise multiple regression analyses revealed that attractivity was the major condition set allowing barbel to migrate successfully through the pass, while feasibility parameters (water velocity) were found not to be relevant. The variables involved in the attractivity condition set refer indirectly to the influence of water catchment by a hydroelectric plant and to the relative importance of the flow in the pass. The study concludes that this additional condition set significantly interferes with the natural environmental stimuli triggering spawning migrations in barbel and questions the effectiveness of the thermally-related reproductive strategy of the species in an environment with restricted longitudinal connectivity. This statement is discussed in parallel with the recent evolution of barbel populations in canalized rivers.

A study of the Chironomidae (Díptera) of the river Meuse and two of its tributaries (Sambre and Samson) during the period 1991 to 1992 resulted in a list of one hundred and twenty species. Thirty one of these (*) are new records to the Belgian fauna. A taxonomic list of the species with locations is given.