Publications of Jean Van Campenhout
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See detailCan coarse bedload pass through weirs?
Peeters, Alexandre ULiege; Houbrechts, Geoffrey ULiege; Hallot, Eric ULiege et al

in Geomorphology (2020), 359

Restoring active bedload transfer in human-impacted rivers has received increasing attention in recent years, notably in response to the European Water Framework Directive (WFD), which requires that the ... [more ▼]

Restoring active bedload transfer in human-impacted rivers has received increasing attention in recent years, notably in response to the European Water Framework Directive (WFD), which requires that the continuity of rivers not be disturbed by anthropogenic features such as dams or weirs. The Bocq River (233 km2), a moderate-gradient stream in Wallonia, Belgium, has a hydraulic resource that was formerly largely exploited with 74 weirs (up to 2.3 m high) along 43 km. We examined the effects of seven old abandoned weirs on bedload transport for three different types of weirs (defined by the presence and position of the sluice gate system). First, the volume estimates of bedload stored in reservoirs indicated that, despite their old age, the reservoirs were not completely filled (between 25 and 50% filled compared to the reservoir volume capacity) and did not evolve very much since 1990. Second, the grain size analysis of bed material upstream, downstream and within the reservoirs, and the direct measurements of sediment transport (slag particles and PIT-tagged pebbles) demonstrated that bedload continues to be transported out of the reservoir, even though the selective trapping of coarser elements was observed within the reservoir. Particles in the range of the median can pass over the crest of weirs, but the coarser elements tend to remain in the reservoirs. This trapping effect is mitigated when the weir has open or collapsed flushing gates that facilitate bedload transfer. This indicates that weirs act as leaky barriers that allow bedload to pass through, although the individual geomorphic setting plays a primary role in determining the local sediment continuity. These findings suggest that river connectivity is less impacted than initially thought and is likely to increase over time as old weirs gradually fall into disrepair. This needs to be acknowledged when planning barrier removal projects. [less ▲]

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See detailReturn Period of Characteristic Discharges From the Comparison Between Partial Duration and Annual Series, Application to the Walloon Rivers (Belgium)
Van Campenhout, Jean ULiege; Houbrechts, Geoffrey ULiege; Peeters, Alexandre ULiege et al

in Water (Switzerland) (2020), 12(3), 792

The determination of the return period of frequent discharges requires the definition of flood peak thresholds. Unlike daily data, the volume of data to be processed with the generalization of hourly data ... [more ▼]

The determination of the return period of frequent discharges requires the definition of flood peak thresholds. Unlike daily data, the volume of data to be processed with the generalization of hourly data loggers or even with an even finer temporal resolution quickly becomes too large to be managed by hand. We therefore propose an algorithm that automatically extracts flood characteristics to compute partial series return periods based on hourly series of flow rates. Thresholds are defined through robust analysis of field observation-independent data to obtain five independent flood peaks per year in order to bypass the 1-year limit of annual series. Peak over thresholds were analyzed using both Gumbel’s graphical method and his ordinary moments method. Hydrological analyses exhibit the value in the convergence point revealed by this dual method for floods with a recurrence interval around 5 years. Pebble-bedded rivers on impervious substratum (Ardenne rivers) presented an average bankfull discharge return period of around 0.6 years. In the absence of field observation, the authors have defined the bankfull discharge as the Q0.625 computed with partial series. Annual series computations allow Q100 discharge determination and extreme floods recurrence interval estimation. A comparison of data from the literature allowed for the confirmation of the value of Myer’s rating at 18, and this value was used to predict extreme floods based on the area of the watershed. [less ▲]

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See detailUn site de référence de très hautes terrasses fluviales dans la zone de confluence Ourthe-Meuse à Bois de Breux (Liège)
Juvigné, Etienne ULiege; Van Campenhout, Jean ULiege

Report (2020)

Fluvial gravel has been widely excavated in Bois de Breux / Liège at the level of very high terraces, thanks to the burial of tubes in the Verger de Fayenbois subdivision. The alluvial deposits are ... [more ▼]

Fluvial gravel has been widely excavated in Bois de Breux / Liège at the level of very high terraces, thanks to the burial of tubes in the Verger de Fayenbois subdivision. The alluvial deposits are described and new data are brought in concerning these shreds which were only known by surface observations. Three well-documented sheets are present in an elevation range of less than 20 m, so this site now has a unique reference value for the terraces concerned. An attempt at a transverse connection between the gravel on both sides of the valley from Bois de Breux to Rocourt highlights the impossibility of proposing correlations according to the traditional method which requires that schreds of the same altitude on opposite sides of a valley belong to the same terrace. [less ▲]

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See detailA propos d’un changement pétrographique majeur dans les terrasses de la Meuse entre Namur et Huy (Belgique) : de la Meuse de Dinant à la capture de la Semois
Juvigné, Etienne ULiege; Houbrechts, Geoffrey ULiege; Van Campenhout, Jean ULiege

Report (2020)

A sedimentological study of shreds of very high terraces of the Meuse River between Namur and Huy has made it possible to improve the knowledge relating to the evolution of the Meuse of Dinant which has ... [more ▼]

A sedimentological study of shreds of very high terraces of the Meuse River between Namur and Huy has made it possible to improve the knowledge relating to the evolution of the Meuse of Dinant which has shaped terraces over a vertical drop of 35 m below the level of the plateau by systematically abandoning a few decimetre thick gravel characterized by a large majority of quartz pebbles and a grain size lower than 32 mm. At the current altitude of 180 m at Andenne / Huy, a coarse gravel rich in quartzites suddenly invaded the basin; it is attributed to the capture of the Semois in Deville (France). This capture is placed in the lower Pleistocene based on its stratigraphic position in the existing terrace models, rather than in the Miocene as the literature says. [less ▲]

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See detailUn site de référence de très hautes terrasses fluviales dans la zone de confluence Ourthe-Meuse à Bois de Breux (Liège)
Juvigné, Etienne ULiege; Van Campenhout, Jean ULiege

in Bulletin de la Société Royale des Sciences de Liège (2020), 89

Fluvial gravels have been widely excavated at Bois de Breux/Liège at the level of very high terraces, in favor of the burial of impetrants from the Verger de Fayenbois subdivision. The alluvial deposits ... [more ▼]

Fluvial gravels have been widely excavated at Bois de Breux/Liège at the level of very high terraces, in favor of the burial of impetrants from the Verger de Fayenbois subdivision. The alluvial deposits thus uncovered are described and new data are brought in concerning these shreds which were only known by surface observations. Three well-documented level are present in an elevation range of less than 20 m, so that this site now has a unique reference value for the very high terraces concerned. An attempt at a transverse connection between gravels on the two sides of the valley highlights the impossibility of proposing correlations according to the traditional method which requires that shreds of same altitude on opposite sides of a valley necessarily belong to the same terraces. [less ▲]

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See detailChanges in climate patterns and their association to natural hazard distribution in South Tyrol (Eastern Italian Alps)
Schlögel, Romy; Kofler, Christian; Gariano, Stefano Luigi et al

in Scientific Reports (2020), 10

In Alpine regions changes in seasonal climatic parameters, such as temperature, rainfall, and snow amount have already been observed. Specifically, in the South Tyrol area, meteorological observations ... [more ▼]

In Alpine regions changes in seasonal climatic parameters, such as temperature, rainfall, and snow amount have already been observed. Specifically, in the South Tyrol area, meteorological observations indicate that temperatures are increasing and the number of snow days has generally diminished over time with perennial snow line now observed at higher elevations. Changes in rainfall have also been observed with more events associated with higher temperatures in the summer season. Natural hazards - mainly debris and mud flows, landslides, avalanches, rock falls, and (flash) floods - that affect this area every year, damaging population and infrastructures, are either weather or cryosphere-related. While these events have been recorded sporadically since the beginning of the 20th century, a systematic approach of their inventory has been done by local authorities since the 1990s. So far, Earth observation data has not been exploited to complete or complement existing inventories nor have they been used to investigate the influence of climate perturbation on potentially dangerous natural phenomena. The research presented here thus has three objectives: (i) analyse long time series of climate data and hazard occurrence in South Tyrol to examine if these records exhibit a coherent response of hazards to changes in climate; (ii) measure the spatio-temporal evolution of climatic and natural hazard events recorded, and (iii) explore potential relations between meteorological conditions and the hazard occurrence. In this context, in-situ and satellite-based climate data are exploited to study natural hazard triggers while the potential of Earth observation data is evaluated as a complement to the existing historical records of natural hazards. Specifically, Copernicus Sentinel-1 images are used to detect the spatio-temporal distribution of slow earth surface deformations and the results used for checking the completeness of the actual slow-moving landslide inventories. Hazard-related changes in the South Tyrolian landscape have also been analysed in relation to particular meteorological events at a regional scale, assessing trends and anomalies. Results show that: (i) satellite data are very useful to complement the existing natural hazard inventories; (ii) in-situ and satellite-based climate records show similar patterns but differ due to regional versus local variability; (iii) even in a data-rich region such as the analysed area, the overall response of natural hazard occurrence, magnitude, and frequency to change in climate variables is difficult to decipher due to the presence of multiple triggers and locally driven ground responses. However, an increase in the average annual duration of rainfall events and debris flow occurrence can be observed. [less ▲]

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See detailMécanismes du transport sédimentaire des cours d’eau et effets sur l'hydro-morphologie
Peeters, Alexandre ULiege; Van Campenhout, Jean ULiege; Houbrechts, Geoffrey ULiege

Conference given outside the academic context (2019)

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See detailCosmogenic data about uplifted river terraces: implications regarding the central north anatolian fault segment and the central pontide orogenic wedge
Hubert, Aurelia ULiege; Drab, Laureen; Benedetti, Lucilla et al

Conference (2019, January 29)

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See detailEfficacité et résistance de techniques de protection de berges en génie végétal
Peeters, Alexandre ULiege; Houbrechts, Geoffrey ULiege; Hallot, Eric ULiege et al

in Géomorphologie: Relief, Processus, Environnement (2018), 24(2 (2018)), 121-138

Nineteen streambank stabilisation projects using bioengineering techniques were monitored in the short and the long term on several rivers in Wallonia. Most of the bank protections, installed between 3 ... [more ▼]

Nineteen streambank stabilisation projects using bioengineering techniques were monitored in the short and the long term on several rivers in Wallonia. Most of the bank protections, installed between 3 and 20 years ago, were effective, although many of them are now partially destroyed. In some cases, damage to the protective structure has led to a renewed erosion of the bank. The main factor of degradation is the magnitude of stream discharge, which is quantified by the critical stream power (the maximum power value at which the bank protection can resist). Permissible stream power thresholds were determined empirically, and are in order of 130 W/m² for fascine, 65 W/m² for tree revetment, 200 W/m² for cribwall and 150 W/m² for groynes system. Nevertheless, several factors might undermine the bank protection before its flood destruction, which lead to a lower threshold of critical power. The deterioration factors highlighted are (i) a poor vegetation recovery due to lack of sunlight, unmanaged cutting, and damage caused by animals (livestock and rodents), (ii) an inadequate design or filling, and (iii) a lack of consideration of fluvial processes, such as unit stream power and Total Suspended Solids (TSS) as most of these structures require filling with fine sediments. As a result, this study underlined the importance of characterising the geomorphological context in addition to the regular hydrological technical factors prior to the bank stabilisation project. [less ▲]

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See detailA unique boulder-bed reach of the Amblève River, Ardenne, at Fonds de Quarreux: Modes of boulder transport
Houbrechts, Geoffrey ULiege; Petit, François ULiege; Van Campenhout, Jean ULiege et al

in Demoulin, Alain (Ed.) Landscapes and landforms of Belgium and Luxembourg (2018)

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See detailDecrease in climatic conditions favouring floods in the south-east of Belgium over 1959-2010 using the regional climate model MAR
Wyard, Coraline ULiege; Scholzen, Chloé ULiege; Fettweis, Xavier ULiege et al

in International Journal of Climatology (2017), 37(5), 27822796

The Ourthe River, in the south-east of Belgium, has a catchment area of 3,500 km2 and is one of the main tributaries of the Meuse River. In the Ourthe, most of the flood events occur during winter and ... [more ▼]

The Ourthe River, in the south-east of Belgium, has a catchment area of 3,500 km2 and is one of the main tributaries of the Meuse River. In the Ourthe, most of the flood events occur during winter and about 50% of them are due to heavy rainfall events combined to an abrupt melting of the snowpack covering the Ardennes massif during winter. This study aims to determine whether trends in extreme hydroclimatic events generating floods can be detected over the last century in Belgium, where a global warming signal can be observed. Hydroclimatic conditions favourable to floods were reconstructed over 1959- 2010 using the regional climate model MAR (“Modèle Atmosphérique Régional”) forced by the ERA-Interim/ERA-40, the ERA-20C and the NCEP/NCAR-v1 reanalyses. Extreme run-off events, which could potentially generate floods, were detected using run-off caused by precipitation events and snowpack melting from the MAR model. In the validation process, the MAR-driven temperature, precipitation and snow depth were successfully compared to daily weather data over the period 2008-2014 for 20 stations in Belgium. MAR also showed its ability to detect up to 90% of the hydroclimatic conditions which effectively generated observed floods in the Ourthe River over the period 1974- 2010. Conditions favourable to floods in the Ourthe River catchment present a negative trend over the period 1959-2010 as a result of a decrease in snow accumulation and a shortening of the snow season. This trend is expected to accelerate in a warmer climate. However, regarding the impact of the extreme precipitation events evolution on conditions favouring floods, the signal is less clear since the trends depend on the reanalysis used to force the MAR model. [less ▲]

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See detailFlux sédimentaires des rivières de Wallonie : du Pléistocène à Demain
Houbrechts, Geoffrey ULiege; Gob, Frédéric; Hallot, Eric ULiege et al

Scientific conference (2016, July 11)

Livret-guide des journées 2016 de la Commission des hydrosystèmes continentaux du CNFG. Depuis plus de 40 ans, de nombreuses études ont été menées par François Petit et ses collaborateurs sur le transport ... [more ▼]

Livret-guide des journées 2016 de la Commission des hydrosystèmes continentaux du CNFG. Depuis plus de 40 ans, de nombreuses études ont été menées par François Petit et ses collaborateurs sur le transport des sédiments par les rivières du massif ardennais et des régions périphériques. La diversité des processus et des problématiques abordées, des méthodes d'analyse et des périodes considérées nous ont amené à proposer un thème relativement général permettant de regrouper les études portant sur les sédiments de taille variée, depuis les fractions fines jusqu'aux éléments les plus grossiers de la charge de fond ainsi que d'aborder des échelles de temps différentes, depuis les héritages géomorphologiques des périodes froides du Quaternaire jusqu'aux futures évolutions dans le cadre de projets de restauration de cours d'eau. [less ▲]

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See detailAnalysis of the temporal dynamics of suspended sediment fluxes using discrete sampling and continuous turbidity measurements in the Meuse and Scheldt watersheds (Wallonia, Belgium)
Van Campenhout, Jean ULiege; Houbrechts, Geoffrey ULiege; Petit, François ULiege

Conference (2016, June 27)

Soil erosion may be apprehended at different scales and different time intervals in order to quantify the transport of suspended sediment at the outlet of large watersheds. In the Walloon region, several ... [more ▼]

Soil erosion may be apprehended at different scales and different time intervals in order to quantify the transport of suspended sediment at the outlet of large watersheds. In the Walloon region, several projects were conducted to estimate the erosion rates in watersheds ranging from 16 to 2900 km². Both discrete sampling methods (allowing the coverage of a large area through field campaigns during major floods or moderate hydrological events) and continuous turbidity measurements devices (studying a small number of locations with a small sampling interval and a wide range of sampled flow rates) were tested in these projects. At the region scale (Figure 1), the mean annual sediment erosion rate reaches several hundreds of tons per square kilometre and per year in the loess belt (Senne, Dyle and Gette watersheds) with a huge sensibility to extreme hydrological events while the mean annual sediment transport value reaches 20 t.km-2.yr-1 in Lorraine, 34 t.km-2.yr-1 in Ardenne and 69 t.km-2.yr-1 in Entre-Vesdre-et-Meuse. The aims of our researches are 1) the determination of the effect of the sampling frequency on the annual sediment transport rate estimation ; 2) the definition of the prerequisites to perform efficient turbidity measurements in rivers with high suspended load concentrations ; 3) the identification of the sources of errors due to the interpolation methods through a comparison of several methods proposed in the literature allowing the quantification of long-term erosion rates using a small number of discrete samples ; 4) the observation and explanation of clockwise and anti-clockwise hysteresis loops in relationship with the sequence of floods occurring in large watersheds and 5) the highlighting of the regional differentiation in the erosion rates, particle size and proportion of organic matter in the suspended load samples due to spatial variations of the soil substrate and the land cover characteristics. [less ▲]

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See detailFlash floods and muddy floods in Wallonia: recent temporal trends, spatial distribution and reconstruction of the hydrosedimentological fluxes using flood marks and sediment deposits
Van Campenhout, Jean ULiege; Hallot, Eric ULiege; Houbrechts, Geoffrey ULiege et al

in Belgeo (2015), 1

Flash floods and muddy floods may cause severe human and material damage despite their small spatial extent and low occurrence. In late May 2008, a major event has affected the area of Liège. This paper ... [more ▼]

Flash floods and muddy floods may cause severe human and material damage despite their small spatial extent and low occurrence. In late May 2008, a major event has affected the area of Liège. This paper describes the methodology used to reconstruct the hydrosedimentological parameters of the flood from the geomorphological evidences observed in the field. Bed load and suspended load transport rates estimated during this extreme event were compared to the average values observed in other Walloon rivers and more specifically in the Ardennes Massif. The spatial distribution and the temporal evolution of the flash flood and muddy flood events are then analysed across Wallonia based on several works compiling press archives since the early twentieth century. The biases associated with this type of historical sources and the consequences of flash floods and muddy floods on the vulnerability and the risk of flooding in Wallonia are finally addressed. [less ▲]

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See detailEvaluation of long-term bedload virtual velocity in gravel-bed rivers (Ardenne, Belgium)
Houbrechts, Geoffrey ULiege; Levecq, Yannick; Peeters, Alexandre ULiege et al

in Geomorphology (2015), 251

In many gravel-bed rivers, bed material transfer has been interrupted or perturbed by anthropogenic activities. Currently, restoration projects are being conducted in many countries in order to re ... [more ▼]

In many gravel-bed rivers, bed material transfer has been interrupted or perturbed by anthropogenic activities. Currently, restoration projects are being conducted in many countries in order to re-establish bedload continuity. However, until now, few studies have provided indications of the velocity of bed material over the long-term (at least decade to century time-scale). In the context of river restoration projects (e.g. weir removal, addition of spawning gravel), these data are nevertheless crucial to predict the downstream propagation of the geomorphological and biological benefits (e.g. supply-transport equilibrium, morphological and substratum diversity). In our study, PIT-tag tracers were used in eight medium-sized gravel-bed rivers (Ardenne Region, Belgium) to propose a flow competence relationship based on specific stream power, on the one hand, and to determine the long-term virtual velocity of the bed material corresponding to the median diameter (D50) of the surface layer of riffles, on the other hand. After each flow event that exceeded the threshold for sediment entrainment, tagged particles were sought and located, even when they were buried in the subsurface layer. Afterwards, all of the data were used to estimate the virtual velocity of the bed material over the long-term using three approaches. Finally, the results were compared with long-term transport estimations based on iron slag dispersed by the rivers since the end of the middle ages. [less ▲]

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See detailQuantitative and qualitative evaluation of sediment and contaminant transport in the Samme river catchment (Brabant region - Belgium)
Denis, Anne-Cécile ULiege; Van Campenhout, Jean ULiege; Bouffioux, Anne et al

in Proceedings of 4th International Symposium on Sediment Management (2014, September)

In Wallonia (Belgium), the maintenance of waterways is currently exclusively managed in a curative way. When local sediment accumulations are detected in waterways, bathymetric surveys are conducted in ... [more ▼]

In Wallonia (Belgium), the maintenance of waterways is currently exclusively managed in a curative way. When local sediment accumulations are detected in waterways, bathymetric surveys are conducted in order to quantify the volume of sediment to be removed and chemical analyses of samples allow the characterization of sediment quality. Collected data only allow a short-term management of the matter generated by dredging operations. Medium- or long-term planning of dredging operations is currently not possible, due to a lack of knowledge on sediment fluxes and associated pollutant transport. In particular, issues related to the interactions and mixing of recent and older sediments, or to the input of sediment from unnavigable waterways into larger navigable waterways, are poorly understood. Operational tools allowing the assessment of the effectiveness of preventive measures to be implemented in order to improve the management of sediment in Walloon waterways also have to be developed. This research project aims at contributing to the development of such tools and focuses on the Samme river watershed (Senne catchment – loamy Brabant Region), deemed to be representative of Walloon issues. The Samme river is categorized as an unnavigable waterway. It runs along the old Charleroi-Brussels canal and flows into the new Charleroi-Brussels canal at the foot of the Ronquières inclined plane. The sediments of the bed of the Samme river are characterized by a high concentration of micropollutants (mainly PCB) and contribute to the contamination of a greater volume of sediments in the new Charleroi-Brussels canal, significantly increasing the cost of periodic dredging operations in the canal. The methodology developed is based on (I) an extended monitoring of sediment and pollutant fluxes at the outlet of the catchment and (II) an assessment of within-catchment sediment and pollutant transport. The origin of the Samme riverbed sediments contamination by PCB is poorly understood. Chemical analyses of the sediments of the bed were carried out along the linear course of the Samme river and its main tributary in order to identify the source of pollution. However, numerous connections between the old canal and the Samme river contribute to the transfer of stream sediments and pollutants between both systems and complicate the identification of the source of PCB. At the outlet of the catchment, different methods of river sediment sampling (automatic samplers, turbidity sensors, Time Integrated Samplers) are currently being implemented in order to (I) monitor the amount of suspended matter carried by the Samme river into the Charleroi-Brussels canal, (II) evaluate the associated fluxes of pollutants and (III) evaluate the possibility of setting up a system of retention of the sediments in the Samme catchment. [less ▲]

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