Publications of Alain Demoulin
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See detailOn different types of adjustment usable to calculate the parameters of the stream power law
Demoulin, Alain ULiege; Beckers, Arnaud ULiege; Bovy, Benoît ULiege

in Geomorphology (2012), 138(1), 203-208

Model parameterization through adjustment to field data is a crucial step in the modeling and the understanding of the drainage network response to tectonic or climatic perturbations. Using as a test case ... [more ▼]

Model parameterization through adjustment to field data is a crucial step in the modeling and the understanding of the drainage network response to tectonic or climatic perturbations. Using as a test case a data set of 18 knickpoints that materialize the migration of a 0.7-Ma-old erosion wave in the Ourthe catchment of northern Ardennes (western Europe), we explore the impact of various data fitting on the calibration of the stream power model of river incision, from which a simple knickpoint celerity equation is derived. Our results show that statistical least squares adjustments (or misfit functions) based either on the streamwise distances between observed and modeled knickpoint positions at time t or on differences between observed and modeled time at the actual knickpoint locations yield significantly different values for the m and K parameters of the model. As there is no physical reason to prefer one of these approaches, an intermediate least-rectangles adjustment might at first glance appear as the best compromise. However, the statistics of the analysis of 200 sets of synthetic knickpoints generated in the Ourthe catchment indicate that the timebased adjustment is the most capable of getting close to the true parameter values. Moreover, this fitting method leads in all cases to an m value lower than that obtained from the classical distance adjustment (for example, 0.75 against 0.86 for the real case of the Ourthe catchment), corresponding to an increase in the non-linear character of the dependence of knickpoint celerity on discharge [less ▲]

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See detailDating uplift events by a composite metric of fluvial landscapes
Demoulin, Alain ULiege

Conference (2012)

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See detailDating uplift events by a composite metric of fluvial landscapes
Demoulin, Alain ULiege

Conference (2012)

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See detailMorphometric dating of the fluvial landscape response to a tectonic perturbation
Demoulin, Alain ULiege

in Geophysical Research Letters (2012), 39

Despite constant progress in numerical and field studies of landscape evolution, time evolution is still poorly constrained in many uplifted areas where low denudation rates prevent the use of low ... [more ▼]

Despite constant progress in numerical and field studies of landscape evolution, time evolution is still poorly constrained in many uplifted areas where low denudation rates prevent the use of low temperature thermochronology, especially outside high relief mountainous areas. Here, I show that regional statistics of the landscape metric R involving hypsometric integrals at three nested levels of a catchment are able to isolate the time effect on landscape geometry during the latter’s transient response to a tectonic perturbation. Analysis of 210 catchments from 9 regions of known uplift age worldwide shows that the regionally characteristic, R-derived SR index is in inverse power law relation with the time elapsed since a base level lowering. Suggesting a response time of 5 My, this finding has important implications for quantifying the rate of landform evolution and determining whether a landscape has reached steady-state form. [less ▲]

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See detailRole of land use change in landslide-related sediment fluxes in tropical mountain regions
Guns, Marie; Vanacker, Veerle; Demoulin, Alain ULiege

in Geophysical Research Abstracts (2012), 14

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See detailValley downcutting in the Ardennes (W Europe): Interplay between tectonically triggered regressive erosion and climatic cyclicity
Demoulin, Alain ULiege; Beckers, Arnaud ULiege; Rixhon, Gilles ULiege et al

in Netherlands Journal of Geosciences - Geologie en Mijnbouw (2012), 91(1-2), 79-90

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See detailModelling the migration of a mid-Pleistocene erosion wave in the Ardennes (western Europe) drainage network: approach and first implications
Beckers, Arnaud ULiege; Bovy, Benoît ULiege; Demoulin, Alain ULiege

Poster (2011, April)

Model parameterization through adjustment to field data is a crucial step in the modelling and the understanding of the drainage network response to tectonic or climatic perturbations. Using a data set of ... [more ▼]

Model parameterization through adjustment to field data is a crucial step in the modelling and the understanding of the drainage network response to tectonic or climatic perturbations. Using a data set of 18 knickpoints that materialize the migration of a 0.7-Ma-old erosion wave in the Ourthe catchment of northern Ardennes (western Europe) as a test case, we explore the impact of various data fitting on the calibration of the detachment-limited stream power model of river incision, from which a simple knickpoint celerity equation is derived. Our results show that statistical least squares adjustments (or misfit functions) based either on the stream-wise distances between observed and modelled knickpoint positions at time t = 0.7 Ma or on differences between observed (0.7 Ma) and modelled time at the actual knickpoint locations yield significantly different values for the m (more exactly, m/n) and K parameters of the model. As there is no physical reason to prefer one or the other approach, we suggest that an intermediate least rectangles adjustment might be the best compromise. In the Ourthe case, this leads to a m/n value lower than that obtained from the classical distance adjustment (0.79 against 0.86), leading to an increase in the non linear character of the dependence of knickpoint celerity on discharge. If we now recall that m/n = c(1-b) (Whipple & Tucker, 1999, JGR 104B: 17661-17674), where c and b are the exponents of the power law relations respectively linking discharge to drainage area and channel width to discharge, we can compare the calculated m/n value with that derived from field measurements of channel width, discharge and drainage area in the presently graded sections of the rivers. Such data taken from Petit et al. (2005, BSGLg 46: 37-50) allow us to derive m/n = 0.48 at equilibrium. As c may be considered constant, the higher m=n value obtained from the knickpoint retreat modelling must be ascribed to a lower b, i.e., to a channel narrowing associated with the transient phase of knickpoint migration. [less ▲]

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See detailBasin and river profile morphometry: A new index with a high potential for relative dating of tectonic uplift
Demoulin, Alain ULiege

in Geomorphology (2011), 126

Geomorphometry may be a powerful tool to describe the characteristics of the landscape's response to tectonic signals, but the meaning of morphometric indices is often obscured by the interplay between ... [more ▼]

Geomorphometry may be a powerful tool to describe the characteristics of the landscape's response to tectonic signals, but the meaning of morphometric indices is often obscured by the interplay between the many variables controlling the geomorphological evolution. Moreover, although the so-called hypsometric integral refers to the basin scale, most indices are generally derived from the river long profiles and thus focus mainly on the short-term response of a drainage network to base level change, providing limited information in regions of older and/or moderate uplift. Here, using the Rhenish shield (western Europe), an area of moderate Quaternary uplift, as a test case, I attempt to build an index yielding a comprehensive view of the stage attained by the landscape's response and, indirectly, an evaluation of the timing of the triggering base level change. This index, called R1, is a ratio of differences between the three integrals linked respectively to the classical basin's hypsometric curve, to the main river's long profile, and at the intermediate level, to a ‘drainage network's hypsometric curve’. While its ratio form minimizes the lithological effect on R1, this index is strongly correlated with basin size (regional correlation coefficients are in the range 0.88–0.93), reflecting the way an erosion wave propagates from the outlet of a basin toward its headwaters. Therefore, it is not directly usable as a proxy for relative uplift age. However, one can show that the relation between R1 and basin size is theoretically expected to change with time. Following uplift, the slope Sr of the linear relation R1=f (lnA) first increases rapidly but briefly, then it gradually diminishes over several million years. This is fully confirmed by the analysis of R1 and Sr in the study area. Once its initial increase is completed (assumedly in a few ten thousand years), Sr appears to be a reliable indicator of relative uplift (or any other cause of base level lowering) age. [less ▲]

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See detailLa grotte Walou dans son cadre géomorphologique
Bovy, Benoît ULiege; Cornet, Yves ULiege; Juvigné, Etienne ULiege et al

in Pirson, Stéphane; Draily, Christelle; Toussaint, Michel (Eds.) La grotte de Walou à Trooz (2011)

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See detailUnraveling the Quaternary river incision in the Meuse catchment (NE Ardennes massif, Belgium): insights from 10Be/26Al dating of fluvial terraces
Rixhon, Gilles; Braucher, Régis; Bourlès, Didier et al

Conference (2011)

Detailed reference viewed: 30 (2 ULiège)
See detailThe presence of Homo erectus in NW Europe (Belle-Roche site, eastern Belgium) at ~600 ka attested by Terrestrial Cosmogenic Nuclide dating (10Be)
Rixhon, Gilles; Braucher, Régis; Bourlès, Didier et al

Conference (2011)

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See detailHuman presence at Belle-Roche, in the Ardenne massif (western Europe) : Terrestrial Cosmogenic Nuclides (10Be) dating of fluvial sediments confirms an age of ∼580 ka
Rixhon, Gilles; Braucher, Régis; Bourlès, Didier et al

in Geophysical Research Abstracts (2011), 13

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See detailQuaternary river incision in NE Ardennes (Belgium). Insights from 10Be-26Al dating of river terraces
Rixhon, Gilles; Braucher, Régis; Bourlès, Didier et al

in Quaternary Geochronology (2011), 6

Although it constitutes a main tool to unravel the regional recent tectonics, the chronology of the Pleistocene river incision is still poorly constrained within the uplifted Ardennes massif (Western ... [more ▼]

Although it constitutes a main tool to unravel the regional recent tectonics, the chronology of the Pleistocene river incision is still poorly constrained within the uplifted Ardennes massif (Western Europe). Here, we use in situ produced cosmogenic 10Be and 26Al concentrations from depth profiles in terrace sediments of several Ardennian rivers (Meuse, Ourthe and Amblève) in order to date the so-called Younger Main Terrace (YMT), a key-level in the drainage network evolution.We present the first absolute dating of the YMT in the lower Meuse valley, where we obtained an age of 725 +/- 120 ka for a terrace deposit buried beneath 3 m of Weichselian loess at Romont. This age is consistent with some previously published estimates based on paleomagnetic data and MIS correlations. However, the ages we obtain for the same terrace level in Ardennian tributaries of the Meuse are significantly younger: 390 +/- 35 ka in the lower Ourthe, and only 220 +/- 31 ka still farther upstream, in the lower Amblève. We thus demonstrate that the post-YMT incision occurred diachronically in NE Ardennes. The ~0.5 Ma timespan needed by the erosion wave to propagate from the lower Meuse towards the Ardennian headwaters contradicts the long-held statement of a climatically driven incision that would have been synchronous throughout the catchments. Finally, we interpret the strong 10Be enrichment displayed by the lower half of the Belle eRoche (lower Amblève) profile as betraying the long-lasting, slow accumulation of the ∼8 m thick terrace deposit in that place. [less ▲]

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See detailContexte chronostratigraphique et paléoenvironnemental de la séquence de la grotte Walou : synthèse et perspectives
Pirson, Stéphane ULiege; Draily, Christelle; Bovy, Benoît ULiege et al

in Pirson, Stéphane; Draily, Christelle; Toussaint, Michel (Eds.) La grotte de Walou à Trooz (2011)

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See detailThe influence of climate on hillslope sediment supply : Insights from numerical modeling
Bovy, Benoît ULiege; Demoulin, Alain ULiege; Braun, Jean

Poster (2010, September)

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See detailDe l'origine sismique de structures sédimentaires pléistocènes à Terreti, Calabre
Cornet, Yves ULiege; Demoulin, Alain ULiege

in Bulletin de la Société Géographique de Liège (2010), 54

Detailed reference viewed: 56 (16 ULiège)