Reference : Modelling the migration of a mid-Pleistocene erosion wave in the Ardennes (western Europ...
Scientific congresses and symposiums : Poster
Physical, chemical, mathematical & earth Sciences : Earth sciences & physical geography
http://hdl.handle.net/2268/91011
Modelling the migration of a mid-Pleistocene erosion wave in the Ardennes (western Europe) drainage network: approach and first implications
English
Beckers, Arnaud mailto [Université de Liège - ULg > > > AESS sc. géographiques]
Bovy, Benoît mailto [Université de Liège - ULg > Département de géographie > Unité de géographie physique et quaternaire (UGPQ) >]
Demoulin, Alain mailto [Université de Liège - ULg > Département de géographie > Unité de géographie physique et quaternaire (UGPQ) >]
Apr-2011
A0
No
No
International
European Geosciences Union General Assembly 2011
du 3 au 8 avril 2011
European Geosciences Union
Vienna
Austria
[en] knickpoints ; stream power ; modelling ; Ourthe ; Ardenne
[en] 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.
http://hdl.handle.net/2268/91011

File(s) associated to this reference

Fulltext file(s):

FileCommentaryVersionSizeAccess
Open access
EGU_poster_abeckers.pdfAuthor postprint1.39 MBView/Open

Bookmark and Share SFX Query

All documents in ORBi are protected by a user license.