Title: Asynchronicity in floodplain processes. An example from the Dijle catchment, Central Belgium
Authors: Broothaerts, Nils
Notebaert, Bastiaan
Verstraeten, Gert
Issue Date: Aug-2013
Conference: IAG International Conference on Geomorphology edition:8 location:Paris date:27-31 August 2013
Abstract: Major changes in fluvial architectures appear in many Holocene floodplains of Western Europe, under influence
of changing catchment properties. Typically, organic and peaty deposits – deposited in a marshy environment
during the Early and Middle Holocene – are replaced by minorganic overbank deposits. This domination of
minorganic deposits is attributed to an increase in soil erosion due to increasing human impact during the last
few millennia. The onset of intense human land use changes is often determined based on a few or one single
dating of this transition in fluvial architecture. In this study, the temporal and spatial variability of this transition
was studied for two cross sections in the Dijle catchment, located in the Belgian loess belt.
Two study sites were selected: one in a small tributary (13 km² catchment area; floodplain width 90 m) and one in
the main trunk valley (760 km²; floodplain width 1020 m), for which the top of the peat layer was dated at several
points along a transect perpendicular to the valley axis. Datable material was handpicked for non-aquatous plant
remains, and dated using AMS radiocarbon dating. Results for the small tributary show that the end of the peat
accumulation is ranging between 376 ±61 and 620 ±40 cal BP (n=6). For the main trunk valley, the top of the
peat layer is even more diachronic (ranging from 715 ±24 to 7415 ±56 cal BP; n=15). The results indicate that for
the broad lower floodplain, sediment supply starts with low quantities only influencing peat accumulation near the
channel, while only later on the distal parts of the floodplain are affected. For the smaller floodplains, the
transitions in the floodplain are more abrupt, affecting the entire floodplain width. Overall, the observed
asynchronicity in the floodplain transitions shows that the reliability of single-core dating results can be doubted.
Publication status: published
KU Leuven publication type: IMa
Appears in Collections:Division of Geography & Tourism

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