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Reconstruction of the Weser Lake outburst flood pathway: integrating field data and hydraulic modeling

Jutta Winsemann1, Janine Meinsen2, Petteri Alho3, Freek Busschers4, Wim Westerhoff5, Jörg Lang6, Josef Klostermann7
1 Institut für Geologie, Leibniz Universität Hannover, Callinstrasse 30, D-30167 Hannover, Germany. winsemann@geowi.uni-hannover.de
2 Institut für Geologie, Leibniz Universität Hannover, Callinstrasse 30, D-30167 Hannover, Germany
3 Department of Geography & Geology, Geography Division, FI-20014, University of Turku, Finland
4 3Geological Survey of the Netherlands - TNO, AL-3508, Utrecht, the Netherlands
5 Geological Survey of the Netherlands - TNO, AL-3508, Utrecht, the Netherlands
6 Institut für Geologie, Leibniz Universität Hannover, Callinstrasse 30, D-30167 Hannover, Germany.
7 Geologischer Dienst NRW, De-Greiff-Straße 195, D-47803 Krefeld, Germany

V 6.5 in Quartäre Landschaftsentwicklung - ein Schlüssel zum Verständnis aktueller Georisiken

19.09.2012, 16:20-16:40, H8

 

This study investigates the impact of the Weser Lake outburst floods on landscape evolution in the Lower Rhine Embayment and the southeastern Netherlands. In particular we want to reconstruct the flow dynamics of these lake-outburst floods and to analyze the impact of floods on erosion and sediment distribution.

During the late Saalian glaciation (MIS 6) outburst floods of glacial Lake Weser repeatedly drained into the Münsterland Embayment, hereby releasing 20-90 km3 of water. A large part of the flood water was initially trapped in the northeastern Münsterland Embayment, where a lake formed, referred to as glacial Lake Münsterland. The enormous water volume must have led to an increase of the ice temperature due to frictional heating and enhanced melting and rapid destabilization of the Münsterland ice lobe, triggering the outburst of glacial Lake Münsterland, catastrophically draining southwestwards (Meinsen et al. 2011).

The pathway of the lake outburst floods towards the Lower Rhine Embayment and the southeastern Netherlands has not been studied in detail yet and is probably indicated by the large Emscher and Lippe Valley and strongly dissected push moraines at the western margin of the Rhine Valley.

High-resolution digital elevation models (DEM) are used to map flood-related landforms and channel systems and will be combined with information from geological maps, outcrop data and borehole data to reconstruct the distribution of flood-related deposits and palaeo-topographic surfaces.

Flood reconstructions will be created with a TUFLOW 2-D hydraulic model, which solves the full two-dimensional, depth-averaged momentum and continuity equations for free-surface flow. The glacial lake outflow hydrographs or water surface elevations can be utilized as boundary conditions. This modelling approach allows grid-by grid-computation of palaeoflow characteristics (e.g., flow velocity, bed shear stresses) for a given flood stage (e.g., Alho 2010 et al.).  

Preliminary modeling results indicate that the outburst flood rapidly spread out into the Lower Rhine Embayment flowing southwards and westwards. Therefore the poorly understood formation of east-west trending channel systems in the Lower Rhine Embayment might be related to the late Saalian lake outburst floods.

 

References:

 

Alho, P. Baker, V.R., Smith, L.N. (2010): Paleohydraulic reconstruction of the largest Glacial Lake Missoula draining(s). Quat. Sci. Rev. 29, 3067-3078.

 

Meinsen, J., Winsemann, J., Weitkamp, A., Landmeyer, N., Lenz, A. & Dölling, M. (2011): Middle Pleistocene (Saalian) lake outburst floods in the Münsterland Embayment (NW Germany): impacts and magnitudes. Quat. Sci. Rev. 30, 2597-2625.



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Letzte Änderung 25.07.2012