Utrecht University | Dept. Physical Geography | www.geo.uu.nl/fg/palaeogeography New results from the Upper Rhine-Meuse delta G. Erkens, M.J.P. Gouw, K.M. Cohen, W.Z. Hoek, E. Stouthamer
Fig. 1 Holocene Rhine-Meuse delta (Berendsen & Stouthamer 2001, updated) New data
140,000 160,0005°30’E 180,000 6°0’E 200,000 220,000 The 2001 Berendsen & Stouthamer map of Fluvial channel belt age (cal yr BP) Miscellaneous Background 800 - 0 BP 3500 - 3000 6500 - 6000 Rivers, canals and lakes AHN (c) RWS-AGI 2005 the Rhine-Meuse delta (Fig. 1) is the reference Embankment 4000 - 3500 7000 - 6500 Cross sections High : 20 map for channel belt age in the Netherlands. 800 - 1500 4500 - 4000 7500 - 7000 A-E Gouw and Erkens NJG 2007 Low : -10 2000 - 1500 5000 - 4500 8000 - 7500 Betuwelijn section, B&S 2001 Research projects over the last decade have Utr. Vecht 2500 - 2000 5500 - 5000 8500 - 8000 3000 - 2500 6000 - 5500 added new data. In the eastern Netherlands E’ ,000
460 this comprises: Utrecht 1. Five SN cross-sections including time lines IJssel D’ (Gouw & Erkens, 2007 NJG) 2. History of sediment delivery to the Arnhem Oude IJssel C’ B’ A’ 52°0’N Holocene delta (PhD thesis Erkens)
,000 3. Mapping and dating Rhine deposition in 440 the Gelderse IJssel valley (Cohen)
Linge 4. Late Glacial/Holocene landscape change in the Oude IJssel- and Niers-valley (Hoek) A Waal Nijmegen Rhine 1000 AD Embanked rivers C ,000 B 420 Former rivers Meuse River floodbasin D Den Bosch E G E R M A N Y
Meuse 51°40’N Niers
0 10 20 30 40 km
140,000 160,0005°30’E 180,000 6°0’E200,000 220,000 Roman-age arrival of Bronze age sediment
Upstream of section A-A in Fig. 1 the delta doubled in size between Erkens & Cohen (2009) 1000 BC and 1000 AD. Analysis of stored amounts of fine-clastic deposits Fig. 3 Palaeogeography 1000 BC - 1000 AD reveals the delta to receive increased amounts fine of sediment, especially since Roman times (last 2000 years; Fig. 2). 1 BC/AD This is due to deforestation in Germany, which was widespread during Bronze and Iron age times. Along the Rhine trunk valley (e.g. the Upper Rhine Graben) the sedimentation increase is also registered but started ~1000 years earlier - indicating a lag time in sediment arrival. Most of the excess sediment was trapped in the upper delta. Around 500 AD this allowed for avulsion of the Gelderse IJssel, which greatly expanded the area of Rhine floodbasin deposition and changed flooding frequencies in the lower delta (Fig. 3).
Fig. 2 Holocene delta growth and deposition history (Erkens & Cohen, in prep.) Erkens & Cohen (2009) 19th century: 4.2 Mton/yr a) areal growth b) deposited fine-clastics modern: 2.5-3.4 Mton/yr 3500 3.0 Reduction in trapped volumes Increase in trapped volumes 1000 BC Legend km2 due to reduced trapping efficiency under stable trapping efficiency: Mton/yr Gld.IJssel and decreasing delivery strongly increased delivery Oude Rijn Utr. Vecht A-A 3000 F-F D-D B-B 2.5 G-G H-H E-E C-C Lower delta Central delta Upper delta 2500 reconstructed suspended load Lower Rhine 2.0
2000 1.5 1500 1.0 1000
0.5 500
0 0 9000- 8500- 8000- 7500- 7000- 6500- 6000- 5500- 5000- 4500- 4000- 3500- 3000- 2500- 2000- 1500- 800-0 9000- 8500- 8000- 7500- 7000- 6500- 6000- 5500- 5000- 4500- 4000- 3500- 3000- 2500- 2000- 1500- 800-0 8500 8000 7500 7000 6500 6000 5500 5000 4500 4000 3500 3000 2500 2000 1500 800 (Emb.) 8500 8000 7500 7000 6500 6000 5500 5000 4500 4000 3500 3000 2500 2000 1500 800 (Emb.)