Strong increases in flood frequency and discharge of the River Meuse over the late Holocene: Impacts of long-term anthropogenic land use change and climate variability

In recent years the frequency of high-flow events on the Meuse (northwest Europe) has been relatively great, and flooding has become a major research theme. To date, research has focused on observed discharge records of the last century and simulations of the coming century. However, it is difficult to delineate changes caused by human activities (land use change and greenhouse gas emissions) and natural fluctuations on these timescales. To address this problem we coupled a climate model (ECBilt-CLIO-VECODE) and a hydrological model (STREAM) to simulate daily Meuse discharge in two time-slices: 4000–3000 BP (natural situation), and 1000–2000 AD (includes anthropogenic influence). For 4000–3000 BP the basin is assumed to be almost fully forested; for 1000–2000 AD we reconstructed land use based on historical sources. For 1000–2000 AD the simulated mean annual discharge (260.9 m<sup>3</sup> s<sup>−1</sup>) is significantly higher than for 4000–3000 BP (244.8 m<sup>3</sup> s<sup>−1</sup>), and the frequency of large high-flow events (discharge >3000 m<sup>3</sup> s<sup>−1</sup>) is higher (recurrence time decreases from 77 to 65 years). On a millennial timescale almost all of this increase can be ascribed to land use changes (especially deforestation); the effects of climatic change are insignificant. For the 20th Century, the simulated mean discharge (270.0 m<sup>3</sup> s<sup>−1</sup>) is higher than in any other century studied, and is ca. 2.5% higher than in the 19th Century (despite an increase in evapotranspiration). Furthermore, the recurrence time of large high-flow events is almost twice as short as under natural conditions (recurrence time decreases from 77 to 40 years). On this timescale climate change (strong increase in annual and winter precipitation) overwhelmed land use change as the dominant forcing mechanism

Human presence in the central Netherlands during early MIS 6 (~170-190 Ka) : evidence from early Middle Paleolithic artefacts in ice-pushed Rhine-Meuse sediments

Part of the gravelly deposits of a combined Rhine-Meuse river of Middle Pleistocene age in the central Netherlands contains early Middle Palaeolithic artefacts. Although not in their original position, a significant part of these artefacts is hardly abraded, indicating limited fluvial transport. The artefacts have mainly been made from fluvial flint gravel boulders, originating from the Meuse catchment. Thus far, inferences for the age of the artefacts are based on the stratigraphic context and floral and faunal remains, which suggest a MIS 7 age. In this paper, OSL dating carried-out in the framework of a research aimed at the paleogeographical reconstruction of the Rhine-Meuse fluvial system in the central Netherlands and a review of published data are used to provide absolute age constraints for the artefact-bearing deposits. It is argued that the deposits were formed during the glacial phase directly preceding the Drenthe substage of the late Saalian (early MIS 6), and that at least a part of the artefacts has approximately the same age

Hydrogeological aspects of fault zones on various scales in the Roer Valley Rift System.

The impact of faults on the groundwater flow system in the Roer Valley Rift System (RVRS) is demonstrated with examples from outcrop scale to regional scale. Faults in the RVRS can form strong barriers to horizontal groundwater flow as well as enhanced vertical groundwater flow paths at the same location. The strongly anisotropic hydraulic conductivity distribution within fault zones has important implications for the modeling of groundwater flow in sedimentary aquifer systems that are cut by faults. In this study, the hydraulic behavior of fault zones is studied at different scales. An outcrop study over the Geleen Fault zone shows deformation mechanisms as particulate flow and clay smearing in great detail. Qualitative and quantitative image analysis allows for an estimate of the micro-scale variation of the hydraulic properties within a fault zone. Additional core-plug measurements indicate that the damage zone around fault zones may form preferential flow paths. On a larger scale, observations over the Peel Boundary fault near the village of Uden also indicate that vertical groundwater flow close to the fault is enhanced, which results in a discharge of the underlying aquifers at the location of the fault zone. Finally, on a regional scale, hydraulic head patterns around the lignite mining areas in Germany show the importance of faults and the variation of their hydraulic properties to regional groundwater flow patterns. © 2003 Elsevier Science B.V. All rights reserved