Reconstructing Phreatic Palaeogroundwater Levels in a Geoarchaeological Context: A Case Study in Flanders, Belgium (original) (raw)
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Catena, 2012
Soil hydraulic properties evolve over time as a result of soil formation processes. We investigated the rate and circumstances of change in soil hydraulic properties as a result of soil and landscape evolution that took place over a period of a few decades to several thousands of years. To this end, a sediment-soil sequence in which different sandy landscapes and associated soils are preserved was studied with respect to its geomorphological and pedohydrological characteristics. Three stages of soil development corresponding to specific landscapes were observed within a 2-m deep profile: 1) a stabilisation surface within an active drift sand landscape, 2) an A-horizon that developed on a stabilised drift sand landscape and 3) a pronounced podzol that developed in a stabilised landscape from the last glacial. Measurement of soil physical properties was conducted including grain size analysis, organic carbon content, soil water retention characteristic and hydraulic conductivity using constant head and air permeability analyses. Age control of soil horizons and vegetation history were obtained from optically stimulated luminescence (OSL) dating, radiocarbon ( 14 C) dating, pollen analysis and historical archives. The results suggest a strong relationship between landscape evolution, soil development and hydraulic properties. Small changes in hydraulic properties may already be observed on a decadal and centennial scale, while long-term podzolisation processes may decrease the hydraulic conductivity of parent material up to three orders of magnitude in several thousands of years. It is concluded that combination of geomorphological and pedohydrological analyses of sediment-soil archives may provide a unique means to gain insight into the rate and extent of past changes in soil hydraulic properties and the consequences of future hydrological changes as a result of these evolving properties.
Geology for Society, Geological Survey of …, 2008
Since 2002, an intensive monitoring scheme at the World Heritage site of Bryggen in Bergen, western Norway, has shown damaging settling rates caused by deterioration of underlying cultural deposits. Monitoring focuses on both chemistry and quantity of groundwater and soil moisture content in the saturated and unsaturated zone. Continuous logging of piezometric head, oxygen and soil moisture content and chemical analyses of water and soil samples are key elements. The monitoring includes registration of movement rates for buildings and soil surface, field measurements and archaeological recording in small excavations, as well as studies of archaeological and modern materials in the subsoil. The results have given good insight into the preservation conditions, with focus on deterioration rates. Groundwater monitoring and chemical analyses reveal a dynamic flow regime under the thick, organic cultural deposits of the site. The flow regime is controlled by interaction of tidal fluctuations, urban drainage systems, natural and urban stratigraphy and bedrock hydraulic features. The documented preservation conditions within the cultural deposits as well as oxygen and moisture-content fluctuations in the unsaturated zone have a significant correlation with the different groundwater flow dynamics found throughout the site. It is demonstrated that groundwater and soil-moisture monitoring, combined with 3D transient modelling are potentially effective routines to improve the understanding of preservation conditions in complex archaeological surroundings and, therefore, protection of archaeological deposits in situ. de Beer, H. and Matthiesen, H. (008) Groundwater monitoring and modelling from an archaeological perspective: possibilities and challenges. In Slagstad, T. (ed.
2019
This document is edited at the occasion of the Geoarchaeological meeting of Brugge: Soils as records of Past and Present: the geoarchaeological approach. Focus on: is there time for fieldwork today? - Bruges (Belgium), 6 & 7.11.2019. It contains the abstracts of talks and posters presented during the scientific meeting and the abstracts of papers of the book edited at this occasion (Deák et al., 2019) In the past few decades, soil science has contributed greatly to discussions on climatic and environmental changes, as well as to the understanding of various topics of human impact on landscapes and the environment. This meeting aims to address these complex issues and to demonstrate how they are approached and unravelled through past and current interdisciplinary research. The plenary talks, the posters and the scientific paper of the book edited at the occasion of this meeting try to answer the following questions: What is the current state of research on soils as a record of past a...
Building data-bases in view of the large-scale hydrogeological modelling of Flanders
Existing groundwater models in Flanders (Belgium) are local small-scale models, which serve various goals and therefore often lead to conflicting results. Therefore, a (hydro)geological database and isohyps, isopach and occurrence maps are developed. The database and the maps are based upon the new numerical, hydrogeological code for Flanders (HCOV). The general purpose of the large-scale model is to stimulate integrated groundwater management.
Geoarchaeology, 2016
Well-preserved prehistoric landscapes and sites have been found, buried deeply below the Holocene peat or floodplain deposits of "Waasland Scheldt polders." During the mid-to-late Holocene, Late Weichselian (river) dunes within the floodplain and river flanks were favored locations for Final Early Neolithic occupation. Available living space was determined by the dune topography and elevation of the peat at that time. Therefore, an elevation model of the peat base was created using multireceiver electromagnetic induction (EMI) survey data. Electrical conductivity data of a dune were collected and 1D inverted within a three-layered soil model with variable electrical conductivity of the top layer and variable depth to the base of the middle layer (i.e., the peat). The modeled peat base depth was calibrated and validated, and eventually replaced by depth data from coring and cone penetration measurements wherever depth modeling from inverting the EMI measurements proved inaccurate. Using the resulting peat base elevation model, a paleogeographic map at the time of the modeled end date of Mesolithic-Neolithic transitional Swifterbant Culture sites nearby was created by chronologically modeling the peat elevation at that time. The developed paleogeographic mapping methodology can be used for subsequent archaeological prospection by core sampling or to contextualize excavated sites.
2010
Intensive archaeological investigations in Sandy Flanders (Belgium) revealed sites dating from the Final Paleolithic to the Neolithic, showing a discontinuous spatial and temporal distribution. To improve the understanding of these occupational patterns, a paleolandscape reconstruction is proposed. A major problem in paleolandscape reconstruction is that basic data are scattered in the temporal and spatial sense. Therefore, we propose an interdisciplinary approach to the application of different process models to soil–water–landscape reconstruction. The process models used include a digital elevation model, a hydrological, a pedogenetic, and a land-evaluation model. The result is a modeling framework in which these discipline-specific models, which provide input to each other, are integrated. Outcomes of the different models are still preliminary, because of the ongoing calibration and application of the models. The paper focuses on the methodological aspects of constructing the modeling framework and the questions one needs to answer in advance to facilitate the integration of the model results. Furthermore, errors within each individual model need to be accounted for and ideally are propagated into the next modeling step. Because of model complexity and runtime this is presently unfeasible. Alternatively, we propose to repeat the last step of the model framework (the land-evaluation procedure) for perturbations of the parameters reflecting the estimated model errors. We emphasize the difficulties occurring when integrating these different models, such as those relating to scale differences and error propagation. © 2010 Wiley Periodicals, Inc.
Topographic Wetness Index and Prehistoric Land Use
2008
A digital terrain model (DTM) of an area of approximately 100 km2 in East Jutland, Denmark, has been created based on information from the oldest available topographic map from the second half of the 19th century. On the basis of this model, a topographic wetness index for a 10 x 10 m cell grid has been calculated. In this index a threshold value has been estimated, which corresponds to an arable/non-arable classification of the area. This was done with the help of information from economic maps dating about 1800 AD. Finally it is argued that DTM’s generated on topographic maps drawn in 1:20,000 are too coarse for detailed modelling of land-use in large parts of prehistory. This conclusion has been achieved by comparing the modelled area with registered observations of archaeological finds and sites.
Environmental Geology, 2008
Aquifers from the same typology can have strongly different groundwater chemistry. Deducing the groundwater quality of less well-characterized aquifers from well-documented aquifers belonging to the same typology should be done with great reserve, and can only be considered as a preliminary approach. In the EU's 6th FP BRIDGE project ''Background cRiteria for the IDentification of Groundwater thrEsholds'', a methodology for the derivation of threshold values (TV) for groundwater bodies is proposed. This methodology is tested on four aquifers in Flanders of the sand and gravel typology. The methodology works well for all but the Ledo-Paniselian aquifer, where the subdivision into a fresh and saline part is disproved, as a gradual natural transition from fresh to saline conditions in the aquifer is observed. The 90 percentile is proposed as natural background level (NBL) for the unconfined Pleistocene deposits, ascribing the outliers to possible influence of pollution. For the Tertiary aquifers, high values for different parameters have a natural origin and the 97.7 percentile is preferred as NBL. The methodology leads to high TVs for parameters presenting low NBL, when compared to the standard used as a reference. This would allow for substantial anthropogenic inputs of these parameters. Keywords Groundwater Á Threshold values Á Natural background levels Á Flanders