Geophysikalische Erfassung von Feuchte- und Substratheterogenitäten im Boden auf unterschiedlichen Skalen

Soils interact with the hydro-, bio- and atmosphere and fulfil different environmental functions. Sufficient analysis of current and historical processes in soils is necessary to optimise soil conservation and to minimize damage to the ecosystem. Modelling of transport processes in soils provides knowledge of the complex environmental interaction. This requires extensive data with an appropriate resolution. The general aim of this thesis was to use geophysical methods for determining spatial and temporal heterogeneity of water and substrate. DC-geoelectrics and GPR provide three-dimensional images of near surface structures based on changes in electromagnetic and electrical conductivity. It is shown that geophysical methods enable spatial mapping of soil properties on different scales and that these methods can be used at different scales. This is important for a variety of reasons in disciplines such as soil sciences, hydrology and agronomy

Application of physical clogging models to Managed Aquifer Recharge: a review of modelling approaches from engineering fields

Managed Aquifer Recharge (MAR) sites suffer from the long-lasting problem of clogging. The causes of clogging are physical, biological, chemical and mechanical processes and their complex interaction, with physical clogging being recognised as the predominant process. The intrusion and deposition of particles during water recharge affect the hydraulic properties of the infiltration surface, resulting in a decline in the infiltration capacity of the site over the operating years. Cleaning operations are necessary to restore the original infiltration rates. For this purpose, assessing the risk of clogging can determine the site’s vulnerability and improve the scheme’s design. Numerical models are essential to replicate physical clogging processes and predict the decline in infiltration rates. So far, predictive tools for physical clogging assessment have been missing in MAR literature. Hence, the purpose of this study is to analyse and reorganise physical clogging models from applied engineering fields dealing with water infiltration in natural heterogeneous systems. The modelling approaches are illustrated, starting from the main assumptions and conceptualisation of the soil volume and intruding particles. The individual processes are untangled from the multiple studies and reorganised in a systematic comparison of mathematical equations relevant to MAR applications. The numerical models’ predictive power is evaluated for transferability, following limitations and recommendations for a process-based model applicable to surface spreading schemes. Finally, perspectives are given for clogging risk assessment at MAR sites from modelling and site characterisation. The predictive tool could assist decision-makers in planning the MAR site by implementing cost-effective strategies to lower the risk of physical clogging

Sediment budgeting of short‐term backfilling processes: The erosional collapse of a Carolingian canal construction

Sediment budgeting concepts serve as quantification tools to decipher the erosion and accumulation processes within a catchment and help to understand these relocation processes through time. While sediment budgets are widely used in geomorphological catchment-based studies, such quantification approaches are rarely applied in geoarchaeological studies. The case of Charlemagne's summit canal (also known as Fossa Carolina) and its erosional collapse provides an example for which we can use this geomorphological concept and understand the abandonment of the Carolingian construction site. The Fossa Carolina is one of the largest hydro-engineering projects in Medieval Europe. It is situated in Southern Franconia (48.9876°N, 10.9267°E; Bavaria, southern Germany) between the Altmühl and Swabian Rezat rivers. It should have bridged the Central European watershed and connected the Rhine–Main and Danube river systems. According to our dendrochronological analyses and historical sources, the excavation and construction of the Carolingian canal took place in AD 792 and 793. Contemporary written sources describe an intense backfill of excavated sediment in autumn AD 793. This short-term erosion event has been proposed as the principal reason for the collapse and abandonment of the hydro-engineering project. We use subsurface data (drillings, archaeological excavations, and direct-push sensing) and geospatial data (a LiDAR digital terrain model (DTM), a pre-modern DTM, and a 3D model of the Fossa Carolina] for the identification and sediment budgeting of the backfills. Dendrochronological findings and radiocarbon ages of macro remains within the backfills give clear evidence for the erosional collapse of the canal project during or directly after the construction period. Moreover, our quantification approach allows the detection of the major sedimentary collapse zone. The exceedance of the manpower tipping point may have caused the abandonment of the entire construction site. The spatial distribution of the dendrochronological results indicates a north–south direction of the early medieval construction progress

The fluvial architecture of buried floodplain sediments of the Weiße Elster River (Germany) revealed by a novel method combination of drill cores with two‐dimensional and spatially resolved geophysical measurements

The complex and non-linear fluvial river dynamics are characterized by repeated periods of fluvial erosion and re-deposition in different parts of the floodplain. Understanding the fluvial architecture (i.e. the three-dimensional arrangement and genetic interconnectedness of different sediment types) is therefore fundamental to obtain well-based information about controlling factors. However, investigating the fluvial architecture in buried floodplain deposits without natural exposures is challenging. We studied the fluvial architecture of the middle Weiße Elster floodplain in Central Germany, an extraordinary long-standing archive of Holocene flooding and landscape changes in sensitive loess-covered Central European landscapes. We applied a novel systematic approach by coupling two-dimensional transects of electrical resistivity tomography (ERT) measurements and closely spaced core drillings with spatially resolved measurements of electromagnetic induction (EMI) of larger floodplain areas at three study sites. This allowed for (i) time and cost-efficient core drillings based on preceding ERT measurements and (ii) spatially scaling up the main elements of the fluvial architecture, such as the distribution of thick silt-clay overbank deposits and paleochannel patterns from the floodplain transects to larger surrounding areas. We found that fine-grained sand and silt-clay overbank deposits overlying basal gravels were deposited during several periods of intensive flooding. Those were separated from each other by periods of reduced flooding, allowing soil formation. However, the overbank deposits were severely laterally eroded before and during each sedimentation period. This was probably linked with pronounced meandering or even braiding of the river. Our preliminary chronological classification suggests that first fine-grained sedimentation must have occurred during the Early to Middle Holocene, and the last phase of lateral erosion and sedimentation during the Little Ice Age. Our study demonstrates the high archive potential of the buried fluvial sediments of the middle Weiße Elster floodplain and provides a promising time and cost-effective approach for future studies of buried floodplain sediments

Quantifizierung von Wurzelparametern in Abhängigkeit von Bodeneigenschaften in einem Silomaisbestand

Information zur Wurzelverteilung stellt eine wichtige Größe für die Charakterisierung und Modellierung von Wasser- und Nährstoffaufnahme, Biomasseproduktion sowie Rhizodeposition dar. Detaillierte, räumlich hochaufgelöste Daten zur Wurzel-, Wasser-, Nährstoff- und Kohlenstoffverteilung im Feld zur Kalibrierung von Modellen stehen aber nur sehr begrenzt zur Verfügung. Ziel der Untersuchungen war es beispielhaft einen solchen Datensatz für einen Silomaisbestand zu erstellen und hierbei durch die Erfassung von geo- und bodenphysikalischen sowie pflanzenphysiologischen Parametern eine räumliche Korrelation zwischen diesen Größen zu testen

High-Resolution Direct Push Sensing in Wetland Geoarchaeology—First Traces of Off-Site Construction Activities at the Fossa Carolina

Wetland environments, with their excellent conservation conditions, provide geoarchaeological archives of past human activities. However, the subsurface soil is difficult to access due to high groundwater tables, unstable sediments, and the high cost of excavation. In this study, we present a ground-based non- and minimal-invasive prospection concept adapted to the conditions of wetlands. We investigated the Fossa Carolina in South Germany, a canal that was intended in 792/793 AD by Charlemagne to bridge the Central European Watershed. Although the resulting Carolingian banks and the fairway with wooden revetments are very imposing, archaeological traces of off-site construction activities have not been identified hitherto. Based on a geophysically surveyed intensive linear magnetic anomaly parallel to the Carolingian canal, we aimed to prove potential off-site traces of Carolingian construction activities. In this context, we built up a high-resolution cross-section using highly depth-accurate direct push sensing and ground-truthing. Our results showed the exact geometry of the canal and the former banks. Thus, the magnetic mass anomaly could be clearly located between the buried organic-rich topsoil and the Carolingian banks. The thermoluminescence dating showed that the position of the magnetic mass anomaly reflected Carolingian activities during the construction phases, specifically due to heat exposure. Moreover, we found hints of the groundwater supply to the 5-metre wide navigable fairway

Deichrückverlegungen in Sachsen-Anhalt und wissenschaftliche Begleituntersuchungen am Beispiel des Roßlauer Oberluchs

Deichbau und andere flussbautechnische Maßnahmen haben dazu geführt, dass die Mittlere Elbe ihre ursprünglichen Überschwemmungsgebiete verloren hat. Um die Auswirkungen der alljährlich auftretenden Hochwasserereignisse einzudämmen, wurden große Bereiche der Talniederung durch Deiche vom Überflutungsgeschehen abgetrennt. Diese Eingriffe in den Naturhaushalt ermöglichten gleichfalls eine intensive ackerbauliche Nutzung oder eine hochwassersichere Bebauung der Auen. Die natürliche Auendynamik ist heute weitestgehend auf einen schmalen Bereich entlang der Elbe beschränkt. Hinter den Deichen sind die für die Elbeauen typischen Lebensräume von der lebenswichtigen Auendynamik abgeschnitten. Angepasste Auenarten und -lebensgemeinschaften treten zugunsten von Allerweltsarten zurück. Eine Wiederanbindung von Altauenbereichen an das Überflutungsgeschehen ist deshalb eine der vordringlichsten Maßnahmen zur Revitalisierung gefährdeter Auenlebensräume und stellt eine Chance dar, einen nachhaltigen und modernen Hochwasserschutz mit Naturschutzzielen zu verbinden. An der Elbe entspricht das aktuelle Hochwasserschutzsystem nicht den heutigen Anforderungen an den Hochwasserschutz. Um jedoch jederzeit auf mögliche große Hochwasserereignisse reagieren zu können, entstanden Anfang der 1990er Jahre in den Anliegerländern der Elbe zahlreiche Pläne für Deichrückverlegungen

Are earth sciences lagging behind in data integration methodologies?

This article reflects discussions German and South African Earth scientists, statisticians and risk analysts had on occasion of two bilateral workshops on Data Integration Technologies for Earth System Modelling and Resource Management. The workshops were held in October 2012 at Leipzig, Germany, and April 2013 at Pretoria, South Africa, and were attended by about 70 researchers, practitioners and data managers of both countries. Both events were arranged as part of the South African-German Year of Science 2012/2013. The South African National Research Foundation (NRF, UID 81579) has supported the two workshops as part of the South African--German Year of Science activities 2012/2013 established by the German Federal Ministry of Education and Research and the South African Department of Science and Technology.http://link.springer.com/journal/12665hb201