We present an approach that permits to predict hydraulic conductivity from extensive, multi-methodical geophysical data collected on a hillslope affected by landslides in Austria. The objective of the investigation is the spatial characterization of a slope affected by mass movements to derive hydrogeological structures and preferential flow paths. The geophysical data sets presented in this study consists of 24 densely distributed complex conductivity (CC) imaging profiles, collocated to these profiles we also collected 517 transient electromagnetic (TEM) soundings and 10 refraction seismic tomography (RST) profiles. Additionally, we also present well-logging data (namely electrical resistivity, natural gamma logs) collected in five boreholes. Cores recovered during the drilling of the boreholes are used to aid in the interpretation of the geophysical units, while analysis of the sediments was conducted to obtain grain size distributions, cation exchange capacity and mineralogy of the subsurface materials. While all geophysical data was processed initially independently, the final complex conductivity imaging results are based on the incorporation of structural constraints about the electrical units obtained from the TEM soundings. The interpretation of the resolved CC units is then sustained by the RST images and the lithological information from the boreholes. We estimate then the hydraulic conductivity of the subsurface derived from the CC images using a two-step approach. In a first step, we investigated the link between the complex conductivity and the different soil volume fractions of gravel, sand, silt and clay. In a second step, we applied a pedo-transfer function, namely the well-known Rosetta model, that permits to predict the hydraulic conductivity from the estimated grain size volumes. This approach allowed a quantitative interpretation of the geophysical data and thus a 3-dimensional (3D) representation of the grain size distribution and hydraulic conductivity in the investigated slope section. Thereby, we observed well-determined site-specific relationships ( R 2 > 0.7) from the comparison of the complex resistivity images and grain size analysis. The obtained hydrogeophysical 3D model permits to delineate the geometry of an aquiclude, and, thus, the analysis of preferential water-flow paths. In particular, we can identify a spatial correlation between the aquiclude interface and morphological features.

The distribution of soil organic carbon (OC) in the landscape shows high variability between landform positions. Soils in depositional sites are characterized by a highly diverse vertical structure and can contain significant amounts of OC over the whole soil profile. However, anthropogenic modifications of the landscape such as land use and artificial drainage can significantly alter the OC balance in a catchment. Here, we analyse the spatial distribution of OC stocks along an agriculturally used catena in a catchment, tributary to the Danube River in the Bavarian Forest in Southern Germany. The combination of geomorphic aspects with highly detailed soil data based on 16 soil profiles along a catena allowed us to closely examine the relationship between soil OC and the factors of landform position, soil inherent properties and grassland vs. cropland land use. We determined bulk density, total carbon (TC) and inorganic carbon (IC) for each soil horizon in order to quantify OC stocks and picture the vertical OC distribution in the soils. Pedogenic oxides were analysed as an indicator for the redox conditions as well as the soil development. Furthermore, we analysed the clay fraction as well as poorly crystalline iron oxides (Feox) as potential binding agents for OC. The persistence of OC in the landform positions could be designated by the proportion of C-14 content of the bulk soil OC. Our data revealed that the amount of OC stored in the topsoil is mostly determined by land use, but subsoil OC stocks highly depend on landform position. Most OC of this catena is stored in the floodplain featuring particularly high amounts of OC in their subsoils. Radiocarbon signatures of the floodplain OC indicated a young C-14 age compared to the footslope subsoils. We assume that these high OC stocks were due to 1.) formerly high input of OC-rich sediments, 2.) preservation of this OC from decomposition due to high water saturation and 3.) current land use (grassland). Dropping of the ground water table due to artificial drainage measures left detectable footprints within a few decades in the depth distribution of pedogenic iron oxides and indicated currently dominant oxic conditions within the uppermost 100 cm of the floodplain soils. We suspect that under these conditions the OC stocks are now vulnerable to OC losses. Even though we found no correlation between Feox and OC, it can be assumed that the interplay between Feox and OC will play a key role for the stabilization of the floodplain OC in the future. Today most floodplains in Central Europe are not in their natural state, but drained and under agricultural land use. Therefore this work points to the necessity of monitoring the OC pools in these landform positions and to consider quick responses when it comes to changes in the hydrologic regime and/or land-use system.

During the last decade, the State of Veracruz (Mexico) experienced a series of intense rainfall seasons with more than 1000 registered landslides. As a consequence, more than 45,000 people had to be evacuated and resettled. Even though the mountainous areas of Veracruz are highly prone to landslides, neither susceptibility maps nor any other relevant information (distribution of landslides, geology, etc.) with high spatial resolution is available. The high social impact of the most recent landslide hazards points out the necessity of detailed investigations in the affected areas. The aim of this study is to improve the understanding of process dynamics for the landslides and to provide the base for future susceptibility mapping. As an example, a young landslide with a high complexity of nested processes from the year 2013 is selected for detailed investigations in the east Trans Mexican Volcanic Belt in the State of Veracruz, related to the complexity of the studied landslide a multi-methodological approach is applied, which includes geomorphological mapping, sediment characterization as well as geophysical methods (electrical resistivity tomography, seismic refraction tomography). Field results indicate that the studied landslide must be regarded as a reactivated older landslide body, with a variety of intricate processes and numerous secondary slides. Detailed investigations provide deep insights in the dynamics and interactions of landslide processes related to their natural and anthropogenic settings.

(1) Institute of Geography and Geology, University of Wuerzburg, Würzburg, Germany (martina.wilde@uni-wuerzburg.de), (2) Institute of Geology, National Autonomous University of Mexico, Mexico City, Mexico (srre@unam.mx), (3) Geomorphology and Soil Science, Technische Universität München, Science Center Weihenstephan, Freising, Germany (daniel.schwindt@tum.de), (4) Department of Geophysics, Steinmann Institute, University of Bonn, Bonn, Germany (buecker.matthias@yahoo.de), (5) Department of Geodesy and Geoinformation, Geophysics Research Group, TU-Wien, Wien, Austria (adrian.flores-orozco@geo.tuwien.ac.at), (6) Geotem Ingeniería S.A. de C.V., Mexico (cpita@geotem.com.mx)

Since the Neolithic Revolution the intensification of agriculture has been causing increased erosion in Bavarian landscapes. The correlated sediments often induce the formation of new colluvial and alluvial soils (WRB: Regic Anthrosol and Fluvisol i.a.). The soils themselves are able to absorb, bind, and store considerable amounts of Cand N-compounds. Therefore, they are important reactors regarding climate-relevant greenhouse-gas balances in the atmosphere. Learning about the exact spatial extent and thickness of these soils in representative landscapes, but also about their geneses and processes is essential. It allows for a detailed quantification and understanding of the current and potential properties and characteristics of these soils in their role of greenhouse-gas reactors.

The landscape units were mapped and the area at the lower slope of a hill was divided into three units: a rinsing surface and a gravel plain, separated by a channel. On these surfaces soil profiles were excavated. Profile description followed the German system (Bodenkundliche Kartieranleitung KA 5) and disturbed samples were taken at various depths and analysed in the lab. Undisturbed soil cores with a volume of 100 cm3 were taken just below the surface at a depth of ∼1-6 cm. Lab analyses included texture and gravel content, colour, pH, electrical conductivity, carbonates, CNS, cation exchange capacity, pedogenic oxides, main and trace elements (XRF), and clay mineral distribution (XRD). Undisturbed samples were used to determine soil water retention curve, air permeability and bulk density.

The southern Kalahari drainage network is in a key position to analyze spatiotemporal changes in the tropical easterly and the temperate westerly circulation over the Southern African subcontinent. However, due to the prevailing aridity, paleoenvironmental archives within the southwestern Kalahari are sparse and often discontinuous. Hence, little is known about Holocene environmental change in this region. This study focuses on reconstructing paleoenvironmental change from the timing and provenance of fluvial deposits located within the Molopo Canyon, which connects the southern Kalahari drainage to the perennial flow regime of the Orange River. To gain insight into temporal aspects of fluvial morphodynamics within the Molopo Canyon, the entire variety of fluvial landforms consisting mainly of slope sediments, alluvial fans and alluvial fills were dated using Optically Stimulated Luminescence (OSL). We additionally applied a provenance analysis on alluvial fill deposits to estimate potential sediment source areas. Source areas were identified by analyzing the elemental and mineralogical composition of tributaries and eolian deposits throughout the course of the lower Molopo. The results allow the first general classification of fluvial landscape development into three temporally distinct deposition phases in the southern Kalahari: (1) A phase of canyon aggradation associated with short lived and spatially restricted flash floods during the early to mid-Holocene; (2) a phase of fan aggradation indicating a decrease in flood intensities during the mid- to late Holocene; and (3) a phase of canyon aggradation caused by the occurrence of supra-regional flood events during the Little Ice Age. We interpret the observed spatiotemporal deposition patterns to latitudinal shifts of the tropical easterly circulation in the early to mid-Holocene and the temperate westerly circulation in the late Holocene. However, despite marked changes in the provenance and timing of fluvial deposits in the Molopo Canyon throughout the Holocene, our analysis did not detect a contribution of sediments originating from the Kalahari interior to the deposition of alluvial fills. These results suggest that the southern Kalahari Drainage remained endorheic and therefore disconnected from the Orange River throughout the Holocene.

Die Region um Ebermannstadt ist stark anfällig für Massenbewegungen. Eine Rutschung aus dem Jahr 1957 wurde geomorphologisch kartiert und mit geophysikalischen Messungen (Gleichstromgeoelektrik sowie Refraktionsseismik) untersucht. Die Ziele der Untersuchungen waren eine Rekonstruktion der Beobachtungen von 1957 sowie deren Vergleich mit der heutigen Oberfläche und dem oberflächennahen Untergrund. Die Ergebnisse zeigen, dass die früheren Beobachtungen auch heute noch Gültigkeit besitzen. Darüber hinaus ist es möglich, einzelne Rutschungselemente und Prozesse zu differenzieren. Die Studie zeigt zudem die Verbreitung von alten Rutschmassen, welche in die Rutschung von 1957 eingebunden waren. Eine erneute Remobilisierung dieser Ablagerungen kann nicht ausgeschlossen werden.