Tobias Heckmann

A network theory approach for a better understanding of overland flow connectivity

Hydrological connectivity describes the physical coupling (linkages) of different elements within a landscape regarding (sub-) surface flows. A firm understanding of hydrological connectivity is important for catchment management applications, for example, habitat and species protection, and for flood resistance and resilience improvement. Thinking about (geomorphological) systems as networks can lead to new insights, which has also been recognized within the scientific community, seeing the recent increase in the use of network (graph) theory within the geosciences. Network theory supports the analysis and understanding of complex systems by providing data structures for modelling objects and their linkages, and a versatile toolbox to quantitatively appraise network structure and properties. The objective of this study was to characterize and quantify overland flow connectivity dynamics on hillslopes in a humid sub-Mediterranean environment by using a combination of high-resolution digital-terrain models, overland flow sensors and a network approach. Results showed that there are significant differences between overland flow connectivity on agricultural areas and semi-natural shrubs areas. Significant positive correlations between connectivity and precipitation characteristics were found. Significant negative correlations between connectivity and soil moisture were found, most likely because of soil water repellency and/or soil surface crusting. The combination of structural networks and dynamic networks for determining potential connectivity and actual connectivity proved a powerful tool for analysing overland flow connectivity. Copyright

Hydrology and geomorphic effects of a high-magnitude flood in an alpine river

Abstract. The catchment of the River Partnach, a torrent situated in a glacial valley in the Northern Calcareous Alps of Bavaria/Germany, was affected by a high‐magnitude flood on 22/23 August 2005 with a peak discharge of more than 16 m3s‐1 at the spring and about 50 m3s‐1 at the catchment outlet. This flood was caused by a long period of intense rainfall with a maximum intensity of 230 mm per day. During this event, a landslide dam, which previously held a small lake, failed. The flood wave originating from the dam breach transported a large volume of sediment (more than 50 000 m3) derived from bank erosion and the massive undercutting of a talus cone. This caused a fundamental transformation of the downstream channel system including the redistribution of large woody debris and channel switching. Using terrestrial survey and aerial photography, erosional and depositional consequences of the event were mapped, pre‐ and post‐event surfaces were compared and the sediment budget of the event calculated for ten consecutive channel reaches downstream of the former lake. According to the calculations more than 100 000 tonnes of sediment were eroded, 75% of which was redeposited within the channel and the proximal floodplain. A previous large flood which occurred a few weeks prior to the August 2005 event had a significant effect on controlling the impact of this event.

Quantification and Modeling of Fluvial Bedload Discharge from Hillslope Channels in two Alpine Catchments (Bavarian Alps, Germany)

Fluvial activity in hillslope channels play a major role for the geomorphic system in alpine catchments as they link sediment sources in the upper parts of the catchment to the channel network. Within the framework of the SEDAG Project (Sediment Cascades in Alpine Geosystems) it was the aim of the presented work to measure the fluvial bedload discharge from such hillslope channels in two catchments in the northern Alps between 2000 and 2006 using 33 sediment traps. In combination with geospatial and statistical analyses, these data made it possible to identify those parameters that influence the fluvial bedload discharge. The spatial variability of the mean annual fluvial bedload di-scharge can be statistically explained by the size of the sediment contributing area. This area is derived by a rule based approach which includes distance to channel, slope and vegetation cover. Based on these results, a statistical model for the Lahnenwiesgraben was developed to predict mean annual bed load using the regression between measured bedload discharge and the size of the sediment contribu-ting area. The model was successfully validated using the measured bed load discharges in a second catchment (Reintal). Thus, by using the model it is possible to regionalize fluvial bedload discharge in the hillslope channels of both catchments and to identify those channels which have a very high sedi-ment output. Furthermore it is possible to calculate the sum of mean annual fluvial bed load input to the main channel (torrent) from all coupled hillslope channels for both catchments. Fluviale Hangprozesse sind ein wichtiger Bestandteil des geomorphologischen Prozessgeschehens in alpinen Einzugsgebieten, da diese haufig als Bindeglied zwischen dem Hauptgerinne und den weiter oberhalb in einem Einzugsgebiet liegenden Schuttdepots fungieren. Im Rahmen des SEDAG Projektes (Sediment Kaskaden in Alpinen Geosystemen) war es das Ziel der vorliegenden Arbeit den fluvialen Geschiebeaustrag aus Hanggerinnen in zwei Untersuchungsgebieten der nordlichen Kalkalpen durch den Einsatz von 33 Sedimentfallen zwischen 2000 und 2006 detailliert zu messen. In Verbindung mit digitalen Reliefanalysen und statistischen Auswertungen, konnten durch diese Daten diejenigen Parameter identifiziert werden, die den fluvialen Geschiebeaustrag aus Hanggerinnen masgeblich beeinflussen. Raumliche Variabilitaten in den mittleren jahrlichen Austragsraten lassen sich statistisch am besten mit der Grose der sedimentliefernden Flache erklaren. Diese wird durch einen regelbasierten Ansatz abgeleitet, der die Vegetationsbedeckung, die Entfernung zum Gerinne und die Hangneigung berucksichtigt. Aufbauend auf diesen Ergebnissen wurde ein statistisches Mod-ell entwickelt, das den Zusammenhang zwischen fluvialem Geschiebeaustrag aus den Hanggerinnen und der Grose der sedimentliefernden Flache verwendet. Um das Modell zu validieren, wurde dieses auch im zweiten Untersuchungsgebiet (Reintal) eingesetzt und das Ergebnis mit den dort gemessenen Geschiebeaustragen verglichen. Die Vorhersage des fluvialen Geschiebeaustrag im Reintal durch das Model war sehr gut. Die Anwendung des Models bietet nun die Moglichkeit den fluvialen Geschie-beaustrag fur alle Hanggerinne der beiden Untersuchungsgebiete zu regionalisieren und so Hangger-inne zu identifizieren, die einen hohen Sedimentaustrag aufweisen. Daruber hinaus ist es moglich die Summe des Geschiebeeintrags durch alle gekoppelten Hanggerinne in die Hauptbache beider Unter-suchungsgebiete zu berechnen.

The influence of historic land-use changes on hillslope erosion and sediment redistribution

Agricultural societies around the world have dramatically altered the natural landscape, particularly through accelerated soil erosion. The expansion of agricultural land use into steeper headwater areas during the Medieval period in central Europe is known to have caused large increases in soil erosion and sediment redistribution downstream. Although land-use practices changed and improved following this initial impact, it is currently unknown whether changes in land-use techniques also improved hillslope soil erosion and sediment redistribution rates. In this paper, we use a variety of techniques, including chrono-stratigraphy, wood charcoal analysis and a geostatistical model, to reconstruct land-use and erosion rates for the period spanning the Medieval Period to the present (1100–300 years ago) in a small headwater catchment in central Europe. Coupling land-use, hillslope erosion and sediment redistribution fluxes, we find the largest flux change occurs because of the initial deforestation at the beginning of the Medieval Period (1100 years ago). Following deforestation, we identified three main types of land-use techniques that were practised between ~1100 and 300 years ago: Horticulture, cropping agriculture and rotational birch silviculture, the last of which represents the earliest evidence for this practice found in central Europe to date. However, we find only small differences in hillslope fluxes throughout the catchment despite the variable land-use techniques employed. This is because the land-use techniques primarily influenced and increased the hillslope sediment storage capacity rather than erosion rates directly, which is an important distinction to consider for future work attempting to link changes in human land use and hillslope erosion.

Fuzzy delineation of drainage basins through probabilistic interpretation of diverging flow algorithms

The assessment of uncertainty is a major challenge in geomorphometry. Methods to quantify uncertainty in digital elevation models (DEM) are needed to assess and report derivatives such as drainage basins. While Monte-Carlo (MC) techniques have been developed and employed to assess the variability of second-order derivatives of DEMs, their application requires explicit error modeling and numerous simulations to reliably calculate error bounds. Here, we develop an analytical model to quantify and visualize uncertainty in drainage basin delineation in DEMs. The model is based on the assumption that multiple flow directions (MFD) represent a discrete probability distribution of non-diverging flow networks. The Shannon Index quantifies the uncertainty of each cell to drain into a specific drainage basin outlet. In addition, error bounds for drainage areas can be derived. An application of the model shows that it identifies areas in a DEM where drainage basin delineation is highly uncertain owing to flow dispersion on convex landforms such as alluvial fans. The model allows for a quantitative assessment of the magnitudes of expected drainage area variability and delivers constraints for observed volatile hydrological behavior in a palaeoenvironmental record of lake level change. Since the model cannot account for all uncertainties in drainage basin delineation we conclude that a joint application with MC techniques is promising for an efficient and comprehensive error assessment in the future.

Quantification and analysis of geomorphic processes on a recultivated iron ore mine on the Italian island of Elba using long-term ground-based lidar and photogrammetric SfM data by a UAV

This study focuses on the quantification and analysis of geomorphic processes on the barely vegetated slopes of a recultivated iron ore mine on the Italian island of Elba using photographs from terrestrial laser scanning (TLS) and digital photogrammetry by an unmanned aerial vehicle (UAV) over a period of 5 1/2 years. Beside this, the study tried to work out the potential and the limitations of both methods to detect surface changes by geomorphic process dynamics within a natural environment. Both UAV and TLS show the pattern of the erosion and accumulation processes on the investigated slope quite well, but the calculated amounts differ clearly between the methods. The reasons for these differences could be found in the different accuracies (variable level of detections) of the methods and the different viewing geometries. Both effects have an impact on the detectable process dynamics over different timescales on the slope and their calculated amounts, which in both cases can lead to an underestimation of erosion and accumulation by fluvial processes.

The integration of plant phenology and land use data to create a GIS-assisted bioclimatic characterisation of Bavaria, Germany

Background: Since phenology is a good bio-indicator of temperature the latter is often used in phenological analyses. However, whilst meteorological data are difficult to interpolate from point measurements at the desired resolution, region-wide digital data, e.g. elevation models or land cover data, are usually readily available. Aims: The potential of environmental variables, other than meteorological data, to create a bioclimatic classification of landscapes at the mesoscale was tested by the joint use of spatial data and the flowering dates of Forsythia suspensa at 70 phenological stations in southern Bavaria, Germany. Methods: A linear discriminant analysis was carried out to identify relevant land use variables that were correlated with phenology and, using these results, to regionalise the observed flowering dates within the framework of a Geographic Information System. Results: The generated map represented dates of onset at the regional scale, mostly influenced by the extent of impervious (hard, sealed) surfaces and forest, altitude and distance to urban areas. Thus, we overcame restrictions resulting from the difficulties of spatially interpolating available climatological data, and from the limited number of phenological datasets. Conclusions: We demonstrated that the selected variables were capable of adequately modelling regional bioclimatic zonation, and that phenology was a useful proxy of regional climate variation arising from both natural and anthropogenic factors.

Geomorphology of Proglacial Systems - Landform and Sediment Dynamics in Recently Deglaciated Alpine Landscapes

This book discusses the recession of alpine glaciers since the end of the Little Ice Age (LIA), which has been accelerating in the past decades. It provides an overview of the research in the field, presenting definitions and information about the different proglacial areas and systems. A number of case studies are from the PROSA project group which encompasses the expertise of geomorphologists, geologists, glaciologists and geodesists. The PROSA joint project (High-resolution measurements of morphodynamics in rapidly changing PROglacial Systems of the Alps) is determined to tackle the problems of geomorphic activity on sediment export through a quantification of sediment fluxes effected by the aforementioned geomorphic processes within the forefield of the Gepatschferner glacier (Central Alps, Austria).

Nachhaltigkeit in Umwelt, Wirtschaft und Gesellschaft

2009 begann an der Katholischen Universitat Eichstatt-Ingolstadt (KU) eine koordinierte mehrjahrige Forschung zu den zentralen Themen Nachhaltigkeit, Migration und Bildung. Die institutionelle Form der Forschung waren Graduiertenkollegs. Mit diesem Band werden die Ergebnisse des Graduiertenkollegs „Nachhaltigkeit in Wirtschaft , Umwelt und Gesellschaft “ vorgelegt. Naturgemas dominieren die Beitrage der Stipendiat_innen, die die Ergebnisse ihrer Forschung in dieser gesammelten Form vorlegen. Der einleitende Beitrag der Projektleiter_innen problematisiert im ersten Kapitel den Begriff der Nachhaltigkeit anhand verschiedener Vorstellungen inter- und transdisziplinarer Zusammenarbeit. Im zweiten Kapitel wird die Forschungslage zur Nachhaltigkeit in den beteiligten Disziplinen resumiert. Das dritte Kapitel spricht ausblickend Konzepte an, die nach praktikablen alternativen Modellen okonomischen und sozialen Austauschs fragen und dabei auf konkrete Beispiele fur eine tatsachlich mogliche Nachhaltigkeit hinweisen.

Ice and Snow as Land-Forming Agents

Abstract Many high-latitude and high-altitude regions are covered by ice and snow for substantial parts of the year, and typically, the landscape of such regions bears the strong imprint of ice- and snow-related processes operating over Quaternary to modern timescales. Despite strong research interest in the nature, rate, and efficacy of cold-region geomorphic processes, most research has been devoted to glacier and permafrost phenomena, whereas comparably few studies have quantitatively addressed the role of snow as a land-forming agent. In this chapter, we review the current research on land-forming processes related to glacial erosion and deposition; permafrost and periglacial processes; and snow-related processes such as nivation, snow creep, and snow avalanching. Our objective is to highlight those questions that drive current research and those that seem sufficiently promising to further our understanding of geomorphic form and process in the cryosphere. We do so bearing in mind that such process knowledge is essential for successfully predicting form and process, and hence avoiding snow- and ice-related hazards. We discuss whether certain aspects concerning the role of ice and snow as land-forming agents may have been overrated or underrated, if not overlooked, in the context of comprehensive studies on landscape evolution in polar and high mountainous terrain. We conclude by outlining a number of recommendations for future research in the field.