@article{BloetheMunackKorupetal.2014, author = {Bloethe, Jan H. and Munack, Henry and Korup, Oliver and Fuelling, Alexander and Garzanti, Eduardo and Resentini, Alberto and Kubik, Peter W.}, title = {Late Quaternary valley infill and dissection in the Indus River, western Tibetan Plateau margin}, series = {Quaternary science reviews : the international multidisciplinary research and review journal}, volume = {94}, journal = {Quaternary science reviews : the international multidisciplinary research and review journal}, publisher = {Elsevier}, address = {Oxford}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2014.04.011}, pages = {102 -- 119}, year = {2014}, abstract = {The Indus, one of Earth's major rivers, drains large parts of the NW Himalaya and the Transhimalayan ranges that form part of the western Tibetan Plateau margin. In the western Himalayan syntaxis, where local topographic relief exceeds 7 km, the Indus has incised a steep bedrock gorge at rates of several mm yr(-1). Upstream, however, the upper Indus and its tributaries alternate between bedrock gorges and broad alluvial flats flanked by the Ladakh and Zanskar ranges. We review the late Quaternary valley history in this region with a focus on the confluence of the Indus and Zanskar Rivers, where vast alluvial terrace staircases and lake sediments record major episodes of aggradation and incision. New absolute dating of high-level fluvial terrace remnants using cosmogenic Be-10, optically and infrared stimulated luminescence (OSL, IRSL) indicates at least two phases of late Quaternary valley infilling. These phases commenced before similar to 200 ka and similar to 50-20 ka, judging from terrace treads stranded >150 m and similar to 30-40 m above modern river levels, respectively. Numerous stacks of lacustrine sediments that straddle the Indus River >200 km between the city of Leh and the confluence with the Shyok River share a distinct horizontal alignment. Constraints from IRSL samples of lacustrine sequences from the Leh-Spituk area reveal a protracted lake phase from >177 ka to 72 ka, locally accumulating >50-m thick deposits. In the absence of tectonic faulting, major lithological differences, and stream capture, we attribute the formation of this and other large lakes in the region to natural damming by large landslides, glaciers, and alluvial fans. The overall patchy landform age constraints from earlier studies can be reconciled by postulating a major deglacial control on sediment flux, valley infilling, and subsequent incision that has been modulated locally by backwater effects of natural damming. While comparison with Pleistocene monsoon proxies reveals no obvious correlation, a lateor post-glacial sediment pulse seems a more likely source of this widespread sedimentation that has partly buried the dissected bedrock topography. Overall, the long residence times of fluvial, alluvial and lacustrine deposits in the region (>500 ka) support previous studies, but remain striking given the dominantly steep slopes and deeply carved valleys that characterise this high-altitude mountain desert. Recalculated late Quaternary rates of fluvial bedrock incision in the Indus and Zanskar of 1.5 +/- 0.2 mm yr(-1) are at odds with the longevity of juxtaposed valley-fill deposits, unless a lack of decisive lateral fluvial erosion helps to preserve these late Pleistocene sedimentary archives. We conclude that alternating, similar to 10(4)-yr long, phases of massive infilling and incision have dominated the late Quaternary history of the Indus valley below the western Tibetan Plateau margin. (C) 2014 Elsevier Ltd. All rights reserved.}, language = {en} } @article{BronstertdeAraujoBatallaVillanuevaetal.2014, author = {Bronstert, Axel and de Araujo, Jos{\`e} Carlos and Batalla Villanueva, Ramon J. and Costa, Alexandre Cunha and Delgado, Jos{\´e} Miguel Martins and Francke, Till and F{\"o}rster, Saskia and Guentner, Andreas and Lopez-Tarazon, Jos{\´e} Andr{\´e}s and Mamede, George Leite and Medeiros, Pedro Henrique Augusto and Mueller, Eva and Vericat, Damia}, title = {Process-based modelling of erosion, sediment transport and reservoir siltation in mesoscale semi-arid catchments}, series = {Journal of soils and sediments : protection, risk assessment and remediation}, volume = {14}, journal = {Journal of soils and sediments : protection, risk assessment and remediation}, number = {12}, publisher = {Springer}, address = {Heidelberg}, issn = {1439-0108}, doi = {10.1007/s11368-014-0994-1}, pages = {2001 -- 2018}, year = {2014}, abstract = {To support scientifically sound water management in dryland environments a modelling system has been developed for the quantitative assessment of water and sediment fluxes in catchments, transport in the river system, and retention in reservoirs. The spatial scale of interest is the mesoscale because this is the scale most relevant for management of water and land resources. This modelling system comprises process-oriented hydrological components tailored for dryland characteristics coupled with components comprising hillslope erosion, sediment transport and reservoir deposition processes. The spatial discretization is hierarchically designed according to a multi-scale concept to account for particular relevant process scales. The non-linear and partly intermittent run-off generation and sediment dynamics are dealt with by accounting for connectivity phenomena at the intersections of landscape compartments. The modelling system has been developed by means of data from nested research catchments in NE-Spain and in NE-Brazil. In the semi-arid NE of Brazil sediment retention along the topography is the main process for sediment retention at all scales, i.e. the sediment delivery is transport limited. This kind of deposition retains roughly 50 to 60 \% of eroded sediment, maintaining a similar deposition proportion in all spatial scales investigated. On the other hand, the sediment retained in reservoirs is clearly related to the scale, increasing with catchment area. With increasing area, there are more reservoirs, increasing the possibility of deposition. Furthermore, the area increase also promotes an increase in flow volume, favouring the construction of larger reservoirs, which generally overflow less frequently and retain higher sediment fractions. The second example comprises a highly dynamic Mediterranean catchment in NE-Spain with nested sub-catchments and reveals the full dynamics of hydrological, erosion and deposition features. The run-off modelling performed well with only some overestimation during low-flow periods due to the neglect of water losses along the river. The simulated peaks in sediment flux are reproduced well, while low-flow sediment transport is less well captured, due to the disregard of sediment remobilization in the riverbed during low flow. This combined observation and modelling study deepened the understanding of hydro-sedimentological systems characterized by flashy run-off generation and by erosion and sediment transport pulses through the different landscape compartments. The connectivity between the different landscape compartments plays a very relevant role, regarding both the total mass of water and sediment transport and the transport time through the catchment.}, language = {en} } @phdthesis{Francke2009, author = {Francke, Till}, title = {Measurement and modelling of water and sediment fluxes in meso-scale dryland catchments}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-31525}, school = {Universit{\"a}t Potsdam}, year = {2009}, abstract = {Water shortage is a serious threat for many societies worldwide. In drylands, water management measures like the construction of reservoirs are affected by eroded sediments transported in the rivers. Thus, the capability of assessing water and sediment fluxes at the river basin scale is of vital importance to support management decisions and policy making. This subject was addressed by the DFG-funded SESAM-project (Sediment Export from large Semi-Arid catchments: Measurements and Modelling). As a part of this project, this thesis focuses on (1) the development and implementation of an erosion module for a meso-scale catchment model, (2) the development of upscaling and generalization methods for the parameterization of such model, (3) the execution of measurements to obtain data required for the modelling and (4) the application of the model to different study areas and its evaluation. The research was carried out in two meso-scale dryland catchments in NE-Spain: Ribera Salada (200 km²) and Is{\´a}bena (450 km²). Adressing objective 1, WASA-SED, a spatially semi-distributed model for water and sediment transport at the meso-scale was developed. The model simulates runoff and erosion processes at the hillslope scale, transport processes of suspended and bedload fluxes in the river reaches, and retention and remobilisation processes of sediments in reservoirs. This thesis introduces the model concept, presents current model applications and discusses its capabilities and limitations. Modelling at larger scales faces the dilemma of describing relevant processes while maintaining a manageable demand for input data and computation time. WASA-SED addresses this challenge by employing an innovative catena-based upscaling approach: the landscape is represented by characteristic toposequences. For deriving these toposequences with regard to multiple attributes (eg. topography, soils, vegetation) the LUMP-algorithm (Landscape Unit Mapping Program) was developed and related to objective 2. It incorporates an algorithm to retrieve representative catenas and their attributes, based on a Digital Elevation Model and supplemental spatial data. These catenas are classified to provide the discretization for the WASA-SED model. For objective 3, water and sediment fluxes were monitored at the catchment outlet of the Is{\´a}bena and some of its sub-catchments. For sediment yield estimation, the intermittent measurements of suspended sediment concentration (SSC) had to be interpolated. This thesis presents a comparison of traditional sediment rating curves (SRCs), generalized linear models (GLMs) and non-parametric regression using Random Forests (RF) and Quantile Regression Forests (QRF). The observed SSCs are highly variable and range over six orders of magnitude. For these data, traditional SRCs performed poorly, as did GLMs, despite including other relevant process variables (e.g. rainfall intensities, discharge characteristics). RF and QRF proved to be very robust and performed favourably for reproducing sediment dynamics. QRF additionally excels in providing estimates on the accuracy of the predictions. Subsequent analysis showed that most of the sediment was exported during intense storms of late summer. Later floods yielded successively less sediment. Comparing sediment generation to yield at the outlet suggested considerable storage effects within the river channel. Addressing objective 4, the WASA-SED model was parameterized for the two study areas in NE Spain and applied with different foci. For Ribera Salada, the uncalibrated model yielded reasonable results for runoff and sediment. It provided quantitative measures of the change in runoff and sediment yield for different land-uses. Additional land management scenarios were presented and compared to impacts caused by climate change projections. In contrast, the application for the Is{\´a}bena focussed on exploring the full potential of the model's predictive capabilities. The calibrated model achieved an acceptable performance for the validation period in terms of water and sediment fluxes. The inadequate representation of the lower sub-catchments inflicted considerable reductions on model performance, while results for the headwater catchments showed good agreement despite stark contrasts in sediment yield. In summary, the application of WASA-SED to three catchments proved the model framework to be a practicable multi-scale approach. It successfully links the hillslope to the catchment scale and integrates the three components hillslope, river and reservoir in one model. Thus, it provides a feasible approach for tackling issues of water and sediment yield at the meso-scale. The crucial role of processes like transmission losses and sediment storage in the river has been identified. Further advances can be expected when the representation of connectivity of water and sediment fluxes (intra-hillslope, hillslope-river, intra-river) is refined and input data improves.}, language = {en} } @masterthesis{Grosse2021, type = {Bachelor Thesis}, author = {Grosse, Peter}, title = {Modellierung der Sedimentdynamik im Rofental, {\"O}tztaler Alpen, unter Verwendung eines nichtparametrischen Modells}, doi = {10.25932/publishup-50669}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-506695}, school = {Universit{\"a}t Potsdam}, pages = {49}, year = {2021}, abstract = {The continued melting of glaciers releases more sediment deposits, making them more susceptible to erosion. Increased sediment discharge rates endanger water quality and water supply due to reservoir siltation. In order to better understand these hazards and their evolvement, erosion processes need to be studied, especially in high alpine catchment areas. In this bachelor thesis, sediment concentrations as well as other environmental variables, such as discharge, precipitation and temperature, were measured in the Rofental catchment ({\"O}tztal Alps) and in a highly glaciated sub-catchment of the Rofental. The quantile regression forest machine learning technique was applied to determine the correlation between sediment concentration and ancillary variables. The variables were aggregated to different levels, which allowed past hydroclimatic conditions to be taken into account. Considering the knowledge regarding the influence of these environment variables, the sediment concentration could be retrospectively simulated using a Monte Carlo approach. The resulting continuous time series was used to calculate the annual sediment export rates. The turbidity, as an indicator for the sediment concentration, was measured as well. By determining the correlation between the modelled data and the measured turbidity, the significance of the model could be assessed. The results show that the quantile regression forest model is a suitable approach to reconstruct the sediment dynamics in the Rofental. It further emerged that the discharge has a great impact on the sediment concentration in both catchments, with the relevance of the other variables varying widely between both study areas. The correlation between the measured turbidity and the simulated sediment concentration is strongly positive, whereby debris flows, measurement errors and the rinse of new sediment reservoirs deteriorated the model's performance.}, language = {de} } @phdthesis{Hoffmann2016, author = {Hoffmann, Bernd}, title = {Plant organic matter mobilization and export in fluvial systems}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-99336}, school = {Universit{\"a}t Potsdam}, pages = {xiii, 131}, year = {2016}, abstract = {The global carbon cycle is closely linked to Earth's climate. In the context of continuously unchecked anthropogenic CO₂ emissions, the importance of natural CO₂ bond and carbon storage is increasing. An important biogenic mechanism of natural atmospheric CO₂ drawdown is the photosynthetic carbon fixation in plants and the subsequent longterm deposition of plant detritus in sediments. The main objective of this thesis is to identify factors that control mobilization and transport of plant organic matter (pOM) through rivers towards sedimentation basins. I investigated this aspect in the eastern Nepalese Arun Valley. The trans-Himalayan Arun River is characterized by a strong elevation gradient (205 - 8848 m asl) that is accompanied by strong changes in ecology and climate ranging from wet tropical conditions in the Himalayan forelad to high alpine tundra on the Tibetan Plateau. Therefore, the Arun is an excellent natural laboratory, allowing the investigation of the effect of vegetation cover, climate, and topography on plant organic matter mobilization and export in tributaries along the gradient. Based on hydrogen isotope measurements of plant waxes sampled along the Arun River and its tributaries, I first developed a model that allows for an indirect quantification of pOM contributed to the mainsetm by the Arun's tributaries. In order to determine the role of climatic and topographic parameters of sampled tributary catchments, I looked for significant statistical relations between the amount of tributary pOM export and tributary characteristics (e.g. catchment size, plant cover, annual precipitation or runoff, topographic measures). On one hand, I demonstrated that pOMsourced from the Arun is not uniformly derived from its entire catchment area. On the other, I showed that dense vegetation is a necessary, but not sufficient, criterion for high tributary pOM export. Instead, I identified erosion and rainfall and runoff as key factors controlling pOM sourcing in the Arun Valley. This finding is supported by terrestrial cosmogenic nuclide concentrations measured on river sands along the Arun and its tributaries in order to quantify catchment wide denudation rates. Highest denudation rates corresponded well with maximum pOM mobilization and export also suggesting the link between erosion and pOM sourcing. The second part of this thesis focusses on the applicability of stable isotope records such as plant wax n-alkanes in sediment archives as qualitative and quantitative proxy for the variability of past Indian Summer Monsoon (ISM) strength. First, I determined how ISM strength affects the hydrogen and oxygen stable isotopic composition (reported as δD and δ18O values vs. Vienna Standard Mean Ocean Water) of precipitation in the Arun Valley and if this amount effect (Dansgaard, 1964) is strong enough to be recorded in potential paleo-ISM isotope proxies. Second, I investigated if potential isotope records across the Arun catchment reflect ISM strength dependent precipitation δD values only, or if the ISM isotope signal is superimposed by winter precipitation or glacial melt. Furthermore, I tested if δD values of plant waxes in fluvial deposits reflect δD values of environmental waters in the respective catchments. I showed that surface water δD values in the Arun Valley and precipitation δD from south of the Himalaya both changed similarly during two consecutive years (2011 \& 2012) with distinct ISM rainfall amounts (~20\% less in 2012). In order to evaluate the effect of other water sources (Winter-Westerly precipitation, glacial melt) and evapotranspiration in the Arun Valley, I analysed satellite remote sensing data of rainfall distribution (TRMM 3B42V7), snow cover (MODIS MOD10C1), glacial coverage (GLIMSdatabase, Global Land Ice Measurements from Space), and evapotranspiration (MODIS MOD16A2). In addition to the predominant ISM in the entire catchment I found through stable isotope analysis of surface waters indications for a considerable amount of glacial melt derived from high altitude tributaries and the Tibetan Plateau. Remotely sensed snow cover data revealed that the upper portion of the Arun also receives considerable winter precipitation, but the effect of snow melt on the Arun Valley hydrology could not be evaluated as it takes place in early summer, several months prior to our sampling campaigns. However, I infer that plant wax records and other potential stable isotope proxy archives below the snowline are well-suited for qualitative, and potentially quantitative, reconstructions of past changes of ISM strength.}, language = {en} } @article{Korup2012, author = {Korup, Oliver}, title = {Earth's portfolio of extreme sediment transport events}, series = {Earth science reviews : the international geological journal bridging the gap between research articles and textbooks}, volume = {112}, journal = {Earth science reviews : the international geological journal bridging the gap between research articles and textbooks}, number = {3-4}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0012-8252}, doi = {10.1016/j.earscirev.2012.02.006}, pages = {115 -- 125}, year = {2012}, abstract = {Quantitative estimates of sediment flux and the global cycling of sediments from hillslopes to rivers, estuaries, deltas, continental shelves, and deep-sea basins have a long research tradition. In this context, extremely large and commensurately rare sediment transport events have so far eluded a systematic analysis. To start filling this knowledge gap I review some of the highest reported sediment yields in mountain rivers impacted by volcanic eruptions, earthquake- and storm-triggered landslide episodes, and catastrophic dam breaks. Extreme specific yields, defined here as those exceeding the 95th percentile of compiled data, are similar to 10(4) t km(-2) yr(-1) if averaged over 1 yr. These extreme yields vary by eight orders of magnitude, but systematically decay with reference intervals from minutes to millennia such that yields vary by three orders of magnitude for a given reference interval. Sediment delivery from natural dam breaks and pyroclastic eruptions dominate these yields for a given reference interval. Even if averaged over 10(2)-10(3) yr, the contribution of individual disturbances may remain elevated above corresponding catchment denudation rates. I further estimate rates of sediment (re-)mobilisation by individual giant terrestrial and submarine mass movements. Less than 50 postglacial submarine mass movements have involved an equivalent of similar to 10\% of the contemporary annual global flux of fluvial sediment to Earth's oceans, while mobilisation rates by individual events rival the decadal-scale sediment discharge from tectonically active orogens such as Taiwan or New Zealand. Sediment flushing associated with catastrophic natural dam breaks is non-stationary and shows a distinct kink at the last glacial-interglacial transition, owing to the drainage of very large late Pleistocene ice-marginal lakes. Besides emphasising the contribution of high-magnitude and low-frequency events to the global sediment cascade, these findings stress the importance of sediment storage for fuelling rather than buffering high sediment transport rates.}, language = {en} } @article{KorupHayakawaCodileanetal.2014, author = {Korup, Oliver and Hayakawa, Yuichi and Codilean, Alexandru T. and Matsushi, Yuki and Saito, Hitoshi and Oguchi, Takashi and Matsuzaki, Hiroyuki}, title = {Japan's sediment flux to the Pacific Ocean revisited}, series = {Earth science reviews : the international geological journal bridging the gap between research articles and textbooks}, volume = {135}, journal = {Earth science reviews : the international geological journal bridging the gap between research articles and textbooks}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0012-8252}, doi = {10.1016/j.earscirev.2014.03.004}, pages = {1 -- 16}, year = {2014}, abstract = {Quantifying volumes and rates of delivery of terrestrial sediment from island arcs to subduction zones is indispensable for refining estimates of the thickness of trench fills that may eventually control the location and timing of submarine landslides and tsunami-generating mega-earthquakes. Despite these motivating insights, knowledge about the rates of erosion and sediment export from the Japanese islands to their Pacific subduction zones remains patchy regardless of the increasing availability of highly resolved data on surface deformation, climate, geology, and topography. Traditionally, natural erosion rates across the island arc have been estimated from regression of topographic catchment metrics and reservoir sedimentation rates that were recorded over several years to decades. We review current research in this context, correct for a systematic bias in one of the most widely used predictions, and present new estimates of decadal to millennial-scale erosion rates of Japan's terrestrial inner forearc. We draw on several independent and unprecedented inventories of mass wasting, reservoir sedimentation, and concentrations of cosmogenic Be-10 in river sands. We find that natural Be-10-derived denudation rates of several mm yr(-1) in the Japanese Alps have been sustained over several centuries to millennia, and are, within error, roughly consistent with sediment yields inferred from artificial reservoir sedimentation. Local exceptions may likely result from release of sediment storage or regional landsliding episodes that trigger transient sediment pulses. Our synopsis further reveals that catchments draining Japan's eastern seaboard differ distinctly in their tectonic, lithological, topographic, and climatic characteristics between the Tohoku, Japanese Alps, and Nankai inner forearc segments, which is underscored by a marked asymmetric pattern of erosion rates along the island arc. Erosion rates are highest (up to at least 3 mm yr(-1)) in the Japanese Alps that mark the collision of two subduction zones, where high topographic relief, hillslope and bedrock-channel steepness foster rapid denudation by mass wasting. Comparable, if slightly lower, erosion rates characterise the Nankai inner forearc in southwest Japan, most likely due to higher typhoon-driven rainfall totals and variability rather than its high topographic relief. In contrast, our estimated erosion and flux rates are lowest in the Tohoku inner forearc catchments that feed sediment into the Japan Trench. We conclude that collisional mountain building of the Japanese Alps drives some of the highest erosion rates in the island arc despite similar uplift and precipitation controls in southwest Japan. We infer that, prior to extensive river damming, reservoir construction, and coastal works, the gross of Japan's total sediment export to the Pacific Ocean entered the accretionary margin of the Nankai Trough as opposed to the comparatively sediment-starved Japan Trench. Compared to documented contemporary rates of sediment flux from mountainous catchments elsewhere in the Pacific, the rivers draining Japan's inner forearc take an intermediate position despite high relief, steep slopes, very high seismicity, and frequent rainstorms. However, the average rates of millennial-scale denudation in the Japanese Alps particularly are amongst the highest reported worldwide. Local mismatches between these late Holocene and modern rates emphasise the anthropogenic fingerprint on sediment retention that may have significantly reduced the island arc's mass flux to its subduction zones, as is the case elsewhere in east and southeast Asia. (C) 2014 Elsevier B.V. All rights reserved.}, language = {en} } @phdthesis{Kuhnert2009, author = {Kuhnert, Matthias}, title = {Quantifizierung von Oberfl{\"a}chenabfluss und Erosion auf B{\"o}den mit hydrophoben Eigenschaften}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-32871}, school = {Universit{\"a}t Potsdam}, year = {2009}, abstract = {Die Zielsetzung der vorliegenden Arbeit ist die Beschreibung hydrophober Bodeneigenschaften und deren Auswirkungen auf Oberfl{\"a}chenabfluss und Erosion auf verschiedenen Skalen. Die dazu durchgef{\"u}hrten Untersuchungen fanden auf einer Rekultivierungsfl{\"a}che im Braunkohlegebiet Welzow S{\"u}d (S{\"u}dostdeutschland) statt. Die Prozesse wurden auf drei Skalen untersucht, die von der Plotskala (1m²) {\"u}ber die Hangskala (300m²) bis zur Betrachtung eines kleinen Einzugsgebietes (4ha) reichen. Der Grad der hydrophoben Bodeneigenschaften wurde sowohl direkt, {\"u}ber die Bestimmung des Kontaktwinkel, als auch indirekt, {\"u}ber die Bestimmung der Persistenz, ermittelt. Dabei zeigte sich, dass der Boden im Winterhalbjahr hydrophil reagierte, w{\"a}hrend er im Sommerhalbjahr hydrophobe Bodeneigenschaften aufwies. Die Ergebnisse deuten darauf hin, dass ansteigende Bodenwassergehalte, die in der Literatur h{\"a}ufig als Ursache f{\"u}r einen Wechsel der Bodeneigenschaften angegeben werden, auf dieser Fl{\"a}che nicht zu einem Umbruch der Bodenbedingungen f{\"u}hren. Stattdessen kam es als Folge des Auftauens von gefrorenem Boden zu hydrophilen Bodeneigenschaften, die zu einem Anstieg des Bodenwassergehalts f{\"u}hrten. R{\"a}umliche Unterschiede zeigten sich in den geomorphologischen Einheiten. Rinnen und Rillen wiesen seltener hydrophobe Eigenschaften als die Zwischenrillenbereiche und Kuppen auf. Diese r{\"a}umlichen und zeitlichen Variabilit{\"a}ten wirkten sich auch auf den Oberfl{\"a}chenabfluss aus, der als Abflussbeiwert (ABW: Quotient aus Abfluss und Niederschlag) untersucht wurde. Der ABW liegt auf B{\"o}den mit hydrophoben Bodeneigenschaften (ABW=0,8) deutlich h{\"o}her als bei jenen mit hydrophilen Eigenschaften(ABW=0,2), wie sie im Winter oder auf anderem Substrat vorzufinden sind (diese Werte beziehen sich auf die Plotskala). Betrachtet man die Auswirkungen auf unterschiedlichen Skalen, nimmt der Abflussbeiwert mit zunehmender Fl{\"a}chengr{\"o}ße ab (ABW = 0,8 auf der Plotskala, ABW = 0,5 auf der Hangskala und ABW = 0,2 im gesamten Gebiet), was in den hydrophil reagierenden Rillen und Rinnen auf der Hangskala und dem hydrophilen Substrat im Einzugsgebiet begr{\"u}ndet ist. Zur Messung der Erosion wurden verschiedene, zum Teil neu entwickelte Methoden eingesetzt, um eine hohe zeitliche und r{\"a}umliche Aufl{\"o}sung zu erreichen. Bei einer neu entwickelten Methode wird der Sedimentaustrag ereignisbezogen {\"u}ber eine Waage bestimmt. In Kombination mit einer Kippwaage erm{\"o}glicht sie die gleichzeitige Messung des Oberfl{\"a}chenabflusses. Die Messapparatur wurde f{\"u}r Gebiete entwickelt, die eine {\"u}berwiegend grobsandige Textur aufweisen und nur geringe Mengen Ton und Schluff enthalten. Zus{\"a}tzlich wurden zwei Lasersysteme zur Messung der r{\"a}umlichen Verteilung der Erosion eingesetzt. F{\"u}r die erste Methode wurde ein punktuell messender Laser in einer fest installierten Apparatur {\"u}ber die Fl{\"a}che bewegt und punktuell H{\"o}henunterschiede in einem festen Raster bestimmt. Durch Interpolation konnten Bereiche mit Sedimentabtrag von Akkumulationsbereiche unterschieden werden. Mit dieser Methode k{\"o}nnen auch gr{\"o}ßere Fl{\"a}chen vermessen werden (hier 16 m²), allerdings weisen die Messungen in den {\"U}bergangsbereichen von Rinne zu Zwischenrille große Fehler auf. Bei der zweiten Methode wird mit einer Messung ein Quadratmeter mit einer hohen r{\"a}umlichen Aufl{\"o}sung komplett erfasst. Um ein dreidimensionales Bild zu erstellen, m{\"u}ssen insgesamt vier Aufnahmen von jeweils unterschiedlichen Seiten aufgenommen werden. So lassen sich Abtrag und Akkumulation sehr genau bestimmen, allerdings ist die Messung relativ aufwendig und erfasst nur eine kleine Fl{\"a}che. Zus{\"a}tzlich wurde der Sedimentaustrag noch auf der Plotskala erfasst. Die Messungen zeigen, korrespondierend zu den Bodeneigenschaften, große Sedimentaustr{\"a}ge w{\"a}hrend des Sommerhalbjahrs und kaum Austr{\"a}ge im Winter. Weiterhin belegen die Ergebnisse eine gr{\"o}ßere Bedeutung der Rillenerosion gegen{\"u}ber der Zwischenrillenerosion f{\"u}r Niederschlagsereignisse hoher Intensit{\"a}t (>25 mm/h in einem zehnmin{\"u}tigem Intervall). Im Gegensatz dazu dominierte die Zwischenrillenerosion bei Ereignissen geringerer Intensit{\"a}t (<20 mm/h in einem zehnmin{\"u}tigem Intervall), wobei mindestens 9 mm Niederschlag in einer Intensit{\"a}t von mindesten 3,6 mm/h n{\"o}tig sind, damit es zur Erosion kommt. Basierend auf den gemessenen Abfl{\"u}ssen und Sedimentaustr{\"a}gen wurden Regressiongleichungen abgeleitet, die eine Berechnung dieser beiden Prozesse f{\"u}r die untersuchte Fl{\"a}che erm{\"o}glichen. W{\"a}hrend die Menge an Oberfl{\"a}chenabfluss einen starken Zusammenhang zu der Menge an gefallenem Niederschlag zeigt (r² = 0,9), ist die Berechnung des ausgetragenen Sedimentes eher ungenau (r² = 0,7). Zusammenfassend beschreibt die Arbeit Einfl{\"u}sse hydrophober Bodeneigenschaften auf verschiedenen Skalen und arbeitet die Auswirkungen, die vor allem auf der kleinen Skala von großer Bedeutung sind, heraus.}, language = {de} } @phdthesis{Marc2016, author = {Marc, Odin}, title = {Earthquake-induced landsliding}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-96808}, school = {Universit{\"a}t Potsdam}, pages = {xvi, 171}, year = {2016}, abstract = {Earthquakes deform Earth's surface, building long-lasting topographic features and contributing to landscape and mountain formation. However, seismic waves produced by earthquakes may also destabilize hillslopes, leading to large amounts of soil and bedrock moving downslope. Moreover, static deformation and shaking are suspected to damage the surface bedrock and therefore alter its future properties, affecting hydrological and erosional dynamics. Thus, earthquakes participate both in mountain building and stimulate directly or indirectly their erosion. Moreover, the impact of earthquakes on hillslopes has important implications for the amount of sediment and organic matter delivered to rivers, and ultimately to oceans, during episodic catastrophic seismic crises, the magnitude of life and property losses associated with landsliding, the perturbation and recovery of landscape properties after shaking, and the long term topographic evolution of mountain belts. Several of these aspects have been addressed recently through individual case studies but additional data compilation as well as theoretical or numerical modelling are required to tackle these issues in a more systematic and rigorous manner. This dissertation combines data compilation of earthquake characteristics, landslide mapping, and seismological data interpretation with physically-based modeling in order to address how earthquakes impact on erosional processes and landscape evolution. Over short time scales (10-100 s) and intermediate length scales (10 km), I have attempted to improve our understanding and ability to predict the amount of landslide debris triggered by seismic shaking in epicentral areas. Over long time scales (1-100 ky) and across a mountain belt (100 km) I have modeled the competition between erosional unloading and building of topography associated with earthquakes. Finally, over intermediate time scales (1-10 y) and at the hillslope scale (0.1-1 km) I have collected geomorphological and seismological data that highlight persistent effects of earthquakes on landscape properties and behaviour. First, I compiled a database on earthquakes that produced significant landsliding, including an estimate of the total landslide volume and area, and earthquake characteristics such as seismic moment and source depth. A key issue is the accurate conversion of landslide maps into volume estimates. Therefore I also estimated how amalgamation - when mapping errors lead to the bundling of multiple landslide into a single polygon - affects volume estimates from various earthquake-induced landslide inventories and developed an algorithm to automatically detect this artifact. The database was used to test a physically-based prediction of the total landslide area and volume caused by earthquakes, based on seismological scaling relationships and a statistical description of the landscape properties. The model outperforms empirical fits in accuracy, with 25 out of 40 cases well predicted, and allows interpretation of many outliers in physical terms. Apart from seismological complexities neglected by the model I found that exceptional rock strength properties or antecedent conditions may explain most outliers. Second, I assessed the geomorphic effects of large earthquakes on landscape dynamics by surveying the temporal evolution of precipitation-normalized landslide rate. I found strongly elevated landslide rates following earthquakes that progressively recover over 1 to 4 years, indicating that regolith strength drops and recovers. The relaxation is clearly non-linear for at least one case, and does not seem to correlate with coseismic landslide reactivation, water table level increase or tree root-system recovery. I suggested that shallow bedrock is damaged by the earthquake and then heals on annual timescales. Such variations in ground strength must be translated into shallow subsurface seismic velocities that are increasingly surveyed with ambient seismic noise correlations. With seismic noise autocorrelation I computed the seismic velocity in the epicentral areas of three earthquakes where I constrained a change in landslide rate. We found similar recovery dynamics and timescales, suggesting that seismic noise correlation techniques could be further developed to meaningfully assess ground strength variations for landscape dynamics. These two measurements are also in good agreement with the temporal dynamics of post-seismic surface displacement measured by GPS. This correlation suggests that the surface healing mechanism may be driven by tectonic deformation, and that the surface regolith and fractured bedrock may behave as a granular media that slowly compacts as it is sheared or vibrated. Last, I compared our model of earthquake-induced landsliding with a standard formulation of surface deformation caused by earthquakes to understand which parameters govern the competition between the building and destruction of topography caused by earthquakes. In contrast with previous studies I found that very large (Mw>8) earthquakes always increase the average topography, whereas only intermediate (Mw ~ 7) earthquakes in steep landscapes may reduce topography. Moreover, I illustrated how the net effect of earthquakes varies with depth or landscape steepness implying a complex and ambivalent role through the life of a mountain belt. Further I showed that faults producing a Gutenberg-Richter distribution of earthquake sizes, will limit topography over a larger range of fault sizes than faults producing repeated earthquakes with a characteristic size.}, language = {en} } @misc{Mathaj2007, type = {Master Thesis}, author = {Mathaj, Martin}, title = {Modellierung von Vegetationsentwicklung und Erosion entlang eines Klimagradienten von mediterran bis semiarid}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27863}, school = {Universit{\"a}t Potsdam}, year = {2007}, abstract = {In dieser Arbeit wurde ein Modell mit einem gitterbasierten Ansatz entwickelt, um im Mediterranen entlang eines Klimagradienten Auswirkungen zu untersuchen, die Klima, Exposition, Hangneigung sowie St{\"o}rungen durch Feuer und Beweidung auf die Vegetations und Erosionsentwicklung besitzen. F{\"u}r die Fragestellung wurden Vegetationsalgorithmen benutzt. In dieser Studie verwendet wurden allgemeine Oberfl{\"a}chenprozesse, wie Wasser- und Sedimenttransport, die durch physikalische und empirische Modelle beschrieben worden sind. Des Weiteren wurde ein Sedimentverlust mit Hilfe der USLE kalkuliert, um ein Vergleich zwischen verschiedenen Erosionsans{\"a}tzen herzustellen. Die Vegetationsentwicklung und Erosion der mediterranen Gebiete konnte mit diesem Modell gut abgebildet werden. F{\"u}r die Vegetation der verschiedenen Klimagebiete und Habitate erwiesen sich die Wasserverf{\"u}gbarkeit und die Infiltrationsrate als maßgeblich. Die Erosion wurde vor allem durch einzelne heftige Niederschlagsereignisse beeinflusst. Dabei war vor allem am Hang und an steilen Neigungen ein hohes Erosionspotential gegeben. St{\"o}rungen durch Beweidung wirkten negativ auf die Vegetation und verst{\"a}rkten die Erosion. Feuer beeinflusste die Vegetations- und Erosionsentwicklung nur geringf{\"u}gig und ist somit zu vernachl{\"a}ssigen. Verschiedene B{\"o}den mit unterschiedlichen Texturen wiesen ein sehr unterschiedliches Erosionsverhalten auf. Dabei wiesen mittlere Korndurchmesser des Oberbodens von 0,02 bis 0,2 mm die h{\"o}chste Erosion auf. Die Vegetationsentwicklung wurde hingegen von der Bodentextur nicht beeinflust. Der Vergleich der Erosion berechnet durch die USLE und den Transportratenansatz verdeutlichte, dass die mittlere Erosion sehr {\"a}hnlich ausf{\"a}llt. Die USLE wies weniger Variabilit{\"a}t in der Erosion auf und ben{\"o}tigte zudem recht detaillierte Bodendaten. Der Ansatz gerade f{\"u}r die Erosionsberechnung in Form der Transportrate zeigte ein gutes Vorhersagepotential auf. In sehr variablen Umwelten ist diese Methode gegen{\"u}ber konservativen Erosionsmodellen zu bevorzugen, da interanuelle Dynamiken miterfasst werden, wie der Vergleich mit der USLE in der Studie gezeigt hatte. Mit Hilfe des Ansatzes der Transportrate besteht die M{\"o}glichkeit, Vorhersagen {\"u}ber Erosion {\"o}konomisch und effizient zu gestalten.}, language = {de} }