TY - THES A1 - Öztürk, Ugur T1 - Learning more to predict landslides T1 - Ein verbessertes Wissen zur Prognose von Hangrutschungen N2 - Landslides are frequent natural hazards in rugged terrain, when the resisting frictional force of the surface of rupture yields to the gravitational force. These forces are functions of geological and morphological factors, such as angle of internal friction, local slope gradient or curvature, which remain static over hundreds of years; whereas more dynamic triggering events, such as rainfall and earthquakes, compromise the force balance by temporarily reducing resisting forces or adding transient loads. This thesis investigates landslide distribution and orientation due to landslide triggers (e.g. rainfall) at different scales (6-4∙10^5 km^2) and aims to link rainfall movement with the landslide distribution. It additionally explores the local impacts of the extreme rainstorms on landsliding and the role of precursory stability conditions that could be induced by an earlier trigger, such as an earthquake. Extreme rainfall is a common landslide trigger. Although several studies assessed rainfall intensity and duration to study the distribution of thus triggered landslides, only a few case studies quantified spatial rainfall patterns (i.e. orographic effect). Quantifying the regional trajectories of extreme rainfall could aid predicting landslide prone regions in Japan. To this end, I combined a non-linear correlation metric, namely event synchronization, and radial statistics to assess the general pattern of extreme rainfall tracks over distances of hundreds of kilometers using satellite based rainfall estimates. Results showed that, although the increase in rainfall intensity and duration positively correlates with landslide occurrence, the trajectories of typhoons and frontal storms were insufficient to explain landslide distribution in Japan. Extreme rainfall trajectories inclined northwestwards and were concentrated along some certain locations, such as coastlines of southern Japan, which was unnoticed in the landslide distribution of about 5000 rainfall-triggered landslides. These landslides seemed to respond to the mean annual rainfall rates. Above mentioned findings suggest further investigation on a more local scale to better understand the mechanistic response of landscape to extreme rainfall in terms of landslides. On May 2016 intense rainfall struck southern Germany triggering high waters and landslides. The highest damage was reported at the Braunsbach, which is located on the tributary-mouth fan formed by the Orlacher Bach. Orlacher Bach is a ~3 km long creek that drains a catchment of about ~6 km^2. I visited this catchment in June 2016 and mapped 48 landslides along the creek. Such high landslide activity was not reported in the nearby catchments within ~3300 km^2, despite similar rainfall intensity and duration based on weather radar estimates. My hypothesis was that several landslides were triggered by rainfall-triggered flash floods that undercut hillslope toes along the Orlacher Bach. I found that morphometric features such as slope and curvature play an important role in landslide distribution on this micro scale study site (<10 km^2). In addition, the high number of landslides along the Orlacher Bach could also be boosted by accumulated damages on hillslopes due karst weathering over longer time scales. Precursory damages on hillslopes could also be induced by past triggering events that effect landscape evolution, but this interaction is hard to assess independently from the latest trigger. For example, an earthquake might influence the evolution of a landscape decades long, besides its direct impacts, such as landslides that follow the earthquake. Here I studied the consequences of the 2016 Kumamoto Earthquake (MW 7.1) that triggered some 1500 landslides in an area of ~4000 km^2 in central Kyushu, Japan. Topography, i.e. local slope and curvature, both amplified and attenuated seismic waves, thus controlling the failure mechanism of those landslides (e.g. progressive). I found that topography fails in explaining the distribution and the preferred orientation of the landslides after the earthquake; instead the landslides were concentrated around the northeast of the rupture area and faced mostly normal to the rupture plane. This preferred location of the landslides was dominated mainly by the directivity effect of the strike-slip earthquake, which is the propagation of wave energy along the fault in the rupture direction; whereas amplitude variations of the seismic radiation altered the preferred orientation. I suspect that the earthquake directivity and the asymmetry of seismic radiation damaged hillslopes at those preferred locations increasing landslide susceptibility. Hence a future weak triggering event, e.g. scattered rainfall, could further trigger landslides at those damaged hillslopes. N2 - Hangrutschungen treten häufig in steilem Gelände auf, wenn die Erdanziehungskraft die Scherkräfte an der Oberfläche übersteigt. Diese Kräfte beinhalten geologische und geomorphologische Faktoren wie den Reibungswinkel oder die Neigung und Krümmung von Hängen, die über Jahrhunderte statisch bleiben können. Dynamische Ereignisse wie Regenfälle und Erdbeben können hingegen das Kräftegleichgewicht beeinträchtigen, indem sie Widerstandskräfte vorübergehend reduzieren oder Lasten temporär hinzufügen. Diese Arbeit untersucht die Verteilung und Orientierung von Hangrutschungen in Abhängigkeit von Auslösern (z.B. Niederschlag) auf verschiedenen Skalenebenen (6-4∙10^5 km^2) und verknüpft die Bewegung des Niederschlagssystems mit der Hangrutschungsverteilung. Zudem werden lokale Auswirkungen von extremen Gewittern auf Hangrutschungen untersucht, sowie vorausgehende Stabilitätsbedingungen, die durch ein früheres Ereignis, beispielsweise ein Erdbeben, verändert werden können. Extremer Niederschlag ist ein weithin bekannter Auslöser für Hangrutschungen. Obwohl mehrere Studien die Verteilung von Hangrutschungen mit der Niederschlagsintensität und -dauer verglichen haben, beachteten nur wenige Fallstudien das räumliche Bewegungsmuster des Niederschlags, i.e. den orographischen Effekt. Eine solche Quantifizierung könnte die Vorhersage von hangrutschungsgefährdete Regionen in Japan verbessern. Hierfür habe ich ein nicht-lineares Korrelationsmaß (event synchronization) auf regionale Sturmbahnen in Japan angewendet, um deren räumliche Verteilung durch satellitengestützen Regenschätzungen nachzuvollziehen. Die durchgeführten Untersuchungen zeigten, dass sich die Verteilung von Hangrutschungen nur unzureichend mit den Zugbahnen von Taifunen und Sturmtiefen erklären lässt. Die Stabilität von Hängen scheint mehr durch mittlere Jahresniederschlagsmengen beeinflusst zu werden. Erzielte Ergebnisse zeigen, dass weitere Untersuchungen auf lokaler Ebene nötig sind, um die unmittelbare Auswirkungen von Extremniederschlägen auf Hangstabilität und -rutschungen besser zu verstehen. Im Mai 2016 kam es in Süddeutschland zu einem heftigen Gewitter, das Hochwasser und Hangrutschungen ausgelöst hat. Der höchste Schaden wurde in Braunsbach, dessen Zentrum sich am Zufluss des Orlacher Bachs befindet, gemeldet. Der Orlacher Bach ist ~3 lang und hat ein Einzugsgebiet von etwa ~6 km^2. Ich habe dieses Einzugsgebiet im Juni 2016 besucht und 48 Hangrutschungen entlang des Baches kartiert. Ich vermutete, dass mehrere Hangrutschungen durch Sturzfluten ausgelöst wurden, welche die Hänge entlang des Orlacher Baches unterspülten. Ich stellte fest, dass morphometrische Merkmale wie die lokale Hangneigung und -krümmung eine wichtige Rolle bei der Hangrutschungsverteilung auf dieser Mikroskala spielen (<10 km^2). Darüber hinaus könnte die hohe Anzahl von Hangrutschungen am Orlacher Bach auch durch Karstverwitterung über längere Zeiträume verstärkt werden. Zahlreiche in der Vergangenheit liegende Ereignisse können die Stabilität eines Hanges beeinflussen. Der Einfluss solcher Ereignisse ist nur sehr schwer unabhängig voneinander abschätzbar. Beispielseise könnte ein Erdbeben die Entwicklung einer Landschaft über Jahrzehnte hin beeinflussen. Hier erforsche ich die Folgen des Kumamoto-Erdbebens 2016 (MW 7.1) das im Zentrum von Kyushu, Japan, ca. 1500 Hangrutschungen in einem Gebiet von ~4000 km^2 ausgelöst hat. Die Topographie (Hangneigung und -krümmung) verstärkte schwächte seismische Wellen gleichermaßen ab, wodurch der Auslösemechanismus dieser Hangrutschungen (z.B. progressiv) gesteuert wird. Ich konnte belegen, dass die Topographie die Verteilung und die bevorzugte Ausrichtung der Hangrutsche nach dem Erdbeben nicht erklären kann; stattdessen waren die Hangrutschungen um den Nordosten des Bruchgebiets herum konzentriert und standen meist senkrecht zur Bruchfläche. Diese bevorzugte Lage der Erdrutsche wurde hauptsächlich durch den Richtwirkungseffekt des Blattverschiebung-Erdbebens dominiert. Bei diesem handelt es sich um die Ausbreitung der Wellenenergie entlang des Bruches in Bruchrichtung, während Amplitudenvariationen der seismischen Strahlung die bevorzugte Orientierung ändern. Ich vermute, dass die Richtwirkung des Erdbebens und die Asymmetrie der seismischen Strahlung die Hangneigung an diesen bevorzugten Stellen schädigten und die Anfälligkeit für Hangrutschungen erhöhten. Daher könnte ein zukünftiges schwaches Ereignis wie z.B. ein unbedeutender Niederschlag an diesen beschädigten Hängen weitere Hangrutschungen auslösen. KW - landslides KW - complex networks KW - event synchronization KW - typhoons KW - Kumamoto earthquake KW - Braunsbach flash flood KW - Hangrutschungen KW - komplexes Netzwerk KW - Synchronisation von Ereignissen KW - Taifune KW - Kumamoto Erdbeben KW - Braunsbach Sturzflut Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-426439 ER - TY - JOUR A1 - Schwanghart, Wolfgang A1 - Ryan, Marie A1 - Korup, Oliver T1 - Topographic and seismic constraints on the vulnerability of himalayan hydropower JF - Geophysical research letters N2 - Plain Language Summary The 2015 Gorkha earthquake in Nepal caused severe losses in the hydropower sector. The country temporarily lost similar to 20% of its hydropower capacity, and >30 hydropower projects were damaged. The projects hit hardest were those that were affected by earthquake-triggered landslides. We show that these projects are located along very steep rivers with towering sidewalls that are prone to become unstable during strong seismic ground shaking. A statistical classification based on a topographic metric that expresses river steepness and earthquake ground acceleration is able to approximately predict hydropower damage during future earthquakes, based on successful testing of past cases. Thus, our model enables us to estimate earthquake damages to hydropower projects in other parts of the Himalayas. We find that >10% of the Himalayan drainage network may be unsuitable for hydropower infrastructure given high probabilities of high earthquake damages. KW - natural hazards KW - hydropower KW - landslides KW - Himalaya Y1 - 2018 U6 - https://doi.org/10.1029/2018GL079173 SN - 0094-8276 SN - 1944-8007 VL - 45 IS - 17 SP - 8985 EP - 8992 PB - American Geophysical Union CY - Washington ER - TY - THES A1 - Schuck, Bernhard T1 - Geomechanical and petrological characterisation of exposed slip zones, Alpine Fault, New Zealand T1 - Geomechanische und petrologische Charakterisierung aufgeschlossener Gleithorizonte, Alpine Fault, Neuseeland N2 - The Alpine Fault is a large, plate-bounding, strike-slip fault extending along the north-western edge of the Southern Alps, South Island, New Zealand. It regularly accommodates large (MW > 8) earthquakes and has a high statistical probability of failure in the near future, i.e., is late in its seismic cycle. This pending earthquake and associated co-seismic landslides are expected to cause severe infrastructural damage that would affect thousands of people, so it presents a substantial geohazard. The interdisciplinary study presented here aims to characterise the fault zone’s 4D (space and time) architecture, because this provides information about its rheological properties that will enable better assessment of the hazard the fault poses. The studies undertaken include field investigations of principal slip zone fault gouges exposed along strike of the fault, and subsequent laboratory analyses of these outcrop and additional borehole samples. These observations have provided new information on (I) characteristic microstructures down to the nanoscale that indicate which deformation mechanisms operated within the rocks, (II) mineralogical information that constrains the fault’s geomechanical behaviour and (III) geochemical compositional information that allows the influence of fluid- related alteration processes on material properties to be unraveled. Results show that along-strike variations of fault rock properties such as microstructures and mineralogical composition are minor and / or do not substantially influence fault zone architecture. They furthermore provide evidence that the architecture of the fault zone, particularly its fault core, is more complex than previously considered, and also more complex than expected for this sort of mature fault cutting quartzofeldspathic rocks. In particular our results strongly suggest that the fault has more than one principal slip zone, and that these form an anastomosing network extending into the basement below the cover of Quaternary sediments. The observations detailed in this thesis highlight that two major processes, (I) cataclasis and (II) authigenic mineral formation, are the major controls on the rheology of the Alpine Fault. The velocity-weakening behaviour of its fault gouge is favoured by abundant nanoparticles promoting powder lubrication and grain rolling rather than frictional sliding. Wall-rock fragmentation is accompanied by co-seismic, fluid-assisted dilatancy that is recorded by calcite cementation. This mineralisation, along with authigenic formation of phyllosilicates, quickly alters the petrophysical fault zone properties after each rupture, restoring fault competency. Dense networks of anastomosing and mutually cross-cutting calcite veins and intensively reworked gouge matrix demonstrate that strain repeatedly localised within the narrow fault gouge. Abundantly undeformed euhedral chlorite crystallites and calcite veins cross-cutting both fault gouge and gravels that overlie basement on the fault’s footwall provide evidence that the processes of authigenic phyllosilicate growth, fluid-assisted dilatancy and associated fault healing are processes active particularly close to the Earth’s surface in this fault zone. Exposed Alpine Fault rocks are subject to intense weathering as direct consequence of abundant orogenic rainfall associated with the fault’s location at the base of the Southern Alps. Furthermore, fault rock rheology is substantially affected by shallow-depth conditions such as the juxtaposition of competent hanging wall fault rocks on poorly consolidated footwall sediments. This means microstructural, mineralogical and geochemical properties of the exposed fault rocks may differ substantially from those at deeper levels, and thus are not characteristic of the majority of the fault rocks’ history. Examples are (I) frictionally weak smectites found within the fault gouges being artefacts formed at temperature conditions, and imparting petrophysical properties that are not typical for most of fault rocks of the Alpine Fault, (II) grain-scale dissolution resulting from subaerial weathering rather than deformation by pressure-solution processes and (III) fault gouge geometries being more complex than expected for deeper counterparts. The methodological approaches deployed in analyses of this, and other fault zones, and the major results of this study are finally discussed in order to contextualize slip zone investigations of fault zones and landslides. Like faults, landslides are major geohazards, which highlights the importance of characterising their geomechanical properties. Similarities between faults, especially those exposed to subaerial processes, and landslides, include mineralogical composition and geomechanical behaviour. Together, this ensures failure occurs predominantly by cataclastic processes, although aseismic creep promoted by weak phyllosilicates is not uncommon. Consequently, the multidisciplinary approach commonly used to investigate fault zones may contribute to increase the understanding of landslide faulting processes and the assessment of their hazard potential. N2 - Die Alpine Fault ist eine große Plattengrenze mit lateralem Versatz, die sich entlang des nordwestlichen Fußes der Südalpen, Südinsel Neuseeland, erstreckt. Regelmäßig ereignen sich große (MW > 8) Erdbeben und gegenwärtig befindet sich die Störung am Ende ihres Erdbebenzyklus, so dass ein baldiges Beben sehr wahrscheinlich ist. Die Alpine Fault stellt eine bedeutende Naturgefahr dar und so wird davon ausgegangen, dass tausende Menschen von dem anstehenden Erdbeben, ko-seismischen Hangrutschungen und den damit einhergehenden großen Schäden an der Infrastruktur betroffen sein werden. Daher zielt die hier vorgestellte interdisziplinäre Studie darauf ab, den Aufbau der Störungszone in 4D (räumlich und zeitlich) zu charakterisieren, weil dies Aufschluss über ihre rheologischen Eigenschaften liefert und damit einen Beitrag zur Einschätzung der von der Störung ausgehenden Gefahr leisten wird. Die durchgeführten Arbeiten umfassen Felduntersuchungen der entlang der Störung aufge- schlossenen Hauptscherzone und sich daran anschließende Laboruntersuchungen dieser Auf- schluss- und zusätzlicher Bohrlochproben. Diese geben Aufschluss über (I) charakteristis- che Mikrostrukturen bis in den Nanometerbereich, was erlaubt Deformationsmechanismen abzuleiten, (II) die Mineralogie und ihren Einfluss auf das geomechanische Verhalten und (III) die geochemische Zusammensetzung, die es ermöglicht, den Einfluss fluid-bezogener Alterationsprozesse auf Materialeigenschaften besser zu verstehen. Die Ergebnisse zeigen, dass Variationen der Eigenschaften der Störungsgesteine, wie Mikrostrukturen und mineralogische Zusammensetzung, entlang der Störung nur untergeord- net auftreten und den Aufbau der Störungszone nicht oder nur unwesentlich beeinflussen. Darüber hinaus zeigen sie, dass der Aufbau der Störungszone, vor allem ihres Kerns, komplexer ist als bisher angenommen. Dies ist unerwartet für eine Störung in quartz- und feldspatreichem Gestein dieses Alters. Diese Sicht wird von Ergebnissen gestützt, die nahelegen, dass die Störung mehr als eine Hauptscherzone hat und dass diese ein anastomisierendes Netzwerk bilden, das sich bis in das Festgestein unterhalb der Deckschicht aus quartären Sedimenten erstreckt. Die Beobachtungen dieser Arbeit zeigen, dass zwei Prozesse, (I) Kataklase und (II) au- thigenes Mineralwachstum, den größten Einfluss auf die Rheologie der Alpine Fault haben. Das “velocity-weakening”-Verhalten der Hauptscherzonen und ihres Gesteinsmehls wird durch die große Anzahl von Nanopartikeln begünstigt, die das Rollen der Partikel zu Ungunsten von Gleitreibungsrutschen fördern. Die Zerstückelung des Umgebungsgesteins geht mit ko- seismischer, fluid-unterstützter Dilatanz einher, die die anschließende Zementierung durch Kalzit begünstigt. Diese, in Kombination mit authigenen Schichtsilikaten, stellt die petro- physikalischen Eigenschaften der Störungszone nach jedem Erdbeben schnell wieder her. Dichte Netzwerke anastomisierender und sich gegenseitig durchschlagender Kalzitadern und umfassend aufgearbeitetes Gesteinsmehl belegen, dass Verformung wiederholt in den dünnen Hauptscherbahnen lokalisiert wurde. Kalzitadern durschlagen sowohl das Gesteinsmehl der Hauptscherbahnen als auch das Geröll, das die oberflächennahe Sedimentabdeckung des Festgesteins im Liegenden darstellt. Dies und allgegenwärtige, undeformierte, euhedrale Chlorit-Kristalle belegen, dass authigenes Schichtsilikatwachstum, fluid-unterstütze Dilatanz und das damit einhergehende Heilen der Störung Prozesse sind, die auch nahe der Erdoberfläche wirken. Freigelegte Gesteine der Alpine Fault sind intensiver Verwitterung als direkter Folge des reichlich vorhandenen Steigungsregens, der sich aus der Lage der Störung am Fuß der Südalpen ergibt, ausgesetzt. Darüber hinaus wird die Rheologie der Störungsgesteine erheblich durch oberflächennahen Randbedingungen wie die Gegenüberstellung kompetenter Störungsgesteine des Hangenden mit wenig-konsolidierten Sedimenten des Liegenden beeinflusst. Dies hat zur Folge, dass sich mikrostrukturelle, mineralogische und geochemische Eigenschaften der freigelegten Störungsgesteine erheblich von denen in größeren Tiefen unterscheiden können und folglich nicht charakteristisch für den Großteil der Deformationsgeschichte sind. Beispiele hierfür sind (I) Smektitphasen in den Hauptscherzonen, die einen niedrigen Reibungskoeffizien- ten aufweisen, allerdings Artefakte von für die Mehrheit der Gesteine dieser Störung atypischer Temperaturen und petrophysikalischer Eigenschaften sind, (II) angelöste Minerale als Ergebnis oberflächennaher Verwitterung und nicht von Drucklösung und (III) ein interner Aufbau des Gesteinsmehls der Hauptscherbahnen, der komplexerer ist, als dies für das Äquivalent in größerer Tiefe zu erwarten wäre. Schließlich werden die Ergebnisse dieser Arbeit gemeinsam mit den Hauptbefunden und methodischen Ansätzen anderer Studien zu Störungszonen diskutiert und in Kontext zu Analysen von Scherzonen in Störungen und Hangrutschungen gestellt. Hangrutschungen sind, wie Störungen, bedeutende Naturgefahren, was die Notwendigkeit, ihre geomechanischen Eigenschaften zu charakterisieren, herausstreicht. Störungen, vor allem jene, die Ober- flächenprozessen ausgesetzt sind, und Hangrutschungen teilen viele Gemeinsamkeiten wie mineralogische Zusammensetzung und geomechanisches Verhalten, was vor allem zu Versagen mittels kataklastischer Mechanismen führt; allerdings ist aseismisches Kriechen, befördert durch Schichtsilikate mit niedrigem Reibungskoeffizienten, nicht ungewöhnlich. Folglich könnte der multidisziplinäre Ansatz, der in der Regel zur Untersuchung von Störungszonen herangezogen wird, dazu beitragen das Verständnis von Hangrutschungen zu verbessern und ihr Gefährdungspotential abzuschätzen. KW - Alpine Fault KW - fluid rock interaction KW - microstructures KW - fault healing KW - authigenic mineral formation KW - brittle deformation KW - fault zone architecture KW - strain localization KW - landslides KW - faults KW - mineral composition KW - deformation mechanisms KW - Alpine Fault KW - Fluid-Gesteins-Wechselwirkung KW - Mikrostrukturen KW - Fault Healing KW - authigene Mineralbildung KW - spröde Deformation KW - Störungszonenarchitektur KW - Lokalisierung von Verformung KW - Erdrutsche KW - Verwerfungen KW - Mineralzusammensetzung KW - Deformationsmechanismen Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-446129 ER - TY - JOUR A1 - Roda-Boluda, Duna C. A1 - Whittaker, Alexander C. A1 - Gheorghiu, Delia M. A1 - Rodes, Angel A1 - D'Arcy, Mitch T1 - Be-10 erosion rates controlled by transient response to normal faulting through incision and landsliding JF - Earth & planetary science letters N2 - Quantifying erosion rates, and how they compare to rock uplift rates, is fundamental for understanding landscape response to tectonics and associated sediment fluxes from upland areas. The erosional response to uplift is well-represented by river incision and the associated landslide activity. However, characterising the relationship between these processes remains a major challenge in tectonically active areas, in some cases because landslides can preclude obtaining reliable erosion rates from cosmogenic radionuclide (CRN) concentrations. Here, we quantify the control of tectonics and its coupled geomorphic response on the erosion rates of catchments in southern Italy that are experiencing a transient response to normal faulting. We analyse in-situ Be-10 concentrations for detrital sediment samples, collected along the strike of faults with excellent tectonic constraints and landslide inventories. We demonstrate that Be-10-derived erosion rates are controlled by fault throw rates and the extent of transient incision and associated landsliding in the catchments. We show that the low-relief sub-catchments above knickpoints erode at uniform background rates of similar to 0.10 mm/yr, while downstream of knickpoints, erosion removes similar to 50% of the rock uplifted by the faults, at rates of 0.10-0.64 mm/yr. Despite widespread landsliding, CRN samples provide relatively consistent and accurate erosion rates, most likely because landslides are frequent, small, and shallow, and represent the integrated record of landsliding over several seismic cycles. Consequently, we combine these validated Be-10 erosion rates and data from a geomorphological landslide inventory in a published numerical model, to gain further insight into the long-term landslide rates and sediment mixing, highlighting the potential of CRN data to study landslide dynamics. (C) 2018 Elsevier B.V. All rights reserved. KW - cosmogenic nuclides KW - erosion rates KW - normal faults KW - incision KW - landslides KW - transient response Y1 - 2019 U6 - https://doi.org/10.1016/j.epsl.2018.11.032 SN - 0012-821X SN - 1385-013X VL - 507 SP - 140 EP - 153 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Roda-Boluda, Duna C. A1 - McDonald, Jordan A1 - Whittaker, Alexander C. A1 - D'Arcy, Mitchell T1 - Lithological controls on hillslope sediment supply BT - insights from landslide activity and grain size distributions JF - Earth surface processes and landforms : the journal of the British Geomorphological Research Group N2 - The volumes, rates and grain size distributions of sediment supplied from hillslopes represent the initial input of sediment delivered from upland areas and propagated through sediment routing systems. Moreover, hillslope sediment supply has a significant impact on landscape response time to tectonic and climatic perturbations. However, there are very few detailed field studies characterizing hillslope sediment supply as a function of lithology and delivery process. Here, we present new empirical data from tectonically-active areas in southern Italy that quantifies how lithology and rock strength control the landslide fluxes and grain size distributions supplied from hillslopes. Landslides are the major source of hillslope sediment supply in this area, and our inventory of similar to 2800 landslides reveals that landslide sediment flux is dominated by small, shallow landslides. We find that lithology and rock strength modulate the abundance of steep slopes and landslides, and the distribution of landslide sizes. Outcrop-scale rock strength also controls the grain sizes supplied by bedrock weathering, and influences the degree of coarsening of landslide supply with respect to weathering supply. Finally, we show that hillslope sediment supply largely determines the grain sizes of fluvial export, from catchments and that catchments with greater long-term landslide rates deliver coarser material. Therefore, our results demonstrate a dual control of lithology on hillslope sediment supply, by modulating both the sediment fluxes from landslides and the grain sizes supplied by hillslopes to the fluvial system. KW - lithology KW - hillslopes KW - landslides KW - grain size KW - sediment supply Y1 - 2018 U6 - https://doi.org/10.1002/esp.4281 SN - 0197-9337 SN - 1096-9837 VL - 43 IS - 5 SP - 956 EP - 977 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Olen, Stephanie M. A1 - Bookhagen, Bodo T1 - Applications of SAR interferometric coherence time series BT - satiotemporal dynamics of geomorphic transitions in the South-Central Andes JF - Journal of geophysical research : Earth surface N2 - Sediment transport domains in mountain landscapes are characterized by fundamentally different processes and rates depending on several factors, including geology, climate, and biota. Accurately identifying where transitions between transport domains occur is an important step to quantify the past, present, and future contribution of varying erosion and sedimentation processes and enhance our predictive capabilities. We propose a new methodology based on time series of synthetic aperture radar (SAR) interferometric coherence images to map sediment transport regimes across arid and semiarid landscapes. Using 4 years of Sentinel-1 data, we analyze sediment transport regimes for the south-central Andes in northwestern Argentina characterized by steep topographic and climatic gradients. We observe seasonally low coherence during the regional wet season, particularly on hillslopes and in alluvial channels. The spatial distribution of coherence is compared to drainage areas extracted from digital topography to identify two distinct transitions within watersheds: (a) a hillslope-to-fluvial and (b) a fluvial-to-alluvial transition. While transitions within a given basin can be well-constrained, the relative role of each sediment transport domain varies widely over the climatic and topographic gradients. In semiarid regions, we observe larger relative contributions from hillslopes compared to arid regions. Across regional gradients, the range of coherence within basins positively correlates to previously published millennial catchment-wide erosion rates and to topographic metrics used to indicate long-term uplift. Our study suggests that a dense time series of interferometric coherence can be used as a proxy for surface sediment movement and landscape stability in vegetation-free settings at event to decadal timescales. KW - Copernicus KW - SAR KW - critical infrastructure resilience KW - early warning KW - landslides Y1 - 2020 U6 - https://doi.org/10.1029/2019JF005141 SN - 2169-9003 SN - 2169-9011 VL - 125 IS - 3 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Obu, Jaroslav A1 - Lantuit, Hugues A1 - Fritz, Michael A1 - Pollard, Wayne H. A1 - Sachs, Torsten A1 - Guenther, Frank T1 - Relation between planimetric and volumetric measurements of permafrost coast erosion: a case study from Herschel Island, western Canadian Arctic JF - Polar research : a Norwegian journal of Polar research N2 - Ice-rich permafrost coasts often undergo rapid erosion, which results in land loss and release of considerable amounts of sediment, organic carbon and nutrients, impacting the near-shore ecosystems. Because of the lack of volumetric erosion data, Arctic coastal erosion studies typically report on planimetric erosion. Our aim is to explore the relationship between planimetric and volumetric coastal erosion measurements and to update the coastal erosion rates on Herschel Island in the Canadian Arctic. We used high-resolution digital elevation models to compute sediment release and compare volumetric data to planimetric estimations of coastline movements digitized from satellite imagery. Our results show that volumetric erosion is locally less variable and likely corresponds better with environmental forcing than planimetric erosion. Average sediment release volumes are in the same range as sediment release volumes calculated from coastline movements combined with cliff height. However, the differences between these estimates are significant for small coastal sections. We attribute the differences between planimetric and volumetric coastal erosion measurements to mass wasting, which is abundant along the coasts of Herschel Island. The average recorded coastline retreat on Herschel Island was 0.68m a(-1) for the period 2000-2011. Erosion rates increased by more than 50% in comparison with the period 1970-2000, which is in accordance with a recently observed increase along the Alaskan Beaufort Sea. The estimated annual sediment release was 28.2 m(3) m(-1) with resulting fluxes of 590 kg C m(-1) and 104 kg N m(-1). KW - Coastal erosion KW - LiDAR KW - carbon fluxes KW - mass wasting KW - landslides KW - digital elevation model Y1 - 2016 U6 - https://doi.org/10.3402/polar.v35.30313 SN - 0800-0395 SN - 1751-8369 VL - 35 SP - 57 EP - 99 PB - Co-Action Publ. CY - Jarfalla ER - TY - JOUR A1 - Huggel, Christian A1 - Clague, John J. A1 - Korup, Oliver T1 - Is climate change responsible for changing landslide activity in high mountains? JF - Earth surface processes and landforms : the journal of the British Geomorphological Research Group N2 - Climate change, manifested by an increase in mean, minimum, and maximum temperatures and by more intense rainstorms, is becoming more evident in many regions. An important consequence of these changes may be an increase in landslides in high mountains. More research, however, is necessary to detect changes in landslide magnitude and frequency related to contemporary climate, particularly in alpine regions hosting glaciers, permafrost, and snow. These regions not only are sensitive to changes in both temperature and precipitation, but are also areas in which landslides are ubiquitous even under a stable climate. We analyze a series of catastrophic slope failures that occurred in the mountains of Europe, the Americas, and the Caucasus since the end of the 1990s. We distinguish between rock and ice avalanches, debris flows from de-glaciated areas, and landslides that involve dynamic interactions with glacial and river processes. Analysis of these events indicates several important controls on slope stability in high mountains, including: the non-linear response of firn and ice to warming; three-dimensional warming of subsurface bedrock and its relation to site geology; de-glaciation accompanied by exposure of new sediment; and combined short-term effects of precipitation and temperature. Based on several case studies, we propose that the following mechanisms can significantly alter landslide magnitude and frequency, and thus hazard, under warming conditions: (1) positive feedbacks acting on mass movement processes that after an initial climatic stimulus may evolve independently of climate change; (2) threshold behavior and tipping points in geomorphic systems; (3) storage of sediment and ice involving important lag-time effects. KW - climate change KW - landslides KW - glaciers KW - permafrost Y1 - 2012 U6 - https://doi.org/10.1002/esp.2223 SN - 0197-9337 VL - 37 IS - 1 SP - 77 EP - 91 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Emberson, Robert A1 - Galy, Albert A1 - Hovius, Niels T1 - Weathering of Reactive Mineral Phases in Landslides Acts as a Source of Carbon Dioxide in Mountain Belts JF - Journal of geophysical research : Earth surface N2 - Bedrock landsliding in mountain belts can elevate overall chemical weathering rates through rapid dissolution of exhumed reactive mineral phases in transiently stored deposits. This link between a key process of erosion and the resultant weathering affects the sequestering of carbon dioxide through weathering of silicate minerals and broader links between erosion in active orogens and climate change. Here we address the effect on the carbon cycle of weathering induced by bedrock landsliding in Taiwan and the Western Southern Alps of New Zealand. Using solute chemistry data from samples of seepage from landslide deposits and river discharge from catchments with variable proportions of landsliding, we model the proportion of silicate and carbonate weathering and the balance of sulfuric and carbonic acids that act as weathering agents. We correct for secondary precipitation, geothermal, and cyclic input, to find a closer approximation of the weathering explicitly occurring within landslide deposits. We find highly variable proportions of sulfuric and carbonic acids driving weathering in landslides and stable hillslopes. Despite this variability, the predominance of rapid carbonate weathering within landslides and catchments where mass wasting is prevalent results at best in limited sequestration of carbon dioxide by this process of rapid erosion. In many cases where sulfuric acid is a key weathering agent, a net release of CO2 to the atmosphere occurs. This suggests that a causal link between erosion in mountain belts and climate change through the sequestration of CO2, if it exists, must operate through a process other than chemical weathering driven by landsliding. Plain Language Summary There is a long-standing debate surrounding the link between erosion and climate. It is often suggested that as temperatures increase, rainier and stormier weather could increase erosion of rock; as that rock is exposed, silicate minerals within could break down, which, on long time scales, can remove CO2 from the atmosphere, lowering global temperatures and acting as a negative feedback. Recent studies have shown that landslide deposits are key locations for the link between chemical weathering and physical erosion in some mountain belts. To test how landslides affect the erosion-climate link, we used samples of water seeping through landslides in Taiwan and New Zealand to calculate the amount of carbon dioxide that is either absorbed or released through this chemical reaction. We find that the large amount of freshly exposed rock in Taiwanese landslide deposits contains significant carbonate rock and sulfide minerals; the net result of the weathering of these minerals is a release of carbon dioxide, which inverts the traditional perspective on the role erosion plays in controlling carbon dioxide release. In some mountain belts, it seems that increased erosion and resulting landsliding may act to increase carbon dioxide in the air, opening further questions into the nature of erosional-climatic links. KW - chemical weathering KW - landslides KW - erosion-climate link KW - carbon dioxide Y1 - 2018 U6 - https://doi.org/10.1029/2018JF004672 SN - 2169-9003 SN - 2169-9011 VL - 123 IS - 10 SP - 2695 EP - 2713 PB - American Geophysical Union CY - Washington ER - TY - THES A1 - Bookhagen, Bodo T1 - Late quaternary climate changes and landscape evolution in the Northwest Himalaya : geomorphologic processes in the Indian Summer Monsoon Domain N2 - The India-Eurasia continental collision zone provides a spectacular example of active mountain building and climatic forcing. In order to quantify the critically important process of mass removal, I analyzed spatial and temporal precipitation patterns of the oscillating monsoon system and their geomorphic imprints. I processed passive microwave satellite data to derive high-resolution rainfall estimates for the last decade and identified an abnormal monsoon year in 2002. During this year, precipitation migrated far into the Sutlej Valley in the northwestern part of the Himalaya and reached regions behind orographic barriers that are normally arid. There, sediment flux, mean basin denudation rates, and channel-forming processes such as erosion by debris-flows increased significantly. Similarly, during the late Pleistocene and early Holocene, solar forcing increased the strength of the Indian summer monsoon for several millennia and presumably lead to analogous precipitation distribution as were observed during 2002. However, the persistent humid conditions in the steep, high-elevation parts of the Sutlej River resulted in deep-seated landsliding. Landslides were exceptionally large, mainly due to two processes that I infer for this time: At the onset of the intensified monsoon at 9.7 ka BP heavy rainfall and high river discharge removed material stored along the river, and lowered the baselevel. Second, enhanced discharge, sediment flux, and increased pore-water pressures along the hillslopes eventually lead to exceptionally large landslides that have not been observed in other periods. The excess sediments that were removed from the upstream parts of the Sutlej Valley were rapidly deposited in the low-gradient sectors of the lower Sutlej River. Timing of downcutting correlates with centennial-long weaker monsoon periods that were characterized by lower rainfall. I explain this relationship by taking sediment flux and rainfall dynamics into account: High sediment flux derived from the upstream parts of the Sutlej River during strong monsoon phases prevents fluvial incision due to oversaturation the fluvial sediment-transport capacity. In contrast, weaker monsoons result in a lower sediment flux that allows incision in the low-elevation parts of the Sutlej River. N2 - Die Indisch-Eurasische Kontinentalkollision ist ein beeindruckendes Beispiel für weitreichenden, tektonisch kontrollierten klimatischen Einfluss. Um den Einfluss von klimatisch bedingter Erosion auf die Orogenese zu testen, habe ich erosive Oberflächenprozesse, Monsunvariationen und fluviatilen Massentransfer auf verschiedenen Zeitscheiben analysiert. Um genaue Niederschläge auf einem grossen Raum zu quantifizieren, habe ich durch Wettersatelliten aufgezeichnete passive Mikrowellendaten für die letzten zehn Jahre untersucht. Erstaunlicherweise variiert der Niederschlag nur wenig von Jahr zu Jahr und ein Großteil des Regens wird durch orographische Effekte gesteuert. Im Jahre 2002 allerdings, habe ich ein abnormal starkes Monsunjahr feststellen können. Zu dieser Zeit ist der Monsunniederschlag weiter in das Gebirge vorgedrungen und hat viele Massenbewegungen wie z.B. Schuttströme und Muren ausgelöst. Dabei verdoppelten sich die Erosionsraten im Einzugsgebiet. Ich zeige anhand von Satellitenbildern, aufgenommen vor und nach dem Monsun, dass sich hierbei vor allen Dingen kleine, neue Flußläufe entwickeln. In höher gelegenen, normalerweise trockenen Gebieten findet man auch Überreste von enormen Bergstürzen und dahinter aufgestauten Seen. Datierungen dieser geomorphologischen Phänomene zeigen, dass sie nur in zwei Phasen während der letzten 30.000 Jahre auftreten: Im späten Pleistozän vor rund 27.000 Jahren und im frühen Holozän vor 8000 Jahre. Diese Zeiten sind durch einen starken Monsun, der durch die Insolation kontrolliert wird, gekennzeichnet. Analog zur Niederschlagsverteilung im Jahre 2002 ist der Monsun aber nicht nur für ein Jahr, sondern mehrere hundert oder tausend Jahre lang kontinuierlich in die heute ariden Gebiete vorgedrungen. Der erhöhte Porenwasserdruck und die erstarkten Flüsse lösten dann durch laterale Unterschneidung große Bergstürze aus, die zu keiner anderen Zeit beobachtet wurden. Die temporären Becken in den Hochlagen, die durch Bergstürze entstanden sind, entstehen in Feuchtphasen und werden in schwächeren Monsunphasen von Flüssen abgetragen und verdeutlicht die komplexe Beziehung zwischen Klima und Massentransfer verdeutlicht. ---- Anmerkung: Der Autor wurde 2005 mit dem 7. Publikationspreis des Leibniz-Kollegs Potsdam für Nachwuchswissenschaftler/innen in Naturwissenschaften ausgezeichnet. T2 - Late quaternary climate changes and landscape evolution in the Northwest Himalaya : geomorphologic processes in the Indian Summer Monsoon Domain KW - Monsun KW - Himalaja KW - Klima KW - Indien KW - Bergstürze KW - Geomorphologie KW - Asian monsoon KW - Himalaya KW - climate KW - landslides KW - geomorphology Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-0001956 ER -