Distribution of landslides in southwest New Zealand

This study examines the size distribution of a regional medium-scale inventory of 778 landslides in the mountainous southwest of New Zealand. The spatial density of mapped landslides per unit area can be expressed as a negative power-law function of Landslide area AL spanning three orders of magnitude (∼10−2-101km2). Although observed in other studies on landslide inventories, this relationship is surprising, given the lack of absolute ages, and thus uncertainty about the temporal observation window encompassed by the data. Large slope failures (arbitrarily defined here as having a total affected area AL>1km2) constitute 83% of the total affected landslide area ALT. This dominance by area affects slope morphology, where large-scale landsliding reduces slope angles below the regional modal value of hillslopes, ϕmod∼39°. More numerous smaller and shallower failures tend to be superimposed on the pre-existing relief. Empirical scaling relationships show that large landslides involve >106m3 of material. The volumes VL of individual preserved and presumably prehistoric (i.e. pre-1840) landslide deposits equate to 100-102 years of total sediment production from shallow landsliding in the respective catchments, and up to 103 years of contemporary regional sediment yield from the mountain ranges. Their presence in an erosional landscape indicates the geomorphic importance of landslides as temporary local sediment storag

Effects of finite source rupture on landslide triggering: the 2016 Mw 7.1 Kumamoto earthquake

The propagation of a seismic rupture on a fault introduces spatial variations in the seismic wave field surrounding the fault. This directivity effect results in larger shaking amplitudes in the rupture propagation direction. Its seismic radiation pattern also causes amplitude variations between the strike-normal and strike-parallel components of horizontal ground motion. We investigated the landslide response to these effects during the 2016 Kumamoto earthquake (Mw 7.1) in central Kyushu (Japan). Although the distribution of some 1500 earthquake-triggered landslides as a function of rupture distance is consistent with the observed Arias intensity, the landslides were more concentrated to the northeast of the southwest–northeast striking rupture. We examined several landslide susceptibility factors: hillslope inclination, the median amplification factor (MAF) of ground shaking, lithology, land cover, and topographic wetness. None of these factors sufficiently explains the landslide distribution or orientation (aspect), although the landslide head scarps have an elevated hillslope inclination and MAF. We propose a new physics-based ground-motion model (GMM) that accounts for the seismic rupture effects, and we demonstrate that the low-frequency seismic radiation pattern is consistent with the overall landslide distribution. Its spatial pattern is influenced by the rupture directivity effect, whereas landslide aspect is influenced by amplitude variations between the fault-normal and fault-parallel motion at frequencies <2 Hz. This azimuth dependence implies that comparable landslide concentrations can occur at different distances from the rupture. This quantitative link between the prevalent landslide aspect and the low-frequency seismic radiation pattern can improve coseismic landslide hazard assessment

Progress and challenges in glacial lake outburst flood research (2017–2021): a research community perspective

Glacial lake outburst floods (GLOFs) are among the most concerning consequences of retreating glaciers in mountain ranges worldwide. GLOFs have attracted significant attention amongst scientists and practitioners in the past 2 decades, with particular interest in the physical drivers and mechanisms of GLOF hazard and in socioeconomic and other human-related developments that affect vulnerabilities to GLOF events. This increased research focus on GLOFs is reflected in the gradually increasing number of papers published annually. This study offers an overview of recent GLOF research by analysing 594 peer-reviewed GLOF studies published between 2017 and 2021 (Web of Science and Scopus databases), reviewing the content and geographical focus as well as other characteristics of GLOF studies. This review is complemented with perspectives from the first GLOF conference (7–9 July 2021, online) where a global GLOF research community of major mountain regions gathered to discuss the current state of the art of integrated GLOF research. Therefore, representatives from 17 countries identified and elaborated trends and challenges and proposed possible ways forward to navigate future GLOF research, in four thematic areas: (i) understanding GLOFs – timing and processes; (ii) modelling GLOFs and GLOF process chains; (iii) GLOF risk management, prevention and warning; and (iv) human dimensions of GLOFs and GLOF attribution to climate change

Less extreme and earlier outbursts of ice-dammed lakes since 1900

Episodic failures of ice-dammed lakes have produced some of the largest floods in history, with disastrous consequences for communities in high mountains1–7. Yet, estimating changes in the activity of ice-dam failures through time remains controversial because of inconsistent regional flood databases. Here, by collating 1,569 ice-dam failures in six major mountain regions, we systematically assess trends in peak discharge, volume, annual timing and source elevation between 1900 and 2021. We show that extreme peak flows and volumes (10 per cent highest) have declined by about an order of magnitude over this period in five of the six regions, whereas median flood discharges have fallen less or have remained unchanged. Ice-dam floods worldwide today originate at higher elevations and happen about six weeks earlier in the year than in 1900. Individual ice-dammed lakes with repeated outbursts show similar negative trends in magnitude and earlier occurrence, although with only moderate correlation to glacier thinning8. We anticipate that ice dams will continue to fail in the near future, even as glaciers thin and recede. Yet widespread deglaciation, projected for nearly all regions by the end of the twenty-first century9, may bring most outburst activity to a halt

Catalytic reactor for operando spatially resolved structure–activity profiling using high-energy X-ray diffraction

In heterogeneous catalysis, operando measurements probe catalysts in their active state and are essential for revealing complex catalyst structure–activity relationships. The development of appropriate operando sample environments for spatially resolved studies has come strongly into focus in recent years, particularly when coupled to the powerful and multimodal characterization tools available at synchrotron light sources. However, most catalysis studies at synchrotron facilities only measure structural information about the catalyst in a spatially resolved manner, whereas gas analysis is restricted to the reactor outlet. Here, a fully automated and integrated catalytic profile reactor setup is shown for the combined measurement of temperature, gas composition and high-energy X-ray diffraction (XRD) profiles, using the oxidative de­hydrogenation of C$_{2}$H$_{6}$ to C$_{2}$H$_{4}$ over MoO$_{3}$/γ-Al$_{2}$O$_{3}$ as a test system. The profile reactor methodology was previously developed for X-ray absorption spectroscopy and is here extended for operando XRD. The profile reactor is a versatile and accessible research tool for combined spatially resolved structure–activity profiling, enabling the use of multiple synchrotron-based characterization methods to promote a knowledge-based optimization of a wide range of catalytic systems in a time- and resource-efficient wa

Progress and challenges in glacial lake outburst flood research (2017–2021):a research community perspective

Glacial lake outburst floods (GLOFs) are among the most concerning consequences of retreating glaciers in mountain ranges worldwide. GLOFs have attracted significant attention amongst scientists and practitioners in the past 2 decades, with particular interest in the physical drivers and mechanisms of GLOF hazard and in socioeconomic and other human-related developments that affect vulnerabilities to GLOF events. This increased research focus on GLOFs is reflected in the gradually increasing number of papers published annually. This study offers an overview of recent GLOF research by analysing 594 peer-reviewed GLOF studies published between 2017 and 2021 (Web of Science and Scopus databases), reviewing the content and geographical focus as well as other characteristics of GLOF studies. This review is complemented with perspectives from the first GLOF conference (7-9 July 2021, online) where a global GLOF research community of major mountain regions gathered to discuss the current state of the art of integrated GLOF research. Therefore, representatives from 17 countries identified and elaborated trends and challenges and proposed possible ways forward to navigate future GLOF research, in four thematic areas: (i) understanding GLOFs - timing and processes; (ii) modelling GLOFs and GLOF process chains; (iii) GLOF risk management, prevention and warning; and (iv) human dimensions of GLOFs and GLOF attribution to climate change.Fil: Emmer, Adam. University of Graz; AustriaFil: Allen, Simon K.. Universitat Zurich; Suiza. Universidad de Ginebra; SuizaFil: Carey, Mark. University of Oregon; Estados UnidosFil: Frey, Holger. Universitat Zurich; SuizaFil: Huggel, Christian. Universitat Zurich; SuizaFil: Korup, Oliver. Universitat Potsdam; AlemaniaFil: Mergili, Martin. University of Graz; AustriaFil: Sattar, Ashim. Universitat Zurich; SuizaFil: Veh, Georg. Universitat Potsdam; AlemaniaFil: Chen, Thomas Y.. Columbia University; Estados UnidosFil: Cook, Simon J.. University Of Dundee; Reino Unido. Unesco. Centre For Water Law, Policy And Science; Reino UnidoFil: Correas Gonzalez, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Das, Soumik. Jawaharlal Nehru University; IndiaFil: Diaz Moreno, Alejandro. Reynolds International Ltd; Reino UnidoFil: Drenkhan, Fabian. Pontificia Universidad Católica de Perú; PerúFil: Fischer, Melanie. Universitat Potsdam; AlemaniaFil: Immerzeel, Walter W.. Utrecht University; Países BajosFil: Izagirre, Eñaut. Universidad del País Vasco; EspañaFil: Joshi, Ramesh Chandra. Kumaun University India; IndiaFil: Kougkoulos, Ioannis. American College Of Greece; GreciaFil: Kuyakanon Knapp, Riamsara. University of Oslo; Noruega. University of Cambridge; Estados UnidosFil: Li, Dongfeng. National University Of Singapore; SingapurFil: Majeed, Ulfat. University Of Kashmir; IndiaFil: Matti, Stephanie. Haskoli Islands; IslandiaFil: Moulton, Holly. University of Oregon; Estados UnidosFil: Nick, Faezeh. Utrecht University; Países BajosFil: Piroton, Valentine. Université de Liège; BélgicaFil: Rashid, Irfan. University Of Kashmir; IndiaFil: Reza, Masoom. Kumaun University India; IndiaFil: Ribeiro De Figueiredo, Anderson. Universidade Federal do Rio Grande do Sul; BrasilFil: Riveros, Christian. Instituto Nacional de Investigación En Glaciares y Ecosistemas de Montaña; PerúFil: Shrestha, Finu. International Centre For Integrated Mountain Development Nepal; NepalFil: Shrestha, Milan. Arizona State University; Estados UnidosFil: Steiner, Jakob. International Centre For Integrated Mountain Development Nepal; NepalFil: Walker-Crawford, Noah. Colegio Universitario de Londres; Reino UnidoFil: Wood, Joanne L.. University of Exeter; Reino UnidoFil: Yde, Jacob C.. Western Norway University Of Applied Sciences; Suiz

Methanoxidation an Platinkatalysatoren - Untersuchungen mit ortsaufgelösten Methoden

Die katalytische Partialoxidation von Methan stellt eine reizvolle Reaktion zur Herstellung von Synthesegas, einer Vorstufe zur Synthese verschiedener Basischemikalien wie Methanol, Dimethylether oder Formaldehyd, dar. Die Reaktion ist mild exotherm und kann autotherm bei Temperaturen von etwa 1000°C, sowie Raumgeschwindigkeiten bis zu 500000 h^(−1) durchgeführt werden. Bei der Verwendung von Edelmetallkatalysatoren wie Rhodium- oder Platin-beschichteten Aluminiumoxid-Schaummonolithen können Gleichgewichtsausbeuten an Synthesegas in Kontaktzeiten in der Gro ̈ßenordnung von Millisekunden erzielt werden. Betrachtet man den Reaktionsverlauf entlang des Katalysatorbettes beobachtet man zwei Reaktionszonen. Im vorderen Teil des Katalysators, in Anwesenheit von Sauerstoff in der Reaktionsmischung, wird eine Kombination aus direkter Methan-Partial- und Methan-Totaloxidation beobachtet. Nachdem der Sauerstoff vollständig umgesetzt wurde, wird die Bildung von Synthesegas fortgesetzt, jetzt jedoch durch Dampfreformierung des verbleibenden Methans und des in der ersten Reaktionszone gebildeten Wasserdampfes. Die beobachteten Reaktionsgeschwindigkeiten von Oxidation und Dampfreformierung über Platin-beschichteten Schaummonolithen sind deutlich niedriger als die über den äquivalenten Rhodiumkatalysatoren. Für die Reaktion über Rhodiumkatalysatoren wurde eine Anzahl hochentwickelter mikrokinetischer Modelle entwickelt, welche die Eduktumsetzung und Produktbildung mit großer Genauigkeit vorhersagen können. Mit Hilfe dieser Modelle konnte ein gutes Verständnis über den Reaktionsmechanismus und die Transportprozesse in Rhodium-beschichteten Schaummonolithen erlangt werden. Im zurückliegenden Jahrzehnt wurde es dann auch möglich die mikrokinetischen Modelle mit experimentellen Daten zu validieren. Ermöglicht wurde dies durch die Entwicklung von speziellen Reaktoren, welche die Gradienten von Spezieskonzentrationen und der Temperatur innerhalb eines arbeitenden Katalysators hoch auflösen konnten. Die Pionierarbeiten von Horn et al., mit Schwerpunkt auf Rhodiumkatalysatoren, finden in der vorliegenden Arbeit ihre Fortführung, wobei Platinkatalysatoren untersucht werden. In einem weiterentwickelten Reaktorsystem wurde eine Serie von Reaktorprofilen gemessen und systematisch die Reaktantzusammensetzung, die Kontaktzeit und der Reaktordruck variiert. Neben Schaummonolithen wurden Experimente mit Kugelbetten und katalytischen Wandreaktoren durchgeführt. Mit mikrokinetischen Simulationen, welche ein pseudo-zweidimensional-heterogenes Reaktormodell mit der detaillierten Kinetik zweier unterschiedlicher State-of the-Art-Reaktionsmechanismen verbinden, wurden die experimentell erhaltenen Reaktorprofile in Platin-beschichteten Schaummonolithen modelliert. Die Ergebnisse der Modellierung zeigen signifikante Abweichungen in den Speziesprofilen von Simulation und Experiment. Durch Charakterisierung der verwendeten Katalysatoren vor und nach der katalytischen Testung (geometrische Oberfläche, BET- und Platinoberfläche, Metalldispersion, Platinkristallitgröße, Raman-Spektroscopy, Elektronmikroskopie, u.a.) konnte eine Umverteilung der Platinpartikel entlang des Katalystorschaumes, sowie eine signifikante Verkokung der Katalysatoroberfläche als Ursache der Abweichungen zwischen Modellierung und Experiment nachgewiesen werden. Die führenden, aktuellen mikrokinetischen Modelle vernachlässigen bislang eine inhomogene Verteilung der aktiven Zentren, und Reaktionspfade zum Aufbau von langkettigen Kohlenwasserstoffen wurden bislang nicht berücksichtigt. Die beobachtete Verkokung der Platin-beschichteten Schaummonolithe wurde durch in-situ-Raman-spektroskopische Experimente an einer polykristallinen Platinfolie bestätigt. Es konnte die Bildung und Modifikation von kohleartigen Ablagerungen auf der Platinfolie mit wachsender Reaktionszeit und/oder steigender Reaktionstemperatur dokumentiert werden. Die Ergebnisse dieser Arbeit geben neue Impulse für die Weiterentwicklung von bestehenden Reaktionsmechanismen für die katalytischen Partialoxidation von Methan über Platin.Catalytic partial oxidation (CPO) of methane is an attractive technology for industrial production of synthesis gas, an important precursor for the production of diverse basic chemicals, e.g. methanol, dimethyl ether, and formaldehyde. The exothermic reaction operates autothermally at temperatures around 1000°C and gas hourly space velocity (GHSV) values up to 500000 h^(−1). On noble metal catalysts such as rhodium and platinum coated alumina foams, equilibrium synthesis gas yields are reached within millisecond contact time. The CPO reaction proceeds in two steps along the catalyst bed. First a combination of direct methane partial oxidation coupled with methane deep oxidation is observed in the catalyst entrance section, where gas phase oxygen is present. After the oxygen is converted, product formation continues by a change in the reaction mechanism to steam reforming chemistry. Quantitative analysis reveals that the rates of oxidation and steam reforming are much lower on platinum than on rhodium coated foam catalysts. For rhodium catalysts sophisticated microkinetic models are available in literature, which can predict the reactant conversion and product formation with high accuracy. These models allow a good understanding of the reaction mechanism and transport properties in rhodium coated foam monoliths. Within the last decade it became possible to validate the microkinetic models, due to the development of high resolution spatial profile measurement techniques, that can measure species and temperature gradients inside the catalyst foams. The pioneering work by Horn et al., mainly focused on rhodium catalysts, is in this work extended to platinum catalysts. In a next generation reactor setup a set of reactor profiles was measured, systematically varying gas feed composition, contact time and reactor pressure. Besides foam monoliths, sphere beds and catalytic wall reactors have been tested. Microkinetic simulations applying a pseudo-2D heterogeneous reactor model that couples heat and mass transport limitations with detailed chemical kinetics of two different state-of-the-art microkinetic models taken from the literature have been used to simulate the experimentally measured reactor profiles through platinum coated foam monoliths. The reaction mechanisms predict species profiles considerably different from the measured profiles. By pre- and post-catalytic characterization of the catalyst by means of geometric, BET and platinum surface area, as well as metal dispersion and platinum crystallite size in combination with spatially resolved Raman spectroscopy and electron microscopy it was possible to identify significant metal redistribution and carbon formation on the catalyst surface as missing reaction pathways in the existing state-of-the-art microkinetic models. These findings are supported by in-situ Raman experiments on a polycrystalline platinum foil that follow the transition of the carbonaceous deposits with time on stream and reaction temperature. The results presented in this thesis give new impulses for ongoing mechanism development

Object-Based Detection of Lakes Prone to Seasonal Ice Cover on the Tibetan Plateau

The Tibetan Plateau, the world’s largest orogenic plateau, hosts thousands of lakes that play prominent roles as water resources, environmental archives, and sources of natural hazards such as glacier lake outburst floods. Previous studies have reported that the size of lakes on the Tibetan Plateau has changed rapidly in recent years, possibly because of atmospheric warming. Tracking these changes systematically with remote sensing data is challenging given the different spectral signatures of water, the potential for confusing lakes with glaciers, and difficulties in classifying frozen or partly frozen lakes. Object-based image analysis (OBIA) offers new opportunities for automated classification in this context, and we have explored this method for mapping lakes from LANDSAT images and Shuttle Radar Topography Mission (SRTM) elevation data. We tested our algorithm for most of the Tibetan Plateau, where lakes in tectonic depressions or blocked by glaciers and sediments have different surface colours and seasonal ice cover in images obtained in 1995 and 2015. We combined a modified normalised difference water index (MNDWI) with OBIA and local topographic slope data in order to classify lakes with an area &gt;10 km2. Our method derived 323 water bodies, with a total area of 31,258 km2, or 2.6% of the study area (in 2015). The same number of lakes had covered only 24,892 km2 in 1995; lake area has increased by ~26% in the past two decades. The classification had estimated producer’s and user’s accuracies of 0.98, with a Cohen’s kappa and F-score of 0.98, and may thus be a useful approximation for quantifying regional hydrological budgets. We have shown that our method is flexible and transferable to detecting lakes in diverse physical settings on several continents with similar success rates

Ice, moraine, and landslide dams in mountainous terrain

We review recent work on ice, moraine, and landslide dams in mountainous terrain, thus complementing several comprehensive summaries on glacier dams in intracontinental and Arctic areas of low relief. We discuss the roles of tectonic and climatic forcing on ice-, moraine-, and landslide-dam formation and sudden drainage, and focus on similarities and differences between their geomorphic impacts on confined valleys drained by steep bedrock and gravel-bed rivers. Despite numerous reported failures of natural dams in mountain belts throughout the world, their relevance to long-term dynamics of mountain rivers remains poorly quantified. All types of dams exert local base-level controls, thus trapping incoming sediment and inhibiting fluvial bedrock incision. Pervasive geomorphic and sedimentary evidence of outburst events is preserved even in areas of high erosion rates, suggesting that sudden dam failures are characterized by processes of catastrophic valley-floor aggradation, active-channel widening, and downstream dispersion of sediment, during which little bedrock erosion seems to be achieved. We find that, in the absence of direct evidence of former dams, a number of similarities among the geomorphic and sedimentologic characteristics of catastrophic outburst flows may give rise to ambiguous inferences on the dam-forming process. This is especially the case for tectonically active mountain belts where there is ample and comparable potential for the formation and failure of ice, moraine, landslide, and polygenetic dams concomitant with climatic oscillations or earthquake disturbance. Hence, the palaeoclimatic implications of erroneously inferring the cause of dam formation may be significant. We recommend that future research on natural dams in mountainous terrain addresses (a) climate- and earthquake-controlled systematics in the pattern of formation and failure; (b) quantification of response of mountain rivers to catastrophic outburst events and their concomitant process sequences; (c) elaboration of a comprehensive classification of natural dams in mountainous terrain with special attention to polygenetic dams; (d) physical-based modelling of dam formation, failure, and routing of water and sediment outbursts; and (e) quantitative controls on the contribution of natural dams to sediment budgets in mountainous terrain