TY - JOUR A1 - Francke, Till A1 - Baroni, Gabriele A1 - Brosinsky, Arlena A1 - Foerster, Saskia A1 - Lopez-Tarazon, José Andrés A1 - Sommerer, Erik A1 - Bronstert, Axel T1 - What Did Really Improve Our Mesoscale Hydrological Model? BT - a Multidimensional Analysis Based on Real Observations JF - Water resources research N2 - Modelers can improve a model by addressing the causes for the model errors (data errors and structural errors). This leads to implementing model enhancements (MEs), for example, meteorological data based on more monitoring stations, improved calibration data, and/or modifications in process formulations. However, deciding on which MEs to implement remains a matter of expert knowledge. After implementing multiple MEs, any improvement in model performance is not easily attributed, especially when considering different objectives or aspects of this improvement (e.g., better dynamics vs. reduced bias). We present an approach for comparing the effect of multiple MEs based on real observations and considering multiple objectives (MMEMO). A stepwise selection approach and structured plots help to address the multidimensionality of the problem. Tailored analyses allow a differentiated view on the effect of MEs and their interactions. MMEMO is applied to a case study employing the mesoscale hydro-sedimentological model WASA-SED for the Mediterranean-mountainous Isabena catchment, northeast Spain. The investigated seven MEs show diverse effects: some MEs (e.g., rainfall data) cause improvements for most objectives, while other MEs (e.g., land use data) only affect a few objectives or even decrease model performance. Interaction of MEs was observed for roughly half of the MEs, confirming the need to address them in the analysis. Calibration and increasing the temporal resolution showed by far stronger impact than any of the other MEs. The proposed framework can be adopted in other studies to analyze the effect of MEs and, thus, facilitate the identification and implementation of the most promising MEs for comparable cases. KW - modeling KW - sensitivity analyses KW - model enhancement KW - sediment Y1 - 2018 U6 - https://doi.org/10.1029/2018WR022813 SN - 0043-1397 SN - 1944-7973 VL - 54 IS - 11 SP - 8594 EP - 8612 PB - American Geophysical Union CY - Washington ER - TY - THES A1 - Jechow, Andreas T1 - Tailoring the emission of stripe-array diode lasers with external cavities to enable nonlinear frequency conversion T1 - Maßgeschneiderte Emission aus Breitstreifenlasern mit externen Resonatoren zur Ermöglichung nichtlinearer Frequenzkonversion N2 - A huge number of applications require coherent radiation in the visible spectral range. Since diode lasers are very compact and efficient light sources, there exists a great interest to cover these applications with diode laser emission. Despite modern band gap engineering not all wavelengths can be accessed with diode laser radiation. Especially in the visible spectral range between 480 nm and 630 nm no emission from diode lasers is available, yet. Nonlinear frequency conversion of near-infrared radiation is a common way to generate coherent emission in the visible spectral range. However, radiation with extraordinary spatial temporal and spectral quality is required to pump frequency conversion. Broad area (BA) diode lasers are reliable high power light sources in the near-infrared spectral range. They belong to the most efficient coherent light sources with electro-optical efficiencies of more than 70%. Standard BA lasers are not suitable as pump lasers for frequency conversion because of their poor beam quality and spectral properties. For this purpose, tapered lasers and diode lasers with Bragg gratings are utilized. However, these new diode laser structures demand for additional manufacturing and assembling steps that makes their processing challenging and expensive. An alternative to BA diode lasers is the stripe-array architecture. The emitting area of a stripe-array diode laser is comparable to a BA device and the manufacturing of these arrays requires only one additional process step. Such a stripe-array consists of several narrow striped emitters realized with close proximity. Due to the overlap of the fields of neighboring emitters or the presence of leaky waves, a strong coupling between the emitters exists. As a consequence, the emission of such an array is characterized by a so called supermode. However, for the free running stripe-array mode competition between several supermodes occurs because of the lack of wavelength stabilization. This leads to power fluctuations, spectral instabilities and poor beam quality. Thus, it was necessary to study the emission properties of those stripe-arrays to find new concepts to realize an external synchronization of the emitters. The aim was to achieve stable longitudinal and transversal single mode operation with high output powers giving a brightness sufficient for efficient nonlinear frequency conversion. For this purpose a comprehensive analysis of the stripe-array devices was done here. The physical effects that are the origin of the emission characteristics were investigated theoretically and experimentally. In this context numerical models could be verified and extended. A good agreement between simulation and experiment was observed. One way to stabilize a specific supermode of an array is to operate it in an external cavity. Based on mathematical simulations and experimental work, it was possible to design novel external cavities to select a specific supermode and stabilize all emitters of the array at the same wavelength. This resulted in stable emission with 1 W output power, a narrow bandwidth in the range of 2 MHz and a very good beam quality with M²<1.5. This is a new level of brightness and brilliance compared to other BA and stripe-array diode laser systems. The emission from this external cavity diode laser (ECDL) satisfied the requirements for nonlinear frequency conversion. Furthermore, a huge improvement to existing concepts was made. In the next step newly available periodically poled crystals were used for second harmonic generation (SHG) in single pass setups. With the stripe-array ECDL as pump source, more than 140 mW of coherent radiation at 488 nm could be generated with a very high opto-optical conversion efficiency. The generated blue light had very good transversal and longitudinal properties and could be used to generate biphotons by parametric down-conversion. This was feasible because of the improvement made with the infrared stripe-array diode lasers due to the development of new physical concepts. N2 - Für eine Vielzahl von interessanten Anwendungen z.B. in den Lebenswissenschaften werden kohärente Strahlquellen im sichtbaren Spektralbereich benötigt. Diese Strahlquellen sollen sich durch eine hohe Effizienz (d.h. Sparsamkeit), Mobilität und eine hohe Güte des emittierten Lichtes auszeichnen. Im Idealfall passt die Lichtquelle in die Hosentasche und kann mit herkömmlichen Batterien betrieben werden. Diodenlaser sind solche kleinen und sehr effizienten Strahlquellen. Sie sind heutzutage allgegenwärtig, begegnen uns in CD-Playern, Laserdruckern oder an Supermarktkassen im täglichen Leben. Diodenlaser zeichnen sich durch ihren extrem hohen Wirkungsgrad aus, da hier elektrischer Strom direkt in Licht umgewandelt wird. Jedoch können bisher noch nicht alle Wellenlängen im sichtbaren Bereich mit diesen Lasern realisiert werden. Eine Möglichkeit, diesen Wellenlängenbereich über einen Umweg zu erreichen, ist Frequenzkonversion von infrarotem in sichtbares Licht mit sogenannten nichtlinearen optischen Kristallen. Dies ist im Prinzip auch mit Diodenlasern möglich, konnte bisher jedoch nur sehr ineffizient oder mit erheblichem Aufwand umgesetzt werden. Allerdings kann mit Hilfe von externen Resonatoren die Emission solcher Standard-Laserdioden maßgeblich beeinflusst und die Qualität des Lichtes erheblich verbessert werden. Hier setzt die Zielsetzung dieser Arbeit an: Das Licht von infraroten Hochleistungslaserdioden, sogenannten „Streifen-Arrays“, sollte durch einen externen Resonator stabilisiert und für die Frequenzverdopplung erschlossen werden. Diese Arrays bestehen aus mehreren dicht nebeneinander angeordneten Einzelemittern und zeichnen sich dadurch aus, dass eine Kopplung dieser Emitter von außen möglich ist. Im ersten Schritt sollte eine solche Synchronisation der Emitter erreicht werden. In einem zweiten Schritt soll das von außen beeinflusste Licht des Arrays mit einer hohen Effizienz in sichtbares (blaues) Licht konvertiert werden um den Wirkungsgrad der Diodenlaser voll auszunutzen. Dafür war es notwendig die Physik der Streifen-Arrays sorgfältig zu untersuchen. Es mussten Methoden entwickelt werden, durch die eine gezielte Beeinflussung der Emitter möglich ist, damit es zu einer globalen Kopplung und Synchronisation der Array Emitter kommt. Dafür wurden mit Hilfe von mathematischen Modellierungen und Experimenten verschiedene Resonatorkonzepte entwickelt und realisiert. Schlussendlich war es möglich, die Emissionseigenschaften der Arrays um mehrere Größenordnungen zu verbessern und sehr effizient kohärentes blaues Licht sehr hoher Güte zu erzeugen. In einem weiteren Experiment ist es zusätzlich gelungen nichtklassisches Licht bzw. Paarphotonen zu generieren, die ebenfalls interessant für die Lebenswissenschaften sind. KW - Diodenlaser KW - Frequenzkonversion KW - Kopplung KW - Modellierung KW - externe Resonatoren KW - diode-lasers KW - diode-laser-arrays KW - external cavities KW - modeling Y1 - 2009 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-39653 SN - 978-3-86956-031-1 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - JOUR A1 - Huber, Robert A1 - Rigling, Andreas A1 - Bebi, Peter A1 - Brand, Fridolin Simon A1 - Briner, Simon A1 - Buttler, Alexandre A1 - Elkin, Che A1 - Gillet, Francois A1 - Gret-Regamey, Adrienne A1 - Hirschi, Christian A1 - Lischke, Heike A1 - Scholz, Roland Werner A1 - Seidl, Roman A1 - Spiegelberger, Thomas A1 - Walz, Ariane A1 - Zimmermann, Willi A1 - Bugmann, Harald T1 - Sustainable land use in Mountain Regions under global change synthesis across scales and disciplines JF - Ecology and society : a journal of integrative science for resilience and sustainability N2 - Mountain regions provide essential ecosystem goods and services (EGS) for both mountain dwellers and people living outside these areas. Global change endangers the capacity of mountain ecosystems to provide key services. The Mountland project focused on three case study regions in the Swiss Alps and aimed to propose land-use practices and alternative policy solutions to ensure the provision of key EGS under climate and land-use changes. We summarized and synthesized the results of the project and provide insights into the ecological, socioeconomic, and political processes relevant for analyzing global change impacts on a European mountain region. In Mountland, an integrative approach was applied, combining methods from economics and the political and natural sciences to analyze ecosystem functioning from a holistic human-environment system perspective. In general, surveys, experiments, and model results revealed that climate and socioeconomic changes are likely to increase the vulnerability of the EGS analyzed. We regard the following key characteristics of coupled human-environment systems as central to our case study areas in mountain regions: thresholds, heterogeneity, trade-offs, and feedback. Our results suggest that the institutional framework should be strengthened in a way that better addresses these characteristics, allowing for (1) more integrative approaches, (2) a more network-oriented management and steering of political processes that integrate local stakeholders, and (3) enhanced capacity building to decrease the identified vulnerability as central elements in the policy process. Further, to maintain and support the future provision of EGS in mountain regions, policy making should also focus on project-oriented, cross-sectoral policies and spatial planning as a coordination instrument for land use in general. KW - adaptive management KW - climate change KW - ecosystem services KW - experiments KW - interdisciplinary research KW - land-use change KW - modeling KW - transdisciplinary research Y1 - 2013 U6 - https://doi.org/10.5751/ES-05499-180336 SN - 1708-3087 VL - 18 IS - 3 PB - Resilience Alliance CY - Wolfville ER - TY - JOUR A1 - Mohr, Christian Heinrich A1 - Manga, Michael A1 - Wald, David T1 - Stronger peak ground motion, beyond the threshold to initiate a response, does not lead to larger stream discharge responses to earthquakes JF - Geophysical research letters N2 - The impressive number of stream gauges in Chile, combined with a suite of past and recent large earthquakes, makes Chile a unique natural laboratory to study several streams that recorded responses to multiple seismic events. We document changes in discharge in eight streams in Chile following two or more large earthquakes. In all cases, discharge increases. Changes in discharge occur for peak ground velocities greater than about 7-11cm/s. Above that threshold, the magnitude of both the increase in discharge and the total excess water do not increase with increasing peak ground velocities. While these observations are consistent with previous work in California, they conflict with lab experiments that show that the magnitude of permeability changes increases with increasing amplitude of ground motion. Instead, our study suggests that streamflow responses are binary. Plain Language Summary Earthquakes deform and shake the surface and the ground below. These changes may affect groundwater flows by increasing the permeability along newly formed cracks and/or clearing clogged pores. As a result, groundwater flow may substantially increase after earthquakes and remain elevated for several months. Here we document streamflow anomalies following multiple high magnitude earthquakes in multiple streams in one of the most earthquake prone regions worldwide, Chile. We take advantage of the dense monitoring network in Chile that recorded streamflow since the 1940s. We show that once a critical ground motion is exceeded, streamflow responses to earthquakes can be expected. KW - earthquake KW - streamflow KW - shaking KW - Chile KW - modeling Y1 - 2018 U6 - https://doi.org/10.1029/2018GL078621 SN - 0094-8276 SN - 1944-8007 VL - 45 IS - 13 SP - 6523 EP - 6531 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Richter, Gudrun A1 - Hainzl, Sebastian A1 - Dahm, Torsten A1 - Zöller, Gert T1 - Stress-based, statistical modeling of the induced seismicity at the Groningen gas field BT - the Netherlands JF - Environmental earth sciences N2 - Groningen is the largest onshore gas field under production in Europe. The pressure depletion of the gas field started in 1963. In 1991, the first induced micro-earthquakes have been located at reservoir level with increasing rates in the following decades. Most of these events are of magnitude less than 2.0 and cannot be felt. However, maximum observed magnitudes continuously increased over the years until the largest, significant event with ML=3.6 was recorded in 2014, which finally led to the decision to reduce the production. This causal sequence displays the crucial role of understanding and modeling the relation between production and induced seismicity for economic planing and hazard assessment. Here we test whether the induced seismicity related to gas exploration can be modeled by the statistical response of fault networks with rate-and-state-dependent frictional behavior. We use the long and complete local seismic catalog and additionally detailed information on production-induced changes at the reservoir level to test different seismicity models. Both the changes of the fluid pressure and of the reservoir compaction are tested as input to approximate the Coulomb stress changes. We find that the rate-and-state model with a constant tectonic background seismicity rate can reproduce the observed long delay of the seismicity onset. In contrast, so-called Coulomb failure models with instantaneous earthquake nucleation need to assume that all faults are initially far from a critical state of stress to explain the delay. Our rate-and-state model based on the fluid pore pressure fits the spatiotemporal pattern of the seismicity best, where the fit further improves by taking the fault density and orientation into account. Despite its simplicity with only three free parameters, the rate-and-state model can reproduce the main statistical features of the observed activity. KW - induced seismicity KW - modeling KW - statistical seismology KW - forecast Y1 - 2020 U6 - https://doi.org/10.1007/s12665-020-08941-4 SN - 1866-6280 SN - 1866-6299 VL - 79 IS - 11 PB - Springer CY - New York ER - TY - JOUR A1 - Engbert, Ralf A1 - Trukenbrod, Hans Arne A1 - Barthelme, Simon A1 - Wichmann, Felix A. T1 - Spatial statistics and attentional dynamics in scene viewing JF - Journal of vision N2 - In humans and in foveated animals visual acuity is highly concentrated at the center of gaze, so that choosing where to look next is an important example of online, rapid decision-making. Computational neuroscientists have developed biologically-inspired models of visual attention, termed saliency maps, which successfully predict where people fixate on average. Using point process theory for spatial statistics, we show that scanpaths contain, however, important statistical structure, such as spatial clustering on top of distributions of gaze positions. Here, we develop a dynamical model of saccadic selection that accurately predicts the distribution of gaze positions as well as spatial clustering along individual scanpaths. Our model relies on activation dynamics via spatially-limited (foveated) access to saliency information, and, second, a leaky memory process controlling the re-inspection of target regions. This theoretical framework models a form of context-dependent decision-making, linking neural dynamics of attention to behavioral gaze data. KW - scene perception KW - eye movements KW - attention KW - saccades KW - modeling KW - spatial statistics Y1 - 2015 U6 - https://doi.org/10.1167/15.1.14 SN - 1534-7362 VL - 15 IS - 1 PB - Association for Research in Vision and Opthalmology CY - Rockville ER - TY - THES A1 - Clodong, Sébastien T1 - Recurrent outbreaks in ecology : chaotic dynamics in complex networks N2 - Gegenstand der Dissertation ist die Untersuchung von wiederkehrenden Ausbrüchen (wie z.B. Epidemien) in der Natur. Dies gelang anhand von Modellen, die die Dynamik von Phytoplankton und die Ausbreitung von Krankheiten zwischen Städten beschreiben. Diese beide Systeme bilden hervorragende Beispiele für solche Phänomene. Die Frage, ob die in der Zeit wiederkehrenden Ausbrüche ein Ausdruck chaotischer Dynamik sein können, ist aktuell in der Ökologie und fasziniert Wissenschaftler dieser Disziplin. Wir konnten zeigen, dass sich das Plankton-Modell im Falle von periodischem Antreiben über die Nährstoffe in einem chaotischen Regime befindet. Diese Dynamik wurde als die komplexe Wechselwirkung zweier Oszillatoren verstanden. Ebenfalls wurde die Ausbreitung von Epidemien in Netzwerken wechselwirkender Städte mit unterschiedlichen Grössen untersucht. Dafür wurde zunächst die Kopplung zwischen zwei Städten als Verhältnis der Stadtgrössen eingeführt. Es konnte gezeigt werden, dass das System sich in einem globalen zweijährigen Zyklus, der auch in den realen Daten beobachtet wird, befinden kann. Der Effekt von Heterogenität in der Grösseverteilung ist durch gewichtete Kopplung von generischen Modellen (Zelt- und Logistische Abbildung) in Netzwerken im Detail untersucht worden. Eine neue Art von Kopplungsfunktion mit nichtlinearer Sättigung wurde eingeführt, um die Stabilität des Systems zu gewährleisten. Diese Kopplung beinhaltet einen Parameter, der es erlaubt, die Netzwerktopologie von globaler Kopplung in gerichtete Netzwerke gleichmässig umzuwandeln. Die Dynamik des Systems wurde anhand von Bifurkationsdiagrammen untersucht. Zum Verständnis dieser Dynamik wurde eine effektive Theorie, die die beobachteten Bifurkationen sehr gut nachahmt, entwickelt. N2 - One of the most striking features of ecological systems is their ability to undergo sudden outbreaks in the population numbers of one or a small number of species. The similarity of outbreak characteristics, which is exhibited in totally different and unrelated (ecological) systems naturally leads to the question whether there are universal mechanisms underlying outbreak dynamics in Ecology. It will be shown into two case studies (dynamics of phytoplankton blooms under variable nutrients supply and spread of epidemics in networks of cities) that one explanation for the regular recurrence of outbreaks stems from the interaction of the natural systems with periodical variations of their environment. Natural aquatic systems like lakes offer very good examples for the annual recurrence of outbreaks in Ecology. The idea whether chaos is responsible for the irregular heights of outbreaks is central in the domain of ecological modeling. This question is investigated in the context of phytoplankton blooms. The dynamics of epidemics in networks of cities is a problem which offers many ecological and theoretical aspects. The coupling between the cities is introduced through their sizes and gives rise to a weighted network which topology is generated from the distribution of the city sizes. We examine the dynamics in this network and classified the different possible regimes. It could be shown that a single epidemiological model can be reduced to a one-dimensional map. We analyze in this context the dynamics in networks of weighted maps. The coupling is a saturation function which possess a parameter which can be interpreted as an effective temperature for the network. This parameter allows to vary continously the network topology from global coupling to hierarchical network. We perform bifurcation analysis of the global dynamics and succeed to construct an effective theory explaining very well the behavior of the system. T2 - Recurrent outbreaks in ecology : chaotic dynamics in complex networks KW - Ökologie KW - Modelierung KW - Chaos KW - Epidemien KW - ecology KW - modeling KW - chaos KW - epidemics Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-0001626 ER - TY - JOUR A1 - Wang, Dedong A1 - Shprits, Yuri Y. T1 - On How High-Latitude Chorus Waves Tip the Balance Between Acceleration and Loss of Relativistic Electrons JF - Geophysical research letters N2 - Modeling and observations have shown that energy diffusion by chorus waves is an important source of acceleration of electrons to relativistic energies. By performing long-term simulations using the three-dimensional Versatile Electron Radiation Belt code, in this study, we test how the latitudinal dependence of chorus waves can affect the dynamics of the radiation belt electrons. Results show that the variability of chorus waves at high latitudes is critical for modeling of megaelectron volt (MeV) electrons. We show that, depending on the latitudinal distribution of chorus waves under different geomagnetic conditions, they cannot only produce a net acceleration but also a net loss of MeV electrons. Decrease in high-latitude chorus waves can tip the balance between acceleration and loss toward acceleration, or alternatively, the increase in high-latitude waves can result in a net loss of MeV electrons. Variations in high-latitude chorus may account for some of the variability of MeV electrons. KW - radiation belts KW - chorus waves KW - high latitude KW - acceleration KW - loss KW - modeling Y1 - 2019 U6 - https://doi.org/10.1029/2019GL082681 SN - 0094-8276 SN - 1944-8007 VL - 46 IS - 14 SP - 7945 EP - 7954 PB - American Geophysical Union CY - Washington ER - TY - THES A1 - Schröder, Sarah T1 - Modelling surface evolution coupled with tectonics T1 - Modellierung von Oberflächenprozessen gekoppelt mit Tektonik BT - A case study for the Pamir BT - Eine Fallstudie zum Pamir N2 - This study presents the development of 1D and 2D Surface Evolution Codes (SECs) and their coupling to any lithospheric-scale (thermo-)mechanical code with a quadrilateral structured surface mesh. Both SECs involve diffusion as approach for hillslope processes and the stream power law to reflect riverbed incision. The 1D SEC settles sediment that was produced by fluvial incision in the appropriate minimum, while the supply-limited 2D SEC DANSER uses a fast filling algorithm to model sedimantation. It is based on a cellular automaton. A slope-dependent factor in the sediment flux extends the diffusion equation to nonlinear diffusion. The discharge accumulation is achieved with the D8-algorithm and an improved drainage accumulation routine. Lateral incision enhances the incision's modelling. Following empirical laws, it incises channels of several cells width. The coupling method enables different temporal and spatial resolutions of the SEC and the thermo-mechanical code. It transfers vertical as well as horizontal displacements to the surface model. A weighted smoothing of the 3D surface displacements is implemented. The smoothed displacement vectors transmit the deformation by bilinear interpolation to the surface model. These interpolation methods ensure mass conservation in both directions and prevent the two surfaces from drifting apart. The presented applications refer to the evolution of the Pamir orogen. A calibration of DANSER's parameters with geomorphological data and a DEM as initial topography highlights the advantage of lateral incision. Preserving the channel width and reflecting incision peaks in narrow channels, this closes the huge gap between current orogen-scale incision models and observed topographies. River capturing models in a system of fault-bounded block rotations reaffirm the importance of the lateral incision routine for capturing events with channel initiation. The models show a low probability of river capturings with large deflection angles. While the probability of river capturing is directly depending on the uplift rate, the erodibility inside of a dip-slip fault speeds up headward erosion along the fault: The model's capturing speed increases within a fault. Coupling DANSER with the thermo-mechanical code SLIM 3D emphasizes the versatility of the SEC. While DANSER has minor influence on the lithospheric evolution of an indenter model, the brittle surface deformation is strongly affected by its sedimentation, widening a basin in between two forming orogens and also the southern part of the southern orogen to south, east and west. N2 - Im Rahmen dieser Studie werden 1D und 2D Erosionsmodelle im Gebirgsmaßstab implementiert und mit Modellen für tektonische Deformation gekoppelt. Die Kopplungsmethode erlaubt unterschiedlich räumliche und zeitliche Auflösungen im tektonischen und im Erosionsmodell. Es werden sowohl vertikale als auch horizontale Bewegungen zwischen den Modellen transferiert. Darüber hinaus enthält die Kopplungsmethode ein Glättungsverfahren, um eventuelle Instabilitäten des tektonischen Modelles zu kompensieren. Beide Erosionsmodelle beziehen Hangerosion, Flusseinschneidung und Sedimentation ein. Der 1D Code nutzt Hack's Law, um die Wassermengen zu berechnen. Er garantiert Massenerhaltung, indem er Sedimente in Senken speichert. Das 2D Erosionsmodell DANSER basiert auf einem zellulären Automaten. Ein zusätzlicher steigungsabhängiger Faktor erweitert lineare zu nichtlinearer Diffusion. Wassermengen werden mit Hilfe des D8-Algorithmus und einer veränderten Form von O'Callaghans (1984) Algorithmus akkumuliert. Laterale Einschneidung, berechnet durch einen neuen Verteilungs-Algorithmus, verbessert die Modellierung von Flusssystemen. Flüsse sind dabei repräsentiert durch eine unterschiedliche Anzahl an Zellen orthogonal zur Fließrichtung. Ihre Breite wird nach empirischen Gesetzen ermittelt. Die präsentierten Anwendungen dienen der Studie des Pamirgebirges. Zunächst werden die Modellparameter anhand von Einschneidungs- und Erosionsraten sowie Sedimentdurchflüssen kalibriert. Ein digitales Höhenmodell dient als Anfangstopographie und zur Extraktion von Flussprofilen. Laterale Einschneidung zeigt eine deutliche Verbesserung zu bisher vorhandenen Modellen. Sie ermöglicht die Erhaltung der Flussbreite und zeigt hohe Einschneidungsraten in engen Flusspassagen. Modelle von Flussanzapfungen in einem System paralleler Verwerfungen bestätigen die Wichtigkeit von lateraler Einschneidung für Flussanzapfungsmodelle, die Hangerosion einbeziehen. Während die Modelle eine geringe Wahrscheinlichkeit von Flussanzapfungen mit hohem Ablenkungswinkel zeigen, belegen sie auch, dass deren (allgemeine) Wahrscheinlichkeit direkt von der Hebungsrate der Verwerfungen abhängt. Die Erodibilität beschleunigt lediglich die Geschwindigkeit von Flussanzapfungen. Ein Modell, das die Codes SLIM 3D und DANSER koppelt, dokumentiert die vielseitige Verwendbarkeit des neuen Codes: Es zeigt einen geringen Einfluss von Oberflächenprozessen auf die Lithosphärendeformation, während die Sedimentationsroutine erheblich auf spröde Oberflächendeformationen einwirkt. Das Modell legt nahe, dass Sedimentation ein zwischen zwei entstehenden Gebirgen gelegenes Becken weitet. Außerdem weitet sich der südlich von der interkontinentalen Kollisionszone gelegene Teil des Gebirge-Models ebenfalls durch Sedimentation. KW - erosion KW - coupling KW - SEC KW - surface evolution KW - thermo-mechanics KW - surface processes KW - DANSER KW - Pamir KW - Tien-Shan KW - Tian-Shan KW - tectonics KW - modelling KW - modeling KW - numerical model KW - simulation KW - surface KW - fluvial incision KW - hillslope diffusion KW - finite differences KW - finite elements KW - Eulerian grid KW - DANSER KW - DANSER KW - Erosion KW - Modellierung KW - Tektonik KW - Koppelung KW - SEC KW - numerische Modellierung KW - Oberflächenprozesse KW - Pamir KW - Tien-Shan KW - Tian-Shan KW - Tiefendeformation KW - Software KW - Simulation KW - Oberfläche KW - fluviale Einschneidung KW - Hangerosion KW - finite Differenzen KW - finite Elemente KW - Eulerische Gitter Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-90385 ER - TY - JOUR A1 - Natho, Stephanie A1 - Tschikof, Martin A1 - Bondar-Kunze, Elisabeth A1 - Hein, Thomas T1 - Modeling the effect of enhanced lateral connectivity on nutrient retention capacity in large river floodplains BT - how much connected floodplain do we need? JF - Frontiers in Environmental Science N2 - Floodplains have been degraded in Central Europe for centuries, resulting in less dynamic and less diverse ecosystems than in the past. They provide essential ecosystem services like nutrient retention to improve overall water quality and thus fulfill naturally what EU legislation demands, but this service is impaired by reduced connectivity patterns. Along the second-longest river in Europe, the Danube, restoration measures have been carried out and are planned for the near future in the Austrian Danube Floodplain National Park in accordance with navigation purposes. We investigated nutrient retention capacity in seven currently differently connected side arms and the effects of proposed restoration measures using two complementary modeling approaches. We modeled nutrient retention capacity in two scenarios considering different hydrological conditions, as well as the consequences of planned restoration measures for side arm connectivity. With existing monitoring data on hydrology, nitrate, and total phosphorus concentrations for three side arms, we applied a statistical model and compared these results to a semi-empirical retention model. The latter was originally developed for larger scales, based on transferable causalities of retention processes and set up for this floodplain with publicly available data. Both model outcomes are in a comparable range for NO3-N (77-198 kg ha(-1)yr(-1)) and TP (1.4-5.7 kg ha(-1)yr(-1)) retention and agree in calculating higher retention in floodplains, where reconnection allows more frequent inundation events. However, the differences in the model results are significant for specific aspects especially during high flows, where the semi-empirical model complements the statistical model. On the other hand, the statistical model complements the semi-empirical model when taking into account nutrient retention at times of no connection between the remaining water bodies left in the floodplain. Overall, both models show clearly that nutrient retention in the Danube floodplains can be enhanced by restoring lateral hydrological reconnection and, for all planned measures, a positive effect on the overall water quality of the Danube River is expected. Still, a frequently hydrologically connected stretch of national park is insufficient to improve the water quality of the whole Upper Danube, and more functional floodplains are required. KW - floodplain KW - lateral hydrological connectivity KW - Danube KW - restoration KW - reconnection KW - inundation KW - nutrient retention KW - modeling Y1 - 2020 U6 - https://doi.org/10.3389/fenvs.2020.00074 SN - 2296-665X VL - 8 PB - Frontiers Media CY - Lausanne ER -