TY - GEN A1 - Varrani, Arianna A1 - Nones, Michael T1 - Vulnerability impacts and assessment of climate change on Jakarta and Venice T2 - International Journal of River Basin Management N2 - In the next future, cities located in coastal areas are likely to suffer for climatic changes more than all other human systems. The demographic growth, combined with sea-level rise and global warming related to natural causes and anthropogenic activities, endanger those systems. Thence, to effectually cope with new climate forcing, coastal cities need improvements to be sustainable, resilient and liveable, applying flexible design approaches rather than a traditional one. The paper highlights such concepts presenting two case studies of important coastal cities: Venice, in Northern Italy, and Jakarta, the capital city of Indonesia. Although characterized by completely different climatic conditions and living habits, these two metropolises are highly impacted by humans and threatened by similar factors like subsidence and sea-level rise, which increase their exposure to future calamities principally driven by climate change but strictly related to anthropic pressures. The present situation shows that, for the future, the resilience of coastal megalopolis can be increased only using a mix of approaches at various levels, spanning from technical measures to adaptable planning instruments that consider future uncertainties. KW - City resilience KW - climate change adaptation KW - flood risk management KW - Jakarta KW - urban planning KW - Venice Y1 - 2018 U6 - https://doi.org/10.1080/15715124.2017.1387125 SN - 1814-2060 SN - 1571-5124 VL - 16 IS - 4 SP - 439 EP - 447 ER - TY - CHAP A1 - Brück, Yasemine A1 - Schulte-Overberg, Philipp A1 - Pohle, Ina A1 - Hinz, Christoph ED - Schütze, Niels ED - Müller, Uwe ED - Schwarze, Robert ED - Wöhling, Thomas ED - Grundmann, Jens T1 - Ökohydrologische Systeme im Wandel: NDVI von Tagebaufolgelandschaften T2 - M³ - Messen, Modellieren, Managen in Hydrologie und Wasserressourcenbewirtschaftung. Beiträge zum Tag der Hydrologie am 22./23. März 2018 an der Technischen Universität Dresden N2 - Tagebau(folge)landschaften bieten gute Möglichkeiten den Wandel ökohydrologische Systeme aufgrund veränderter Umweltbedingungen zu untersuchen: Im Zuge des Tagebaubetriebs wird die Vegetation vollständig entfernt, nach dem Tagebau wächst die Vegetation entweder durch aktive Rekultivierung oder natürliche Sukzession wieder auf. Von Interesse ist, ob und wie bzw. wie schnell sich die Tagebauflächen von der Störung erholen und ähnliche Bedingungen wie vor dem Tagebau bzw. auf ungestörten Flächen herrschen. Klimatische, geomorphologische und ökologische Gegebenheiten sowie die Rekultivierungsstrategie spielen eine große Rolle in der Phase der Rehabilitation und bestimmen die Rate der Wiederbesiedlung mit Pflanzen bzw. deren Wachstum. Der NDVI (normalisierter differenzierter Vegetationsindex) bietet die Möglichkeit generelle Muster der Vegetation quantitativ zu detektieren, um die Regenerationsrate der Vegetation für verschiedene Klima- und Ökoregionen abzuschätzen. Wir analysierten den MODIS Terra NDVI (achttägliche Werte) für Tagebaulandschaften verschiedener Klimate (äquatoriale, trockene, warm gemäßigte und Schnee-Klimate nach Köppen-Geiger) im Zeitraum 2001 bis 2015. Es wurden Kohletagebaue betrachtet, da diese gut definierte Chronosequenzen der Störung erzeugen. Bei der Analyse der NDVI-Zeitreihen sollten Charakteristiken der Rehabilitationsphase erfasst werden. Um die räumliche Heterogenität der Zellen (ca. 250 x 250 m²) der Tagebaulandschaft abzubilden, wurde je Tagebau eine hierarchische Clusteranalyse durchgeführt. Die einzelnen Zeitreihen der Cluster wurden mit einer Methode zur Detektion von Bruchpunkten und zur Zeitreihenzerlegung auf Konsistenz bezüglich Eigenschaften der Zeitreihen (Beginn des Tagebaus, Ende des Tagebaus/Beginn der Rehabilitation, Rate der Rehabilitation) untersucht. Die Clusteranalyse führt zu einer Einordnung der Zellen in vom Tagebau nicht direkt beeinflusste Flächen, aktiven Tagebau und in der Rehabilitation befindliche Fläche verschiedenen Alters bzw. rehabilitierte Flächen. Das Zeitfenster der Entfernung der Vegetation kann im NDVI-Signal identifiziert werden, es zeigt sich meist in einer abrupten Änderung des NDVI. Die Rehabilitationsphase hingegen verläuft graduell und kann mehrere Jahre bis Jahrzehnte andauern. Die Zeitreihenzerlegung zeigt auf, dass in der Rehabilitationsphase der Trend dominiert, während mit Voranschreiten der Rehabilitation die Saisonalität im NDVI-Signal vorherrschend wird. Durch die ermittelte Rate der Rehabilitation können die Flächen innerhalb eines Tagebaus miteinander verglichen werden. Die mittlere Rehabilitationsrate der Tagebaue kann in Zusammenhang mit den vorherrschenden hydroklimatischen Bedingungen der Klimazonen und mit Rekultivierungsstrategien gebracht werden. Zudem ist auch eine Betrachtung hydrometeorologischer Größen zur Erkennung von kurzzeitigen Veränderungen des Pflanzenwachstums im NDVI-Signal möglich. Y1 - 2018 UR - https://tu-dresden.de/bu/umwelt/hydro/ihm/hydrologie/ressourcen/dateien/tdh2018/TdH_2018_Abstractband.pdf SP - S. 113 PB - Technische Universität CY - Dresden ER - TY - CHAP A1 - Caviedes-Voullieme, Daniel A1 - Andezhath Mohanan, Anju A1 - Brück, Yasemine A1 - Zaplata, Markus K. A1 - Hinz, Christoph ED - Schütze, Niels ED - Müller, Uwe ED - Schwarze, Robert ED - Wöhling, Thomas ED - Grundmann, Jens T1 - Effect of surface water redistribution on vegetation encroachment in the constructed Hühnerwasser catchment T2 - M³ - Messen, Modellieren, Managen in Hydrologie und Wasserressourcenbewirtschaftung. Beiträge zum Tag der Hydrologie am 22./23. März 2018 an der Technischen Universität Dresden N2 - The artificial Hühnerwasser catchment has experienced a significant and monitored evolution since 2005, changing from a post-mining landscape to an almost fully vegetated ecosystem. The early stages showed a fast rate of ecohydrological evolution with changing dominating processes and feedbacks. The evolution of rill vegetation encroachment is one of such complex co-evolving processes. We hypothesise that rill vegetation encroachment is driven by the evolution of the hydrologic/hydraulic regime of the rill network, which in turn affects the regime, potentially creating a stabilising positive feedback. We further hypothesise that rill vegetation occurs later than hillslope vegetation, and follows a particular establishment and encroachment timeline in response to the changing hydrological/hydraulic regimes. That is, the early runoff-dominated regime results in higher flows, velocities, transport and erosion capacity, thus favouring seed flushing and seedling uprooting. On the other hand, as the system transitions from a runoffdominated into an infiltration- and ET-dominated system, flow, velocity, transport and erosion capacity in the rill network are reduced, making seed establishment in the rills more likely. We explore these hypothesis with two complementary approaches: an analysis of the spatiotemporal distribution of vegetation and a process-based numerical modelling study. Firstly, we assess aerial photography of rill vegetation encroachment between 2007 and 2012 in terms of several vegetation types to derive temporal indicators of encroachment. The analysis reveals that in the initial stages, a rill network developed in the hillslope. Shortly after vegetation first established on hillslopes, the rill network became progressively vegetated. Different pioneering species established heterogeneously, at different times and encroached into the rills at different rates. However, despite the volume of data, it is difficult to assess which are the governing and limiting processes which respectively drive and constrain how and at which rate vegetation encroaches into the rills. In consequence, a pilot modelling study to identify the relative relevance of rill network geometry, bare soil infiltration, hillslope vegetation heterogeneity and intra-storm variability on the hydraulic response of the rill network and its possible impact on encroachment. The overall results suggest that vegetation encroachment may be controlled by the rill network hydraulic regime, but such regime is the result of a complex superposition of responses of all the aforementioned factors, of which rill geometry appears to be a dominant one. Furthermore, the simulations showed that vegetation spatial heterogeneity has an impact on the hydraulic regime coupled to the presence of temporal rainfall variability. Altogether, these results show that the governing coevolving ecohydrological processes are interacting and are strongly affected by spatial and temporal heterogeneities. Y1 - 2018 UR - https://tu-dresden.de/bu/umwelt/hydro/ihm/hydrologie/ressourcen/dateien/tdh2018/TdH_2018_Abstractband.pdf SP - S. 91 PB - Technische Universität CY - Dresden ER - TY - CHAP A1 - Pohle, Ina A1 - Gädeke, Anne A1 - Koch, Hagen A1 - Schümberg, Sabine A1 - Hinz, Christoph ED - Schütze, Niels ED - Müller, Uwe ED - Schwarze, Robert ED - Wöhling, Thomas ED - Grundmann, Jens T1 - Kann Wasserressourcenbewirtschaftung die Unsicherheiten projizierter Klimafolgen auf den Abfluss vermindern? - Ein Vergleich in zwei hydrologisch ähnlichen Einzugsgebieten mit unterschiedlichem Ausmaß des Bewirtschaftungseinflusses T2 - M³ - Messen, Modellieren, Managen in Hydrologie und Wasserressourcenbewirtschaftung. Beiträge zum Tag der Hydrologie am 22./23. März 2018 an der Technischen Universität Dresden N2 - Studien zum Einfluss des zukünftigen Klimawandels auf das Abflussgeschehen fokussieren oft auf die Fortpflanzung von Unsicherheiten in Modellkaskaden, berücksichtigen meist jedoch die Wasserressourcenbewirtschaftung nur ungenügend. Wir untersuchten den Einfluss der Wasserressourcenbewirtschaftung auf die Abflussvariabilität und die Fortpflanzung von Unsicherheiten von Klimaprojektionen auf Abflusssimulationen in den Einzugsgebieten von Spree (bis Pegel Große Tränke: 6200 km²) und Schwarzer Elster (5700 km²). Die Einzugsgebiete ähneln sich hinsichtlich Klima, Topographie, Boden und Landnutzung, jedoch ist das Spreeeinzugsgebiet stärker durch den Braunkohletagebau und die damit verbundenen Bewirtschaftung geprägt und durch einen höheren Speicherausbaugrad gekennzeichnet. Um zwischen Bewirtschaftungseinflüssen und meteorologischen Einflüssen zu separieren, wurden für den Zeitraum 1961-2005 beobachtete Abflüsse mit durch das Modell SWIM rekonstruierten natürlichen (d.h. ohne Bewirtschaftungseinfluss) Abflüssen der Vergangenheit verglichen. Mögliche Einflüsse des Klimawandels wurden für den Zeitraum 2018-2052 auf Grundlage von 3 Szenarien des statistischen Regionalmodells STAR (je 100 Realisierungen) mit SWIM (natürliche Abflüsse) und dem Langfristbewirtschaftungsmodell WBalMo (bewirtschaftete Abflüsse) modelliert. Die Analyse erfolgte mit Fokus auf Saisonalität, Oszillation, Verteilung und räumliche Variabilität der Abflüsse. Der Vergleich zwischen beobachteten und natürlichen Abflüssen der vergangenen Jahrzehnte zeigt, dass die zwischenjährliche Abflussvariabilität im Spreeeinzugsgebiet stärker durch Grubenwassereinleitungen als durch natürliche hydrologische Prozesse bestimmt wurde. Zusätzlich führt der höhere Speicherausbaugrad dazu, dass die kurzzeitliche und saisonale Variabilität im Spreeeinzugsgebiet geringer als im Einzugsgebiet der Schwarzen Elster ist. Simulationen mit Klimaszenarien, welche steigende Jahresmitteltemperaturen und einen Rückgang der Niederschlagsjahressummen enthalten, führen zu deutlichen Abflussrückgängen. Die Unterschiede der natürlichen Abflüsse beider Einzugsgebiete sind gering, die Unsicherheiten der Klimaprojektionen werden durch die hydrologische Modellierung verstärkt. Die natürlichen und bewirtschafteten Abflüsse der Schwarzen Elster unter Klimawandel unterscheiden sich kaum. Im Spreeeinzugsgebiet zeigt sich eine deutliche Verringerung der Variabilität und Unsicherheiten unter Klimawandel von den natürlichen zu den bewirtschafteten Abflüssen. Die Analysen zeigen, dass effektive Wasserressourcenbewirtschaftung die Abflussvariabilität verringern kann und damit auch dazu beitragen kann, die sich aus Klimawandelprojektionen ergebenden Unsicherheiten zu vermindern. Einzugsgebiete mit einem hohen Ausbaugrad weisen weniger Vulnerabilität bezüglich klimatischer Änderungen auf. Dies unterstreicht die Bedeutung von Wasserresourcenbewirt-schaftungfür die Anpassung an den Klimawandel. Y1 - 2018 UR - https://tu-dresden.de/bu/umwelt/hydro/ihm/hydrologie/ressourcen/dateien/tdh2018/TdH_2018_Abstractband.pdf SP - S. 30 PB - Technische Universität CY - Dresden ER - TY - CHAP A1 - Caviedes-Voullieme, Daniel A1 - Martı́nez-Aranda, Sergio A1 - Fernández-Pato, Javier A1 - García-Palacín, Ignacio A1 - García-Navarro, Pilar ED - Schütze, Niels ED - Müller, Uwe ED - Schwarze, Robert ED - Wöhling, Thomas ED - Grundmann, Jens T1 - Measuring 2D transient shallow water surfaces: raising the benchmark challenges for 2D shallow water solvers T2 - M³ - Messen, Modellieren, Managen in Hydrologie und Wasserressourcenbewirtschaftung. Beiträge zum Tag der Hydrologie am 22./23. März 2018 an der Technischen Universität Dresden N2 - In the past decade, shallow water (SW) solvers have been dramatically improved both in terms of accuracy and computational power. The mathematical, numerical and computational improvements available in state-of-the-art solvers now allow for large scale, long term, high resolution simulations of river flooding, flash floods, dam-break phenomena, rainfall-runoff simulation and extensions into pollutants, substance and sediment transport, etc. SW solvers have been benchmarked against a set of test cases, ubiquitious in the literature. The solvers have been systematically verified against 1D and some 2D analytical solutions and validated further against 1D and 2D laboratory experiments, as well as some well-documented real-scale field cases. However, despite the 2D nature of many of these benchmark tests, none of them report 2D water surface elevation. Typically a few profiles are measured and reported, and more often, only a few points are available. Moreover, in field cases, often not even fully transient data is available. The reason for the inavailability of 2D transient water surface data is due to the technical difficulty of measuring a (fast) moving water surface. In most of the reported experiments, pressure gauges are often used to register water depth evolution, and sometimes PIV techniques have been used to obtain velocity fields. In experimental fluid mechanics, measuring the evolution of a free surface has received little attention, as it has been mainly understood as a problem for SW flows, and more recently for free surface granular flows. In consequence, this work aims to generate a new benchmarking dataset in which 2D transient water surfaces are available for SW model developers and users to further test and challenge these models. We argue that the availability of this new data can help identify limitations in the current generation of solvers, thus laying the ground for improvements in the near future. We present laboratory-scale experimental results on steady and unsteady 2D water surfaces performed in a laboratory flume, ranging from steady transcritical flow to dam-break flows around obstacles. The transient water surface was captured using a commercial-grade RGBD sensing device which allows to capture a high-frequency succession of 3D color-coded point clouds. The channel bed can also be registered in the same manner, thus also allowing to compute the 2D transient water-depth field. Color coding also allows to easily differentiate the channel bed, sidewalls and obstacles. The result of the experimental study is a novel collection of 2D benchmark SW cases, with transient water depth and water elevation data for the entire visible flow field. Furthermore, we compare the experimental measurements to 2D shallow water simulations performed with an extensively tested state-of-the-art solver to assess the suitability of this dataset to perform as benchmark test cases and identify some potential limitations of current models. Y1 - 2018 UR - https://tu-dresden.de/bu/umwelt/hydro/ihm/hydrologie/ressourcen/dateien/tdh2018/TdH_2018_Abstractband.pdf SP - S. 23 PB - Technische Universität CY - Dresden ER - TY - CHAP A1 - Caviedes-Voullième, Daniel A1 - Hinz, Christoph T1 - The role of topography and intra-annual rainfall variability in semi-arid vegetation self-organisation: a multi-scale modelling study T2 - European Geosciences Union, General Assembly 2018, Vienna, Austria N2 - Coevolution of hydrological and vegetation dynamics in semi-arid regions has been widely observed to result in vegetation self-organisation (VSO). Many hypothesis of VSO’s underlying ecohydrological processes and feedbacks have been studied relying on mathematical models, which have been key to evaluate the sensitivity of ecohydrological systems to environmental factors and drivers. Although this ecohydrological coevolution is essentially multiscale, researchers have continued to be constrained by the simplicity of the models which are unable to cope with the multiscale, process-based complexity of fast-moving surface water over complex topographies driven by varying rainfall, during decade-to-century long VSO processes. This limitation has not allowed deep exploration of the role and sensitivity of key environmental factors such as topography and rainfall variability, and the lack of proper hydrodynamics still constrains adequate sediment transport modelling and its feedback effects on VSO. We hypothesize that the intra-storm water redistribution by surface runoff at the hillslope scale is strongly controlled by both topography and storm intensity and may control VSO. This requires for these environmental factors to be accurately represented in models and their their hydraulic and hydrological effects properly reflected. This work provides the first systematic study of the effects of topography and intra-annual rainfall distributions on vegetation band formation at the hillslope scale. Simulations were performed with a physically-based numerical model solving the Zero-Inertia approximation to the shallow water equations for surface flow coupled to the HilleRisLambers-Rietkerk vegetation model, allowing to explicitly represent arbitrary topography. An idealized study of ecohydrological evolution over 30 years was performed, solving with a temporal resolution in the seconds scale. Plane, convex and convex hillslope topologies with different slopes were used, while forcing the model with different annual rainfalls along a semi-arid rainfall gradient, with discrete events of different frequencies. We describe results in terms of evolution of total biomass, hydrological water balance, and of the spatial properties of banded vegetation. Results show that both topography and intra-annual rainfall distribution can play a shaping and governing role in VSO by controlling surface water redistribution and the hydrologic water balance. Increasing slopes favours runoff over infiltration, reducing the available water for vegetation and resulting in different evolutions of vegetation band geometry and band migration. Hillslope topology plays a strong role in the internal water redistribution of the system. Plane and convex surfaces behave similarly, but concave surfaces exhibit a different ecohydrological behaviour, despite the very small topological differences. Different intra-annual rainfall distributions result in different rainfall intensities for the same total annual rainfall which strongly affect the band formation and evolution process: higher intensities lead to less available water, to which vegetation adapts by spatially clustering in bands with different geometrical properties. The study also shows that it is computationally feasible (a few hours runtime) to perform decade-to-century long simulations of these systems with physically-based numerical models paving the way to simulate natural systems with arbitrary topography and high-resolution rainfall data, and is a first step in introducing physically-based sediment transport processes and feedbacks in these studies. Y1 - 2018 UR - https://meetingorganizer.copernicus.org/EGU2018/EGU2018-17423.pdf N1 - EGU2018-17423 PB - European Geophysical Society CY - Katlenburg-Lindau ER - TY - CHAP A1 - Brück, Yasemine A1 - Andezhath Mohanan, Anju A1 - Caviedes-Voullième, Daniel A1 - Hinz, Christoph A1 - Zaplata, Markus K. T1 - Spatio-temporal development of rill vegetation in the Hühnerwasser Catchment T2 - European Geosciences Union, General Assembly 2018, Vienna, Austria N2 - The artificial catchment “Hühnerwasser” was built in a post-mining landscape, as a field experiment to observe and monitor early-development ecosystems at hillslope scale. Early on, rain-induced rill and channels formation was observed, followed by vegetation growth in between rills, and later on inside the rills. In this work, we aim to describe the temporal evolution of the spatial distribution of rill vegetation. In general terms, we hypothesize four different encroachment patterns might occur: (1) The vegetation spreads from the top of the rills downstream. The underlying hypothesis would be a higher establishment probability due to a lower velocity of surface runoff and therefore less transport probability compared to downstream rill segments. (2) The vegetation starts growing downstream and moves upwards. In this case we can hypothesize that the spatial distribution of the vegetation is dominated by water availability, which is higher or more stable downstream. (3) The vegetation encroaches from the sides into the rills, meaning that inter-rill vegetation governs vegetation encroachment inside the rills. (4) If no patterns are detected it might mean that the encroachment process depends strongly on very local conditions, or perhaps that the underlying assumption of an initially homogeneous seed distribution is false. To investigate the rills formation and rill vegetation encroachment processes, rills and vegetation patches inside these rills were identified and digitized from aerial photographs of the catchment from 2007 to 2012. Different vegetation types were identified based on the colour and texture of the patches. The geometrical properties of the rill segments and vegetation patches were used to define how the different vegetation types have distributed in space and how this distribution has changed over time. Rill mapping reveals a large increase of rill area from 2007 to 2008 and only a small rise from 2008 to 2009. Starting in 2010 dense vegetation prevents a precise mapping of the rills in the aerial photographs, so we assume that there is no change in rill area from 2009 to 2012. In 2007 vegetation covered only 1.4% of the rill area. There is only a small increase of this area in 2008 compared to the later years. In 2012 more than 50% of the rill area is covered by plants. Ten different vegetation types have been identified in the aerial photographs, starting with two types in 2007. By 2012 nine types are spotted in the rills of the catchment. Some of these vegetation types show an encroachment from up- to downstream (e.g. Tussilago farfara), some from down- to upstream like Phragmites australis, whose creeping rhizomes can also promote such spreading. Others reveal no patterns. To better assess and identify the underlying processes leading to these encroachment processes shown by the different vegetation types further data analysis –e.g. comparison with ground based vegetation mapping– and process-based hydrological modelling is necessary to fully explain these observations and assessing additional competition effects, which may be at play. Y1 - 2018 UR - https://meetingorganizer.copernicus.org/EGU2018/EGU2018-13391.pdf N1 - EGU2018-13391 PB - European Geophysical Society CY - Katlenburg-Lindau ER - TY - CHAP A1 - Caviedes-Voullième, Daniel A1 - Andezhath Mohanan, Anju A1 - Brück, Yasemine A1 - Hinz, Christoph T1 - Rill hydrodynamics and its impact on rill vegetation encroachment: a modelling study of the constructed Hühnerwasser catchment T2 - European Geosciences Union, General Assembly 2018, Vienna, Austria N2 - The Hühnerwasser catchment is a monitored, early-development constructed catchment within the Lower Lausatia post-mining landscape in Germany. Observations have shown that a sequence of landscape-forming processes occurred, including the initial vegetation establishment stages, which are the main interest of this study. In the initial stages of geomorphic development a surface drainage network of rills was formed as vegetation started to appear on the hillslopes and subsequently inside the rill network. Observations and analysis of the rill vegetation establishment suggest that different vegetation types encroach into the rill network at different times, rates and form different directions. We hypothesize that these encroachment processes may respond to the runoff properties of the catchment at such time: velocity distribution in the rills might play a significant role in flushing seeds in high-velocity reaches of the rill network, thus favouring the appearance of vegetation in low-velocity regions. Consequently, the goal of this study is to assess the magnitudes and spatiotemporal behaviour of velocity in the rill network, to assess its possible impact on seed flushing and rill vegetation encroachment. One rill subcatchment of Hühnerwasser was selected to perform an explorative study of rill hydrodynamics and their impact on vegetation establishment. Two vegetation states were simulated: bare hillslopes and vegetated hillslopes. The vegetated cover polygons were obtained from digitized aerial photography, and stochastically dissagregated 10-minute resolution precipitation data were used, selecting events with early, middle and late peak storm intensities. A 2D explicit finite volume scheme solving the Zero-Inertia approximation to the shallow water equations was used to simulate surface flow in the subcatchment. The preliminary modelling results suggest that that there is no clear overall velocity gradient in the downstream direction along the rills. In fact, velocity in the rills may increase or decrease along the rill following local topography and rill geometry. Consequently, no global trend for the probability of seeds being transported can be established. The results also shows that varying rainfall intensity and rainfall intrastorm distribution –in the absence of hillslope vegetation– does not affect the rill locations of maximum velocities, but mostly affect the magnitude of velocity. In the presence of hillslope vegetation –and thus heterogeneous infiltration conditions in the hillslopes– the spatial distribution of velocity is strongly affected, and can be in fact governed not by topography or rill geometry, but by the spatial heterogeneity of infiltration capacity. Furthermore, the time at which maximum discharge and velocities occur may not match that of maximum intensity. That is, emerging temporal dynamics arise due to the introduction of spatial heterogeneity, which also manifests in the fact that outflow from the subcatchment exhibits a intensity-thresholded behaviour. Y1 - 2018 UR - https://meetingorganizer.copernicus.org/EGU2018/EGU2018-13392.pdf N1 - EGU2018-13392 PB - European Geophysical Society CY - Katlenburg-Lindau ER - TY - CHAP A1 - Caviedes-Voullième, Daniel A1 - Hinz, Christoph T1 - Convergent biomass, divergent patterns: Can initial conditions govern vegetation self-organisation? T2 - European Geosciences Union, General Assembly 2018, Vienna, Austria N2 - Vegetation self-organisation in water-limited ecosystems in semi-arid climates has been extensively studied by means of numerical simulation using a set of different reaction-diffusion-equations. Most of such models and studies have been concerned with the long-term steady ecohydrological states on domains with periodic boundaries and forced by steady rainfall, whilst little interest has been given to the transient states which lead to them as well as the spatiotemporal multiscale nature of the feedback processes. It is generally accepted that alternative random initial biomass distributions do not significantly affect the resulting steady state vegetation patterns. However, the role of the initial hydrological conditions –initial surface and subsurface water– has not been explored, mainly due to the interest in the long-term steady state. Nonetheless, vegetation patterns are directly linked to the water distribution occurring at much shorter time scales than vegetation growth, and because they have been shown to be sensitive to annual rainfall, it is reasonable that the initially available water will also play a role. We therefore hypothesize that the initially available water will play a role in the transient process leading to a steady ecohydrological state, and that the steady vegetation patterns will differ in response to the water availability in time during the entire process. In this contribution we explore the role of initial hydrological conditions on both the transient and longterm steady ecohydrological state. A simulation study was performed using the HilleRisLambers-Rietkerk ecohydrological model on a flatland varying the initial available water whilst also spanning the rainfall gradient (90 – 360 mm/year) . The results were assessed in terms of the evolution and steady state of total biomass yield and hydrological water balance, as well as a quantitative assessment of both transient and steady vegetation patterns. The results show that the initially available water does play a role, not only in the early transient state, but in the long-term steady state, and indeed in the geometry of the converged vegetation pattern. Furthermore, although the steady state biomass yield may be the same for varying initial conditions, the final patterns still differ, e.g., a reduction to one-fourth initial water availability results in more but smaller vegetation patches, while a reduction to one-eigth initial water results in less, but larger patches, and a reduction to one-sixteenth results in a completely new pattern, although total biomass is the same for all. This suggests that long-term average rainfall may govern the total biomass but the initial conditions may play a relevant shaping role in the long term spatial distributions of steady ecohydrological states of water-limited ecohydrosystems. This is relevant, among other reasons, because the resilience of the system is associated to the vegetation patterns. It also suggests that neither the temporal distribution of rainfall nor the system’s evolution cannot be neglected to understand the environmental factors which lead to a steady ecohydrological state, since multiple paths may be possible. This warrants further developments from the ecohydrological modelling community and further study of transient states through process-based models. Y1 - 2018 UR - https://meetingorganizer.copernicus.org/EGU2018/EGU2018-13684.pdf N1 - EGU2018-13684 PB - European Geophysical Society CY - Katlenburg-Lindau ER - TY - CHAP A1 - Gupana, Remika A1 - Ziemba, Alexander A1 - El Serafy, Ghada T1 - Quantification of Benthic Phytoplankton using Remote Sensing and Machine Learning in the Wadden Sea T2 - European Geosciences Union, General Assembly 2018, Vienna, Austria N2 - One of the main indicators of ecosystem stability in coastal regions is the occurrence and distribution of primary producers. In the intertidal flats of the Wadden Sea, benthic phytoplankton such as microphytobenthos are significant primary providers of energy. However, the Wadden Sea monitoring data inventory states that there is low availability of microphytobenthos data despite its high demand. To address this gap, a remote sensing approach coupled with data fusion through machine learning using the Random Forest algorithm was adopted and developed. This study also maximized existing datasets to demonstrate other possible applications of such data and subsequently, the added practical value these datasets offer. Microphytobenthos thrive in areas where the sediments have high mud and nutrient content. These organisms are also known to aid in sediment stability due to excreted extracellular polymeric substances. Following this rationale, it was assumed that sediment grain size, Total Suspended Matter (TSM), Chlorophyll-a (Chl-a) and Photosynthetically Active Radiation (PAR) can be combined in determining microphytobenthos occurrence. The microphytobenthos model derived using Random Forest algorithm has the following input parameters: sediment grain size map derived from Landsat images, MERIS Products TSM, Chl-a and PAR. The benthic diatom model from Het Koninklijk Nederlands Instituut voor Onderzoek der Zee (NIOZ) was used as baseline data for the training model. Another scenario was considered using TSM and Chl-a modelling output from the Generic Ecological Model-Algal Bloom (GEM/BLOOM) model. Two main training models were derived from the microphytobenthos prediction algorithm. These models were distinct from each other; in that the first model had a higher and wider microphytobenthos concentration range (0 – 7000 mg C m-2) and the second model had a lower and narrower range (0 —- 1000 mg C m-2) suitable for warmer and colder time periods, respectively. Although more extensive data is required to further validate this procedure, this alternative method has proven to be a feasible non-invasive technique to quantify microphytobenthos while utilizing existing datasets. Y1 - 2018 UR - https://meetingorganizer.copernicus.org/EGU2018/EGU2018-16069.pdf N1 - EGU2018-16069-1 N1 - This work has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 641762. PB - European Geophysical Society CY - Katlenburg-Lindau ER -