TY - GEN A1 - Seleem, Omar A1 - Ayzel, Georgy A1 - Bronstert, Axel A1 - Heistermann, Maik T1 - Transferability of data-driven models to predict urban pluvial flood water depth in Berlin, Germany T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Data-driven models have been recently suggested to surrogate computationally expensive hydrodynamic models to map flood hazards. However, most studies focused on developing models for the same area or the same precipitation event. It is thus not obvious how transferable the models are in space. This study evaluates the performance of a convolutional neural network (CNN) based on the U-Net architecture and the random forest (RF) algorithm to predict flood water depth, the models' transferability in space and performance improvement using transfer learning techniques. We used three study areas in Berlin to train, validate and test the models. The results showed that (1) the RF models outperformed the CNN models for predictions within the training domain, presumable at the cost of overfitting; (2) the CNN models had significantly higher potential than the RF models to generalize beyond the training domain; and (3) the CNN models could better benefit from transfer learning technique to boost their performance outside training domains than RF models. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1323 Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-589168 SN - 1866-8372 IS - 1323 SP - 809 EP - 822 ER - TY - JOUR A1 - Seleem, Omar A1 - Ayzel, Georgy A1 - Bronstert, Axel A1 - Heistermann, Maik T1 - Transferability of data-driven models to predict urban pluvial flood water depth in Berlin, Germany JF - Natural Hazards and Earth System Sciences N2 - Data-driven models have been recently suggested to surrogate computationally expensive hydrodynamic models to map flood hazards. However, most studies focused on developing models for the same area or the same precipitation event. It is thus not obvious how transferable the models are in space. This study evaluates the performance of a convolutional neural network (CNN) based on the U-Net architecture and the random forest (RF) algorithm to predict flood water depth, the models' transferability in space and performance improvement using transfer learning techniques. We used three study areas in Berlin to train, validate and test the models. The results showed that (1) the RF models outperformed the CNN models for predictions within the training domain, presumable at the cost of overfitting; (2) the CNN models had significantly higher potential than the RF models to generalize beyond the training domain; and (3) the CNN models could better benefit from transfer learning technique to boost their performance outside training domains than RF models. Y1 - 2023 U6 - https://doi.org/10.5194/nhess-23-809-2023 SN - 1684-9981 SN - 1561-8633 VL - 23 IS - 2 SP - 809 EP - 822 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Mtilatila, Lucy Mphatso Ng'ombe A1 - Bronstert, Axel A1 - Vormoor, Klaus Josef T1 - Temporal evaluation and projections of meteorological droughts in the Greater Lake Malawi Basin, Southeast Africa JF - Frontiers in Water N2 - The study examined the potential future changes of drought characteristics in the Greater Lake Malawi Basin in Southeast Africa. This region strongly depends on water resources to generate electricity and food. Future projections (considering both moderate and high emission scenarios) of temperature and precipitation from an ensemble of 16 bias-corrected climate model combinations were blended with a scenario-neutral response surface approach to analyses changes in: (i) the meteorological conditions, (ii) the meteorological water balance, and (iii) selected drought characteristics such as drought intensity, drought months, and drought events, which were derived from the Standardized Precipitation and Evapotranspiration Index. Changes were analyzed for a near-term (2021–2050) and far-term period (2071–2100) with reference to 1976–2005. The effect of bias-correction (i.e., empirical quantile mapping) on the ability of the climate model ensemble to reproduce observed drought characteristics as compared to raw climate projections was also investigated. Results suggest that the bias-correction improves the climate models in terms of reproducing temperature and precipitation statistics but not drought characteristics. Still, despite the differences in the internal structures and uncertainties that exist among the climate models, they all agree on an increase of meteorological droughts in the future in terms of higher drought intensity and longer events. Drought intensity is projected to increase between +25 and +50% during 2021–2050 and between +131 and +388% during 2071–2100. This translates into +3 to +5, and +7 to +8 more drought months per year during both periods, respectively. With longer lasting drought events, the number of drought events decreases. Projected droughts based on the high emission scenario are 1.7 times more severe than droughts based on the moderate scenario. That means that droughts in this region will likely become more severe in the coming decades. Despite the inherent high uncertainties of climate projections, the results provide a basis in planning and (water-)managing activities for climate change adaptation measures in Malawi. This is of particular relevance for water management issues referring hydro power generation and food production, both for rain-fed and irrigated agriculture. KW - meteorological drought KW - drought intensity KW - climate change KW - drought events KW - Lake Malawi KW - Shire River KW - drought projections KW - South-Eastern Africa Y1 - 2022 U6 - https://doi.org/10.3389/frwa.2022.1041452 SN - 2624-9375 SP - 1 EP - 16 PB - Frontiers Media S.A. CY - Lausanne, Schweiz ER - TY - JOUR A1 - Mtilatila, Lucy Mphatso Ng'ombe A1 - Bronstert, Axel A1 - Vormoor, Klaus Josef T1 - Temporal evaluation and projections of meteorological droughts in the Greater Lake Malawi Basin, Southeast Africa JF - Frontiers in water N2 - The study examined the potential future changes of drought characteristics in the Greater Lake Malawi Basin in Southeast Africa. This region strongly depends on water resources to generate electricity and food. Future projections (considering both moderate and high emission scenarios) of temperature and precipitation from an ensemble of 16 bias-corrected climate model combinations were blended with a scenario-neutral response surface approach to analyses changes in: (i) the meteorological conditions, (ii) the meteorological water balance, and (iii) selected drought characteristics such as drought intensity, drought months, and drought events, which were derived from the Standardized Precipitation and Evapotranspiration Index. Changes were analyzed for a near-term (2021-2050) and far-term period (2071-2100) with reference to 1976-2005. The effect of bias-correction (i.e., empirical quantile mapping) on the ability of the climate model ensemble to reproduce observed drought characteristics as compared to raw climate projections was also investigated. Results suggest that the bias-correction improves the climate models in terms of reproducing temperature and precipitation statistics but not drought characteristics. Still, despite the differences in the internal structures and uncertainties that exist among the climate models, they all agree on an increase of meteorological droughts in the future in terms of higher drought intensity and longer events. Drought intensity is projected to increase between +25 and +50% during 2021-2050 and between +131 and +388% during 2071-2100. This translates into +3 to +5, and +7 to +8 more drought months per year during both periods, respectively. With longer lasting drought events, the number of drought events decreases. Projected droughts based on the high emission scenario are 1.7 times more severe than droughts based on the moderate scenario. That means that droughts in this region will likely become more severe in the coming decades. Despite the inherent high uncertainties of climate projections, the results provide a basis in planning and (water-)managing activities for climate change adaptation measures in Malawi. This is of particular relevance for water management issues referring hydro power generation and food production, both for rain-fed and irrigated agriculture. KW - meteorological drought KW - drought intensity KW - climate change KW - drought KW - events KW - Lake Malawi KW - Shire River KW - drought projections KW - South-Eastern KW - Africa Y1 - 2022 U6 - https://doi.org/10.3389/frwa.2022.1041452 SN - 2624-9375 VL - 4 PB - Frontiers Media CY - Lausanne ER - TY - GEN A1 - Seleem, Omar A1 - Ayzel, Georgy A1 - Costa Tomaz de Souza, Arthur A1 - Bronstert, Axel A1 - Heistermann, Maik T1 - Towards urban flood susceptibility mapping using data-driven models in Berlin, Germany T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Identifying urban pluvial flood-prone areas is necessary but the application of two-dimensional hydrodynamic models is limited to small areas. Data-driven models have been showing their ability to map flood susceptibility but their application in urban pluvial flooding is still rare. A flood inventory (4333 flooded locations) and 11 factors which potentially indicate an increased hazard for pluvial flooding were used to implement convolutional neural network (CNN), artificial neural network (ANN), random forest (RF) and support vector machine (SVM) to: (1) Map flood susceptibility in Berlin at 30, 10, 5, and 2 m spatial resolutions. (2) Evaluate the trained models' transferability in space. (3) Estimate the most useful factors for flood susceptibility mapping. The models' performance was validated using the Kappa, and the area under the receiver operating characteristic curve (AUC). The results indicated that all models perform very well (minimum AUC = 0.87 for the testing dataset). The RF models outperformed all other models at all spatial resolutions and the RF model at 2 m spatial resolution was superior for the present flood inventory and predictor variables. The majority of the models had a moderate performance for predictions outside the training area based on Kappa evaluation (minimum AUC = 0.8). Aspect and altitude were the most influencing factors on the image-based and point-based models respectively. Data-driven models can be a reliable tool for urban pluvial flood susceptibility mapping wherever a reliable flood inventory is available. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1297 KW - Urban pluvial flood susceptibility KW - convolutional neural network KW - deep learning KW - random forest KW - support vector machine KW - spatial resolution KW - flood predictors Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-576806 SN - 1866-8372 IS - 1297 SP - 1640 EP - 1662 ER - TY - JOUR A1 - Seleem, Omar A1 - Ayzel, Georgy A1 - Costa Tomaz de Souza, Arthur A1 - Bronstert, Axel A1 - Heistermann, Maik T1 - Towards urban flood susceptibility mapping using data-driven models in Berlin, Germany JF - Geomatics, natural hazards and risk N2 - Identifying urban pluvial flood-prone areas is necessary but the application of two-dimensional hydrodynamic models is limited to small areas. Data-driven models have been showing their ability to map flood susceptibility but their application in urban pluvial flooding is still rare. A flood inventory (4333 flooded locations) and 11 factors which potentially indicate an increased hazard for pluvial flooding were used to implement convolutional neural network (CNN), artificial neural network (ANN), random forest (RF) and support vector machine (SVM) to: (1) Map flood susceptibility in Berlin at 30, 10, 5, and 2 m spatial resolutions. (2) Evaluate the trained models' transferability in space. (3) Estimate the most useful factors for flood susceptibility mapping. The models' performance was validated using the Kappa, and the area under the receiver operating characteristic curve (AUC). The results indicated that all models perform very well (minimum AUC = 0.87 for the testing dataset). The RF models outperformed all other models at all spatial resolutions and the RF model at 2 m spatial resolution was superior for the present flood inventory and predictor variables. The majority of the models had a moderate performance for predictions outside the training area based on Kappa evaluation (minimum AUC = 0.8). Aspect and altitude were the most influencing factors on the image-based and point-based models respectively. Data-driven models can be a reliable tool for urban pluvial flood susceptibility mapping wherever a reliable flood inventory is available. KW - Urban pluvial flood susceptibility KW - convolutional neural network KW - deep KW - learning KW - random forest KW - support vector machine KW - spatial resolution; KW - flood predictors Y1 - 2022 U6 - https://doi.org/10.1080/19475705.2022.2097131 SN - 1947-5705 SN - 1947-5713 VL - 13 IS - 1 SP - 1640 EP - 1662 PB - Taylor & Francis CY - London ER - TY - GEN A1 - Mtilatila, Lucy Mphatso Ng'ombe A1 - Bronstert, Axel A1 - Vormoor, Klaus Josef T1 - Temporal evaluation and projections of meteorological droughts in the Greater Lake Malawi Basin, Southeast Africa T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - The study examined the potential future changes of drought characteristics in the Greater Lake Malawi Basin in Southeast Africa. This region strongly depends on water resources to generate electricity and food. Future projections (considering both moderate and high emission scenarios) of temperature and precipitation from an ensemble of 16 bias-corrected climate model combinations were blended with a scenario-neutral response surface approach to analyses changes in: (i) the meteorological conditions, (ii) the meteorological water balance, and (iii) selected drought characteristics such as drought intensity, drought months, and drought events, which were derived from the Standardized Precipitation and Evapotranspiration Index. Changes were analyzed for a near-term (2021–2050) and far-term period (2071–2100) with reference to 1976–2005. The effect of bias-correction (i.e., empirical quantile mapping) on the ability of the climate model ensemble to reproduce observed drought characteristics as compared to raw climate projections was also investigated. Results suggest that the bias-correction improves the climate models in terms of reproducing temperature and precipitation statistics but not drought characteristics. Still, despite the differences in the internal structures and uncertainties that exist among the climate models, they all agree on an increase of meteorological droughts in the future in terms of higher drought intensity and longer events. Drought intensity is projected to increase between +25 and +50% during 2021–2050 and between +131 and +388% during 2071–2100. This translates into +3 to +5, and +7 to +8 more drought months per year during both periods, respectively. With longer lasting drought events, the number of drought events decreases. Projected droughts based on the high emission scenario are 1.7 times more severe than droughts based on the moderate scenario. That means that droughts in this region will likely become more severe in the coming decades. Despite the inherent high uncertainties of climate projections, the results provide a basis in planning and (water-)managing activities for climate change adaptation measures in Malawi. This is of particular relevance for water management issues referring hydro power generation and food production, both for rain-fed and irrigated agriculture. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1287 KW - meteorological drought KW - drought intensity KW - climate change KW - drought events KW - Lake Malawi KW - Shire River KW - drought projections KW - South-Eastern Africa Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-571284 SN - 1866-8372 IS - 1287 ER - TY - JOUR A1 - Schmidt, Lena Katharina A1 - Francke, Till A1 - Rottler, Erwin A1 - Blume, Theresa A1 - Schöber, Johannes A1 - Bronstert, Axel T1 - Suspended sediment and discharge dynamics in a glaciated alpine environment BT - identifying crucial areas and time periods on several spatial and temporal scales in the Ötztal, Austria JF - Earth surface dynamics N2 - Glaciated high-alpine areas are fundamentally altered by climate change, with well-known implications for hydrology, e.g., due to glacier retreat, longer snow-free periods, and more frequent and intense summer rainstorms. While knowledge on how these hydrological changes will propagate to suspended sediment dynamics is still scarce, it is needed to inform mitigation and adaptation strategies. To understand the processes and source areas most relevant to sediment dynamics, we analyzed discharge and sediment dynamics in high temporal resolution as well as their patterns on several spatial scales, which to date few studies have done. We used a nested catchment setup in the Upper Ötztal in Tyrol, Austria, where high-resolution (15 min) time series of discharge and suspended sediment concentrations are available for up to 15 years (2006–2020). The catchments of the gauges in Vent, Sölden and Tumpen range from 100 to almost 800 km2 with 10 % to 30 % glacier cover and span an elevation range of 930 to 3772 m a.s.l. We analyzed discharge and suspended sediment yields (SSY), their distribution in space, their seasonality and spatial differences therein, and the relative importance of short-term events. We complemented our analysis by linking the observations to satellite-based snow cover maps, glacier inventories, mass balances and precipitation data. Our results indicate that the areas above 2500 m a.s.l., characterized by glacier tongues and the most recently deglaciated areas, are crucial for sediment generation in all sub-catchments. This notion is supported by the synchronous spring onset of sediment export at the three gauges, which coincides with snowmelt above 2500 m but lags behind spring discharge onsets. This points at a limitation of suspended sediment supply as long as the areas above 2500 m are snow-covered. The positive correlation of annual SSY with glacier cover (among catchments) and glacier mass balances (within a catchment) further supports the importance of the glacier-dominated areas. The analysis of short-term events showed that summer precipitation events were associated with peak sediment concentrations and yields but on average accounted for only 21 % of the annual SSY in the headwaters. These results indicate that under current conditions, thermally induced sediment export (through snow and glacier melt) is dominant in the study area. Our results extend the scientific knowledge on current hydro-sedimentological conditions in glaciated high-alpine areas and provide a baseline for studies on projected future changes in hydro-sedimentological system dynamics. Y1 - 2022 U6 - https://doi.org/10.5194/esurf-10-653-2022 SN - 2196-632X SN - 2196-6311 VL - 10 IS - 3 SP - 653 EP - 669 PB - Copernicus Publications CY - Göttingen ER - TY - JOUR A1 - Bronstert, Axel A1 - Bürger, Gerhard A1 - Pfister, Angela T1 - Vorhersage und Projektion von Sturzfluten - Vorwort JF - Hydrologie und Wasserbewirtschaftung : HyWa = Hydrology and water resources management, Germany / Hrsg.: Fachverwaltungen des Bundes und der Länder T2 - Forecasting and projection of flash flood Y1 - 2021 SN - 1439-1783 SN - 2749-859X VL - 65 IS - 6 SP - 260 EP - 261 PB - Bundesanst. für Gewässerkunde, BfG CY - Koblenz ER - TY - GEN A1 - Vogel, Johannes A1 - Paton, Eva A1 - Aich, Valentin A1 - Bronstert, Axel T1 - Increasing compound warm spells and droughts in the Mediterranean Basin T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - The co-occurrence of warm spells and droughts can lead to detrimental socio-economic and ecological impacts, largely surpassing the impacts of either warm spells or droughts alone. We quantify changes in the number of compound warm spells and droughts from 1979 to 2018 in the Mediterranean Basin using the ERA5 data set. We analyse two types of compound events: 1) warm season compound events, which are extreme in absolute terms in the warm season from May to October and 2) year-round deseasonalised compound events, which are extreme in relative terms respective to the time of the year. The number of compound events increases significantly and especially warm spells are increasing strongly – with an annual growth rates of 3.9 (3.5) % for warm season (deseasonalised) compound events and 4.6 (4.4) % for warm spells –, whereas for droughts the change is more ambiguous depending on the applied definition. Therefore, the rise in the number of compound events is primarily driven by temperature changes and not the lack of precipitation. The months July and August show the highest increases in warm season compound events, whereas the highest increases of deseasonalised compound events occur in spring and early summer. This increase in deseasonalised compound events can potentially have a significant impact on the functioning of Mediterranean ecosystems as this is the peak phase of ecosystem productivity and a vital phenophase. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1127 KW - Compound events KW - Warm spells KW - Droughts KW - Mediterranean basin KW - Extreme events KW - Climate change Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-496294 SN - 1866-8372 IS - 1127 ER - TY - JOUR A1 - Bürger, Gerd A1 - Pfister, Angela A1 - Bronstert, Axel T1 - Zunehmende Starkregenintensitäten als Folge der Klimaerwärmung T1 - Increasing intensity of heavy rainfall caused by global warming BT - Datenanalyse und Zukunftsprojektion BT - data analysis and future projections JF - Hydrologie und Wasserbewirtschaftung : HyWa = Hydrology and water resources management, Germany / Hrsg.: Fachverwaltungen des Bundes und der Länder N2 - Extreme rainfall events of short duration in the range of hours and below are increasingly coming into focus due to the resulting damage from flash floods and also due to their possible intensification by anthropogenic climate change. The current study investigates possible trends in heavy rainfall intensities for stations from Swiss and Austrian alpine regions as well as for the Emscher-Lippe area in North Rhine-Westphalia on the basis of partly very long (> 50 years) and temporally highly resolved time series (<= 15 minutes). It becomes clear that there is an increase in extreme rainfall intensities, which can be well explained by the warming of the regional climate: the analyses of long-term trends in exceedance counts and return levels show considerable uncertainties, but are in the order of 30 % increase per century. In addition, based on an "average" climate simulation for the 21st century, this paper describes a projection for extreme precipitation intensities at very high temporal resolution for a number of stations in the Emscher-Lippe region. A coupled spatial and temporal "downscaling" is applied, the key innovation of which is the consideration of the dependence of local rainfall intensity on air temperature. This procedure involves two steps: First, large-scale climate fields at daily resolution are statistically linked by regression to station temperature and precipitation values (spatial downscaling). In the second step, these station values are disaggregated to a temporal resolution of 10 minutes using a so-called multiplicative stochastic cascade model (MC) (temporal downscaling). The novel, temperature-sensitive variant additionally considers air temperature as an explanatory variable for precipitation intensities. Thus, the higher atmospheric moisture content expected with warming, which results from the Clausius-Clapeyron (CC) relationship, is included in the temporal downscaling.
For the statistical evaluation of the extreme short-term precipitation, the upper quantiles (99.9 %), exceedance counts (P > 5mm), and 3-yr return levels of the <= 15-min duration step has been used. Only by adding temperature is the observed temperature observed of the extreme quantiles ("CC scaling") well reproduced. When comparing observed data and present-day simulations of the model cascade, the temperature-sensitive procedure shows consistent results. Compared to trends in recent decades, similar or even larger increases in extreme intensities are projected for the future. This is remarkable in that these appear to be driven primarily by local temperature, as the projected trends in daily precipitation values are negligible for this region. N2 - Extreme Regenereignisse von kurzer Dauer im Bereich von Stunden und darunter rücken aufgrund der dadurch bedingten Schäden durch Sturzfluten und auch wegen ihrer möglichen Intensivierungen durch den anthropogenen Klimawandel immer stärker in den Fokus. Die vorliegende Studie untersucht auf Basis von teilweise sehr langen (> 50 Jahre) und zeitlich hochaufgelösten Zeitreihen (≤ 15 Minuten) mögliche Trends in Starkregenintensitäten für Stationen aus schweizerischen und österreichischen Alpenregionen sowie für das Emscher-Lippe-Gebiet in Nordrhein-Westfalen. Es wird deutlich, dass es eine Zunahme der extremen Niederschlagsintensitäten gibt, welche gut durch die Erwärmung des regionalen Klimas erklärt werden kann: Die Analysen langfristiger Trends der Überschreitungssummen und Wiederkehrniveaus zeigen zwar erhebliche Unsicherheiten, lassen jedoch eine Zunahme in einer Größenordnung von 30 % pro Jahrhundert erkennen. Zudem wird in diesem Beitrag, basierend auf einer "mittleren" Klimasimulation für das 21. Jahrhundert, für ausgewählte Stationen der Emscher-Lippe-Region eine Projektion für extreme Niederschlagsintensitäten in sehr hoher zeitlicher Auflösung beschrieben. Dabei wird ein gekoppeltes räumliches und zeitliches "Downscaling" angewendet, dessen entscheidende Neuerung die Berücksichtigung der Abhängigkeit der lokalen Regenintensität von der Lufttemperatur ist. Dieses Verfahren beinhaltet zwei Schritte: Zuerst werden großräumige Klimafelder in täglicher Auflösung durch Regression mit den Temperatur- und Niederschlagswerten der Stationen statistisch verbunden (räumliches Downscaling). Im zweiten Schritt werden dann diese Stationswerte mithilfe eines sogenannten multiplikativen stochastischen Kaskadenmodells (MC) auf eine zeitliche Auflösung von 10 Minuten disaggregiert (zeitliches Downscaling). Die neuartige, temperatursensitive Variante berücksichtigt zusätzlich die Lufttemperatur als erklärende Variable für die Niederschlagsintensitäten. Dadurch wird der mit einer Erwärmung zu erwartende höhere atmosphärische Feuchtegehalt, welcher sich aus der Clausius-Clapeyron-Beziehung (CC) ergibt, mit in das zeitliche Downscaling einbezogen. Für die statistische Auswertung der extremen kurzfristigen Niederschläge wurden die oberen Quantile (99,9 %), Überschreitungssummen (ÜS, P > 5 mm) und 3-jährliche Wiederkehrniveaus (WN) einer Dauerstufe von ≤ 15-Minuten betrachtet. Diese Auswahl erlaubt die gleichzeitige Analyse sowohl von Extremwertstatistiken als auch von deren langfristigen Trends; leichte Abweichungen von dieser Wahl beeinflussen die Hauptergebnisse nur unwesentlich. Nur durch die Hinzunahme der Temperatur wird die beobachtete Temperaturabhängigkeit der extremen Quantile (CC-Scaling) gut wiedergegeben. Bei Vergleich von Beobachtungsdaten und Gegenwartssimulationen der Modellkaskade zeigt das temperatursensitive Verfahren konsistente Ergebnisse. Im Vergleich zu den Entwicklungen der letzten Jahrzehnte werden für die Zukunft ähnliche oder sogar noch stärkere Anstiege der extremen Niederschlagsintensitäten projiziert. Dies ist insofern bemerkenswert, als diese anscheinend hauptsächlich durch die örtliche Temperatur bestimmt werden, denn die projizierten Trends der Niederschlags-Tageswerte sind für diese Region vernachlässigbar. KW - heavy rainfall KW - short duration KW - global warming KW - Clausius-Clapeyron KW - equation KW - precipitation intensity KW - multiplicative cascade model KW - Strakregen KW - kurzfristige Dauerstufe KW - Klimawandel KW - Clausius-Clapeyron-Gleichung KW - Niederschlagsintensitäten KW - Multiplikatives Kaskadenmodel Y1 - 2021 U6 - https://doi.org/10.5675/HyWa_2021.6_1 SN - 1439-1783 SN - 2749-859X VL - 65 IS - 6 SP - 262 EP - 271 PB - Bundesanst. für Gewässerkunde CY - Koblenz ER - TY - GEN A1 - Seleem, Omar A1 - Heistermann, Maik A1 - Bronstert, Axel T1 - Efficient Hazard Assessment For Pluvial Floods In Urban Environments BT - A Benchmarking Case Study For The City Of Berlin, Germany T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - The presence of impermeable surfaces in urban areas hinders natural drainage and directs the surface runoff to storm drainage systems with finite capacity, which makes these areas prone to pluvial flooding. The occurrence of pluvial flooding depends on the existence of minimal areas for surface runoff generation and concentration. Detailed hydrologic and hydrodynamic simulations are computationally expensive and require intensive resources. This study compared and evaluated the performance of two simplified methods to identify urban pluvial flood-prone areas, namely the fill–spill–merge (FSM) method and the topographic wetness index (TWI) method and used the TELEMAC-2D hydrodynamic numerical model for benchmarking and validation. The FSM method uses common GIS operations to identify flood-prone depressions from a high-resolution digital elevation model (DEM). The TWI method employs the maximum likelihood method (MLE) to probabilistically calibrate a TWI threshold (τ) based on the inundation maps from a 2D hydrodynamic model for a given spatial window (W) within the urban area. We found that the FSM method clearly outperforms the TWI method both conceptually and effectively in terms of model performance. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1163 KW - urban pluvial flooding KW - digital elevation model (DEM) KW - fill–spill–merge method KW - topographic wetness index (TWI) KW - TELEMAC-2D model KW - flood-prone area Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-522158 SN - 1866-8372 IS - 18 ER - TY - JOUR A1 - Seleem, Omar A1 - Heistermann, Maik A1 - Bronstert, Axel T1 - Efficient Hazard Assessment For Pluvial Floods In Urban Environments BT - A Benchmarking Case Study For The City Of Berlin, Germany JF - Water N2 - The presence of impermeable surfaces in urban areas hinders natural drainage and directs the surface runoff to storm drainage systems with finite capacity, which makes these areas prone to pluvial flooding. The occurrence of pluvial flooding depends on the existence of minimal areas for surface runoff generation and concentration. Detailed hydrologic and hydrodynamic simulations are computationally expensive and require intensive resources. This study compared and evaluated the performance of two simplified methods to identify urban pluvial flood-prone areas, namely the fill–spill–merge (FSM) method and the topographic wetness index (TWI) method and used the TELEMAC-2D hydrodynamic numerical model for benchmarking and validation. The FSM method uses common GIS operations to identify flood-prone depressions from a high-resolution digital elevation model (DEM). The TWI method employs the maximum likelihood method (MLE) to probabilistically calibrate a TWI threshold (τ) based on the inundation maps from a 2D hydrodynamic model for a given spatial window (W) within the urban area. We found that the FSM method clearly outperforms the TWI method both conceptually and effectively in terms of model performance. KW - urban pluvial flooding KW - digital elevation model (DEM) KW - fill–spill–merge method KW - topographic wetness index (TWI) KW - TELEMAC-2D model KW - flood-prone area Y1 - 2021 U6 - https://doi.org/10.3390/w13182476 SN - 2073-4441 VL - 13 IS - 18 PB - MDPI CY - Basel ER - TY - JOUR A1 - Rottler, Erwin A1 - Vormoor, Klaus Josef A1 - Francke, Till A1 - Warscher, Michael A1 - Strasser, Ulrich A1 - Bronstert, Axel T1 - Elevation-dependent compensation effects in snowmelt in the Rhine River Basin upstream gauge Basel JF - Hydrology research : an international journal / Nordic Association of Hydrology ; British Hydrological Society N2 - In snow-dominated river basins, floods often occur during early summer, when snowmelt-induced runoff superimposes with rainfall-induced runoff. An earlier onset of seasonal snowmelt as a consequence of a warming climate is often expected to shift snowmelt contribution to river runoff and potential flooding to an earlier date. Against this background, we assess the impact of rising temperatures on seasonal snowpacks and quantify changes in timing, magnitude and elevation of snowmelt. We analyse in situ snow measurements, conduct snow simulations and examine changes in river runoff at key gauging stations. With regard to snowmelt, we detect a threefold effect of rising temperatures: snowmelt becomes weaker, occurs earlier and forms at higher elevations. Due to the wide range of elevations in the catchment, snowmelt does not occur simultaneously at all elevations. Results indicate that elevation bands melt together in blocks. We hypothesise that in a warmer world with similar sequences of weather conditions, snowmelt is moved upward to higher elevation. The movement upward the elevation range makes snowmelt in individual elevation bands occur earlier, although the timing of the snowmelt-induced runoff stays the same. Meltwater from higher elevations, at least partly, replaces meltwater from elevations below. KW - compensation effects KW - elevation-dependency KW - Rhine River KW - snowmelt KW - timing Y1 - 2021 U6 - https://doi.org/10.2166/nh.2021.092 SN - 2224-7955 VL - 52 IS - 2 SP - 536 EP - 557 PB - IWA Publ. CY - London ER - TY - JOUR A1 - Rottler, Erwin A1 - Vormoor, Klaus Josef A1 - Francke, Till A1 - Bronstert, Axel T1 - Hydro Explorer BT - an interactive web app to investigate changes in runoff timing and runoff seasonality all over the world JF - River research and applications N2 - Climatic changes and anthropogenic modifications of the river basin or river network have the potential to fundamentally alter river runoff. In the framework of this study, we aim to analyze and present historic changes in runoff timing and runoff seasonality observed at river gauges all over the world. In this regard, we develop the Hydro Explorer, an interactive web app, which enables the investigation of >7,000 daily resolution discharge time series from the Global Runoff Data Centre (GRDC). The interactive nature of the developed web app allows for a quick comparison of gauges, regions, methods, and time frames. We illustrate the available analytical tools by investigating changes in runoff timing and runoff seasonality in the Rhine River Basin. Since we provide the source code of the application, existing analytical approaches can be modified, new methods added, and the tool framework can be re-used to visualize other data sets. KW - global runoff database KW - interactive web app KW - R Shiny KW - runoff KW - seasonality KW - runoff timing Y1 - 2021 U6 - https://doi.org/10.1002/rra.3772 SN - 1535-1459 SN - 1535-1467 VL - 37 IS - 4 SP - 544 EP - 554 PB - Wiley CY - New York ER - TY - JOUR A1 - Vogel, Johannes A1 - Paton, Eva A1 - Aich, Valentin A1 - Bronstert, Axel T1 - Increasing compound warm spells and droughts in the Mediterranean Basin JF - Weather and climate extremes N2 - The co-occurrence of warm spells and droughts can lead to detrimental socio-economic and ecological impacts, largely surpassing the impacts of either warm spells or droughts alone. We quantify changes in the number of compound warm spells and droughts from 1979 to 2018 in the Mediterranean Basin using the ERA5 data set. We analyse two types of compound events: 1) warm season compound events, which are extreme in absolute terms in the warm season from May to October and 2) year-round deseasonalised compound events, which are extreme in relative terms respective to the time of the year. The number of compound events increases significantly and especially warm spells are increasing strongly – with an annual growth rates of 3.9 (3.5) % for warm season (deseasonalised) compound events and 4.6 (4.4) % for warm spells –, whereas for droughts the change is more ambiguous depending on the applied definition. Therefore, the rise in the number of compound events is primarily driven by temperature changes and not the lack of precipitation. The months July and August show the highest increases in warm season compound events, whereas the highest increases of deseasonalised compound events occur in spring and early summer. This increase in deseasonalised compound events can potentially have a significant impact on the functioning of Mediterranean ecosystems as this is the peak phase of ecosystem productivity and a vital phenophase. KW - Compound events KW - Warm spells KW - Droughts KW - Mediterranean basin KW - Extreme events KW - Climate change Y1 - 2021 U6 - https://doi.org/10.1016/j.wace.2021.100312 SN - 2212-0947 VL - 32 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Rottler, Erwin A1 - Bronstert, Axel A1 - Bürger, Gerd A1 - Rakovec, Oldrich T1 - Projected changes in Rhine River flood seasonality under global warming JF - Hydrology and earth system sciences : HESS / European Geosciences Union N2 - Climatic change alters the frequency and intensity of natural hazards. In order to assess potential future changes in flood seasonality in the Rhine River Basin, we analyse changes in streamflow, snowmelt, precipitation, and evapotranspiration at 1.5, 2.0 and 3.0 ◦C global warming levels. The mesoscale Hydrological Model (mHM) forced with an ensemble of climate projection scenarios (five general circulation models under three representative concentration pathways) is used to simulate the present and future climate conditions of both, pluvial and nival hydrological regimes. Our results indicate that the interplay between changes in snowmelt- and rainfall-driven runoff is crucial to understand changes in streamflow maxima in the Rhine River. Climate projections suggest that future changes in flood characteristics in the entire Rhine River are controlled by both, more intense precipitation events and diminishing snow packs. The nature of this interplay defines the type of change in runoff peaks. On the sub-basin level (the Moselle River), more intense rainfall during winter is mostly counterbalanced by reduced snowmelt contribution to the streamflow. In the High Rhine (gauge at Basel), the strongest increases in streamflow maxima show up during winter, when strong increases in liquid precipitation intensity encounter almost unchanged snowmelt-driven runoff. The analysis of snowmelt events suggests that at no point in time during the snowmelt season, a warming climate results in an increase in the risk of snowmelt-driven flooding. We do not find indications of a transient merging of pluvial and nival floods due to climate warming. Y1 - 2020 U6 - https://doi.org/10.5194/hess-25-2353-2021 SN - 1607-7938 SN - 1027-5606 VL - 25 IS - 5 SP - 2353 EP - 2371 PB - Copernicus Publications CY - Göttingen ER - TY - CHAP A1 - Bronstert, Axel A1 - Crisologo, Irene A1 - Heistermann, Maik A1 - Öztürk, Ugur A1 - Vogel, Kristin A1 - Wendi, Dadiyorto T1 - Flash-floods: more often, more severe, more damaging? BT - An analysis of hydro-geo-environmental conditions and anthropogenic impacts T2 - Climate change, hazards and adaptation options: handling the impacts of a changing climate N2 - In recent years, urban and rural flash floods in Europe and abroad have gained considerable attention because of their sudden occurrence, severe material damages and even danger to life of inhabitants. This contribution addresses questions about possibly changing environmental conditions which might have altered the occurrence frequencies of such events and their consequences. We analyze the following major fields of environmental changes. Altered high intensity rain storm conditions, as a consequence of regionalwarming; Possibly altered runoff generation conditions in response to high intensity rainfall events; Possibly altered runoff concentration conditions in response to the usage and management of the landscape, such as agricultural, forest practices or rural roads; Effects of engineering measures in the catchment, such as retention basins, check dams, culverts, or river and geomorphological engineering measures. We take the flash-flood in Braunsbach, SW-Germany, as an example, where a particularly concise flash flood event occurred at the end of May 2016. This extreme cascading natural event led to immense damage in this particular village. The event is retrospectively analyzed with regard to meteorology, hydrology, geomorphology and damage to obtain a quantitative assessment of the processes and their development. The results show that it was a very rare rainfall event with extreme intensities, which in combination with catchment properties and altered environmental conditions led to extreme runoff, extreme debris flow and immense damages. Due to the complex and interacting processes, no single flood cause can be identified, since only the interplay of those led to such an event. We have shown that environmental changes are important, but-at least for this case study-even natural weather and hydrologic conditions would still have resulted in an extreme flash flood event. KW - Flash flood KW - Climate change KW - Extreme rainfall KW - Anthropogenic impacts Y1 - 2020 SN - 978-3-030-37425-9 SN - 978-3-030-37424-2 U6 - https://doi.org/10.1007/978-3-030-37425-9_12 SN - 1610-2010 SP - 225 EP - 244 PB - Springer CY - Cham ER - TY - JOUR A1 - Mtilatila, Lucy Mphatso Ng'ombe A1 - Bronstert, Axel A1 - Shrestha, Pallav A1 - Kadewere, Peter A1 - Vormoor, Klaus Josef T1 - Susceptibility of water resources and hydropower production to climate change in the tropics BT - the case of Lake Malawi and Shire River Basins, SE Africa JF - Hydrology : open access journal N2 - The sensitivity of key hydrologic variables and hydropower generation to climate change in the Lake Malawi and Shire River basins is assessed. The study adapts the mesoscale Hydrological Model (mHM) which is applied separately in the Upper Lake Malawi and Shire River basins. A particular Lake Malawi model, which focuses on reservoir routing and lake water balance, has been developed and is interlinked between the two basins. Climate change projections from 20 Coordinated Regional Climate Downscaling Experiment (CORDEX) models for Africa based on two scenarios (RCP4.5 and RCP8.5) for the periods 2021-2050 and 2071-2100 are used. An annual temperature increase of 1 degrees C decreases mean lake level and outflow by 0.3 m and 17%, respectively, signifying the importance of intensified evaporation for Lake Malawi's water budget. Meanwhile, a +5% (-5%) deviation in annual rainfall changes mean lake level by +0.7 m (-0.6 m). The combined effects of temperature increase and rainfall decrease result in significantly lower flows in the Shire River. The hydrological river regime may change from perennial to seasonal with the combination of annual temperature increase and precipitation decrease beyond 1.5 degrees C (3.5 degrees C) and -20% (-15%). The study further projects a reduction in annual hydropower production between 1% (RCP8.5) and 2.5% (RCP4.5) during 2021-2050 and between 5% (RCP4.5) and 24% (RCP8.5) during 2071-2100. The results show that it is of great importance that a further development of hydro energy on the Shire River should take into account the effects of climate change, e.g., longer low flow periods and/or higher discharge fluctuations, and thus uncertainty in the amount of electricity produced. KW - Lake Malawi Basin KW - Shire River Basin KW - lake water balance KW - climate change impacts in the tropics KW - hydropower generation KW - response surface analysis KW - sensitivity analysis Y1 - 2020 U6 - https://doi.org/10.3390/hydrology7030054 SN - 2306-5338 VL - 7 IS - 3 PB - MDPI CY - Basel ER - TY - GEN A1 - Rottler, Erwin A1 - Francke, Till A1 - Bürger, Gerd A1 - Bronstert, Axel T1 - Long-term changes in central European river discharge for 1869–2016 BT - Impact of changing snow covers, reservoir constructions and an intensified hydrological cycle T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Recent climatic changes have the potential to severely alter river runoff, particularly in snow-dominated river basins. Effects of changing snow covers superimpose with changes in precipitation and anthropogenic modifications of the watershed and river network. In the attempt to identify and disentangle long-term effects of different mechanisms, we employ a set of analytical tools to extract long-term changes in river runoff at high resolution. We combine quantile sampling with moving average trend statistics and empirical mode decomposition and apply these tools to discharge data recorded along rivers with nival, pluvial and mixed flow regimes as well as temperature and precipitation data covering the time frame 1869-2016. With a focus on central Europe, we analyse the long-term impact of snow cover and precipitation changes along with their interaction with reservoir constructions. Our results show that runoff seasonality of snow-dominated rivers decreases. Runoff increases in winter and spring, while discharge decreases in summer and at the beginning of autumn. We attribute this redistribution of annual flow mainly to reservoir constructions in the Alpine ridge. During the course of the last century, large fractions of the Alpine rivers were dammed to produce hydropower. In recent decades, runoff changes induced by reservoir constructions seem to overlap with changes in snow cover. We suggest that Alpine signals propagate downstream and affect runoff far outside the Alpine area in river segments with mixed flow regimes. Furthermore, our results hint at more (intense) rain-fall in recent decades. Detected increases in high discharge can be traced back to corresponding changes in precipitation. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1412 KW - empirical mode decomposition KW - atmospheric blocking KW - heavy precipitation KW - streamflow trends KW - climate-change KW - rhine basin KW - time-series KW - events KW - Switzerland KW - variability Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-517763 SN - 1866-8372 IS - 4 ER - TY - JOUR A1 - Rottler, Erwin A1 - Francke, Till A1 - Bürger, Gerd A1 - Bronstert, Axel T1 - Long-term changes in central European river discharge for 1869–2016 BT - impact of changing snow covers, reservoir constructions and an intensified hydrological cycle JF - Hydrology and Earth System Sciences N2 - Recent climatic changes have the potential to severely alter river runoff, particularly in snow-dominated river basins. Effects of changing snow covers superimpose with changes in precipitation and anthropogenic modifications of the watershed and river network. In the attempt to identify and disentangle long-term effects of different mechanisms, we employ a set of analytical tools to extract long-term changes in river runoff at high resolution. We combine quantile sampling with moving average trend statistics and empirical mode decomposition and apply these tools to discharge data recorded along rivers with nival, pluvial and mixed flow regimes as well as temperature and precipitation data covering the time frame 1869-2016. With a focus on central Europe, we analyse the long-term impact of snow cover and precipitation changes along with their interaction with reservoir constructions. Our results show that runoff seasonality of snow-dominated rivers decreases. Runoff increases in winter and spring, while discharge decreases in summer and at the beginning of autumn. We attribute this redistribution of annual flow mainly to reservoir constructions in the Alpine ridge. During the course of the last century, large fractions of the Alpine rivers were dammed to produce hydropower. In recent decades, runoff changes induced by reservoir constructions seem to overlap with changes in snow cover. We suggest that Alpine signals propagate downstream and affect runoff far outside the Alpine area in river segments with mixed flow regimes. Furthermore, our results hint at more (intense) rain-fall in recent decades. Detected increases in high discharge can be traced back to corresponding changes in precipitation. KW - empirical mode decomposition KW - atmospheric blocking KW - heavy precipitation KW - streamflow trends KW - climate-change KW - rhine basin KW - time-series KW - events KW - Switzerland KW - variability Y1 - 2020 U6 - https://doi.org/10.5194/hess-24-1721-2020 SN - 1027-5606 SN - 1607-7938 VL - 24 IS - 4 SP - 1721 EP - 1740 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Didovets, Iulii A1 - Krysanova, Valentina A1 - Bürger, Gerd A1 - Snizhko, Sergiy A1 - Balabukh, Vira A1 - Bronstert, Axel T1 - Climate change impact on regional floods in the Carpathian region JF - Journal of hydrology : Regional studies N2 - Study region: Tisza and Prut catchments, originating on the slopes of the Carpathian mountains. Study focus: The study reported here investigates (i) climate change impacts on flood risk in the region, and (ii) uncertainty related to hydrological modelling, downscaling techniques and climate projections. The climate projections used in the study were derived from five GCMs, downscaled either dynamically with RCMs or with the statistical downscaling model XDS. The resulting climate change scenarios were applied to drive the eco-hydrological model SWIM, which was calibrated and validated for the catchments in advance using observed climate and hydrological data. The changes in the 30-year flood hazards and 98 and 95 percentiles of discharge were evaluated for the far future period (2071-2100) in comparison with the reference period (1981-2010). New hydrological insights for the region: The majority of model outputs under RCP 4.5 show a small to strong increase of the 30-year flood level in the Tisza ranging from 4.5% to 62%, and moderate increase in the Prut ranging from 11% to 22%. The impact results under RCP 8.5 are more uncertain with changes in both directions due to high uncertainties in GCM-RCM climate projections, downscaling methods and the low density of available climate stations. KW - Climate change impact KW - Floods KW - Hydrological modelling KW - SWIM KW - Tisza KW - Prut KW - Carpathians KW - Ukraine Y1 - 2019 U6 - https://doi.org/10.1016/j.ejrh.2019.01.002 SN - 2214-5818 VL - 22 PB - Elsevier CY - Amsterdam ER - TY - GEN A1 - Lopez Tarazon, José Andrés A1 - Bronstert, Axel A1 - Thieken, Annegret A1 - Petrow, Theresia T1 - The effects of global change on floods, fluvial geomorphology and related hazards in mountainous rivers T2 - The science of the total environment : an international journal for scientific research into the environment and its relationship with man Y1 - 2019 U6 - https://doi.org/10.1016/j.scitotenv.2019.03.026 SN - 0048-9697 SN - 1879-1026 VL - 669 SP - 7 EP - 10 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Rottler, Erwin A1 - Kormann, Christoph Martin A1 - Francke, Till A1 - Bronstert, Axel T1 - Elevation-dependent warming in the Swiss Alps 1981-2017 BT - Features, forcings and feedbacks JF - International journal of climatology : a journal of the Royal Meteorological Society N2 - Due to the environmental and socio-economic importance of mountainous regions, it is crucial to understand causes and consequences of climatic changes in those sensitive landscapes. Daily resolution alpine climate data from Switzerland covering an elevation range of over 3,000m between 1981 and 2017 have been analysed using highly resolved trends in order to gain a better understanding of features, forcings and feedbacks related to temperature changes in mountainous regions. Particular focus is put on processes related to changes in weather types, incoming solar radiation, cloud cover, air humidity, snow/ice and elevation dependency of temperature trends. Temperature trends in Switzerland differ depending on the time of the year, day and elevation. Warming is strongest during spring and early summer with enhanced warming of daytime maximum temperatures. Elevation-based differences in temperature trends occur during autumn and winter with stronger warming at lower elevations. We attribute this elevation-dependent temperature signal mainly to elevation-based differences in trends of incoming solar radiation and elevation-sensitive responses to changes in frequencies of weather types. In general, effects of varying frequencies of weather types overlap with trends caused by transmission changes in short- and long-wave radiation. Temperature signals arising from snow/ice albedo feedback mechanisms are probably small and might be hidden by other effects. KW - cloud cover KW - elevation dependency KW - mountain climate KW - snow KW - ice-albedo feedback KW - Swiss Alps KW - temperature trend KW - weather types Y1 - 2018 U6 - https://doi.org/10.1002/joc.5970 SN - 0899-8418 SN - 1097-0088 VL - 39 IS - 5 SP - 2556 EP - 2568 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Meißl, Gertraud A1 - Formayer, Herbert A1 - Klebinder, Klaus A1 - Kerl, Florian A1 - Schöberl, Friedrich A1 - Geitner, Clemens A1 - Markart, Gerhard A1 - Leidinger, David A1 - Bronstert, Axel T1 - Climate change effects on hydrological system conditions influencing generation of storm runoff in small Alpine catchments JF - Hydrological processes : an international journal N2 - Floods and debris flows in small Alpine torrent catchments (<10km(2)) arise from a combination of critical antecedent system state conditions and mostly convective precipitation events with high precipitation intensities. Thus, climate change may influence the magnitude-frequency relationship of extreme events twofold: by a modification of the occurrence probabilities of critical hydrological system conditions and by a change of event precipitation characteristics. Three small Alpine catchments in different altitudes in Western Austria (Ruggbach, Brixenbach and Langentalbach catchment) were investigated by both field experiments and process-based simulation. Rainfall-runoff model (HQsim) runs driven by localized climate scenarios (CNRM-RM4.5/ARPEGE, MPI-REMO/ECHAM5 and ICTP-RegCM3/ECHAM5) were used in order to estimate future frequencies of stormflow triggering system state conditions. According to the differing altitudes of the study catchments, two effects of climate change on the hydrological systems can be observed. On one hand, the seasonal system state conditions of medium altitude catchments are most strongly affected by air temperature-controlled processes such as the development of the winter snow cover as well as evapotranspiration. On the other hand, the unglaciated high-altitude catchment is less sensitive to climate change-induced shifts regarding days with critical antecedent soil moisture and desiccated litter layer due to its elevation-related small proportion of sensitive areas. For the period 2071-2100, the number of days with critical antecedent soil moisture content will be significantly reduced to about 60% or even less in summer in all catchments. In contrast, the number of days with dried-out litter layers causing hydrophobic effects will increase by up to 8%-11% of the days in the two lower altitude catchments. The intensity analyses of heavy precipitation events indicate a clear increase in rain intensities of up to 10%. KW - climate change KW - hydrophobic effects KW - small Alpine catchments KW - soil moisture KW - storm runoff events KW - system conditions Y1 - 2016 U6 - https://doi.org/10.1002/hyp.11104 SN - 0885-6087 SN - 1099-1085 VL - 31 IS - 6 SP - 1314 EP - 1330 PB - Wiley CY - New York ER - TY - JOUR A1 - Miegel, Konrad A1 - Gräff, Thomas A1 - Franck, Christian A1 - Salzmann, Thomas A1 - Bronstert, Axel A1 - Walther, Marc A1 - Oswald, Sascha T1 - Auswirkungen des Sturmhochwassers der Ostsee am 4./5. Januar 2017 auf das renaturierte Nieder- moor „Hütelmoor und Heiligensee“ an der deut- schen Ostseeküste BT - Effects of the January 4/5 2017 storm surge on a restored fen at the German Baltic Sea coast JF - Hydrologie und Wasserbewirtschaftung N2 - Entlang der Küstenniederung des Naturschutzgebietes „Hütelmoor und Heiligensee“, ca. 6 km nordöstlich von Rostock-Warnemünde gelegen, wird seit dem Jahr 2000 die Küstendüne nicht mehr instand gehalten. Im Rahmen der Renaturierung des Gebietes werden so grundsätzlich wieder Überflutungen bei Ostseehochwassern zugelassen, was bisher jedoch noch nicht eingetreten ist. Am 4./5. Januar 2017 ereignete sich ein Sturmhochwasser der Ostsee, mit einem Scheitelwasserstand in Warnemünde, der sich zwischen dem 10- und 20-jährlichen Hochwasserstand einordnet. Dennoch kam es bei diesem Ereignis nicht zum Dünendurchbruch und zur seeseitigen Überflutung, wohl aber zum binnenseitigen Einstrom von Salz- bzw. Brackwasser. Dieser erfolgte über den Graben, durch den das Gebiet normalerweise über die Warnow in die Ostsee entwässert. Durch das Einströmen über die Sohlschwelle, sonst Auslass des Gebietes, stiegen die Wasserstände und Salzkonzentrationen in der südwestlichen Hälfte der Niederung an. Mit zunehmender Entfernung zur Sohlschwelle waren diese Auswirkungen jedoch geringer spürbar. Dies gilt wegen der Retentionswirkung der Niederung mehr für den Wasserstand als für die Salzkonzentration. Während der Wasserstand durch den Einstau der Niederung und Überschwemmungen flächenhaft anstieg, breitete sich die Salzfront präferentiell in den ehemaligen Entwässerungsgräben, die trotz des Einstaus nach wie vor hydraulisch aktiv sind, eher linienhaft aus. Diese Interpretation beruht auf Messergebnissen von Wasserstand, elektrischer Leitfähigkeit und Wassertemperatur. N2 - Maintenance and repair of the coastal dunes of the conservation area, Hutelmoor und Heiligensee" have been ceased for renaturation purposes since the year 2000 to aid flooding of the area during high water levels of the Baltic Sea. On January 4th and 5th 2017, the Baltic Sea experienced a storm surge resulting in a water level in Warnemunde with a 10-to 20-year reoccurrence rate. Nevertheless, the event caused neither a dune failure nor a sea-sided flooding, but did result in an upstream inflow of salt and brackwater through the trench which normally drains the area into the Baltic Sea via the Warnow. Water levels and salinity concentrations rose in the south-western part of the area due to the influx via a ground sill, which normally acts as the outlet of the lowland. The effects within the lowland were less pronounced with increasing distance to the ground sill, which proved to be even more significant for the water levels than for salinities due to the retention capabilities of the area. While water levels increased extensively as a result of the flooding, the salinity front is presumed to have spread primarily along the former draining channels. This interpretation is based on monitoring data of the water level as well as the environmental tracers electrical conductivity and water temperature. KW - Baltic Sea KW - storm surge KW - coastal lowland KW - flooding KW - salinization KW - environmental tracer KW - process analysis KW - Ostsee KW - Sturmhochwasser KW - Küstenniederung KW - Überflutung KW - Versalzung KW - Umwelttracer KW - Prozessgeschehen Y1 - 2017 U6 - https://doi.org/10.5675/HyWa_2017,4_2 SN - 1439-1783 VL - 61 IS - 4 SP - 232 EP - 243 PB - Bundesanst. für Gewässerkunde CY - Koblenz ER - TY - JOUR A1 - Heistermann, Maik A1 - Crisologo, Irene A1 - Abon, Catherine Cristobal A1 - Racoma, B. A. A1 - Jacobi, S. A1 - Servando, N. T. A1 - David, C. P. C. A1 - Bronstert, Axel T1 - Using the new Philippine radar network to reconstruct the Habagat of August 2012 monsoon event around Metropolitan Manila JF - Natural hazards and earth system sciences N2 - From 6 to 9 August 2012, intense rainfall hit the northern Philippines, causing massive floods in Metropolitan Manila and nearby regions. Local rain gauges recorded almost 1000mm within this period. However, the recently installed Philippine network of weather radars suggests that Metropolitan Manila might have escaped a potentially bigger flood just by a whisker, since the centre of mass of accumulated rainfall was located over Manila Bay. A shift of this centre by no more than 20 km could have resulted in a flood disaster far worse than what occurred during Typhoon Ketsana in September 2009. Y1 - 2013 U6 - https://doi.org/10.5194/nhess-13-653-2013 SN - 1561-8633 VL - 13 IS - 3 SP - 653 EP - 657 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Costa, A. C. A1 - Bronstert, Axel A1 - de Araujo, Jose Carlos T1 - A channel transmission losses model for different dryland rivers JF - Hydrology and earth system sciences : HESS N2 - Channel transmission losses in drylands take place normally in extensive alluvial channels or streambeds underlain by fractured rocks. They can play an important role in streamflow rates, groundwater recharge, freshwater supply and channel-associated ecosystems. We aim to develop a process-oriented, semi-distributed channel transmission losses model, using process formulations which are suitable for data-scarce dryland environments and applicable to both hydraulically disconnected losing streams and hydraulically connected losing(/gaining) streams. This approach should be able to cover a large variation in climate and hydro-geologic controls, which are typically found in dryland regions of the Earth. Our model was first evaluated for a losing/gaining, hydraulically connected 30 km reach of the Middle Jaguaribe River (MJR), Ceara, Brazil, which drains a catchment area of 20 000 km(2). Secondly, we applied it to a small losing, hydraulically disconnected 1.5 km channel reach in the Walnut Gulch Experimental Watershed (WGEW), Arizona, USA. The model was able to predict reliably the streamflow volume and peak for both case studies without using any parameter calibration procedure. We have shown that the evaluation of the hypotheses on the dominant hydrological processes was fundamental for reducing structural model uncertainties and improving the streamflow prediction. For instance, in the case of the large river reach (MJR), it was shown that both lateral stream-aquifer water fluxes and groundwater flow in the underlying alluvium parallel to the river course are necessary to predict streamflow volume and channel transmission losses, the former process being more relevant than the latter. Regarding model uncertainty, it was shown that the approaches, which were applied for the unsaturated zone processes (highly nonlinear with elaborate numerical solutions), are much more sensitive to parameter variability than those approaches which were used for the saturated zone (mathematically simple water budgeting in aquifer columns, including backwater effects). In case of the MJR-application, we have seen that structural uncertainties due to the limited knowledge of the subsurface saturated system interactions (i.e. groundwater coupling with channel water; possible groundwater flow parallel to the river) were more relevant than those related to the subsurface parameter variability. In case of the WEGW application we have seen that the non-linearity involved in the unsaturated flow processes in disconnected dryland river systems (controlled by the unsaturated zone) generally contain far more model uncertainties than do connected systems controlled by the saturated flow. Therefore, the degree of aridity of a dryland river may be an indicator of potential model uncertainty and subsequent attainable predictability of the system. Y1 - 2012 U6 - https://doi.org/10.5194/hess-16-1111-2012 SN - 1027-5606 VL - 16 IS - 4 SP - 1111 EP - 1135 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Kneis, David A1 - Buerger, Gerd A1 - Bronstert, Axel T1 - Evaluation of medium-range runoff forecasts for a 50 km(2) watershed JF - Journal of hydrology N2 - We generated medium-range forecasts of runoff for a 50 km(2) headwater catchment upstream of a reservoir using numerical weather predictions (NWPs) of the past as input to an operational hydrological model. NWP data originating from different sources were tested. For a period of 8.5 years, we computed daily forecasts with a lead time of +120 h based on an empirically downscaled version of the ECMWF's ensemble prediction system. For the last 3.5 years of the test period, we also tried the deterministic COSMO-EU forecast disseminated by the German Weather Service for lead times of up to +72 h. Common measures of skill indicate superiority of the ensemble runoff forecast over single-value forecasts for longer lead times. However, regardless of which NWP data were being used, the probability of event detection (POD) was found to be generally lower than 50%. In many cases, values in the range of 20-30% were obtained. At the same time, the false alarms ratio (FAR) was often found to be considerably high. The observed uncertainties in the hydrological forecasts were shown to originate from both the insufficient quality of precipitation forecasts as well as deficiencies in hydrological modeling and quantitative precipitation estimation. With respect to the anticipatory control of reservoirs in the studied catchment, the value of the tested runoff forecasts appears to be limited. This is due to the unfavorably low POD/FAR ratio in conjunction with a high cost-loss ratio. However, our results indicate that, in many cases, major runoff events related to snow melt can be successfully predicted as early as 4-5 days in advance. KW - Runoff forecast KW - Small catchments KW - Forecast verification KW - Reservoir control Y1 - 2012 U6 - https://doi.org/10.1016/j.jhydrol.2011.11.005 SN - 0022-1694 VL - 414 IS - 2 SP - 341 EP - 353 PB - Elsevier CY - Amsterdam ER - TY - GEN A1 - Blume, Theresa A1 - Zehe, Erwin A1 - Bronstert, Axel T1 - Use of soil moisture dynamics and patterns at different spatio-temporal scales for the investigation of subsurface flow processes N2 - Spatial patterns as well as temporal dynamics of soil moisture have a major influence on runoff generation. The investigation of these dynamics and patterns can thus yield valuable information on hydrological processes, especially in data scarce or previously ungauged catchments. The combination of spatially scarce but temporally high resolution soil moisture profiles with episodic and thus temporally scarce moisture profiles at additional locations provides information on spatial as well as temporal patterns of soil moisture at the hillslope transect scale. This approach is better suited to difficult terrain (dense forest, steep slopes) than geophysical techniques and at the same time less cost-intensive than a high resolution grid of continuously measuring sensors. Rainfall simulation experiments with dye tracers while continuously monitoring soil moisture response allows for visualization of flow processes in the unsaturated zone at these locations. Data was analyzed at different spacio-temporal scales using various graphical methods, such as space-time colour maps (for the event and plot scale) and binary indicator maps (for the long-term and hillslope scale). Annual dynamics of soil moisture and decimeterscale variability were also investigated. The proposed approach proved to be successful in the investigation of flow processes in the unsaturated zone and showed the importance of preferential flow in the Malalcahuello Catchment, a datascarce catchment in the Andes of Southern Chile. Fast response times of stream flow indicate that preferential flow observed at the plot scale might also be of importance at the hillslope or catchment scale. Flow patterns were highly variable in space but persistent in time. The most likely explanation for preferential flow in this catchment is a combination of hydrophobicity, small scale heterogeneity in rainfall due to redistribution in the canopy and strong gradients in unsaturated conductivities leading to self-reinforcing flow paths. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 125 KW - Repellent sandy soil KW - Poorly gauged catchment KW - Volcanic ash soils KW - Water repellency KW - Preferential flow Y1 - 2009 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-44924 ER - TY - JOUR A1 - Kneis, David A1 - Förster, Saskia A1 - Bronstert, Axel T1 - Simulation of water quality in a flood detention area using models of different spatial discretization N2 - Detention areas provide a means to lower peak discharges in rivers by temporarily storing excess water. In the case of extreme flood events, the storage effect reduces the risk of dike failures or extensive inundations for downstream reaches and near the site of abstraction. Due to the large amount of organic matter contained in the river water and the inundation of terrestrial vegetation in the detention area, a deterioration of water quality may occur. In particular, decay processes can cause a severe depletion of dissolved oxygen (DO) in the temporary water body. In this paper, we studied the potential of a water quality model to simulate the DO dynamics in a large but shallow detention area to be built at the Elbe River (Germany). Our focus was on examining the impact of spatial discretization on the model's performance and usability. Therefore, we used a zero-dimensional (OD) and a two-dimensional (2D) modeling approach in parallel. The two approaches solely differ in their spatial discretization, while conversion processes, parameters, and boundary conditions were kept identical. The dynamics of DO simulated by the two models are similar in the initial flooding period but diverge when the system starts to drain. The deviation can be attributed to the different spatial discretization of the two models, leading to different estimates of flow velocities and water depths. Only the 2D model can account for the impact of spatial variability on the evolution of state variables. However, its application requires high efforts for pre- and post-processing and significantly longer computation times. The 2D model is, therefore, not suitable for investigating various flood scenarios or for analyzing the impact of parameter uncertainty. For practical applications, we recommend to firstly set up a fast-running model of reduced spatial discretization, e.g. a OD model. Using this tool, the reliability of the simulation results should be checked by analyzing the parameter uncertainty of the water quality model. A particular focus may be on those parameters that are spatially variable and, therefore, believed to be better represented in a 2D approach. The benefit from the application of the more costly 2D model should be assessed, based on the analyses carried out with the OD model. A 2D model appears to be preferable only if the simulated detention area has a complex topography, flow velocities are highly variable in space, and the parameters of the water quality model are well known. Y1 - 2009 UR - http://www.sciencedirect.com/science/journal/03043800 U6 - https://doi.org/10.1016/j.ecolmodel.2009.04.006 SN - 0304-3800 ER - TY - JOUR A1 - Bronstert, Axel A1 - Kneis, David A1 - Bogena, Heye R. T1 - Interaktionen und Rückkopplungen beim hydrologischen Wandel : Relevanz und Möglichkeiten der Modellierung Y1 - 2009 SN - 1439-1783 ER - TY - JOUR A1 - Breuer, Lutz A1 - Bormann, Helge A1 - Bronstert, Axel A1 - Croke, Barry F. W. A1 - Frede, Hans-Georg A1 - Gräff, Thomas A1 - Hubrechts, Lode A1 - Kite, Geoffrey A1 - Lanini, Jordan A1 - Leavesley, George A1 - Lettenmaier, Dennis P. A1 - Lindstroem, Goeran A1 - Seibert, Jan A1 - Sivapalan, Mayuran A1 - Viney, Neil R. A1 - Willems, Patrick T1 - Assessing the impact of land use change on hydrology by ensemble modeling (LUCHEM) III : scenario analysis N2 - An ensemble of 10 hydrological models was applied to the same set of land use change scenarios. There was general agreement about the direction of changes in the mean annual discharge and 90% discharge percentile predicted by the ensemble members, although a considerable range in the magnitude of predictions for the scenarios and catchments under consideration was obvious. Differences in the magnitude of the increase were attributed to the different mean annual actual evapotranspiration rates for each land use type. The ensemble of model runs was further analyzed with deterministic and probabilistic ensemble methods. The deterministic ensemble method based on a trimmed mean resulted in a single somewhat more reliable scenario prediction. The probabilistic reliability ensemble averaging (REA) method allowed a quantification of the model structure uncertainty in the scenario predictions. It was concluded that the use of a model ensemble has greatly increased our confidence in the reliability of the model predictions. Y1 - 2009 UR - http://www.sciencedirect.com/science/journal/03091708 U6 - https://doi.org/10.1016/j.advwatres.2008.06.009 SN - 0309-1708 ER - TY - JOUR A1 - Gräff, Thomas A1 - Zehe, Erwin A1 - Reusser, Dominik A1 - Lueck, Erika A1 - Schroeder, Boris A1 - Wenk, Gerald A1 - John, Hermann A1 - Bronstert, Axel T1 - Process identification through rejection of model structures in a mid-mountainous rural catchment : observations of rainfall-runoff response, geophysical conditions and model inter-comparison N2 - The intention of the presented study is to gain a better understanding of the mechanisms that caused the bimodal rainfall-runoff responses which occurred up to the mid-1970s regularly in the Schafertal catchment and vanished after the onset of mining activities. Understanding, this process is a first step to understanding the ongoing hydrological change in this area. It is hypothesized that either subsurface stormflow, or fast displacement of groundwater, could cause the second delayed peak. A top-down analysis of rainfall-runoff data, field observations as well as process modelling are combined within a rejectionistic framework. A statistical analysis is used to test whether different predictors. which characterize the forcing. near surface water content and deeper subsurface store, allow the prediction of the type of rainfall-runoff response. Regression analysis is used with generalized linear models Lis they can deal with non-Gaussian error distributions Lis well its a non-stationary variance. The analysis reveals that the dominant predictors are the pre-event discharge (proxy of state of the groundwater store) and the precipitation amount, In the field campaign, the subsurface at a representative hillslope was investigated by means of electrical resistivity tomography in order to identify possible strata as flow paths for subsurface stormflow. A low resistivity in approximately 4 in depth-either due to a less permeable layer or the groundwater surface-was detected. The former Could serve as a flow path for subsurface stormflow. Finally, the physical-based hydrological model CATFLOW and the groundwater model FEFLOW are compared with respect to their ability to reproduce the bimodal runoff responses. The groundwater model is able to reproduce the observations, although it uses only an abstract representation of the hillslopes. Process model analysis as well Lis statistical analysis strongly suggest that fast displacement of groundwater is the dominant process underlying the bimodal runoff reactions. Y1 - 2009 UR - http://www3.interscience.wiley.com/journal/4125/home U6 - https://doi.org/10.1002/Hyp.7171 SN - 0885-6087 ER - TY - JOUR A1 - Zehe, Erwin A1 - Gräff, Thomas A1 - Morgner, Markus A1 - Bauer, Andreas A1 - Bronstert, Axel T1 - Plot and field scale soil moisture dynamics and subsurface wetness control on runoff generation in a headwater in the Ore Mountains N2 - This study presents an application of an innovative sampling strategy to assess soil moisture dynamics in a headwater of the Weißeritz in the German eastern Ore Mountains. A grassland site and a forested site were instrumented with two Spatial TDR clusters (STDR) that consist of 39 and 32 coated TDR probes of 60 cm length. Distributed time series of vertically averaged soil moisture data from both sites/ensembles were analyzed by statistical and geostatistical methods. Spatial variability and the spatial mean at the forested site were larger than at the grassland site. Furthermore, clustering of TDR probes in combination with long-term monitoring allowed identification of average spatial covariance structures at the small field scale for different wetness states. The correlation length of soil water content as well as the sill to nugget ratio at the grassland site increased with increasing average wetness and but, in contrast, were constant at the forested site. As soil properties at both the forested and grassland sites are extremely variable, this suggests that the correlation structure at the forested site is dominated by the pattern of throughfall and interception. We also found a strong correlation between average soil moisture dynamics and runoff coefficients of rainfall-runoff events observed at gauge Rehefeld, which explains almost as much variability in the runoff coefficients as pre-event discharge. By combining these results with a recession analysis we derived a first conceptual model of the dominant runoff mechanisms operating in this catchment. Finally, long term simulations with a physically based hydrological model were in good/acceptable accordance with the time series of spatial average soil water content observed at the forested site and the grassland site, respectively. Both simulations used a homogeneous soil setup that closely reproduces observed average soil conditions observed at the field sites. This corroborates the proposed sampling strategy of clustering TDR probes in typical functional units is a promising technique to explore the soil moisture control on runoff generation. Long term monitoring of such sites could maybe yield valuable information for flood warning. The sampling strategy helps furthermore to unravel different types of soil moisture variability. Y1 - 2008 ER - TY - JOUR A1 - De Araujo, Josè Carlos A1 - Güntner, Andreas A1 - Bronstert, Axel T1 - Loss of reservoir volume by sediment deposition and its impact on water availability in semiarid Brazil N2 - A methodology is presented to assess the impact of reservoir silting oil water availability for semiarid environments, applied to seven representative watersheds in the state of Ceara, Brazil. Water yield is computed using stochastic modelling for several reliability levels and water yield reduction is quantified for the focus areas. The yield-volume elasticity concept, which indicates the relative yield reduction in terms of relative storage capacity of the reservoirs, is presented and applied. Results chow that storage capacity was reduced by 0.2% year(-1) due to silting, that the risk of water shortage almost doubled in less than 50 years for the most critical reservoir, and that reduction of storage capacity had three times more impact oil yield reduction than the increase in evaporation. Average 90% reliable yield-volume elasticity was 0.8, which means that the global water yield (Q(90)) in Ceara is expected to diminish yearly by 388 L s(-1) due to reservoir silting Y1 - 2006 UR - http://www.atypon-link.com/IAHS/loi/hysj U6 - https://doi.org/10.1623/hysj.51.1.157 SN - 0262-6667 ER - TY - CHAP A1 - Zehe, Erwin A1 - Bronstert, Axel A1 - Itzerott, Sibylle A1 - Bárdossy, András A1 - Ihringer, Jürgen T1 - Hochwasservorhersage, Großhangbewegungen, Schadstofftransport BT - IMAF-relevante Projektbeispiele und Vorhaben am Institut für Geoökologie N2 - Interdisziplinäres Zentrum für Musterdynamik und Angewandte Fernerkundung Workshop vom 9. - 10. Februar 2006 Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-7128 ER - TY - CHAP A1 - Bronstert, Axel T1 - Interdisziplinäres Zentrum für Musterdynamik und angewandte Fernerkundung (IMAF) an der Universität Potsdam : Gegenwart und Zukunft N2 - Stand des IMAF zu Beginn des Jahres 2006 Zum 1. April 2005 wurde per Beschluss des Rektorats der Universität Potsdam das Interdisziplinäre Zentrum für Musterdynamik und Angewandte Fernerkundung (IMAF) an der Universität Potsdam eingerichtet. Diesem Beschluss gingen knapp zwei Jahre konzeptionelle, organisatorische und administrative Vorarbeiten voraus. Inzwischen ist das IMAF also offiziell gegründet, der Vorstand wurde „bestellt“ (Prof. M. Mutti. Prof. E. Zehe, Prof. A. Bronstert), der Geschäftsführer bzw. wissenschaftliche Koordinator Dr. M. Kühling arbeitet in dieser Funktion seit Sommer 2005 und seit kurzem ist auch die 1. Version der Homepage des IMAF (http://www.uni-potsdam.de/imaf/) frei geschaltet. Auch die Infrastruktur des IMAF ist in der Entstehungsphase: Büroräume sind versprochen (wenn auch noch nicht bezugsfertig) im Haus 13 auf dem Campus Golm der Universität Potsdam und der 1. erfolgreiche Drittmittelantrag erbrachte 8 leistungsfähige Tischrechner und einen Server für das IMAF aus EU-Mitteln. Wichtiger als die administrativen und organisatorischen Arbeiten sind aber die inhaltlichen Forstschritte. Hier ist die große Resonanz, die die Gründung des IMAF sowohl innerhalb als auch außerhalb der Universität gefunden hat, besonders erfreulich. Über 30 Angehörige des Zentrums sind inzwischen zu verzeichnen und es gibt bereits eine Reihe von wissenschaftlichen Projektinitiativen und Ideen für dieses Zentrum. Neben den wissenschaftlichen Arbeiten am IMAF ist ein zweites Hauptziel für dieses Zentrum die Entwicklung und der Ausbau eines strukturierten Ausbildungsangebotes für Musterdynamik und angewandte Fernerkundung. Dies sollen gleichermaßen Masterstudenten als auch Doktoranden der Universität Potsdam und der mit ihr assoziierten außeruniversitären Institute nutzen. Zudem werden Kurse und Weiterbildungsveranstaltungen mit nationalen und internationalen Experten angestrebt. Neben diesen positiven Entwicklungen gibt es auch (noch ??) über einige Mängel zu berichten: Das Sekretariat ist nach wie vor unbesetzt, die Finanzausstattung des Zentrums ist völlig ungenügend und die im Konzept für das Zentrum beantragte Wissenschaftlerstelle für Softwareanwendung ist nicht in Sicht. Für einen Erfolg des Zentrums ist es unbedingt notwendig, dass sich diese Situation deutlich verbessert!! Forschungsschwerpunkte des IMAF Räumliche Muster und deren Struktur in der Umwelt Räumliche Muster sind in vielen naturwissenschaftlichen Disziplinen (Hydrologie, Ökologie, Geologie, Biologie, Chemie, Physik) von zentraler Bedeutung. Z.B. bestimmen die räumlichen (und zeitlichen) Muster von Bodeneigenschaften und Vegetation in ihrem Zusammenspiel mit den Mustern von Niederschlag und Strahlungsinput maßgeblich den Wasser- und Stoffhaushalt auf unterschiedlichsten Skalen und führen über Rückkopplung wiederum zu Veränderungen in Klima, Vegetation und Ökosystemen. Vom kleinräumigen Transport von Schadstoffen und von der Hochwasserentstehung bis zur Frage nach den regionalen und globalen Veränderungen von Klima, Vegetation und Landnutzung seien hier nur einige Problemkreise genannt, in denen Muster und Musterdynamik eine zentrale Stellung einnehmen. Darüber hinaus liefert die Betrachtung der zeitlichen Veränderung von räumlichen Mustern, in Ergänzung zur klassischen Erfassung dynamischer Prozesse in Form von Messungen lokaler zeitlicher Änderungen, eine völlig neue Perspektive auf Dynamik und eröffnet damit völlig neue wissenschaftliche Möglichkeiten. Aktuelle und sehr drängende Fragen innerhalb dieses Forschungsschwerpunktes sind unter anderem: • Analyse der generelle Raumstruktur von Geodaten (Variabilität, Struktur, Konnektivität); • Thematische Verbindungen verschiedener Datenebenen und Möglichkeiten für deren Assimilation; • Möglichkeiten und Grenzen des Skalenübergangs zwischen verschiedenen räumlichen Auflösungen und Informationsquellen; • Ableitung der zeitlichen Dynamik bzw. Entwicklung von großen flächenhaften Datenfeldern. Angewandte Fernerkundung Wie keine andere Technik bietet die Fernerkundung in jeglicher Form (unter anderem Satelliten, flugzeuggetragene Sensoren, Wetterradar und auch geophysikalische Methoden) umfangreiche Möglichkeiten, räumliche Muster und deren zeitliche Veränderungen zu erfassen. Allen Methoden der Fernerkundung gemein ist, dass sie nur indirekte Ergebnisse liefern. Das heißt, es besteht nur ein mittelbarer Zusammenhang zwischen dem beobachteten Signal, meist der Reflektivität oder Emissivität elektromagnetischer Strahlung in verschiedenen Spektralbereichen (optisch oder Radar), und der eigentlich interessierenden Größe, wie dem Feuchtezustand der Vegetation, der Bodenfeuchte oder Bodenrauhigkeit, der Niederschlagsintensität, dem Zustand der Schneedecke oder der Ausdehnung eines Oberflächenfilms auf Gewässern. Ein Satellitenbild enthält beispielsweise immer die spektrale Signatur des räumlichen Musters mehrerer der oben genannten Einflussgrößen, was die Extraktion oder Diskriminierung der eigentlich interessierenden Größe erschwert. Dieser „vermischte“ Charakter der Fernerkundungsdaten bietet aber auch immense Chancen. So lassen sich durch geeignete Interpretationsverfahren aus jedem mit hohem finanziellem und technischem Aufwand erstellten Satellitenbild zahlreiche und im Detail völlig unterschiedliche Fragestellungen bearbeiten. Die Extraktion der gewünschten Information aus dem Fernerkundungssignal führt mathematisch gesehen meist auf die Lösung so genannter inverser, schlecht gestellter Probleme. Somit beinhaltet die interdisziplinäre Nutzung von Fernerkundung auch ein hohes methodisches Synergiepotential. Durch die heutigen technischen Möglichkeiten zur Archivierung auch sehr umfangreicher raumbezogener Informationen ist die Bearbeitung zu jedem beliebigen Zeitpunkt nach der Aufnahme möglich – zum Beispiel bis entsprechend lange Zeitreihen und/oder geeignete Interpretationsverfahren zur Verfügung stehen. Tatsächlich dürfte der weitaus größte Teil der raumbezogenen Informationen, die in den bisher erhobenen Fernerkundungsdaten stecken, nur in Ansätzen ausgewertet sein. Einer bereits sehr hoch entwickelten technischen Dimension der Fernerkundung steht ein gewisses Defizit im Umfang ihrer Anwendung in den verschiedenen naturwissenschaftlichen Disziplinen gegenüber. Aktuelle und sehr drängende Fragen innerhalb dieses Forschungsschwerpunktes sind unter anderem: • Nutzung der räumlichen und inhaltlichen Breite von Fernerkundungsinformationen; • Verbindung mit automatisierten, u.a. geophysikalischen Methoden des „ground-truthings“; • Identifizierung der Grenzen bzgl. Repräsentanz der Daten (spektral, raum-zeitliche Auflösung); • Verbindung unterschiedlicher Methoden der Fernerkundung und der Geophysik. Dieser Beitrag illustriert die o.g. Fragestellungen anhand einiger Darstellungen aus verschiedenen wissenschaftlichen Disziplinen und erläutert 2 Beispiele zu beabsichtigten Forschungsprojekten: • Erfassung und Bedeutung von Boden-Oberflächeneigenschaften auf die Abflussbildung von Landschaften; • Phänomene des Stofftransportes in homogenen vs. heterogenen Böden. Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-7021 N1 - Dokument 1: Foliensatz | Dokument 2: Abstract | Dokumente 3 und 4: Animation Interdisziplinäres Zentrum für Musterdynamik und Angewandte Fernerkundung Workshop vom 9. - 10. Februar 2006 ER - TY - BOOK A1 - Bronstert, Axel A1 - Carrera, Jesus A1 - Kabat, Pavel A1 - Lütkemeier, Sabine T1 - Coupled models for the hydrological cycle : integrating atmosphere, biosphere and pedosphere Y1 - 2005 SN - 3-540-22371-1 U6 - https://doi.org/10.1007/b138919 PB - Springer-Verlag Berlin Heidelberg CY - Berlin, Heidelberg ER - TY - JOUR A1 - Bronstert, Axel A1 - Engel, H. T1 - Veränderung der Abflüsse JF - Warnsignal Klima - genug Wasser für alle? : wissenschaftliche Fakten Y1 - 2005 SN - 978-3-9809668-0-1 SP - 175 EP - 181 PB - Wissenschaftliche Auswertungen CY - Hamburg ER - TY - JOUR A1 - Bronstert, Axel T1 - Rainfall-runoff modelling for assessing impacts of climate and land-use change Y1 - 2004 ER - TY - JOUR A1 - Bronstert, Axel T1 - Probleme, Grenzen und Herausforderungen der hydrologischen Modellierung: Wasserhaushalt und Abfluss Y1 - 2004 ER - TY - JOUR A1 - Krause, Stefan A1 - Bauer, Andreas A1 - Morgner, Markus A1 - Bronstert, Axel T1 - Wasserhaushaltsmodellierung als Beitrag zur Erstellung eines nachhaltigen Flusseinzugsgebietsmanagements an der Unteren Havel Y1 - 2004 SN - 3-937758-18-6 ER - TY - JOUR A1 - Krause, Stefan A1 - Bronstert, Axel T1 - Approximation of Groundwater - Surface Water - Interactions in a Mesoscale Lowland River Catchment Y1 - 2004 ER - TY - JOUR A1 - Kneis, David A1 - Knösche, Rüdiger A1 - Bronstert, Axel T1 - Ist eine Auswaschung von Nährstoffen aus Flussgewässersedimenten eine realistische Option zur Trophiesenkung? Y1 - 2004 SN - 3-937758-18-6 ER - TY - BOOK A1 - Zehe, Erwin A1 - Bolduan, Rainer A1 - Bärdossy, Andräs A1 - Bronstert, Axel A1 - Plate, Erich T1 - Stofftransport in einem Lösseinzugsgebiet: Experimentelle Evidenz und numerische Modellierung. Y1 - 2004 SN - 3-937758-18-6 ER - TY - JOUR A1 - Blume, Theresa A1 - Bauer, Andreas A1 - Bronstert, Axel T1 - Experimental techniques for the Investigation of Runoff Processes in a Small Catchment in the Chilean Andes Y1 - 2004 SN - 3-937758-18-6 ER - TY - JOUR A1 - Krause, Stefan A1 - Bronstert, Axel T1 - Wasserhaushaltssimulationen unter Einbeziehung von Grundwasser - Oberflächenwasser - Kopplung zur Optimierung szenarienbasierter Handlungsoptionen für ein nachhaltiges Flussgebietsmanagement an der Unteren Havel Y1 - 2004 SN - 3-89958-072-9 ER - TY - JOUR A1 - Güntner, Andreas A1 - Bronstert, Axel T1 - Representation of landscape variability and lateral redistribution processes for large-scale hydrological modelling in semi-arid areas N2 - The spatial variability of landscape features such as topography, soils and vegetation defines the spatial pattern of hydrological state variables like soil moisture. Spatial variability thereby controls the functional behaviour of the landscape in terms of its runoff response. A consequence of spatial variability is that exchange processes between landscape patches can occur at various spatial scales ranging from the plot to the basin scale. In semi-arid areas, the lateral redistribution of surface runoff between adjacent landscape patches is an important process. For applications to large river basins of 10(4)-10(5) km(2) in size, a multi-scale landscape discretization scheme is presented in this paper. The landscape is sub-divided into modelling units within a hierarchy of spatial scale levels. By delineating areas characterized by a typical toposequence, organised and random variability of landscape characteristics is captured in the model. Using runoff-runon relationships with transition frequencies based on areal fractions of modelling units, lateral surface and subsurface water fluxes between modelling units at the hillslope scale are represented. Thus, the new approach allows for a manageable description of interactions between fine-scale landscape features for inclusion in coarse-scale models. Model applications for the State of Ceara (148,000 km(2)) in the north- east of Brazil demonstrate the importance of taking into account landscape variability and interactions between landscape patches in a semi-arid environment. Using mean landscape characteristics leads to a considerable underestimation of infiltration-excess surface runoff and total simulated runoff. Re-infiltration of surface runoff and lateral redistribution processes between landscape patches cause a reduction of runoff volumes at the basin scale and contribute to the amplification of variations in runoff volumes relative to variations in rainfall volumes for semi-arid areas. (C) 2004 Elsevier B.V. All rights reserved Y1 - 2004 SN - 0022-1694 ER - TY - JOUR A1 - Güntner, Andreas A1 - Krol, Marten S. A1 - de Arajo, José Carlos A1 - Bronstert, Axel T1 - Simple water balance modelling of surface reservoir systems in a large data-scarce semiarid region N2 - Water resources in dryland areas are often provided by numerous surface reservoirs. As a basis for securing future water supply, the dynamics of reservoir systems need to be simulated for large river basins, accounting for environmental change and an increasing water demand. For the State of Ceara in semiarid Northeast Brazil, with several thousands of reservoirs, a simple deterministic water balance model is presented. Within a cascade-type approach, the reservoirs are grouped into six classes according to storage capacity, rules for flow routing between reservoirs of different size are defined, and water withdrawal and return flow due to human water use is accounted for. While large uncertainties in model applications exist, particularly in terms of reservoir operation rules, model validation against observed reservoir storage volumes shows that the approach is a reasonable simplification to assess surface water availability in large river basins. The results demonstrate the large impact of reservoir storage on downstream flow and stress the need for a coupled simulation of runoff generation, network redistribution and water use Y1 - 2004 SN - 0262-6667 ER - TY - BOOK A1 - Bronstert, Axel A1 - Thieken, Annegret A1 - Merz, Bruno A1 - Rode, Michael A1 - Menzel, Lucas T1 - Wasser- und Stofftransport in heterogenen Einzugsgebieten : Beiträge zum Tag der Hydrologie 2004, 22./ 23. März 2004 in Potsdam ; Bd. 1 Vorträge Y1 - 2004 SN - 3-937758-18-6 VL - 5 PB - ATV-DVWK CY - Hennef (Sieg) ER - TY - BOOK A1 - Bronstert, Axel A1 - Thieken, Annegret A1 - Merz, Bruno A1 - Rode, Michael A1 - Menzel, Lucas T1 - Wasser- und Stofftransport in heterogenen Einzugsgebieten : Beiträge zum Tag der Hydrologie 2004, 22./ 23. März 2004 in Potsdam ; Bd. 2 Poster Y1 - 2004 SN - 3-937758-18-6 PB - ATV-DVWK CY - Hennef ER - TY - JOUR A1 - Bronstert, Axel T1 - Floods and climate change : interactions and impacts Y1 - 2003 SN - 0272-4332 ER - TY - JOUR A1 - Günter, A. A1 - Bronstert, Axel T1 - Large-scale hydrological modelling of a semi-arid environment : model development, validation and application Y1 - 2003 ER - TY - JOUR A1 - Bronstert, Axel A1 - Bardossy, Andras T1 - Uncertainty of runoff modelling at the hillslope scale due to temporal variations of rainfall intensity Y1 - 2003 ER - TY - JOUR A1 - Krol, Marten S. A1 - Jaeger, Annekathrin A1 - Bronstert, Axel T1 - Integrated modelling of climate change impacts in northeastern brazil Y1 - 2003 ER - TY - JOUR A1 - Pfister, L. A1 - Kwadijk, J. A1 - Musy, A. A1 - Bronstert, Axel A1 - Hoffmann, L. T1 - Climate change, land use change and run-off prediction in the Rhine-Meuse basins N2 - As a consequence of increasing winter rainfall totals and intensities over the second half of the 20th century, signs of increased flooding probability in many areas of the Rhine and Meuse basins have been documented. These changes affecting rainfall characteristics are most evidently due to an increase in westerly atmospheric circulation types. Land use changes, particularly urbanization, can have significant local effects in small basins (headwaters) with respect to flooding, especially during heavy local rainstorms, but no evidence exists that land use change has had significant effects on peak flows in the rivers Rhine and Meuse. For the 21st century, most global circulation models suggest higher winter rainfall totals. Most hydrological simulations of the Rhine-Meuse river basins suggest an increased flooding probability, with a progressive shift of the Rhine from a 'rain-fed/meltwater' river into a mainly 'rain-fed' river. A very limited effect of changes in land use on the discharge regime seems to exist for the main branches of the Meuse and Rhine rivers. For mesoscale basins, future changes in peak flows depend on the changes in the variability of extreme precipitations in combination with land use changes. Copyright (C) 2004 John Wiley Sons, Ltd Y1 - 2003 SN - 1535-1459 ER - TY - JOUR A1 - Bronstert, Axel A1 - Niehoff, Daniel A1 - Bürger, Gerd T1 - Effects of climate and land-use change on storm runoff generation : present knowledge and modelling capabilities Y1 - 2002 ER - TY - JOUR A1 - Menzel, Lucas A1 - Niehoff, Daniel A1 - Bürger, Gerd A1 - Bronstert, Axel T1 - Climate change impacts on river flooding : a modelling study of three meso-scale catchments Y1 - 2002 ER - TY - JOUR A1 - Niehoff, Daniel A1 - Fritsch, Uta A1 - Bronstert, Axel T1 - Land-use impacts on storm-runoff generation : scenarios of land-use change and simulation of hydrological response in a meso-scale catchment in SW-Germany Y1 - 2002 ER - TY - JOUR A1 - Bronstert, Axel A1 - Krol, Marten S. A1 - Jaeger, Annekathrin A1 - Güntner, Andreas T1 - Integrated modelling of climate, water, soil, agricultural and socio-economic processes : a general introduction to the methodology and some exemplary results from the semi-arid Northeast of Brazil Y1 - 2002 ER - TY - JOUR A1 - Güntner, Andreas A1 - Bronstert, Axel T1 - Process-based modelling of large-scale water availability in a semi-arid environment : process representation and scaling issues Y1 - 2002 ER - TY - JOUR A1 - Niehoff, Daniel A1 - Bronstert, Axel T1 - Landnutzung und Hochwasserentstehung : Modellierung anhand dreier mesoskaliger Einzugsgebiete Y1 - 2002 ER - TY - JOUR A1 - Bronstert, Axel A1 - Menzel, Lucas T1 - Advances in Flood Research Y1 - 2002 ER - TY - JOUR A1 - Bronstert, Axel T1 - The role of infiltration conditions for storm runoff generation at the hillslope and small catchment scale Y1 - 2001 ER - TY - JOUR A1 - Katzenmaier, Daniel A1 - Fritsch, Uta A1 - Bronstert, Axel T1 - Quantifizierung des Einflusses von Landnutzung und dezentraler Versickerung auf die Hochwasserentstehung Y1 - 2001 SN - 3-503-06021-9 ER - TY - JOUR A1 - Bronstert, Axel A1 - Menzel, Lucas A1 - Middelkoop, H. A1 - de Roo, A. P. A1 - Van Beek, E. T1 - River basin research and management : integrated modelling and investigation of land-use impacts on the hydrological cycle Y1 - 2001 ER - TY - JOUR A1 - Bronstert, Axel A1 - Fritsch, Uta A1 - Leonhardt, H. A1 - Niehoff, Daniel T1 - Quantifizierung des Einflusses von Landnutzungs- und Klimaänderungen auf die Hochwasserentstehung am Beispiel ausgewählter Flussgebiete Y1 - 2001 ER - TY - JOUR A1 - Güntner, Andreas A1 - Bronstert, Axel T1 - Modelling the effects of climate change on water availability in the semi-arid of North-East Brazil Y1 - 2001 ER - TY - JOUR A1 - Krol, Marten S. A1 - Jaeger, Annekathrin A1 - Bronstert, Axel A1 - Krywkow, J. T1 - The Semi-arid Integrated Model (SIM), a regional integrated model assessing water availability, vulnerability of ecosystems and society in NE-Brazil Y1 - 2001 ER - TY - JOUR A1 - Niehoff, Daniel A1 - Bronstert, Axel T1 - Influences of land-use and land-surface conditions on flood generation : a simulation study Y1 - 2001 ER - TY - JOUR A1 - Güntner, Andreas A1 - Bronstert, Axel T1 - WAVES - Water availability, vulnerability of ecosystems and society in the northeast of Brazil : sub-project large-scale hydrological modelling Y1 - 2001 ER - TY - BOOK A1 - Kundzewicz, Zbigniew W. A1 - Budhakooncharoen, Saisunee A1 - Bronstert, Axel A1 - Hoff, Holger A1 - Lettenmaier, Dennis P. A1 - Menzel, Lucas A1 - Schulze, Roland T1 - Floods and droughts : coping with variability and climate change ; thematic backround paper [for the International Conference on Freshwater 2001, Bonn, 3-7 December 2001] Y1 - 2001 UR - http://www.water-2001.de/co_doc/Floods.pdf PB - Secretariat of the International Conference on Freshwater CY - Bonn ER - TY - JOUR A1 - Kundzewicz, Zbigniew W. A1 - Budhakooncharoen, Saisunee A1 - Bronstert, Axel A1 - Hoff, Holger A1 - Lettenmaier, Dennis P. A1 - Menzel, Lucas A1 - Schulze, Roland T1 - Coping with variability and climate change : floods and droughts Y1 - 2001 ER - TY - JOUR A1 - Bronstert, Axel A1 - Fritsch, Uta A1 - Katzenmaier, Daniel A1 - Bismuth, Christine T1 - Quantification of the influence of the land-surface and river training on flood discharge of the Rhine Basin Y1 - 2000 ER - TY - JOUR A1 - Bronstert, Axel A1 - Krol, Marten S. A1 - Jaeger, Annekathrin T1 - WAVES : water availability, vulnerability of ecosystems and society in northeast brazil ; an overview of the interdisciplinary project and integrated modelling Y1 - 2000 ER - TY - JOUR A1 - Bronstert, Axel A1 - Katzenmaier, Daniel A1 - Fritsch, Uta T1 - Hochwasserproblematik und der Zusammenhang mit Landnutzungs- und Klimaänderungen Y1 - 2000 ER - TY - JOUR A1 - Fritsch, Uta A1 - Katzenmaier, Daniel A1 - Bronstert, Axel T1 - Land-use and land-cover scenarios for flood risk analysis and river basin management Y1 - 2000 ER - TY - JOUR A1 - Bronstert, Axel A1 - Köhler, Birgit T1 - Simulation der Einflüsse anthropogener Klimaänderungen auf die Hochwasserentstehung : eine Fallstudie in einem kleinen ländlichen Einzugsgebiet im Ostharz Y1 - 2000 ER - TY - JOUR A1 - Katzenmaier, Daniel A1 - Fritsch, Uta A1 - Bronstert, Axel T1 - Influences of land-use and land-cover changes on storm-runoff generation Y1 - 2000 ER - TY - JOUR A1 - Bronstert, Axel T1 - The possible impacts of environmental changes on flood formation : relevant processes and model requirements Y1 - 2000 ER - TY - JOUR A1 - Menzel, Lucas A1 - Bronstert, Axel A1 - Bürger, Gerd A1 - Krysanova, Valentina T1 - Environmental change scenarios and flood responses in the Elbe catchment (Germany) Y1 - 2000 ER - TY - JOUR A1 - Bronstert, Axel A1 - Kundzewicz, Zbigniew W. A1 - Menzel, Lucas T1 - Achievements and future needs towards improved flood protection in the Oder river basin : results of the EU- expert meeting on the Oder flood in Summer '97 Y1 - 2000 SN - 0-7923-6451-1, 0-7923-6452-X ER - TY - JOUR A1 - Bronstert, Axel A1 - Lahmer, Werner T1 - Bewirtschaftungsmöglichkeiten im Einzugsgebiet der Havel Y1 - 2000 ER - TY - JOUR A1 - Bronstert, Axel A1 - Güntner, Andreas T1 - A large-scale hydrological model for the semi-arid environment of north-eastern Brazil Y1 - 2000 ER - TY - JOUR A1 - Bárdossy, Andras A1 - Bronstert, Axel A1 - Buiteveld, Hendrik A1 - Disse, Markus A1 - Fritsch, Uta A1 - Katzenmaier, Daniel A1 - Lammersen, Rita T1 - Influence of the land surface and river training on flood conditions in the Rhine basin Y1 - 2000 ER - TY - JOUR A1 - Niehoff, Daniel A1 - Bronstert, Axel T1 - Influences of land-use and land-surface conditions on flood generation : a simulation study Y1 - 2000 ER - TY - BOOK A1 - Bronstert, Axel A1 - Jürgens, M. T1 - Modellsystem Hillflow : physikalisch begründete und flächendetalierte Modellierung der Abflußbildung und der Bodenwasserdynamik von ebenen Standorten, Hängen und Kleineinzugsgebieten ; Modelldokumentation und Benutzerhandbuch, Version 1.0 Y1 - 1994 PB - Inst. für Hydrologie und Wasserwirtschaft, Universität Karlsruhe CY - Karlsruhe ER - TY - BOOK A1 - Bronstert, Axel A1 - Seiert, S. A1 - Oberholzer, Gustav T1 - Maßnahmen der Flurbereinigung und ihre Wirkung auf das Abflußverhalten ländlicher Gebiete : gemeinsamer Bericht des Instituts für Hydrologie und Wasserwirtschaft, Universität Karlsruhe, und des Instituts für Liegenschaftswesen, Planung und Bodenordnung, Universität der Bundeswehr, Neubiberg bei München T3 - Flurneuordnung und Landentwicklung Baden Württemberg Y1 - 1993 VL - 3 PB - LfU CY - Karlsruhe ER -