Hydrodynamic simulation of the effects of stable in-channel large wood on the flood hydrographs of a low mountain range creek, Ore Mountains, Germany

Large wood (LW) can alter the hydromorphological and hydraulic characteristics of rivers and streams and may act positively on a river's ecology by i.e. leading to increased habitat availability. On the contrary, floating as well as stable LW is a potential threat for anthropogenic goods and infrastructure during flood events. Concerning the contradiction of potential risks and positive ecological impacts, addressing the physical effects of stable large wood is highly important. Hydrodynamic models offer the possibility of investigating the hydraulic effects of anchored large wood. However, the work and time involved varies between approaches that incorporate large wood in hydrodynamic models. In this study, a two-dimensional hydraulic model is set up for a mountain creek to simulate the hydraulic effects of stable LW and to compare multiple methods of accounting for LW-induced roughness. LW is implemented by changing in-channel roughness coefficients and by adding topographic elements to the model; this is carried out in order to determine which method most accurately simulates observed hydrographs and to provide guidance for future hydrodynamic modelling of stable large wood with two-dimensional models. The study area comprises a 282 m long reach of the Ullersdorfer Teichbächel, a creek in the Ore Mountains (south-eastern Germany). Discharge time series from field experiments allow for a validation of the model outputs with field observations with and without stable LW. We iterate in-channel roughness coefficients to best fit the mean simulated and observed flood hydrographs with and without LW at the downstream reach outlet. As an alternative approach for modelling LW-induced effects, we use simplified discrete topographic elements representing individual LW elements in the channel. In general, the simulations reveal a high goodness of fit between the observed flood hydrographs and the model results without and with stable in-channel LW. The best fit of the simulation and mean observed hydrograph with in-channel LW can be obtained when increasing in-channel roughness coefficients throughout the reach instead of an increase at LW positions only. The best fit in terms of the hydrograph's general shape can be achieved by integrating discrete elements into the calculation mesh. The results illustrate that the mean observed hydrograph can be satisfactorily modelled using an adjustment of roughness coefficients. In conclusion, a time-consuming and work-intensive mesh manipulation is suitable for analysing the more detailed effects of stable LW on a small spatio-temporal scale where high precision is required. In contrast, the reach-wise adjustment of in-channel roughness coefficients seems to provide similarly accurate results on the reach scale and, thus, could be helpful for practical applications of model-based impact assessments of stable LW on flood hydrographs of small streams and rivers

Research report of the quantitative survey

Im Sommer 2013 wurde die Verbandsgemeinde Elbe-Havel-Land in Sachsen-Anhalt während des Elbehochwassers nach einem Deichbruch weiträumig überflutet: Häuser, Straßen und Grundstücke wurden zerstört. Der Bericht beleuchtet die Folgen des Hochwassers 2013 und ihre Bewältigung aus Sicht der Bewohner*innen, basierend auf Ergebnissen einer quantitativen Bevölkerungsbefragung drei Jahre nach dem Ereignis. Ausgehend von erlebten materiellen und immateriellen Auswirkun-gen und dem Stand der Verarbeitung des Ereignisses, wird der Bedarf an Unterstützung aufgezeigt, fehlende Hilfeleistungen identifiziert und die Bedeutung verschiedener Akteure im Verlauf der Katastrophe dargestellt. Dabei zeigen sich insbesondere zeitliche Variationen der Hilfebedarfe und ein anhaltender Bedarf an Unterstützung sowie Nachwirkungen des Ereignisses bis zum Zeitpunkt der Befragung.During the 2013 European floods, the municipalities of the Elbe-Havel-Land in Saxony-Anhalt were flooded after the water masses of the Elbe River caused a levee to break; houses, streets and plots of land were destroyed. This report, based on the results of a quantitative survey carried out three years after the event, shines light on the effects of the 2013 Flood, and how well, according to the perception of residents, the disaster has been dealt with. Based on personally experienced materi-al and immaterial impacts and on the state of psychological recuperation, we highlight the need for further support needed, identify what kinds of aid have been missing, and illustrate the relative importance of different actors throughout the disaster. The results indicate that the need for assis-tance varies especially with regard to time, that after-effects continued to linger at the time of questioning, and that accordingly there is a continued need for support

Porous translucent electrodes enhance current generation from photosynthetic biofilms.

Some photosynthetically active bacteria transfer electrons across their membranes, generating electrical photocurrents in biofilms. Devices harvesting solar energy by this mechanism are currently limited by the charge transfer to the electrode. Here, we report the enhancement of bioelectrochemical photocurrent harvesting using electrodes with porosities on the nanometre and micrometre length scale. For the cyanobacteria Nostoc punctiforme and Synechocystis sp. PCC6803 on structured indium-tin-oxide electrodes, an increase in current generation by two orders of magnitude is observed compared to a non-porous electrode. In addition, the photo response is substantially faster compared to non-porous anodes. Electrodes with large enough mesopores for the cells to inhabit show only a small advantage over purely nanoporous electrode morphologies, suggesting the prevalence of a redox shuttle mechanism in the electron transfer from the bacteria to the electrode over a direct conduction mechanism. Our results highlight the importance of electrode nanoporosity in the design of electrochemical bio-interfaces

Forschungsbericht zur quantitativen Datenerhebung

Im Sommer 2013 wurde die Verbandsgemeinde Elbe-Havel-Land in Sachsen-Anhalt während des Elbehochwassers nach einem Deichbruch weiträumig überflutet: Häuser, Straßen und Grundstücke wurden zerstört. Der Bericht beleuchtet die Folgen des Hochwassers 2013 und ihre Bewältigung aus Sicht der Bewohner*innen, basierend auf Ergebnissen einer quantitativen Bevölkerungsbefragung drei Jahre nach dem Ereignis. Ausgehend von erlebten materiellen und immateriellen Auswirkungen und dem Stand der Verarbeitung des Ereignisses, wird der Bedarf an Unterstützung aufgezeigt, fehlende Hilfeleistungen identifiziert und die Bedeutung verschiedener Akteure im Verlauf der Katastrophe dargestellt. Dabei zeigen sich insbesondere zeitliche Variationen der Hilfebedarfe und ein anhaltender Bedarf an Unterstützung sowie Nachwirkungen des Ereignisses bis zum Zeitpunkt der Befragung