An approach to simulate interstitial processes in river beds to meet biological requirements

River engineeringRiver habitat management and restoratio

Safety criteria for the trafficability of inundated roads in urban floodings

The probability of unexpected urban flood hazards is steadily increasing due to global warming and climate change. Consequently, there is a growing need for safety criteria determining the trafficability of inundated roads to ensure a fast and safe evacuation of people in case of such events. In order to determine those criteria, experimental investigations on the stability of two scaled watertight vehicle models and of one prototype passenger car are conducted in a laboratory flume and a steel tank.The conducted flume experiments clearly show a dependency of vehicle stability on the flow angle, whereas the prototype experiments indicate that floating water depths are higher in prototype than in model scale, which is due to the use of a watertight vehicle model. Based on both experiments, a constant total head is proposed as decisive parameter for determining trafficability. This parameter approximates the measured stability curves and can be easily adopted in practice. Furthermore, it is in accordance with fording depths evaluated from relevant literature or by means of manufacturer inquiry. The recommended safety criteria for passenger cars and emergency vehicles are total heads of h(E) =0.3 m =const. and h(E)=0.6 m=const., respectively. (C) 2016 Elsevier Ltd. All rights reserved

Penetration depth of plunging liquid jets – A data driven modelling approach

© 2016 Elsevier Inc. In the case of impinging water jets or droplets, air entrainment processes are crucial to the casing design of hydraulic impulse turbines in the micro-hydro sector. To initiate first steps towards a precise prediction of the complex, multi-phase casing flow of impulse turbines, single aspects such as the penetration depth of impinging liquid jets have to be separated and fully understood. Existing investigations determining penetration depths are related to a very small range of flow rates and therefore show an underestimation of the penetration depth being applied to the casing flow of impulse turbines, which are generally operated at higher flow rates. For a more general description of the air entrainment process, investigations of plunging water jets within an extended flow rate range are conducted and the penetration depth is modelled using a data driven artificial neural network (ANN) approach and a non-linear regression model.At low flow rates, experiments results are in accordance with existing studies, whereas penetration depths up to 170 cm are measured at higher flow rates. For the mathematical models to achieve a wide range applicability, a large data base is used, including published and measured data. The modelled penetration depths can be precisely verified by the performed measurements and show correct physical behaviour, even in areas without underlying data. Calculation rules, weight matrices and biases of the trained ANN are published to achieve high transparency and scientific improvement in neural modelling of penetration depths of impinging liquid jets

Avaliando a Justiça Ambiental em grandes projetos hidrelétricos: o caso de São Luiz do Tapajós, no Brasil

Electricity supply in a sustainable manner is one of the greatest challenges for human society today. Hydropower is by far the most important renewable electricity technology, but equally far from uncontroversial. Indeed, it is situated at the crossroad of socio-environmentalism trends, as strongly promoted by some as opposed by other environmentalist arguments, organisations and movements. This paper suggests Environmental Justice as an alternative approach on how to incorporate sustainability into energy planning, particularly in hydropower projects. Whereas several methods have been developed to assess Environmental Justice in an urban context, little attention has been given to electricity projects so far. A qualitative method to assess hydropower projects regarding their performance in Environmental Justice is discussed and illustrated in the case of the large hydropower project São Luiz do Tapajós in the Brazilian Amazon. As will be shown, fundamental change is necessary in Brazil if energy planning in general and hydropower projects in particular are to meet the principles of Environmental Justice.O fornecimento de energia elétrica numa maneira sustentável se encontra entre os maiores desafios para a sociedade humana hoje em dia. Energia hidrelétrica é de longe a tecnologia de eletricidade renovável mais importante, porém igualmente longe de incontroversa. De fato, se encontra na encruzilhada de correntes socioambientais, tão fortemente promovido por uns quanto rejeitado por outros argumentos, organizações e movimentos ambientalistas. Este artigo sugere a Justiça Ambiental como abordagem alternativa para incorporar a sustentabilidade no planejamento energético, particularmente em projetos hidrelétricos. Enquanto vários métodos foram desenvolvidos para avaliar Justiça Ambiental no contexto urbano, pouca atenção foi dada a projetos elétricos até agora. Um método qualitativo para avaliar projetos hidrelétricos em relação ao seu desempenho em Justiça Ambiental é discutido e ilustrado no caso do projeto hidrelétrico São Luiz do Tapajós, na Amazônia brasileira. Como vai ser mostrado, mudanças fundamentais serão necessárias no Brasil para que o planejamento energético em geral e projetos hidrelétricos em específico cumpram os princípios de Justiça Ambiental

Assessment of Hydropeaking Impact on Macrozoobenthos Using Habitat Modelling Approach

The effects of daily discharge variation as a result of hydropeaking on the macrozoobenthos species of Litzauer Schleife, one of the last few free-flowing reaches of the River Lech in Germany, are assessed using habitat modelling approach. Integrated distributions of habitat quality within a river reach under two typical hydropeaking regimes with the range of the base to peak discharges of 10 m³/s to 155 m³/s and 25 m³/s to 135 m³/s respectively are  compared to the habitat quality distribution at the reference constant discharge of 30 m3/s. Habitat quality is assessed using the so called Fliesswasserstammtisch (FST) preference curves for the selected macrozoobenthos species Baetis alpinus, Baetis rhodani, Rhithrogena semicolorata, Allogamus auricollis, and Hydropsyche incognita. Hydropeaking causes a pronounced reduction in suitable habitats compared to the situation at a constant flow. While large areas of suitable habitats can still be found for the species B. rhodani, R. semicolorata, and H. incognita at the tested flow regimes, very less areas remain suitable for B. alpinus and A. auricollis. All target species react sensitive to flows below the reference discharge while only B. rhodani, R. semicolorata, and H. incognita show tolerance to high flows. Modelling results show that riffle areas offer more sustainable habitat during the whole range of hydropeaking discharges as pool areas for macrozoobenthos species. Among the target species, R. semicolarata is the most tolerant to changes in hydraulic conditions while A. auricollis is the least. From the analysis of habitat modeling results a hydropeaking regime with the base flow of 30 m³/s and a peak flow of 70 m3/s is suggested to be acceptable for the selected macrozoobenthos species of Litzauer Schleife. Keywords: hydropeaking, FST hemisphere number, preference function, habitat modelling, macrozoobentho

An interdisciplinary model chain quantifies the footprint of global change on reservoir sedimentation

Global change alters hydro-climatic conditions, affects land use, and contributes to more frequent droughts and floods. Large artificial reservoirs may effectively alleviate hydro-climatic extremes, but their storage capacities are threatened by sedimentation processes, which in turn are exacerbated by land use change. Envisioning strategies for sustainable reservoir management requires interdisciplinary model chains to emulate key processes driving sedimentation under global change scenarios. Therefore, we introduce a model chain for the long-term prediction of complex three-dimensional (3d) reservoir sedimentation considering concurrent catchment, hydro-climatic, and land-use conditions. Applied to a mountainous Mediterranean catchment, the model chain predicts increased sediment production and decreased discharge for high and medium emission pathways. Increased winter precipitation, accompanied by a transition from snowfall to rainfall, is projected to aggravate reduced summer precipitation, emphasizing a growing need for reservoirs. Additionally, higher winter precipitation proliferates sediment production and reservoir sedimentation. Land use change can outweigh the increased reservoir sedimentation originating from hydro-climatic change, which highlights the significance of localized actions to reduce sediment production. Finally, a 3d hydro-morphodynamic model provides insights into interactions between global change and reservoir sedimentation with spatially explicit information on future sedimentation patterns facilitating the implementation of management strategies