Mixed alluvial and non-alluvial bed topographies: observations, modeling and implications

River morphodynamics and sediment transportRiver morphology and morphodynamic

Downstream fining in sand-bed rivers

River morphodynamics and sediment transportMechanics of sediment transpor

Why do published models for fluvial and estuarine morphodynamics use unrealistic representations of the effects of transverse bed slopes?

The sediment transport direction is affected by the bed slope. This effect is of crucial importance for two- and three-dimensional modelling of the interaction between the flow of water and the alluvial bed. It is not uncommon to find applications of numerical morphodynamic models in the literature that exaggerate the effects of transverse bed slopes on sediment transport compared to results from laboratory experiments. We investigate mathematically the consequences of such an approach, and we analyse through numerical simulations different explanations for the need to apply deviating values. The study reveals that the reason often lies in the setup of the numerical models, such as the choice of mesh resolution or the necessity to comply with specific aspects of the numerical scheme. The missing or inadequate implementation of physical processes in the model is another cause. All of these effects can be compensated by artificial diffusion added through the bed slope effect coefficients. Since increased diffusion strongly alters the physical processes of self-formed bed morphology, we recommend that modellers address the root causes of inflated erosion and deposition. Bed slope effect coefficients should be applied within the range found in the original publications

Assessment of a numerical model to reproduce event-scale erosion and deposition distributions in a braided river

Becky Goodsell and Eric Scott are thanked for field assistance. Antony Smith assisted with figure production. The field campaign wa funded by NERC Grant NE/G005427/1 and NERC Geophysical Equipment Facility Loan 892. Richard Williams was funded by NERC Grant NE/G005427/1during fieldwork and by a British Hydrological Society Travel Grant whilst visiting NIW

Dakmagazine : meer licht, lucht en ruimte, voor minder

Het project ‘Duurzame Daken’ ging op zoek naar oplossingen. Met het oog op de kostprijs zijn namelijk goedkope alternatieven voor het traditionele zadeldak gewenst. Sterker nog, het wordt een uitdaging om het dak te gaan zien als een plek waar meeropbrengsten zijn te halen. Er is veel te kiezen en de mogelijkheden voor meeropbrengsten van het dak nemen toe. Voldoende aanleiding voor deze special ter inspiratie en met veel beslisinformatie voor veehouders met nieuw- of verbouwplannen

Hidrelétricas na Amazônia: renovabilidade e não renovabilidade da política energética. Se é desejável a renovabilidade das formas de conversão de energia, por que não é desejável renovar a política energética?

O ensaio tem a intenção de discutir, apresentando como pano de fundo os recentes projetos hidrelétricos propostos e em andamento na Amazônia brasileira, aspectos referentes aos processos de licenciamento ambiental, problemas conceituais que dizem respeito à caracterização da conversão hidrelétrica como energia limpa e renovável. Este trabalho parte da análise de planos governamentais e das discussões sobre projetos hidrelétricos, identificando a necessidade de implementar mudanças institucionais e de fortalecer as leis ambientais e de proteção dos direitos de populações tradicionais e indígenas. Propõe-se uma nova maneira de formular problemas energéticos e de planejar a oferta de energia, que leva em consideração aspectos sustentáveis e patrocinadores da discussão pública, além do entendimento e da incorporação das consequências sobre os grandes ciclos biogeoquímicos que dão suporte às conversões de energia.The essay intends to discuss, with the background of the recent hydroelectric plants under way in the Brazilian Amazon, aspects relating to processes of environmental licensing, conceptual problems that concern the characterization of hydropower conversion as clean and renewable energy. This work starts from the analysis of government plans and discussions on hydropower projects, identifying the need to implement institutional changes and strengthen environmental laws and the protection of the rights of traditional and indigenous populations. We propose a new way of formulating energy problems and energy supply planning, which takes into consideration sustainable aspects and the public discussion, beyond understanding and incorporating the effects on the major biogeochemical cycles that support energy conversions.Universidade Estadual Paulista Júlio de Mesquita FilhoUniversidade Estadual Paulista Júlio de Mesquita Filh