Braiding process and bank erosion in the Brahmaputra River

The present work explores relations between stream power,braiding intensities and bank erosion in certain stretches of the Brahmaputra River.In this paper,an objective approach is presented to enable quantitative assessment of spatio-temporal behaviour of channel braiding process of the Brahmaputra River by using the Plan Form Index and corresponding estimation of stream power to establish a behavioural pattern of variability of potential energy expenditure.The braiding index is compared for discrete years to understand the morphological behaviour.Subsequently,a real time estimation of stream power for certain stretches of Brahmaputra River is done in order to analyse its variability in braiding intensity and bank erosion.The paper presents the dynamic behaviour of the channel pattern of the Brahmaputra River System in Assam valley of India over a time span of 18 years.The procedure addresses the selection of input parameters from digital satellite images,comprising scenes for the years 1990,1997 and 2007 with specific dates,from Dhubri near Indo-Bangladesh Border to Upper Assam.Deployment of GIS technique has been made to extract the required parameters to derive Plan Form Indices for the entire study reach.Stream power estimation is done for corresponding latest floods and for corresponding dates of image scenes.The study indicated that due to consistent aggradation of riverbed inducing temporal declination of stream power,there is an occurrence of wide spread braiding.This in turn incurs substantial yearly land loss due to bank erosion,caused by flow concentrations due to temporal evolution of multiple channels in the Brahmaputra River.     

干扰井群渗透系数计算的简便公式

干扰井群渗透系数计算的简便,公式是依据雅可布公式,根据叠加原理建立的。克服了计算方法烦杂,需解诸多未知数和使用范围窄及图解法计算时人为的随意性。增加了计算结果的可靠性。     

Oil spill fishery impact assessment model: Sensitivity to spill location and timing

An oil spill fishery impact assessment model system has been applied to the Georges Bank-Gulf of Maine region to assess the sensitivity of probable impact on several key fisheries to spill location and timing. Simulations of the impact on the fishery of tanker spills (20 million gallons released over 5 days), at two separate locations for each season of the year, and blowout spills (68 million gallons released over 30 days) at one location, with monthly releases and at six other locations with seasonal spills have been studied. Atlantic cod has been employed as the principal fish species throughout the simulations. Impacts on Atlantic herring and haddock have also been investigated for selected cases. All spill sites are located on Georges Bank with the majority in the general region of OCS leasing activity.The results of these simulations suggest a complex interaction among spill location and timing, the spatial and temporal distribution of spawning, the population dynamics of the species under study, and the hydrodynamics of the area. For the species studied, spills occurring during the winter and spring have the largest impact with cod being the most heavily impacted followed by haddock and herring. In all cases, the maximum cumulative loss to the fishery of a one time spill event never exceeded 25% of the annual catch with the exact value depending on the number of ichthyoplankton impacted by the spill and the compensatory dynamics of the population.     

高压喷射灌浆技术在强透水堤基处理中的应用

本文介绍了高压喷射灌浆技术在北江大堤强透水堤基处理中的应用．文中在分析堤基地层结构特征和物性指标的基础上，论述了高喷防渗墙的设计施工参数，根据已有围井检验结果，分析了各种地层高喷防渗墙的防渗效果，提出了用“单位渗水率”指标评价围封质量的新方法．文中根据大堤渗流观测资料和检验指标“单位渗水率”，建立了高喷防渗墙垂直截流堤基的渗流计算公式，并得出高喷防渗墙能有效地抑制住大堤堤基的渗流形变．     

How does the World Bank shape global environmental governance agendas for coasts? 50 years of small-scale fisheries aid reveals paradigm shifts over time

Small-scale fisheries are becoming a global social and environmental concern. The contribution of marine small-scale fisheries to global food security and coastal livelihoods, coupled with the significant challenges they face, has attracted increasing attention and aid from environmental organizations, philanthropies, and multilateral agencies over recent decades. Our study attends to the understudied role of the World Bank, the largest individual funder shaping present and future sustainability of coastal marine regions, as a key actor shaping global environmental governance paradigms. We asked how funding to the sector has changed over the last 50 years and why, outlining distinct patterns in the flow of small-scale fisheries aid and the underlying intervention models. We contextualize our quantitative analysis of aid patterns over time with qualitative interview data with bank staff, identifying underlying paradigm shifts driven by internal and external factors. More than $2.48 billion was allocated by the World Bank to marine fisheries over the last 50 years, approximately 47% (~$1.17 billion) of which was targeted to marine small-scale fisheries. Three distinct funding periods are identified: rising support to SSF from the 1970s to mid-1980s; a sharp decline in funding in the mid-to-late 1980s and low levels of funding throughout the 1990s; and a steady return to funding SSF in the mid-2000s up to the present. Over time, Bank-funded interventions shifted from pure economic development in the earlier era, to an emphasis on governance and multi-dimensional environmental goals in the recent period. To understand why, we used key-informant interviews to unpack major internal drivers: internal staff changes and presence of key individuals, the decentralization and recentralization of decision-making, and the organization’s shifting emphasis from traditional economic growth to multi-dimensional objectives of poverty reduction, among others. External drivers behind funding and paradigm shifts included pressure from the environmental movement, the rise of sustainable development discourses, key global environmental summits in the 1990s, and rising levels of interest in the fisheries sector by the governments of both donor and recipient countries. Processes of ‘paradigm shifts’ were not swift or singular, rather they were affected by multiple, convergent factors over time. Our findings contribute to the literature on multi-lateral institutions as key actors in environmental governance shaping global development thinking, illustrating the arc of the last half-century of fisheries aid at the Bank while highlighting present dilemmas and future challenges that actors interested in working towards sustainable marine small-scale fisheries face.     

A biological oil adsorption filter

A new oil adsorption method called adsorption filtration (AF) has been developed. It is a technology where by oil residues can be cleaned from water by running it through a simple filter made from freeze treated, dried, milled and then fragmented plant material. By choosing suitable plants and fragmentation sizes it is possible to produce filters, which pass water but adsorb oil. The aim of this study was to investigate the possibilities of manufacturing oil adsorbing filter materials from reed canary grass (Phalaris arundinacea), flax (Linum usitatissimum L.) or hemp fibre (Cannabis sativa L.). The oil (80 ml) was mixed with de-ionised water (200 ml) and this mixture was filtered through 10 or 20 g adsorption filters. Fine spring harvested hemp fibre (diameter less than 1 mm) and reed canary grass fragments adsorb 2-4 g of oil per gram of adsorption material compared to 1-3 g of water. Adsorption filtration is thus a novel way of gathering spilled oil in shallow coastal waters before the oil reaches the shore.     

Experimental study of the working principal and efficiency of a superposed inclined planes wave absorber

The swell reflection leads to problems in full scale conditions, shipping near seawalls and inside harbors, and for experiments in basins or channels, as well. Consequently, many studies were carried out to define wave absorbers with best efficiency. In this paper, the three main working principals of the wave absorbers, breaking waves, viscous dissipation resonating mechanism, are detailed to see how it is possible to enhance the efficiency. Through this analysis, a wave absorber made up of several superposed inclined planes in front of a wall is defined and its working principal is explained. Through experiments, it is shown that in spite of its short size its efficiency is one of the best compared to the more classical wave absorbers. Moreover, this superposed inclined planes wave absorber presents two main advantages: its short size and the possibility to be adjusted to the swell caracteristics, which make it interesting to be used in real scale and in laboratory environment, as well.     

Balancing end-to-end budgets of the Georges Bank ecosystem

Oceanographic regimes on the continental shelf display a great range in the time scales of physical exchange, biochemical processes and trophic transfers. The close surface-to-seabed physical coupling at intermediate scales of weeks to months means that the open ocean simplification to a purely pelagic food web is inadequate. Top-down trophic depictions, starting from the fish populations, are insufficient to constrain a system involving extensive nutrient recycling at lower trophic levels and subject to physical forcing as well as fishing. These pelagic-benthic interactions are found on all continental shelves but are particularly important on the relatively shallow Georges Bank in the northwest Atlantic. We have generated budgets for the lower food web for three physical regimes (Well-mixed, Transitional and Stratified) and for three seasons (Spring, Summer and Fall/Winter). The calculations show that vertical mixing and lateral exchange between the three regimes are important for zooplankton production as well as for nutrient input. Benthic suspension feeders are an additional critical pathway for transfers to higher trophic levels. Estimates of production by mesozooplankton, benthic suspension feeders and deposit feeders, derived primarily from data collected during the GLOBEC years of 1995-1999, provide input to an upper food web. Diets of commercial fish populations are used to calculate food requirements in three fish categories, planktivores, benthivores and piscivores, for four decades, 1963-2002, between which there were major changes in the fish communities. Comparisons of inputs from the lower web with fish energetic requirements for plankton and benthos indicate that we obtained reasonable agreement for the last three decades, 1973-2002. However, for the first decade, the fish food requirements were significantly less than the inputs. This decade, 1963-1972, corresponds to a period characterized by a strong Labrador Current and lower nitrate levels at the shelf-edge, demonstrating how strong bottom-up physical forcing may determine overall fish yields.