The need for operational reasoning in data‐driven rating curve prediction of suspended sediment

The use of data‐driven modelling techniques to deliver improved suspended sediment rating curves has received considerable interest in recent years. Studies indicate an increased level of performance over traditional approaches when such techniques are adopted. However, closer scrutiny reveals that, unlike their traditional counterparts, data‐driven solutions commonly include lagged sediment data as model inputs, and this seriously limits their operational application. In this paper, we argue the need for a greater degree of operational reasoning underpinning data‐driven rating curve solutions and demonstrate how incorrect conclusions about the performance of a data‐driven modelling technique can be reached when the model solution is based upon operationally invalid input combinations. We exemplify the problem through the re‐analysis and augmentation of a recent and typical published study, which uses gene expression programming to model the rating curve. We compare and contrast the previously published solutions, whose inputs negate their operational application, with a range of newly developed and directly comparable traditional and data‐driven solutions, which do have operational value. Results clearly demonstrate that the performance benefits of the published gene expression programming solutions are dependent on the inclusion of operationally limiting, lagged data inputs. Indeed, when operationally inapplicable input combinations are discounted from the models and the analysis is repeated, gene expression programming fails to perform as well as many simpler, more standard multiple linear regression, piecewise linear regression and neural network counterparts. The potential for overstatement of the benefits of the data‐driven paradigm in rating curve studies is thus highlighted. Copyright © 2011 John Wiley & Sons, Ltd.     

“Natural cycles” in lay understandings of climate change

This article analyses lay understandings of climate change elicited through a longitudinal population-based survey of climate change, place and community among 1162 residents in the Hunter Valley, Southeast Australia. We explore how older residents in contrasting rural and coastal geographic areas perceive climate change information in terms of culturally relevant meanings and values, lived experiences and emotional responses to seasonal cycles, temperature fluctuations and altered landscapes. Thematic analysis of comments given by 467 interviewees to an open-ended question identified a significant subset for whom the concepts of “nature” and “science” express competing views about changing climatic conditions. For them, the idea of “natural cycles” is a significant cultural construct that links nature and humans through time in a way that structures stable and resilient understandings of environmental change, drawing on established cosmological frameworks for contemplating the future in relation to the past. In contrast to other studies that postulate scepticism and denial as individuals’ fear management strategies in the face of climate change threat, we found that the natural cycles view is founded on a reassuring deeper conviction about how nature works, and is linked to other pro-environmental values not commonly found in sceptical groups. It is a paradox of natural cycles thinking that it rejects the anthropocentrism that is at the heart of science-based environmentalism. By contrast, it places humans as deeply integrated with nature, rather than operating outside it and attempting with uncertain science to control something that is ultimately uncontrollable.     

Quantitative assessment of the hydraulic role of subglaciofluvial interbeds in promoting deposition of deformation till (Northern Till,Ontario)

The Northern Till is a thick (>65 m) deformation till underlying some 7500 km² of Southern Ontario, Canada including the Peterborough Drumlin Field. It was deposited below the Lake Ontario ice stream of the Laurentide Ice Sheet. The till rests on glaciotectonized aquifer sediments and consists of multiple beds of till up to 6 m thick. These are separated by boulder lags, sometimes in the form of striated pavements, with thin (<30 cm) interbeds of poorly sorted waterlaid sand. The composite till stratigraphy indicates ‘punctuated aggradation’ where the subglacial bed was built up incrementally by the repeated ‘immobilization’ of deforming overpressured till layers. Boulders and sands indicate pauses in subglacial aggradation marked by sluggish sheet flows of water that reworked the top of the underlying till. Interbeds are laterally extensive and correlated using downhole electrical conductivity, core recovery and natural gamma data. A 3-D finite element model (FEFLOW) using data from 200 cored and geophysically logged boreholes, and a large digital water well dataset of 3400 individual records shows that the till functions as a ‘leaky aquitard’ as a consequence of water flow through interbeds. It is proposed that interbeds played a similar role in the subglacial hydraulic system below the Laurentide Ice Sheet by allowing drainage of excess porewater pressures in deforming sediment and promoting deposition of till. This is in agreement with theoretical studies of deforming bed dynamics and observations at modern glaciers where porewater in the deforming layer is discharged into underlying aquifers. In this way, the presence of interbeds may be fundamental in retarding downglacier transport of deforming bed material thereby promoting the build-up of thick subglacial till successions.     

Socioeconomic impacts of environmental risks in the western Makran zone (Chabahar,Iran)

Natural Hazards - The western Makran subduction zone is capable of producing considerable tsunami run-up heights that penetrate up to 5&nbsp;km inland. In this study, we show how climate change...     

Climate change or nuclear power—No thanks! A quantitative study of public perceptions and risk framing in Britain

The UK is witnessing a new line in political debate around new nuclear energy generation as one potential feature of future energy policy, specifically for contributing to climate change mitigation alongside energy security. Little is known about how ordinary citizens might be responding to this reframing. This paper reports the results from a major British survey (n=1491) undertaken in the autumn of 2005. The consistent message is that while higher proportions of the British public are prepared to accept nuclear power if they believe it contributes to climate change mitigation, this is a highly conditional view, with very few actively preferring this over renewable sources given the choice. People see both climate change and nuclear power as problematic in terms of risks and express only a ‘reluctant acceptance’ of nuclear power as a ‘solution’ to climate change. The combined data from this survey can also be interpreted as an indication of the complexity surrounding beliefs about energy futures and the difficulty of undertaking simplistic risk–risk tradeoffs within any single framing of the issues; such as nuclear energy versus climate change. The results also indicate that it would be unwise, in the UK as elsewhere, to simplistically assume that there exists any single or stable public ‘opinion’ on such complex matters. We conclude with a discussion of the role and implications of the survey evidence for the policy process.     

伊犁京希—伊尔曼德金矿床的热液蚀变及成矿流体演化特征

京希－伊尔曼德金矿床的热液蚀变在空间上有明显的分带性，中心蚀变带以强烈的硅化为主，典型的蚀变矿物组合为石英或玉髓和地开石，中间带为高级泥化带，以地开石－高岭石－石英或玉髓为特征；外带为以蒙脱石－高岭石－伊利石－其他粘土矿物等矿物组合为主的泥化带，蚀变强度和矿物组合的分带性是温度、压力和化学梯度的反映，是流体在不断的水或流体－岩石反应和成分交换的产物。该矿床成矿流体演化过程为：早期酸性（pH=2-3)含矿流体在沿断裂上升过程中，受围岩灰岩中的流体（pH为中性）缓冲，在其进入高渗透性的碎屑岩层时，流速和水－岩石或流休－岩石反应大大加快，并在与大气降水的混合作用下，pH值逐步升高（3－5），产生了流体的温度及成分梯度，在温度和压力迅速下降的条件下，金及蚀变矿物沉淀、结晶生长，形成了蚀变空间分带，中心带保存完好的多孔状石英和地开石等高级泥化矿物组合说明该矿床是高硫化热液体系作用下的产物。     

Review of Late Proterozoic sutures,ophiolitic mélanges and tectonics of eastern Egypt and north-east Sudan

The distribution, structural relations and ages of ophiolites and ophiolitic melanges in the Eastern Deserts of Egypt and north-east Sudan, and their relation to arc and post-arc magmatism, are used to infer the probable positions of sutures and the directions of obduction and subduction. The ages of the successive tectonic stages in the terranes decrease northwards, by about 100 Ma in the region discussed. Obduction was north-westwards. The obducted sheets of ophiolite and ophiolitic melange, extending about 500 km north from the Onib-Sol Flamed suture, may all represent a single back-arc basin. The direction of subduction is still not clearly proved: more geochemical evidence of arc-magmatic polarity is needed. The late tectonic north-westward thrusting, the NW - SE stretching lineation, the transpressional north-south Hamisama Shear Zone and the NW-SE sinistral Najd faults are all attributed to north-westward movement (present coordinates) of terranes towards the older craton west of the Nile. The Najd faults are interpreted as intracontinental transform faults.