The dynamics of sediment transport capacity in gravel‐bed rivers is critical to understanding the formation and preservation of fluvial landforms and formulating sediment‐routing models in drainage systems. We examine transport‐storage relations during cycles of aggradation and degradation by augmenting observations of three events of channel aggradation and degradation in Cuneo Creek, a steep (3%) gravel‐bed channel in northern California, with measurements from a series of flume runs modeling those events. An armored, single‐thread channel was formed before feed rates were increased in each aggradation run. Output rates increased as the channel became finer and later widened, steepened, and braided. After feed rates were cut, output rates remained high or increased in early stages of degradation as the incising channel remained fine‐grained, and later decreased as armoring intensified. If equilibrium was not reached before sediment feed rate was cut, then a rapid transition from a braided channel to a single‐thread channel caused output rates for a given storage volume to be higher during degradation than during aggradation. Variations in channel morphology, and surface bed texture during runs that modeled the three cycles of aggradation and degradation were similar to those observed in Cuneo Creek and provide confidence in interpretations of the history of change: Cuneo Creek aggraded rapidly as it widened, shallowed, and braided, then degraded rapidly before armoring stabilized the channel. Such morphology‐driven changes in transport capacity may explain the formation of flood terraces in proximal channels. Transport‐storage relations can be expected to vary between aggradation and degradation and be influenced by channel conditions at the onset of changes in sediment supply. Published in 2011. This article is a US Government work and is in the public domain in the USA. 相似文献
Social vulnerability is a term that has been widely used in the natural hazards literature for quite a few years now. Yet, regardless of how scholars
define the term, the approaches and indicators they use remain contested. This article presents findings from social vulnerability
assessments conducted in different case studies of flood events in Europe (Germany, Italy and the UK). The case studies relied
upon a common set of comparable indicators, but they also adopted a context-sensitive, qualitative approach. A shared finding
across the case studies was that it was not possible to identify a common set of socio-economic–demographic indicators to
explain social vulnerability of groups and/or individuals for all phases of the disastrous events. Similarly, network-related
indicators as well as location- and event-specific indicators did not have the relevance we expected them to have. The results
underline that vulnerability is a product of specific spatial, socio-economic–demographic, cultural and institutional contexts
imposing not only specific challenges to cross-country research concerning social vulnerability to flooding but also to attempts
at assessing social vulnerability in general. The study ends with some reflections upon the methodological, practical and
theoretical implications of our findings. 相似文献
This paper offers a critical review of modeling practice in the field of integrated assessment of climate change and ways forward. Past efforts in integrated assessment have concentrated on developing baseline trajectories of emissions and mitigation scenario analyses. A key missing component in Integrated Assessment Models (IAMs) is the representation of climate impacts and adaptation responses. In this paper, we identify key biases that are introduced when climate impacts and adaptation responses are omitted from the analysis and review the state of modeling studies that attempt to capture these feedbacks. A common problem in these IAM studies is the lack of connection with empirical studies. We therefore also review the state of the empirical work on climate impacts and identify ways that this connection could be improved. 相似文献
Natural Hazards - Quang Nam province, central Vietnam, is situated within the tropical monsoon and typhoon zone of south-east Asia and is susceptible to extreme floods. Historical water level data... 相似文献
Stakeholders in natural resource management decisions are also multifaceted individuals and members of communities; as such, they bring complex histories, experiences, values, aspirations, and relationships to public participation processes. When these processes fail to take this social context into account, multiple problems can result, including a perceived lack of process trustworthiness; perceived focus on issues that seem immaterial or irrelevant; failure to equitably represent and take account of diverse voices; and failure to engage participants in productive dialogue. In this article we evaluate the Community Voice Method (CVM) as a way of addressing those problems by better situating public participation in place. CVM is a mixed-method approach to public participation in which stakeholders are interviewed and the interview data is presented through a film, which is then screened at public meetings to catalyze dialogue. We draw on 14 years of CVM projects addressing natural resource management issues in the United States, the United Kingdom, and the Caribbean. Through an overview of nine projects and their results, and more in-depth consideration of three, we elucidate how this method fosters trustworthy, relevant, representative, and productive public participation that has resulted in community capacity-building, institutional capacity-building, and stakeholder-guided policymaking.
Abstract– Carbonaceous matter in Stardust samples returned from comet 81P/Wild 2 is observed to contain a wide variety of organic functional chemistry. However, some of this chemical variety may be due to contamination or alteration during particle capture in aerogel. We investigated six carbonaceous Stardust samples that had been previously analyzed and six new samples from Stardust Track 80 using correlated transmission electron microscopy (TEM), X‐ray absorption near‐edge structure spectroscopy (XANES), and secondary ion mass spectroscopy (SIMS). TEM revealed that samples from Track 35 containing abundant aliphatic XANES signatures were predominantly composed of cometary organic matter infilling densified silica aerogel. Aliphatic organic matter from Track 16 was also observed to be soluble in the epoxy embedding medium. The nitrogen‐rich samples in this study (from Track 22 and Track 80) both contained metal oxide nanoparticles, and are likely contaminants. Only two types of cometary organic matter appear to be relatively unaltered during particle capture. These are (1) polyaromatic carbonyl‐containing organic matter, similar to that observed in insoluble organic matter (IOM) from primitive meteorites, interplanetary dust particles (IDPs), and in other carbonaceous Stardust samples, and (2) highly aromatic refractory organic matter, which primarily constitutes nanoglobule‐like features. Anomalous isotopic compositions in some of these samples also confirm their cometary heritage. There also appears to be a significant labile aliphatic component of Wild 2 organic matter, but this material could not be clearly distinguished from carbonaceous contaminants known to be present in the Stardust aerogel collector. 相似文献
The anthropological machine is the discursive framework, the dispositif that grounds “Western man” in a sense of civility, secured through a violent division within and between the human and nonhuman: not the after-effect of the civilizing act but its very foundation. This paper explores Agamben’s machine at multiple sites: in its expression in everyday lives of urban citizens, and its legitimation of capitalist urbanization on broader spatial and temporal scales, its “worlding” through planetary urbanization and normalization of climate change. Complicit in capitalist urbanization and climate change, the anthropological machine has acted as a “switch point” since the 1600s. It now frames an emergent response: triage as the inevitable sacrifice of some peoples and parts of the planet to preserve others. If the urban is to become the site of mondialization, confronting the apparent inevitability of triage we must think beyond the either-or of a people or a planet. Thought in relation to the urban, the anthropological machine offers a meeting ground between urban political economy and assemblage urbanism. It enables us to situate the Anthropocene and differentiate the urban. But it also exposes a deep divide between scholars reframing the human beyond “Western man”: between those for whom the more-than-human expresses the dreams of a biophilic city and those for whom the less-than-human is increasingly its living nightmare. 相似文献