Recent shifts in coastline change and shoreline stabilization linked to storm climate change   总被引：1，自引：0，他引：1       下载免费PDF全文

Jennifer M. Johnson  Laura J. Moore  Kenneth Ells  A. Brad Murray  Peter N. Adams  Richard A. MacKenzie III  John M. Jaeger 《地球表面变化过程与地形》2015,40(5):569-585

Since cuspate coastlines are especially sensitive to changes in wave climate, they serve as potential indicators of initial responses to changing wave conditions. Previous work demonstrates that Cape Hatteras and Cape Lookout, North Carolina, which are largely unaffected by shoreline stabilization efforts, have become increasingly asymmetric over the past 30 years, consistent with model predictions for coastline response to increases in Atlantic Ocean summer wave heights and resulting changes in the distribution of wave‐approach angles. Historic and recent shoreline change observations for Cape Fear, North Carolina, and model simulations of coastline response to an increasingly asymmetric wave climate in the presence of beach nourishment, produce comparable differences in shoreline change rates in response to changes in wave climate. Results suggest that the effect of beach nourishment is to compensate for – and therefore to mask – natural responses to wave climate change that might otherwise be discernible in patterns of shoreline change alone. Therefore, this case study suggests that the effects of wave climate change on human‐modified coastlines may be detectable in the spatial and temporal patterns of shoreline stabilization activities. Similar analyses of cuspate features in areas where the change in wave climate is less pronounced (i.e. Fishing Point, Maryland/Virginia) and where local geology appears to exert control on coastline shape (i.e. Cape Canaveral, Florida), suggest that changes in shoreline configuration that may be arising from shifting wave climate are currently limited to sandy wave‐dominated coastlines where the change in wave climate has been most pronounced. However, if hurricane‐generated wave heights continue to increase, large‐scale shifts in patterns of erosion and accretion will likely extend beyond sensitive cuspate features as the larger‐scale coastline shape comes into equilibrium with changing wave conditions. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

The performance of churches in the 2012 Emilia earthquakes     

Luigi Sorrentino  Laura Liberatore  Luis D. Decanini  Domenico Liberatore 《Bulletin of Earthquake Engineering》2014,12(5):2299-2331

In this study the damage suffered by churches during the 2012 Emilia seismic sequence in Italy is analysed, based on surveys and inspections carried out in the area. Similarly to what was observed after other Italian earthquakes, the damage to churches was severe. However, the Emilia churches present some characteristic features such as the use of unreinforced clay brick masonry. In order to appropriately address the performance of this class of buildings, typical architectural layouts and construction techniques are described. Such techniques are interpreted also in the light of the local seismic catalogue. Fifty churches are then selected and their damage is studied, with reference to typical local-collapse mechanisms of different macro-elements. The study highlights that the damage is often concentrated at the top section of the façade, in the clerestory walls, in the vaults and in the bell towers. Structural analyses are performed to explain some of the observations. The overturning of the top section of the façade is analytically addressed, modelling the friction interlocking. With reference to the case study of San Francesco in Mirandola, non-linear static and dynamic analyses allow us to correlate the directionality of damage to the higher seismic demand along the NS direction, to point out the negligible role of the large vertical component of ground motion and to emphasise the relevance of the buttresses for the seismic response of the façade.  相似文献   

Stability and Removal of Naproxen and Its Metabolite by Advanced Membrane Wastewater Treatment Plant and Micelle–Clay Complex          下载免费PDF全文

Mohannad Qurie  Mustafa Khamis  Fida Malek  Shlomo Nir  Sabino A. Bufo  Jihad Abbadi  Laura Scrano  Rafik Karaman 《洁净——土壤、空气、水》2014,42(5):594-600

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Evolution of a debris-rock slide causing a natural dam: the flash flood of Río Santa Cruz,Province of San Juan—November 12, 2005     

Laura P. Perucca  M. Yanina Esper Angillieri 《Natural Hazards》2009,50(2):305-320

Between 2001 and 2005, a large debris rock slide occurred on the western slope of the Cordillera de Santa Cruz in the southeast Andean corner of the Province of San Juan (31°40′ S–70°16′ W). The landslide material accumulated in a downstream gorge as a natural dam of the Santa Cruz river, forming a large-volume lake. In November 2005, probably as a result of the increasing pressure of the water volume, this natural dam breached off with a violent and unexpected flash flood. In addition to life-threatening instances lived by some people downstream, this flood caused great economic loss to main localities of the Department of Calingasta, as well as considerable damage to one of the most relevant projects of the Province, the Caracoles Hydropower Project dam on the San Juan river. Considering the high costs of any physical remediation for a natural dam located in this high, remote, and inaccessible mountain area with no reliable road access, the main protective measures left to be pondered are the installation of a flash-flood early-warning system connected to downstream localities, along with a program of hydrological monitoring at the dam-forming area and annual satellital monitoring to verify the evolution of accumulated mass movements.  相似文献   

Cement Deep Soil Mixing (CDSM) for Solidification of Soft Estuarine Sediments     

A. Maher  W. S. Douglas  D. Yang  F. Jafari  V. R. Schaefer 《Marine Georesources & Geotechnology》2013,31(3-4):221-235

A preliminary study was conducted to determine the potential for cement deep soil mixing (CDSM) technology as a method for in-situ solidification of contaminated river and estuarine sediments. The study was conducted in Newark Bay, near the mouth of the Passaic River, New Jersey. The primary objective of the study was to evaluate the viability of CDSM for the in-situ S/S with a focus on: 1) determining the correct mix of the cement slurry, which provides rapid stabilization of the sediment matrix, 2) potential resuspension of solids during CSDM operations, 3) the effects of high organic content on the solidification process, and 4) the feasibility of using conventional dredging/extraction methods once the sediments have been stabilized and allowed to cure. The results of the study show CDSM slurry mixtures, as low as 7% in cement content, result in significant solidification and strength gain of in-situ sediments under ambient conditions. In sediments with very high organic contents (> 20%), the slurry mix would need to be adjusted to account for retardation effects of organics on cement hydration. Sediment resuspension during application was shown to be minimal at a distance of as little as 75 feet from the mixing head. Strength gains were considerable, effectively consolidating the sediment particles in a secure matrix, but not so high as to preclude extraction of solidified sediments with conventional dredging equipment. Dredged solidified sediment exhibited characteristics of a stiff glacial clay, and as such was easier to handle and transport than untreated dredged sediments. This technique has high potential to be used as an interim remedial measure prior to either extraction and decontamination/disposal or proper capping.  相似文献   

Eddy covariance imaging of diffuse volcanic CO<Subscript>2</Subscript> emissions at Mammoth Mountain,CA, USA     

Jennifer L. Lewicki  George E. Hilley  Laura Dobeck  Bruno D. V. Marino 《Bulletin of Volcanology》2012,74(1):135-141

Use of eddy covariance (EC) techniques to map the spatial distribution of diffuse volcanic CO₂ fluxes and quantify CO₂ emission rate was tested at the Horseshoe Lake tree-kill area on Mammoth Mountain, California, USA. EC measurements of CO₂ flux were made during September–October 2010 and ranged from 85 to 1,766 g m⁻² day⁻¹. Comparative maps of soil CO₂ flux were simulated and CO₂ emission rates estimated from three accumulation chamber (AC) CO₂ flux surveys. Least-squares inversion of measured eddy covariance CO₂ fluxes and corresponding modeled source weight functions recovered 58–77% of the CO₂ emission rates estimated based on simulated AC soil CO₂ fluxes. Spatial distributions of modeled surface CO₂ fluxes based on EC and AC observations showed moderate to good correspondence (R ² = 0.36 to 0.70). Results provide a framework for automated monitoring of volcanic CO₂ emissions over relatively large areas.  相似文献   

Combining long- and short-term probabilistic volcanic hazard assessment with cost-benefit analysis to support decision making in a volcanic crisis from the Auckland Volcanic Field,New Zealand   总被引：2，自引：2，他引：0  

Laura Sandri  Gill Jolly  Jan Lindsay  Tracy Howe  Warner Marzocchi 《Bulletin of Volcanology》2012,74(3):705-723

By using BET_VH, we propose a quantitative probabilistic hazard assessment for base surge impact in Auckland, New Zealand. Base surges resulting from phreatomagmatic eruptions are among the most dangerous phenomena likely to be associated with the initial phase of a future eruption in the Auckland Volcanic Field. The assessment is done both in the long-term and in a specific short-term case study, i.e. the simulated pre-eruptive unrest episode during Exercise Ruaumoko, a national civil defence exercise. The most important factors to account for are the uncertainties in the vent location (expected for a volcanic field) and in the run-out distance of base surges. Here, we propose a statistical model of base surge run-out distance based on deposits from past eruptions in Auckland and in analogous volcanoes. We then combine our hazard assessment with an analysis of the costs and benefits of evacuating people (on a 1 × 1-km cell grid). In addition to stressing the practical importance of a cost-benefit analysis in creating a bridge between volcanologists and decision makers, our study highlights some important points. First, in the Exercise Ruaumoko application, the evacuation call seems to be required as soon as the unrest phase is clear; additionally, the evacuation area is much larger than what is recommended in the current contingency plan. Secondly, the evacuation area changes in size with time, due to a reduction in the uncertainty in the vent location and increase in the probability of eruption. It is the tradeoff between these two factors that dictates which cells must be evacuated, and when, thus determining the ultimate size and shape of the area to be evacuated.  相似文献   

Coming to the table: Early stakeholder engagement in marine spatial planning   总被引：1，自引：0，他引：1  

Morgan Gopnik  Clare Fieseler  Laura Cantral  Kate McClellan  Linwood Pendleton  Larry Crowder 《Marine Policy》2012

From 2009 to 2011, marine spatial planning (MSP) rapidly gained visibility in the United States as a promising ocean management tool. A few small-scale planning efforts were completed in state waters, and the Obama Administration proposed a framework for large-scale regional MSP throughout the U.S. Exclusive Economic Zone. During that same time period, the authors engaged a variety of U.S ocean stakeholders in a series of dialogs with several goals: to share information about what MSP is or could be, to hear stakeholder views and concerns about MSP, and to foster better understanding between those who depend on ocean resources for their livelihood and ocean conservation advocates. The stakeholder meetings were supplemented with several rounds of in-depth interviews and a survey. Despite some predictable areas of conflict, project participants agreed on a number of issues related to stakeholder engagement in MSP: all felt strongly that government planners need to engage outsiders earlier, more often, more meaningfully, and through an open and transparent process. Equally important, the project affirmed the value of bringing unlike parties together at the earliest opportunity to learn, talk, and listen to others with whom they rarely engage.  相似文献   

Flow dynamics at the origin of thin clayey sand lacustrine turbidites: Examples from Lake Hazar,Turkey          下载免费PDF全文

Sophie Hage  Aurélia Hubert‐Ferrari  Laura Lamair  Ulaş Avşar  Meriam El Ouahabi  Maarten Van Daele  Frédéric Boulvain  Mohamed Ali Bahri  Alain Seret  Alain Plenevaux 《Sedimentology》2017,64(7):1929-1956

Turbidity currents and their deposits can be investigated using several methods, i.e. direct monitoring, physical and numerical modelling, sediment cores and outcrops. The present study focused on thin clayey sand turbidites found in Lake Hazar (Turkey) occurring in eleven clusters of closely spaced thin beds. Depositional processes and sources for three of those eleven clusters are studied at three coring sites. Bathymetrical data and seismic reflection profiles are used to understand the specific geomorphology of each site. X‐ray, thin sections and CT scan imagery combined with grain‐size, geochemical and mineralogical measurements on the cores allow characterization of the turbidites. Turbidites included in each cluster were produced by remobilization of surficial slope sediment, a process identified in very few studies worldwide. Three types of turbidites are distinguished and compared with deposits obtained in flume studies published in the literature. Type 1 is made of an ungraded clayey silt layer issued from a cohesive flow. Type 2 is composed of a partially graded clayey sand layer overlain by a mud cap, attributed to a transitional flow. Type 3 corresponds to a graded clayey sand layer overlain by a mud cap issued from a turbulence‐dominated flow. While the published experimental studies show that turbulence is damped by cohesion for low clay content, type 3 deposits of this study show evidence for a turbulence‐dominated mechanism despite their high clay content. This divergence may in part relate to input variables, such as water chemistry and clay mineralogy, that are not routinely considered in experimental studies. Furthermore, the large sedimentological variety observed in the turbidites from one coring site to another is related to the evolution of a sediment flow within a field‐scale basin made of a complex physiography that cannot be tackled by flume experiments.  相似文献   

Exploring the impact of diagenesis on (isotope) geochemical and microstructural alteration features in biogenic aragonite          下载免费PDF全文

Ann‐Christine Ritter  Vasileios Mavromatis  Martin Dietzel  Ola Kwiecien  Felix Wiethoff  Erika Griesshaber  Laura A. Casella  Wolfgang W. Schmahl  Jennifer Koelen  Rolf D. Neuser  Albrecht Leis  Dieter Buhl  Andrea Niedermayr  Sebastian F. M. Breitenbach  Stefano M. Bernasconi  Adrian Immenhauser 《Sedimentology》2017,64(5):1354-1380

For the Quaternary and Neogene, aragonitic biogenic and abiogenic carbonates are frequently exploited as archives of their environment. Conversely, pre‐Neogene aragonite is often diagenetically altered and calcite archives are studied instead. Nevertheless, the exact sequence of diagenetic processes and products is difficult to disclose from naturally altered material. Here, experiments were performed to understand biogenic aragonite alteration processes and products. Shell subsamples of the bivalve Arctica islandica were exposed to hydrothermal alteration. Thermal boundary conditions were set at 100°C, 175°C and 200°C. These comparably high temperatures were chosen to shorten experimental durations. Subsamples were exposed to different ¹⁸O‐depleted fluids for durations between two and twenty weeks. Alteration was documented using X‐ray diffraction, cathodoluminescence, fluorescence and scanning electron microscopy, as well as conventional and clumped isotope analyses. Experiments performed at 100°C show redistribution and darkening of organic matter, but lack evidence for diagenetic alteration, except in Δ₄₇ which show the effects of annealing processes. At 175°C, valves undergo significant aragonite to calcite transformation and neomorphism. The δ¹⁸O signature supports transformation via dissolution and reprecipitation, but isotopic exchange is limited by fluid migration through the subsamples. Individual growth increments in these subsamples exhibit bright orange luminescence. At 200°C, valves are fully transformed to calcite and exhibit purple‐blue luminescence with orange bands. The δ¹⁸O and Δ₄₇ signatures reveal exchange with the aqueous fluid, whereas δ¹³C remains unaltered in all experiments, indicating a carbonate‐buffered system. Clumped isotope temperatures in high‐temperature experiments show compositions in broad agreement with the measured temperature. Experimentally induced alteration patterns are comparable with individual features present in Pleistocene shells. This study represents a significant step towards sequential analysis of diagenetic features in biogenic aragonites and sheds light on reaction times and threshold limits. The limitations of a study restricted to a single test organism are acknowledged and call for refined follow‐up experiments.  相似文献