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1.
Shore protection in lakes is an issue of major importance in Switzerland where several big lakes in plains suffer from a pronounced bank erosion. For the moment, in shallow lakes, soft and biotechnical protection measures proved their reliability. Unfortunately, the scientific basis for the design of such techniques does not exist in some cases or not appropriate enough in order to have an optimized effect. Therefore, the aim of an on-going research project is to study, on the basis of physical and numerical modeling, the impact of such measures on the shores regarding bank erosion, and to establish the main basis for their dimensioning. A 2-D numerical model was used to simulate the eroded beach of Préverenges on the North coast of Lake Geneva. Hence, this case study allowed a better understanding of the numerical capacities of the program by modelling wave effect on bedload sediment transport and shore erosion as well as wind role in the generation of littoral currents. 相似文献
2.
全球范围内的湖泊生态环境均出现了不同程度的退化,对其进行生态修复的最终目的,就是要将受损的生态系统尽量恢复到人类干扰前或接近人类干扰前的生态状况,即基准环境.湖泊生态系统是长期演化的产物,其形成及演化机制必须从历史的视角加以考察,因此基于湖泊沉积物的古生态学技术在制定基准环境方面有着独特的优势.本文从基准环境的定义、建立的常用方法、基本特征和典型应用几个方面介绍了古生态学手段在湖泊生态修复中的应用,提出中国今后利用古生态学手段在水环境治理工作的应用前景. 相似文献
3.
A Survey of Techniques for Predicting Earthquake Ground Motions for Engineering Purposes 总被引：2，自引：0，他引：2
Over the past four or five decades many advances have been made in earthquake ground-motion prediction and a variety of procedures
have been proposed. Some of these procedures are based on explicit physical models of the earthquake source, travel-path and
recording site while others lack a strong physical basis and seek only to replicate observations. In addition, there are a
number of hybrid methods that seek to combine benefits of different approaches. The various techniques proposed have their
adherents and some of them are extensively used to estimate ground motions for engineering design purposes and in seismic
hazard research. These methods all have their own advantages and limitations that are not often discussed by their proponents.
The purposes of this article are to: summarise existing methods and the most important references, provide a family tree showing
the connections between different methods and, most importantly, to discuss the advantages and disadvantages of each method.
相似文献
| John DouglasEmail: |
4.
地壳形变与地震前兆探索回顾和展望 总被引：2，自引：0，他引：2
本文回顾了我国地震预报中地壳形变观测技术、 数据处理方法和软件及地壳形变前兆观测研究进展。 1966年邢台地震后, 我国地震预报工作经历了难得的成功、 更多惨痛失败和“地震不可预报论”等干扰, 发展曲折。 尽管2008年汶川和2011年东日本大地震预报失败,但这两次和其他大地震前后GPS和其他观测得到的地壳形变表明, 大地震是有前兆的, 是可以预报的。 比较了我国地震预报所采用的主要的地形变观测技术和分析方法, 讨论了观测和数据处理方法的特点, 简要介绍了地壳形变地震前兆新近的研究结果, 重点阐述了GPS观测技术多方面的优势。 事实证明, GPS观测得到的汶川大地震前的形变异常或前兆, 是我国地壳形变观测与地震前兆探索最突出的成果。 相似文献
5.
John Wainwright Anthony J. Parsons Eva N. Müller Richard E. Brazier D. Mark Powell Bantigegne Fenti 《地球表面变化过程与地形》2008,33(7):1113-1128
In the two previous papers of this series, we demonstrated how a novel approach to erosion modelling (Mahleran – Model for Assessing Hillslope‐Landscape Erosion, Runoff And Nutrients) provided distinct advantages in terms of process representation and explicit scaling characteristics when compared with existing models. A first evaluation furthermore demonstrated the ability of the model to reproduce spatial and temporal patterns of erosion and their particle‐size characteristics on a large rainfall‐simulation plot. In this paper, we carry out a more detailed evaluation of the model using monitored erosion events on plots of different size. The evaluation uses four plots of 21·01, 115·94, 56·84 and 302·19 m2, with lengths of 4·12, 14·48, 18·95 and 27·78 m, respectively, on similar soils to the rainfall‐simulation plot, for which runoff and erosion were monitored under natural rainfall. Although the model produces the correct ranking of the magnitude of erosion events, it performs less well in reproducing the absolute values and particle‐size distributions of the eroded sediment. The implications of these results are evaluated in terms of requirements for process understanding and data for parameterization of improved soil‐erosion models. We suggest that there are major weaknesses in the current understanding and data underpinning existing models. Consequently, a more holistic re‐evaluation is required that produces functional relationships for different processes that are mutually consistent, and that have appropriate parameterization data to support their use in a wide range of environmental conditions. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
6.
Various methods have been used to study soil redistribution in the Loam Belt of Belgium. These methods have had contrasting levels of spatial coverage and time-scale. Ideally, a technique to assess soil redistribution patterns should provide the determination of dense networks of X, Y and Z terrain coordinates (digital elevation models) at different time intervals. Sequential stereoscopic aerial photographs contain this information, which can be extracted with standard photogrammetric techniques. In this study, aerial photographs taken by the National Geographic Institute of Belgium in 1947 and 1991 were used to determine the soil redistribution pattern between these years. This was done by overlaying the two digital elevation models and subtracting the corresponding Z coordinate values (heights). The results indicate that most severe surface lowering occurs on the top of the hillslope and on the hillslope convexities. Important deposition occurs on the lowermost parts of the hillslope, in most hillslope concavities and in the topographically defined concentration line. The observed pattern differs markedly from that expected from water erosion processes, and suggests that the soil redistribution is dominated by tillage operations. 相似文献
7.
Runoff and water erosion modelling using WEPP on a Mediterranean cultivated catchment 总被引：1，自引：0，他引：1
Soil erosion due to water is a major environmental problem in many parts of the world. Most of Mediterranean countries are concerned because of their specific climate and soils sensitivity, but also because of the recent intensification of human activities and agricultural practices. Accurate estimation of soil water erosion for various land-use and climate scenarios is so an important key to define sustainable management policies. In the last decades, several studies have been carried out to build models suitable for quantifying soil erosion. Among these models, the Water Erosion Prediction Project (WEPP, Flanagan, D.C., Nearing, M.A., 1995. USDA-Water Erosion Prediction Project: Hillslope profile and watershed model documentation. NSERL Report 10, USDA-ARS National Soil Erosion Research Laboratory, West Lafayette, IN, USA.) is a physically based, distributed-parameter model that has been developed and mainly validated in USA. Only few studies have investigated its applicability to environmental conditions that differs from those where the model was developed. The aim of this work is to test the efficiency of WEPP model to predict soil erosion at catchment scale in a Mediterranean semi-arid area. Continuous simulations have been conducted between 1995 and 2002 on an cultivated experimental catchment located upstream from a hill reservoir (Kamech catchment, 2.45 km2, Cap Bon, Tunisia) where runoff and soil erosion measurements are available at the outlet. Comparison between predictions and measurements shows significant differences. Processes related to seasonal effects (as cracking soils) are pointed out as a weakness of WEPP model for Mediterranean conditions. 相似文献
8.
D. M. Lawler 《地球表面变化过程与地形》1993,18(9):777-821
A detailed review and chronological survey is presented of the various techniques which have been used for the measurement of river bank erosion and channel change. The techniques are classified according to the time scales involved (long, intermediate and short) and each is discussed with respect to accuracy and repeatability. The methods covered include sedimentological evidence, botanical evidence, historical sources, planimetric resurvey, repeated cross-profiling, erosion pins and terrestrial photogrammetry. Prospects for future developments are also discussed. 相似文献
9.
本文以我国塔里木油田石油地球物理勘探实例为基础,概述了石油勘探过程中地震解释技术类型、特征、现状和发展趋势.本文认为,在地震勘探技术飞速发展的今天,地球物理学家及地质学家希望获得的地震信息,应当是能够直接反应地下岩石物理特性或油气水的分布,而利用常规的地震解释技术是很难做到这些;随着石油勘探的进一步深化,一些新的地震解释技术涌现出来,并在油气勘探与开发过程中发挥着巨大作用.未来的石油勘探将会面临前所未有的困难,新情况、新问题将层出不穷,地震解释技术也同样面临着考验,因此,只有立足在现有的成熟解释技术之上,并不断探索新的技术与思路,才能与未来的石油勘探步伐相一致. 相似文献
10.
Jean Poesen 《地球表面变化过程与地形》2018,43(1):64-84
Soil erosion is a geomorphological and, at the same time, a land degradation process that may cause environmental and property damage, loss of livelihoods and services as well as social and economic disruption. Erosion not only lowers soil quality on‐site, but causes also significant sediment‐related problems off‐site. Given the large number of research papers on this topic, one might therefore conclude that we know now almost everything about soil erosion and its control so that little new knowledge can be added. This conclusion can be refuted by pointing to some major research gaps. There is a need for more research attention to (1) improved understanding of both natural and anthropogenic soil erosion processes and their interactions, (2) scaling up soil erosion processes and rates in space and time, and (3) innovative techniques and strategies to prevent soil erosion or reduce erosion rates. This is illustrated with various case studies from around the world. If future research addresses these research gaps, we will (1) better understand processes and their interactions operating at a range of spatial and temporal scales, predict their rates as well as their on‐site and off‐site impacts, which is academically spoken rewarding but also crucial for better targeting erosion control measures, and (2) we will be in a better position to select the most appropriate and effective soil erosion control techniques and strategies which are highly necessary for a sustainable use of soils in the Anthropocene. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
11.
Weimin Dong Ph.D 《地震工程与工程振动(英文版)》2002,1(1):145-151
Internationally earthquake insurance, like all other insurance (fire, auto), adopted actuarial approach in the past, which
is, based on historical loss experience to determine insurance rate. Due to the fact that earthquake is a rare event with
severe consequence, irrational determination of premium rate and lack of understanding scale of potential loss led to many
insurance companies insolvent after Northridge earthquake in 1994.
Along with recent advances in earth science, computer science and engineering, computerized loss estimation methodologies
based on first principles have been developed to the point that losses from destructive earthquakes can be quantified with
reasonable accuracy using scientific modeling techniques.
This paper intends to introduce how engineering models can assist to quantify earthquake risk and how insurance industry can
use this information to manage their risk in the United States and abroad.
Supported partially by: Institute of Engineering Mechanics, CSB 相似文献
12.
Peter Ian Alexander Kinnell 《水文研究》2013,27(18):2567-2578
Sediment, nutrients and pollutants discharged from sheet and interrill erosion areas by rain‐impacted flows may influence water quality in streams and rivers. The depth of water on the soil surface influences the capacity of raindrop impacts to detach soil material underlying rain‐impacted flows, and a number of so‐called process‐based and mechanistic models erroneously use equations on the basis of the effect of water depth on splash erosion to account for this effect. Also, a number of these models require complex mathematical solutions to make them operate and can only predict sediment composition and discharges well if many of their parameters are calibrated specifically to the situations where they are being applied. Experiments with rain‐impacted flows, where flow depth and velocity over eroding surfaces have been controlled, have been reported in the literature and provide more appropriate equations to account for the drop size – flow depth interactions that affect detachment and transport of particles in rain‐impacted flows. There is a need to develop modeling approaches that rely on relevant data obtained under well‐controlled flow conditions where flow depths and velocities are known. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
13.
Accelerated sediment fluxes by water and tillage erosion on European agricultural land 总被引：1，自引：0，他引：1
Soil loss on arable agricultural land is typically an order of magnitude higher than under undisturbed native vegetation. Although there have been several recent attempts to quantify these accelerated fluxes at the regional, continental and even global scale, all of these studies have focused on erosion by water and wind and no large scale assessment of the magnitude of tillage erosion has been made, despite growing recognition of its significance on agricultural land. Previous field scale simulations of tillage erosion severity have relied on use of high resolution topographic data to derive the measures of slope curvature needed to estimate tillage erosion rates. Here we present a method to derive the required measures of slope curvature from low resolution, but large scale, databases and use high resolution topographical datasets for several study areas in the UK to evaluate the reliability of the approach. On the basis of a tillage model and land‐use databases, we estimate the mean gross tillage erosion rates for the part of Europe covered by the CORINE database (6·5% of global cropland) and we obtained an average of 3·3 Mg ha–1 y–1, which corresponds to a sediment flux of 0·35 Pg y–1. Water erosion rates derived for the same area are of a similar magnitude. This redistribution of soil within agricultural fields substantially accelerates soil profile truncation and sediment burial in specific landscape positions and has a strong impact on medium‐term soil profile evolution. It is, therefore, clear that tillage erosion must be accounted for in regional assessments of sediment fluxes and in analyses that employ these in the analysis of land management strategies and biogeochemical cycles. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
14.
Advances in Earth Observation (EO) technology, particularly over the last two decades, have shown that soil moisture content (SMC) can be measured to some degree or other by all regions of the electromagnetic spectrum, and a variety of techniques have been proposed to facilitate this purpose.In this review we provide a synthesis of the efforts made during the last 20 years or so towards the estimation of surface SMC exploiting EO imagery, with a particular emphasis on retrievals from microwave sensors. Rather than replicating previous overview works, we provide a comprehensive and critical exploration of all the major approaches employed for retrieving SMC in a range of different global ecosystems. In this framework, we consider the newest techniques developed within optical and thermal infrared remote sensing, active and passive microwave domains, as well as assimilation or synergistic approaches. Future trends and prospects of EO for the accurate determination of SMC from space are subject to key challenges, some of which are identified and discussed within.It is evident from this review that there is potential for more accurate estimation of SMC exploiting EO technology, particularly so, by exploring the use of synergistic approaches between a variety of EO instruments. Given the importance of SMC in Earth’s land surface interactions and to a large range of applications, one can appreciate that its accurate estimation is critical in addressing key scientific and practical challenges in today’s world such as food security, sustainable planning and management of water resources. The launch of new, more sophisticated satellites strengthens the development of innovative research approaches and scientific inventions that will result in a range of pioneering and ground-breaking advancements in the retrievals of soil moisture from space. 相似文献
15.
Improving Seismic Resolution Through Array Processing Techniques 总被引：4，自引：0，他引：4
Seismic arrays, first introduced in the late 1950s to detect underground nuclear explosions, have helped to improve our knowledge about the structure of the Earth for the last 40 years. During these years, numerous array processing methods have been developed that use the high signal coherence and accurate timing of array data to generate high-resolution images of Earth structure. Here, we present an overview of resolution issues related to seismic array studies of Earth structure by first introducing basic array processing techniques and then discussing more advanced techniques applied to array data recently. The increase of seismic stations deployed in experiments or permanently in many regions of the globe allows a much denser sampling of the seismic wavefield. This dense sampling enables the adaptation of controlled source analysis techniques for the study of Earth structure using earthquakes with higher resolution than previously possible. Here we will discuss different migration methods of teleseismic data that use the incidence angle information of scattered arrivals to obtain images of Earth structure. Finally, we show data examples how these methods can be used to increase our knowledge of the structure of the Earth’s deep interior. 相似文献
16.
研究地质体的边缘位置是重、磁位场数据解释永恒的主题,也是其优势.最近几年,国内外利用重、磁位场进行地质体边缘识别研究的文章明显增多,但没有作者系统整理和对比各方法的优点和缺点,给使用者带来诸多不便.本文首先将现有重、磁位场边缘识别方法分为数理统计、数值计算和其他三大类,并概述了各类方法的研究现状;之后较详细总结了数值计算类中垂向导数、总水平导数、解析信号振幅、倾斜角、θ图这5种基本的边缘识别方法以及在这些基本方法之上发展起来的诸如倾斜角总水平导数、增强解析信号振幅等方法的研究历史和应用效果;并用理论模型对比了几种主要边缘识别方法的识别效果.通过以上总结、对比和分析,指出了重、磁位场边缘识别方法使用中需要注意的问题以及将来的研究重点及发展方向. 相似文献
17.
Determining sources, quantities and travel distances of eroding soil is of increasing importance given its impact on‐ and off‐site, the sediment‐associated transport of nutrients, metals and micro‐organisms and the ongoing need to provide data for soil erosion model development and validation. Many soil tracers have been developed; however, most comprise foreign materials, such as fluorescent beads and rare earth oxides, which cast doubts on the validity of tracing results given their different physical characteristics. To avoid these problems, we have investigated the potential of soil, which has been heated under reducing conditions to enhance its ferrimagnetic content, as a soil erosion tracer; while the technique has been used successfully to trace river sediment it has not been successfully applied to soil erosion studies. For a suite of 16 magnetic concentration‐dependent properties, values were found to be significantly greater, by at least one order of magnitude, after heating, both for the bulk soil and nine individual particle size fractions. Individual size fractions could be differentiated using two different magnetic properties, thus illustrating the technique's potential to provide information on particle size‐specific erosion. Soil box experiments demonstrated the potential for both in situ measurement of magnetic susceptibility and laboratory measurement of the magnetic properties of eroded sediment, to trace and quantify soil erosion. Thus, heated soil, with artificially‐enhanced ferrimagnetic properties, is successfully demonstrated to have great potential as a size‐specific, cost‐effective and representative soil erosion tracer. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
18.
Nicholas J. C. Doriean Andrew P. Brooks Peter R. Teasdale David T. Welsh William W. Bennett 《水文研究》2020,34(16):3426-3438
Gully erosion is a significant source of fine suspended sediment (<63 μm) and associated nutrient pollution to freshwater and marine waterways. Researchers, government agencies, and monitoring groups are currently using monitoring methods designed for streams and rivers (e.g., autosamplers, rising stage samplers, and turbidity loggers) to evaluate suspended sediment in gullies. This is potentially problematic because gullies have several hydrological features and monitoring operational challenges that differ to those of continually flowing streams and rivers (e.g., short and intense flows, high suspended sediment concentrations, and rapid scouring and aggradation). Here we present a laboratory and field-based assessment of the performance of common suspended sediment monitoring techniques applied to gullies. We also evaluate a recently-described method; the pumped active suspended sediment (PASS) sampler, which has been modified for monitoring suspended sediment in gully systems. Discrete autosampling provided data at high temporal resolution, however, it had poor collection efficiency (25 ± 10%) of coarser sediment particles (i.e., sand). Rising stage sampling, while robust and cost-effective, suffered from large amounts of condensation under field conditions (25–35% of sampler volume), due to harsh climatic conditions creating large diurnal temperature differences at the field site, thereby diluting sample concentrations and introducing additional measurement uncertainty. The turbidity logger exhibited a highly variable response when calibrated at each site with physically collected suspended sediment samples (R2 = 0.17–0.83), highlighting that this approach should be used with caution. The modified PASS sampler proved to be a reliable and representative measurement method for gully sediment water quality, however, the time-integrated nature of the method limits its temporal resolution compared to the other monitoring methods. We recommend monitoring suspended sediment in alluvial gully systems using a combination of complementary techniques (e.g., PASS and RS samplers) to account for the limitations associated with individual methods. 相似文献
19.
基于CUDA的三维数据并行可视化 总被引：1，自引：0，他引：1
科学计算可视化是发达国家20世纪80年代后期提出并发展起来的一个新的研究领域,它运用计算机图形学和图像处理技术,将三维数据转换为图形及图像在屏幕上显示出来并进行交互处理,主要包括面绘制和体绘制两种方法。光线投射算法是最经典的三维数据体绘制方法,图像质量较高,但计算时间较长,基于CUDA的编程技术利用GPU的多核并行运算功能可显著提高计算速度,实现大规模三维数据的实时可视化。 相似文献
20.
The measurement and prediction of soil erosion is important for understanding both natural and disturbed landscape systems. In particular numerical models of soil erosion are important tools for managing landscapes as well as understanding how they have evolved over time. Over the last 40 years a variety of methods have been used to determine rates of soil loss from a landscape and these can be loosely categorized into empirical and physically based models. Alternatively, physically based landscape evolution models (LEMs) have been developed that provide information on soil erosion rates at much longer decadal or centennial scales, over large spatial scales and examine how they may respond to environmental and climatic changes. Both soil erosion LEMs are interested in similar outcomes (landscape development and sediment delivery) yet have quite different methodologies and parameterizations. This paper applies a LEM (the CAESAR model) for the first time at time and space scales where soil erosion models have largely been used. It tests the ability of the LEM to predict soil erosion on a 30 m experimental plot on a trial rehabilitated landform in the Northern Territory, Australia. It then continues to discuss the synergies and differences between soil erosion and LEMs. The results demonstrate that once calibrated for the site hydrology, predicted suspended sediment and bedload yields from CAESAR show a close correspondence in both volume and timing of field measured data. The model also predicts, at decadal scales, sediment loads close to that of field measured data. Findings indicate that the small‐scale drainage network that forms within these erosion plots is an important control on the timing and magnitude of sediment delivery. Therefore, it is important to use models that can alter the DEM to reflect changing topography and drainage network as well as having a greater emphasis on channel processes. Copyright © 2012 John Wiley & Sons, Ltd. and Commonwealth of Australia 相似文献