Analysis of dune erosion processes in large-scale flume experiments   总被引：1，自引：0，他引：1  

J.S.M. van Thiel de Vries  M.R.A. van Gent  D.J.R. Walstra  A.J.H.M. Reniers   《Coastal Engineering》2008,55(12):1028-1040

Large-scale physical model tests were conducted with different wave periods to examine the physical processes driving dune erosion. The model tests have been carried out in a flume (2DV) with a sandy dune exposed to extreme surge and wave conditions [Van Gent, M.R.A., Van Thiel de Vries, J.S.M., Coeveld, E.M., De Vroeg, J.H. and Van de Graaff, J., 2008. Large-scale dune erosion tests to study the effect of wave periods. Coastal Engineering. doi:10.1016/j.coastaleng.2008.04.003.]. Detailed measurements in time and space of water pressure, flow velocities and sediment concentrations were performed in the near shore area. The data revealed that both short- and long waves are important to inner surf hydrodynamics. Depth averaged flows are directed offshore and increase towards the shore line. The corresponding mean sediment concentrations rise sharply towards the dune face (up to 50 g/l near the bed). The strong increase in the mean sediment concentration towards the dune face correlates well with the maximum wave surface slope which in turn is coupled to both the pressure gradient and the near-bed wave-breaking induced turbulence. Analysis shows that the pressure gradient is only partially coupled to the flow acceleration suggesting that the latter cannot always be used as a proxy for the first. Weak correlation is obtained with the near-bed flows related to the bed shear stress. Tests with a larger wave period resulted in a larger dune erosion volume. During these tests more wave energy (combined incident and infragravity waves) reached the dune face, but more importantly, this wave energy is dissipated by fewer waves resulting in more intense wave breakers and steeper wave fronts. It is therefore expected that the wave-breaking induced near-bed turbulence increases resulting in significantly higher (O(100%)) mean sediment concentrations. In addition the mean flow velocities are comparable, yielding a substantially larger offshore directed sediment transport capacity. This increase in offshore directed transport is only partially compensated by a concurrent increase in the wave related onshore transport capacity associated with intrawave processes, resulting in a net increase in the dune erosion rate.  相似文献   

Mapping seascapes of international environmental arrangements in the Coral Triangle     

Pedro Fidelman  Julia A. Ekstrom 《Marine Policy》2012

The Coral Triangle Initiative on Coral Reefs, Fisheries and Food Security (CTI), adopted recently in response to the degradation of coastal and marine environments in the Southeast Asia-Pacific’s Coral Triangle, emphasises the need for using existing international and regional fora to promote implementation. Large-scale marine initiatives, including the CTI, very often must contend with a remarkably complex institutional system. This raises the question of whether and how such complexity can be conducive to marine resources management. To answer this question, this paper aims to better understand the governance context in which the CTI was established (i.e., map governance fragmentation/complexity), and explore how such a context may support the implementation of the CTI goals (i.e., examine normative interplay). To conduct this examination, it uses an objective method that allows users to view and explore institutional arrangements through a network approach. By documenting the system of existing institutions in the Coral Triangle, the study shows that the Coral Triangle governance system is illustrative of those of international environmental governance. It involves multiple policy domains, and features different institutional arrangements and variability in terms of geographical scope and main subject matter. Such a system is complex and fragmented, marked by jurisdiction and functional overlaps. The paper suggests interplay management, such as inter-institutional learning and enhancing institutional synergy, as a promising process to promote inter-institutional coordination.  相似文献   

地磁场大尺度变化特征分析     

黄建平  丁鉴海  余素荣  申旭辉  杜则澄 《地震》2008,28(3):49-54

利用20世纪50年代至21世纪初中国出版的7次《中国地磁图》资料, 根据构造磁效应和震磁相关性研究了地质构造(构造微动态)、 强震活动与中国地磁图等变线每个不同年代动态演化图像的关系, 从大区域尺度的角度分析了中国大陆及其邻近地区的7级以上强震与地磁分量等变线轴线方向的变化特征。  相似文献   

International Comparisons of Large-scale Natural Disasters Damage and Loss Assessment: Based on “Statistical System of Large-scale Natural Disasters” and PDNA     

Zhou Hongjian  Wang Xi 《地球科学进展》2017,32(10):1030-1038

In June 2014, the Ministry of Civil Affairs, the National Disaster Reduction Committee Office issued the “Statistical System of Large-scale Natural Disasters Damage and Loss” (SSLNDD&L), in which the standard statistical content and index were explored. Examined by several major natural disasters in recent years, such as Ludian earthquake (Ms 6.5) on 3 August 2014, Nepal earthquake (Ms 8.1) on 25 April 2015, SSLNDD&L provided good basis for post disaster recovery and reconstruction planning, but the direct guidance of reconstruction planning was still limited. Post Disaster Needs Assessment (PDNA), the mainstream of the international disaster needs assessment system, was taken as the main research object, and the content and characteristics of PDNA system were analyzed in detail. The comparison analysis was made from the objectives, contents and index system, evaluation methodology, evaluation parameters between the SSLNDD&L and PDNA. In the future, expanding and increasing various industries and local evaluation index focusing on recovery and reconstruction needs, optimizing the disaster assessment parameter database used for the multi-user such as the Central-Province-County scale, supporting the preparation of technical standard optimization evaluation process to form a complete assessment technical specification should be put forward as the future development of the SSLNDD&L. It is of great practical significance to optimize and perfect the content and index of the SSLNDD&L to better serve the decision making of the recovery and reconstruction after large-scale disasters, and to achieve international standards on large-scale disaster damage & loss statistics and assessment in China.  相似文献   

Why people matter in ocean governance: Incorporating human dimensions into large-scale marine protected areas     

《Marine Policy》2017

Large-scale marine protected areas (LSMPAs) are rapidly increasing. Due to their sheer size, complex socio-political realities, and distinct local cultural perspectives and economic needs, implementing and managing LSMPAs successfully creates a number of human dimensions challenges. It is timely and important to explore the human dimensions of LSMPAs. This paper draws on the results of a global “Think Tank on the Human Dimensions of Large Scale Marine Protected Areas” involving 125 people from 17 countries, including representatives from government agencies, non-governmental organizations, academia, professionals, industry, cultural/indigenous leaders and LSMPA site managers. The overarching goal of this effort was to be proactive in understanding the issues and developing best management practices and a research agenda that address the human dimensions of LSMPAs. Identified best management practices for the human dimensions of LSMPAs included: integration of culture and traditions, effective public and stakeholder engagement, maintenance of livelihoods and wellbeing, promotion of economic sustainability, conflict management and resolution, transparency and matching institutions, legitimate and appropriate governance, and social justice and empowerment. A shared human dimensions research agenda was developed that included priority topics under the themes of scoping human dimensions, governance, politics, social and economic outcomes, and culture and tradition. The authors discuss future directions in researching and incorporating human dimensions into LSMPAs design and management, reflect on this global effort to co-produce knowledge and re-orient practice on the human dimensions of LSMPAs, and invite others to join a nascent community of practice on the human dimensions of large-scale marine conservation.  相似文献   

地震前兆与短临预报探索   总被引：8，自引：2，他引：6  

丁鉴海  余素荣  肖武军 《地震》2003,23(3):43-50

针对地震短临预报面临的科学问题,分析研究了地震前兆(近场前兆、远场前兆和大尺度动态前兆)预报地震的物理基础;总结了地震短临前兆时空演化特征和同步耦合现象。高空技术在地震前兆观测中的应用将有利于短临预报实践与探索。  相似文献   

利用等高线数据制作大规模3D遥感影像   总被引：1，自引：0，他引：1  

李远华  姜琦刚  张秉仁 《国土资源遥感》2005,16(2):76-79

把图像数据库的建库思想引入到大规模3D遥感影像的制作中。在此基础上，提出利用合并分割法制作大规模3D遥感影像。将经 过特殊处理的等高线数据制成小块DEM，采用两种模式将遥感影像与这些DEM进行纹理映射，从而制作成大规模3D遥感影像。这种方法提 高了大规模3D遥感影像的制作水平，进一步增强了大规模3D遥感影像的信息量与实用性。  相似文献   

Response of 1 × 2 pile group under eccentric lateral loading     

《Computers and Geotechnics》2014

A large scale model test of a 1 × 2 pile group was conducted in silts to investigate its behavior under eccentric lateral loading. The model pile group consisted of two well instrumented steel piles and was installed in a large soil tank with a close spacing of three-pile diameters on centers. The test results revealed that the eccentricity of lateral loads had limited effect on the overall performances of the 1 × 2 pile group, but significantly contributed to the unevenness of internal forces of the individual piles. The coupling effect between the lateral deflection and torque gave rise to the substantial increase in the torsional resistance of individual piles within the group, comparing to that of a torsionally loaded single pile. The contribution provided by the torsional resistances of individual piles in resisting the external torque continually decreased when the applied lateral load increased. In addition, a three-dimensional finite-element analysis for the pile group was performed and the simulated response was found to be in good agreement with the measured test results. Based on the same model, more cases with different loading conditions were further analyzed. It could be concluded from the analyses that the layout of individual piles within the group obviously affected the behavior of the 1 × 2 pile group under eccentric lateral loads.  相似文献   

强度再生效应在大型滑坡稳定性评价中的应用   总被引：2，自引：2，他引：0  

任光明聂德新  韩爱果 《山地学报》2000,18(Z1):60-64

通过大量现场调查、室内外试验及计算等研究的基础上,揭示了只要具有一定滑体厚度的滑带土,沿滑面具有强度再生效应。利用该观点,结合滑坡破坏特征,滑带土的物质组成及其赋存环境条件,对滑面强度参数的选取及其对稳定性的影响进行了详细探讨,该研究为滑坡滑面强度参数的选取提供了重要的理论依据。  相似文献   

西北太平洋热带气旋活动影响区域大尺度环流的数值模拟研究          下载免费PDF全文

陈宪  钟中  江静  孙源 《地球物理学报》2019,62(2):489-498

本文利用"模式手术"方法研究了西北太平洋热带气旋(TC)对东亚—西北太平洋区域大尺度环流的影响.结果表明,夏季频繁的西北太平洋TC活动导致东亚夏季风增强,季风槽加深;西太平洋副热带高压东退,位置偏北;东亚副热带高空急流强度增强,北太平洋(东亚大陆)上急流轴偏北(偏南);热带地区(副热带地区)的对流层中低层出现异常上升气流(下沉气流),并且从低纬向高纬呈现异常上升气流和异常下沉气流交替分布特征.在中国东南沿海,TC降水导致夏季降水量明显增加;而在长江中下游和华北地区,TC活动引起的异常下沉气流使夏季降水量显著减少.因此,夏季西北太平洋TC活动对东亚—西北太平洋区域气候有显著影响.  相似文献