Soil saturation index of salt marshes subjected to spring‐neap tides: a new variable for describing marsh soil aeration condition     

Pei Xin  Badin Gibbes  Ling Li  Zhiyao Song  David Lockington 《水文研究》2010,24(18):2564-2577

Organized spatial distribution of plants (plant zonation) in salt marshes has been linked to the soil aeration condition in the rhizosphere through simplistic tidal inundation parameters. Here, a soil saturation index (ratio of saturation period to tidal period at a soil depth) is introduced to describe the soil aeration condition. This new index captures the effects of not only the tidal inundation period and frequency but also the flow dynamics of groundwater in the marsh soil. One‐dimensional numerical models based on saturated flow with the Boussinesq approximations and a two‐dimensional variably saturated flow model were developed to explore the behaviour of this new soil aeration variable under the influence of spring‐neap tides. Simulations revealed two characteristic zones of soil aeration across the salt marsh: a relatively well aerated near‐creek zone and a poorly aerated interior zone. In the near‐creek zone, soils undergo periodic wetting and drying as the groundwater table fluctuates throughout the spring‐neap cycle. In the interior, the soil remains largely water saturated except for neap tide periods when limited drainage occurs. Although such a change of soil aeration condition has been observed in previous numerical simulations, the soil saturation index provides a clear delineation of the zones that are separated by an ‘inflexion point’ on the averaged index curve. The results show how the saturation index represents the effects of soil properties, tidal parameters and marsh platform elevation on marsh soil aeration. Simulations of these combined effects have not been possible with traditional tidal inundation parameters. The saturation index can be easily derived using relatively simple models based on five non‐dimensional variables. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Perceptions and responses to climate policy risks among California farmers     

Meredith T. Niles  Mark Lubell  Van R. Haden 《Global Environmental Change》2013,23(6):1752-1760

This paper considers how farmers perceive and respond to climate change policy risks, and suggests that understanding these risk responses is as important as understanding responses to biophysical climate change impacts. Based on a survey of 162 farmers in California, we test three hypotheses regarding climate policy risk: (1) that perceived climate change risks will have a direct impact on farmer's responses to climate policy risks, (2) that previous climate change experiences will influence farmer's climate change perceptions and climate policy risk responses, and (3) that past experiences with environmental policies will more strongly affect a farmer's climate change beliefs, risks, and climate policy risk responses. Using a structural equation model we find support for all three hypotheses and furthermore show that farmers’ negative past policy experiences do not make them less likely to respond to climate policy risks through participation in a government incentive program. We discuss how future research and climate policies can be structured to garner greater agricultural participation. This work highlights that understanding climate policy risk responses and other social, economic and policy perspectives is a vital component of understanding climate change beliefs, risks and behaviors and should be more thoroughly considered in future work.  相似文献   

The role of social norms in climate adaptation: Mediating risk perception and flood insurance purchase     

Alex Y. Lo 《Global Environmental Change》2013,23(5):1249-1257

Flood insurance plays an important role in climate adaptation by recovering insured losses in the event of catastrophic flooding. Voluntary adoption of flood insurance has been seen as a function of risk perception that is shaped by social norms. This paper attempts to clarify the relationship between these factors. It is based on a household survey conducted in the eastern cities of Australia and involving a total of 501 randomly selected residents. Results of a path analysis show that the likelihood of having flood insurance cover was associated with perceived social norms, but not perceived flood risk. In addition, perceived norms and risk were statistically related to each other. It is concluded that social norms played a mediating role between insuring decision and risk perception. Risk perception might influence the insuring decision indirectly through shaping perception of social norms. This implies that adaptive behaviour is not necessarily a function of risk perception, but an outcome of its impacts upon the ways in which the individuals situate themselves in their social circles or the society. There is a feedback process in which individual perceptions of risk manifest as both a cause and effect, shaping and being shaped by the socio-cultural context.  相似文献   

The anatomy of a disaster, an overview of Hurricane Katrina and New Orleans     

Lewis E. Link 《Ocean Engineering》2010,37(1):4-12

Hurricane Katrina created the one of the worst natural disaster in the history of the United States, resulting in over 1600 fatalities and $30B in direct economic losses in southern Louisiana. The Louisiana and Mississippi coastlines experienced the highest surge level recorded in North America and Katrina-generated waves in the Gulf of Mexico that equaled the highest previously measured by NOAA buoys. What happened in New Orleans epitomizes the risk of living below sea level in a coastal city, depending on structures that were the result of considerable compromise and piecemeal funding and construction. The Interagency Performance Evaluation Task Force was established to examine the performance of the New Orleans and southeast Louisiana hurricane protection system and provide real-time input to the repairs and rebuilding of the system. In addition to this atypical just-in-time forensic analysis, the task force examined the risk of living in New Orleans prior to and following the repairs to the hurricane protection system. Much of the forensic analysis depended on modeling and simulation of hurricane surge and waves. With virtually all measurement instruments swept away by Katrina, only models and high-water marks were available to recreate the conditions that the structures experienced during the storm. Because of the complexities of the region and the processes involved, simulation of hurricane surge and waves required many fresh ideas and new approaches and these topics, along with new concepts for future planning and design, are the focus of this special issue. Yet, the need to influence the repair and rebuilding of the damaged structures prior to the next hurricane season (roughly 9 months) dictated using existing computational tools that were ready to go. The same modeling and simulation approach was put to work to define the surge and wave hazard New Orleans faces for the future. To put this important body of work in context, this paper provides a broad overview of the entire scope of work of the task force and summarizes its principal findings.  相似文献   

Reconstructing tsunami run-up from the characteristics of tsunami deposits on the Thai Andaman Coast     

Chanchai Srisutam  Jean-Frank Wagner 《Coastal Engineering》2010

Tsunamis can leave deposits on the land surface they inundate. The characteristics of tsunami deposits can be used to calculate tsunami run-up height and velocity. This paper presents a reconstruction of tsunami run-up from tsunami deposit characteristics in a simple mathematical model. The model is modified and applied to reconstruct tsunami run-ups at Ao Kheuy beach and Khuk Khak beach, Phangnga province, Thailand. The input parameters are grain-size and maximum run-up distance of the sediment. The reconstructed run-up heights are 4.16–4.91 m at Ao Kheuy beach and 5.43–9.46 m at Khuk Khak beach. The estimated run-up velocities (maximum velocity) at the still water level are 12.78–19.21 m/s. In the area located 70–140 m inland to the end of run-up inundation, estimated mean run-up velocities decrease from approximately 1.93 m/s to 0 m/s. Reasonably good agreements are found between reconstructed and observed run-up heights. The tsunami run-up height and velocity can be used for risk assessment and coastal development programs in the tsunami affected area. The results show that the area from 0 to 140 m inland was flooded by high velocity run-ups and those run-up energies were dissipated mainly in this area. The area should be designated as either an area where settlement is not permitted or an area where effective protection is provided, for example with flood barriers or forest.  相似文献   

Risk identification and perception in the fisheries sector: Comparisons between the Faroes,Greece, Iceland and UK     

Diana Tingley  Jóhann Ásmundsson  Edward Borodzicz  Alexis Conides  Ben Drakeford  Ingi Rúnar Eðvarðsson  Dennis Holm  Kostas Kapiris  Sakari Kuikka  Bogi Mortensen 《Marine Policy》2010

This paper presents the findings of risk identification and risk perception research conducted in relation to the fisheries systems of four distinct and diverse European countries: Faroes, Iceland, Greece and the UK. Risk research traditionally attempts to quantify the potential threat or consequences from a range of risk events or hazards. This research, however, adopted a social sciences perspective and so assumed that a risk event or hazard can mean different things to different people and that these perceptions are also context and culturally dependent. Risk perceptions were examined and risk registers developed in each country for a range of stakeholder groups. A ‘mental modelling’ approach was adopted in a series of qualitative interviews. Findings were examined in terms of a wide range of psychological, social and cultural risk theories. Differences in risk perceptions were noted between stakeholder groups and countries and contextual influences were examined such as the widely differing fisheries management systems used in each country. This research provides one of the first attempts to systematically evaluate risks and perceptions across a range of fisheries-systems. The findings support social science theories which argue that risk is a subjective, as opposed to objective, concept and that this subjectivity will therefore affect our attempts to assess and manage those hazards we think we can potentially influence or control.  相似文献   

四川省小麦条锈病春季流行的农业气候风险区划     

游超  肖天贵  李金建  张菡 《成都信息工程学院学报》2012,27(4):405-411

针对当前从气象风险角度开展小麦条锈病与气象关系研究甚少的状况,从农业气象灾害风险分析理论出发,采用相关分析、层次分析和极差正规化等方法,建立了包含气候条件和寄主存在数量两个环境因子的四川省小麦条锈病春季流行农业气候风险模型,并划分了高、中、低风险等级的指标.在此基础上,利用GIS技术对四川省小麦条锈病春季流行的农业气候风险进行了区划.结果表明,四川省的川西高原地区、川西南山地和盆地西南部是小麦条锈病春季流行低风险区,盆地大部地区是中、高风险的集中区.区划结果为进一步做好四川省小麦条锈病的分区预报和综合防治方面提供科学依据.  相似文献   

Whitefish wars: Pangasius, politics and consumer confusion in Europe   总被引：1，自引：0，他引：1  

David C. Little  Simon R. BushBen Belton  Nguyen Thanh PhuongJames A. Young  Francis J. Murray 《Marine Policy》2012,36(3):738-745

Rapid growth in production of the farmed Vietnamese whitefish pangasius and its trade with the European Union has provoked criticism of the fish's environmental, social and safety credentials by actors including WWF and Members of the European Parliament and associated negative media coverage. This paper reviews the range of claims communicated about pangasius (identified as a form of mass mediated risk governance), in light of scientific evidence and analysis of data from the EU's Rapid Alert System for Food and Feeds food safety notification system for imported seafood. This analysis shows pangasius to be generally safe, environmentally benign and beneficial for actors along the international value chains that characterise the trade. The case is made that increasingly politicised debates in Europe around risk and uncertainty are potentially counterproductive for EU seafood security and European aquaculture industry, and that the trade in pangasius can contribute to sustainable seafood consumption in a number of ways. Transparent evidence-based assessment and systems for communicating complex issues of risk for products such as pangasius are required in order to support continuance of fair and mutually beneficial trade.  相似文献   

黑龙江省草地螟第三暴发周期气候特征及风险概率          下载免费PDF全文

陈莉  方丽娟  张少锋  陈红  王承伟  安晓存  张洪文  杜岩  汪喜江 《气象与环境学报》2011,27(3):67-72

1996年以来黑龙江省草地螟第三暴发周期持续至今,危害日益加重。以1959-2008年黑龙江省28个国家基本站的气象资料以及草地螟暴发期等资料为基础,分析了黑龙江省草地第三暴发周期的气候特征及风险概率。结果表明：近50 a来,黑龙江省年平均气温、年平均最低气温呈显著的上升趋势,通过0.001显著性检验,气温在1988年前后出现突变。其它要素,如降水量、降水日数、风速、日照时数均呈减少趋势,但只有年日照时数和年平均风速的减少趋势通过了显著性检验。哈尔滨草地螟始发日期与同期平均气温、日最高气温、最低气温、最小相对湿度关系密切,应该是本地越冬虫源春季羽化对气温、相对湿度敏感性较高;同时始见日期与最大风速的风向相关较为密切,可能是由于外地虫源对风向敏感性较高。通过对黑龙江省草地螟高峰期首日的风险概率分析,得到黑龙江省草地螟高峰期出现在5月最后一个候的风险概率为23.6%;出现在6月上旬的风险概率为36.6%;出现在6月中旬的风险概率为24%;出现在6月下旬的风险概率为14.4%。  相似文献   

新疆西克尔地区下奥陶统鹰山组岩溶分带性研究   总被引：1，自引：0，他引：1  

冯海霞  李树新  陈冬梅  和虎  周彩虹 《现代地质》2010,24(6):1065-1071

塔里木盆地岩溶缝洞型储层作为重要的油气储层备受关注,而目前预测此类型储层的方法较有限。在新疆伽什县西克尔野外露头区地表岩溶现象丰富,志留系地层以填平补齐的方式充填在一系列的溶沟和溶槽中,部分洼地中还有志留系地层残留,表明该区发育加里东中期岩溶。在本区岩溶古地貌的基础上,基于排泄基准面的分析,划分出3级岩溶台面并对应发育3期岩溶。据现代地貌学和岩溶学理论,按照水动力条件的不同并结合本区岩溶发育特征,运用岩溶旋回的观点将第二期岩溶剖面分为表层岩溶带、垂直渗滤带和水平潜流带,认识到西克尔地区古岩溶地下水发育规律及洞穴发育程度。构造运动是垂向岩溶分带性的主控因素;因此,在大的构造背景的前提下,可以有效地预测巴楚地区的缝洞型储层。  相似文献