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排序方式: 共有343条查询结果,搜索用时 515 毫秒
91.
基于ArcGIS的陕西山洪灾害易发程度区划 总被引:2,自引:0,他引:2
以ArcGIS为工作平台,利用1:25万数字地形地质图,以小流域为单元,对陕西全省山洪灾害,包括溪河洪水、滑坡和泥石流灾害在陕北风沙高原和黄土高原与陕南秦巴山地二个一级区划的基础上进行灾害易发程度二级区划,分为高易发、中易发和低易发三种级别18个区。 相似文献
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Kenneth E. Bencala Ronald E. Rathbun Alan P. Jackman Vance C. Kennedy Gary W. Zellweger Ronald J. Avanzino 《Journal of the American Water Resources Association》1983,19(6):943-950
ABSTRACT: A significant fraction of rhodamine WT dye was lost during a short term multitracer injection experiment in a mountain stream environment. The conservative anion chloride and the sorbing cation lithium were concurrently injected. In-stream rhodamine WT concentrations were as low as 45 percent of that expected, based on chloride data. Concentration data were available from shallow‘wells’dug near the stream course and from a seep of suspected return flow. Both rhodamine WT dye and lithium were nonconservative with respect to the conservative chloride, with rhodamine WT dye closely following the behavior of the sorbing lithium. Nonsorption and sorption mechanisms for rhodamine WT loss in a mountain stream were evaluated in laboratory experiments. Experiments evaluating nonsorption losses indicated minimal losses by such mechanisms. Laboratory experiments using sand and gravel size streambed sediments show an appreciable capacity for rhodamine WT sorption. The detection of tracers in the shallow wells and seep indicates interaction between the stream and the flow in the surrounding subsurface, intergravel water, system. The injected tracers had ample opportunity for intimate contact with materials shown in the laboratory experiments to be potentially sorptive. It is suggested that in the study stream system, interaction with streambed gravel was a significant mechanism for the attenuation of rhodamine WT dye (relative to chloride). 相似文献
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Burchard H. Heede 《Journal of the American Water Resources Association》1972,8(3):523-530
ABSTRACT The influence of a forest on the formation of steps in two small streams of the Colorado Rocky Mountains was studied. Steps provided by logs fallen across the channel added to flow energy reduction. The streams required additional gravel bars to adjust to slope. Average step length between logs and gravel bars was strongly related to channel gradient and median bed material size. Based on the average number of log steps per 50 feet of channel, an average of 116 percent of gravel bars were added at Fool Creek and 60 percent at Deadhorse Creek. The latter had 52 percent more logs in the channel and therefore required less bed material movement than the former. Although these are “rushing mountain streams,” most flow velocities ranged between 0.5 and 2.5 f.p.s. Exponents of a function relating rate of change of depth or velocity to discharge indicated that dynamic stream equilibrium was attained. Implications for forest management are that sanitation cuts (removal of dead and dying trees) would not be permissible where a stream is in dynamic equilibrium and bed material movement should be minimized. 相似文献
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作为国家级风景区的云台山蕴藏着丰富的生物资源,本文从生物资源的可持续开发和经济学角度出发,对合理利用云台山的生物资源作了初步探讨。 相似文献
97.
西部地区重大工程建设中的泥石流灾害 --兼论其与环境的互馈作用 总被引:2,自引:0,他引:2
在西部大开发过程中,许多重大工程建设涉及泥石流灾害的问题.讨论了工程活动、泥石流及山地环境之间的相互作用和影响.工程活动往往受到泥石流、山地环境的制约,同时它作为活的因素,又积极地影响着泥石流和山地环境,促使其产生次生演化,泥石流和山地环境的次生演化常会对工程活动产生次生制约.泥石流的发生会危及工程和人类的安全,破坏地表,破坏生态环境;人类工程活动若不遵守自然规律,过度向山地索取,必将导致山地环境退化和泥石流的广泛活动及频繁发生,甚至引起泥石流活动范围扩大和成灾规律改变. 相似文献
98.
FunctionalfeaturesoftheecosystemintheprimitivesubtropicalkarstmountainareaandtheirdegradationundertheinfluenceofhumanactivitiesInthepast 50years ,humanactivitieshavebroughtaboutthefollowinggreatchangesintheecosystemofthesubtropicalkarstmountainarea :(1 )FromtheinvestigationandanalysisofMaolanKarstNaturalConservationDistrictinGuizhouandNonggangKarstNaturalConservationDistrictinGuangxi,andtheresearchesonthechangesinthenaturalandgeographicalenvironmentinthekarstmountainareainRenhuaiCity ,Gu… 相似文献
99.
Who should manage protected areas in the Swedish mountain region? A survey approach to co-management
Zachrisson A 《Journal of environmental management》2008,87(1):154-164
This article investigates attitudes towards co-management of protected areas in Sweden, at the national, county and local level. In Sweden, protected areas are still primarily designated and managed hierarchically-a practice increasingly contested by people living close to them, including indigenous Sámi reindeer herders whose economic activities are located within protected areas. The general view could, on the contrary, be anticipated to be pro-state since protected areas are considered to be of national interest. For democratic reasons, however, the opinions of the whole population should be considered. In order to measure both local and general views, this study is based on a two-sample survey of 8868 respondents. The objectives are to map and explain attitudes regarding who should manage protected areas in Sweden, and to test the usefulness of a multi-level quantitative method. Such an approach is unusual in co-management literature that is empirically mainly based on local case studies. The explanatory ambition sets out to test three hypotheses drawn from common-pool resource theory; resource dependency, common understanding, and trust. Perhaps surprisingly, the results show that a considerable majority of the respondents (at all levels) wish to see self- or co-management. All three hypotheses are important to understand attitudes toward the management of protected areas, but not always in the way that the theory anticipates. 相似文献
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