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2010年7月河南省栾川县连续降雨达半月之久,24日又突降大暴雨,导致县境内暴发区域性泥石流(简称“7·24”暴雨泥石流),全县14个乡镇普遍受灾,死亡68人、失踪21人,直接经济损失约19.8亿元.为给当地政府提供合理的泥石流防治建议,对栾川县“7·24”暴雨泥石流中31个灾害点进行了野外调查并进行了工程地质分析.调查发现,此次栾川县暴雨泥石流类型丰富,泥流、泥石流及水石流均有发育;地貌上看,泥石流多属于坡面型,水石流基本上为沟谷型.同时,因栾川县采矿业发达,矿渣型泥石流发育十分典型,且大多为尾矿坝溃决所致.鉴于栾川“7·24”暴雨泥石流范围大、类型多的特点,若按规范分类则很难提供针对性的泥石流防治建议,而若按启动模式分类则能在防治建议中对症下药.因此结合前人研究成果和此次调查分析结论,按启动模式将栾川县泥石流划分为7种类型,分别为:沟道拖拽-溃决型、沟道冲切-崩滑型、冲击液化型、坡面崩滑型、坡面冲刷-沟道启动型、尾矿溃决型及其复合型.同时,对7种类型中典型泥石流点的启动模式进行了详细分析. 相似文献
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2013-07-10四川省汶川县岷江干流沿线群发性泥石流(简称"7·10"泥石流)对都(江堰)汶(川)公路(G213线)和都汶高速桥梁、路基、隧道造成重大破坏,G213线和都汶高速共16处中断,尤以G213线破坏严重。苏坡店沟毛家湾大桥是"7·10"泥石流冲毁桥梁、造成交通中断的典型模式。在野外调查、采样和数据分析的基础上,确定苏坡店"7·10"泥石流的重度18.5 k N/m2,流速9.3 m/s,峰值流量232.5 m3/s,剪应力13.3 k Pa。高速、大流量泥石流沿陡峻的主沟排泄过程中,强烈侵蚀和起动沟床,左侧桥基基础强烈淘蚀悬空,形成1.65 m宽的临空面;在泥石流的作用下,桥基沿主沟发生5 m位移变形,导致桥梁垮塌,交通中断。经计算,桥墩下部土体支撑面积为42.8 m2,基底最大压力达545 k Pa,大于规范规定允许承载力,并且从抗倾覆角度计算也超出了规范要求,处于失稳状态。针对跨越高陡泥石流沟的桥梁,建议加强泥石流沟排导、预设足够的桥下净空高度、增加桥梁防护等措施来减少桥梁的破坏。 相似文献
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2011-06-06贵州省望谟县北部普降百年一遇暴雨,引发大规模群发性泥石流灾害,给当地居民生活及交通造成严重损害。其中以打蒿沟泥石流灾害尤为突出,该流域内支沟发育,沟床比降相对较缓,但陡峻的岸坡和较大的汇水面积为泥石流的发生提供了良好的水动力条件。打蒿沟地处碎屑岩发育地区,松散堆积体较厚,并受岸坡坡度影响浅层滑坡发育,现场调查共19处。另外流域内人为破坏严重,村民沿沟垒筑大量梯田也为泥石流活动提供了特殊的人工物源。通过对其4条支沟的研究发现,泥石流形成特征并不一致,其中坡度较缓的2#支沟浅层滑坡发育,为浅层滑坡型泥石流;而坡度较陡的其他3条支沟浅层滑坡发育较少,以沟床物源为主,为沟床启动型泥石流。通过对沟道两侧斜坡坡度的调查统计和分级得出流域内25°～40°的岸坡最易形成浅层滑坡,且当山坡呈上缓下陡时,更利于滑坡的形成。打蒿沟在强降雨条件下依然可暴发泥石流,规模会有所减小,但在类似2011-06-06这类稀遇暴雨作用下仍可造成较大危害。 相似文献
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第四纪泥石流蕴含了关于河流地貌演化、新构造运动和气候变化的丰富信息。对发育于云南省德钦白马里你共卡雪山垭口海拔2700 m,年代为2.48~1.54MaBP的古泥石流堆积物进行了系统研究。研究表明:泥石流堆积体呈扇状分布,其沉积构造有叠瓦构造、砾石支撑-叠置构造和石线构造,以稀性泥石流为主。古泥石流夹含的红色古风化壳由古泥石流堆积物风化形成,属于弱风化的红化土类型,反映了温和较湿的气候特征。主量化学元素和孢粉分析表明,古泥石流形成的早更新世时期金沙江河谷地区气候温和湿润,远比现在气候温暖。青藏高原东南缘白马雪山剥蚀面上发育的巨厚层古泥石流扇形堆积体的发现,表明青藏高原东南缘在早更新世早期已经有稀性泥石流出现,青藏高原快速隆升、夏季风加强和暴雨形式降水出现是该区早更新世泥石流发育的重要动力学因素。依据现代红化土的发育条件,估算自~1.54Ma以来青藏高原东南缘白马雪山一带的地表隆升幅度达1300m。 相似文献
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2003年中国西南山区典型灾害性暴雨泥石流运动堆积特征 总被引：19，自引：7，他引：12
2003年发生在中国西南山区的大规模泥石流为典型的灾害性暴雨泥石流,造成了巨大的经济损失和人员伤亡。作者实地考察其中7条造成较大损失的典型泥石流沟,分析得出,这一地区泥石流的流速一般都比较大,流量变化也比较大,流量大小与流域面积相关,总体上流量随流域面积的增大有增加的趋势,但流量与面积并非正相关关系。同时,在这些流域的堆积物的组成中,粗大颗粒极多,最大的颗粒普遍比较大,另外漂石含量很高。粘性泥石流中砾石含量相对于中国西南山区其它粘性泥石流较低,砂砾含量相对较高,大部分泥石流堆积物的有效粒径(d10)。 相似文献
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强震区都江堰市龙池镇泥石流物源的遥感动态演变 总被引：1，自引：0，他引：1
"5·12"汶川大地震导致大量碎屑物质在陡峭的斜坡积累,当遇到强降雨时极易成为泥石流的物源地。2010-08-13一场暴雨导致都江堰市48条沟同时暴发泥石流。选择汶川地震高烈度区的龙池镇境内12条泥石流沟为研究区,采用基于遥感的手段研究"5·12"震前、震后、"8·13"暴雨后泥石流流域内物源的变化特征。强震后研究区泥石流流域物源重要变化是大量的崩滑体被诱发。暴雨后研究区泥石流流域物源变化是震后产生的滑坡产生了不同程度的滑移扩张。通过开展遥感解译,结合野外调查,详细论述了研究区泥石流物源的变化情况。将"5·12"汶川地震前(2007-09-18)经波段融合后15 m的TM影像与地震后(2009-02-10)的2.5 m全色SPOT5影像相比较,发现泥石流流域内的滑坡体积由震前的0.86×106m3增加到地震后的42.30×106m3,即汶川高烈度区经过地震后新增滑坡体积达4 835.94%。而经过暴雨后(2011年7月)的0.5 m全色波段WorldView-2影像,泥石流流域内的滑坡体积又增加到68.85×106m3,即研究区经过暴雨后新增滑坡体积达62.76%。研究结果表明,汶川震区在地震及暴雨下物源量猛增,导致泥石流暴发的概率很高。 相似文献
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四川省绵竹市清平乡地处绵远河上游,位于龙门山腹心地带,属2008-05-12汶川8级地震的极重灾区,地震烈度达Ⅹ度,由地震引起的次生山地灾害极为发育。受地震激发,在绵远河左侧支流文家沟内形成了一个巨型滑坡——文家沟滑坡,其堆积物体积约达5×107m3,成为形成泥石流的松散固体物质来源。此后,在2008—2010年的汛期,受暴雨作用,文家沟先后暴发了5次大规模和特大规模的泥石流灾害,其中以 相似文献
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泥石流物源、流体和堆积物的颗粒分布满足P(D)=CD~(-μ)exp(-D/Dc),其中参数C,μ和D_c由传统的粒径分布特征决定。μ随细颗粒(特别是粘粒)含量的增大而增大,D_c刻画粒径的范围,且随粗粒含量而增大。蒋家沟泥石流的观测表明,同一场泥石流包含着数十到数百个不同性质、流态和规模的阵流。阵流的涨落和多样性是与流体的颗粒组成密切相关的。一定的颗粒组成对应着一定的饱和颗粒浓度,决定一定的饱和流体状态。阵流的涨落,是在没有达到饱和状态时的随机运动的状态。阵流涨落随D_c增大而趋于平缓;当流体达到饱和态时,阵流达到最大的流深、流速和流量,且与颗分参数(μ,D_c)具有幂函数关系。运用本文的方法,可根据颗分参数来预估泥石流的性质和规模。 相似文献
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Ibipo Johnston-Anumonwo 《The Professional geographer》1997,49(3):306-317
This study investigates whether women's short commutes should be interpreted as constrained or convenient work trips by examining how race, gender, travel mode, occupation, residential location, workplace location, and Inc.ome affect commuting time. The analysis is restricted to a sample of European American and African American male and female workers residing in Buffalo, New York, and the surrounding county using data drawn from the Public Use Microdata Samples of the 1990 U.S. census. Given the pervasive gender wage gap, women unsurprisingly have more compromised (short commutes to low-Inc.ome jobs) work trips than do men. Multivariate analysis reveals that among those who reverse commute to suburban locations, African American women have the longest work trips. 相似文献
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《The Professional geographer》2013,65(3):306-317
This study investigates whether women's short commutes should be interpreted as constrained or convenient work trips by examining how race, gender, travel mode, occupation, residential location, workplace location, and Inc.ome affect commuting time. The analysis is restricted to a sample of European American and African American male and female workers residing in Buffalo, New York, and the surrounding county using data drawn from the Public Use Microdata Samples of the 1990 U.S. census. Given the pervasive gender wage gap, women unsurprisingly have more compromised (short commutes to low-Inc.ome jobs) work trips than do men. Multivariate analysis reveals that among those who reverse commute to suburban locations, African American women have the longest work trips. 相似文献
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Spatial relationships among species, above-ground biomass, N, and P in degraded grasslands in Ordos Plateau, northwestern China 总被引：6，自引：0，他引：6
We chose five communities, representing a mild to severe gradient of grassland desertification in a semi-arid area of Ordos Plateau, northwestern China, to explore the spatial relationships among plant species, above-ground biomass (AGB), and plant nutrients (N and P). Community 1 (C1) was dominated by Stipa bungeana; Community 2 (C2) by a mix of S. bungeana and the shrub Artemisia ordosica; Community 3 (C3) by A. ordosica; Community 4 (C4) by a mix of Cynanchum komarovii and C. komorovii; and Community 5 (C5) by C. komorovii. Quantitative methods, including geostatistics, were used to compare community composition, structure, and indicators of ecosystem function (i.e. AGB, plant N and P) in five 16-m2 plots. The highest AGB, plant nitrogen (N) and plant phosphorus (P) were found in lightly degraded community C2. With increasing desertification effects from C3 to C5, the AGB, N, and P decreased significantly while plant density remained unchanged. The spatial variations of AGB were higher in shrub-dominated communities (C1 and C5) than in grass-dominated communities (C2–C4). Strong spatial relationships were detected within and among the communities, with stronger relationships between AGB and density than between AGB and species richness. Spatial patterns of plant N and P were different from those of AGB, reflecting different N and P contents of individual plants and different species that can redistribute soil resources in these communities. The AGB was positively correlated with soil nutrients (TOC, TN, TP, and IN), except for soil AP. We concluded that several specific aspects of ecosystem properties were directly associated with the conversion of the grass and shrub “functional types” in these degraded grasslands. 相似文献
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Ahmed M. El-Makky 《Natural Resources Research》2011,20(3):157-176
A prospective lithochemical survey (scale 1:50,000) was carried out at the Um Garayat gold mine area within the central wadi Allaqi shear zone. The metavolcanic samples were analyzed for Ti, P, Zr, Nb, Y, La, Nd, and Ce. The background and threshold values were determined using histograms, box-plots, and Q-mode cluster analysis. Discriminant analysis classifies the samples into four groups: Group 1 (Au mineralization) characterizes Phase III of the hydrothermal stage; Group 2 (Cu?CAu mineralization) characterizes Phases I and II; Groups 3 and 4 comprise the least altered samples. Cubic trend surface and residual maps display groups of elements: (P, Ti, Zr), (Nb, Y), and (La, Nd, Ce) each group has similar areal distribution pattern. R-mode factor analysis, using the cubic residuals, produces a model with three factors. Factors 1 (P, Ti, Zr) and 2 (Nb, Y) are referred to the magmatic minerals of the least altered volcanic rocks. In addition, Factor 1 associates with the Au-rich site at the shafts area, whereas Factor 2 is referred to albitization western to the shafts area with high contents of Nb and Y. In Factors 1 and 2, major P and Ti with traces Nb and Y are attributed to the accessories rutile, sphene, anatase, and calcite that were developed during propylitization as well as apatite and calcite-accompanying Phase I of the hydrothermal stage. Phosphorous could be considered as an indicator element for the Au mineralization at the study area. The principal elements of Factor 3 (La, Nd, Ce) associate with the Cu?CAu-rich site at the southern adits area, and attributed to the secondary Ca-bearing accessories calcite, sphene, and apatite. In general, these elements associate with the regional propylitization and the three phases of hydrothermal stage in zones of alkali metasomatism. In these alteration zones, La, Nd, and Ce could be used as indicators during geochemical exploration at the study area. In general, the secondary accessory minerals calcite, apatite, rutile, sphene, and anatase associating with zones of alkali metasomatism are significant carriers for the investigated elements. These accessories are possible indicators during geochemical exploration in the adjacent similar mineralizations of the central Allaqi shear zone area. 相似文献
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DIANA K DAVIS 《The Geographical journal》2006,172(2):88-105
Neoliberal restructuring in Morocco has been taking place for over twenty years. Beginning with a decade of structural adjustment, from the early 1980s to the early 1990s, parts of the public sector have been privatized, state services such as health care and education reduced, tariffs lowered and exports heavily promoted. In the dryland agricultural areas, a declensionist colonial environmental narrative has been appropriated to help justify and implement the neoliberal goals of land privatization and the intensification of agricultural production in the name of environmental protection. This paper contributes to areas of growing interest for geographers through an analysis of the underexplored relationship between neoliberalism and environmentalism, in the form of questionable environmental narratives, in Morocco. Land degradation in the dryland agricultural areas of Morocco is commonly blamed on overgrazing by local pastoralists despite existing documentation that suggests instead that ploughing of marginal lands and over-irrigation are the primary drivers of land degradation in the region. The deployment of this colonial environmental narrative of 'native improvidence' has facilitated an expansion of state power over collective rangelands under neoliberalism at the same time that government involvement has decreased in other sectors. The effects of neoliberalism in Morocco have been complex and thus the paper argues that current neoliberal reforms such as the Morocco–US free trade agreement need to be scrutinized carefully to prevent a further exacerbation of poverty as well as to prevent further land degradation in these areas. 相似文献
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This study examines the experiences of geography graduates who work in business, government, and nonprofit organizations. We analyzed 352 logs from eighty-two professionals detailing professional activities, challenges, and opportunities during one work week each month, over a period of six months. Our analysis explores interpersonal relationships and working conditions affecting participants’ progress toward work goals, workplace climate, and professional identity. Geographic information systems and technology accounted for more than half of the geographic skills respondents reported using on the job, and administrative and leadership factors were the most commonly cited types of transferable skills. Professional geographers value collaborative workplaces as well as opportunities to work independently with the confidence of their supervisors, and their sense of a professional identity is enhanced when they feel valued and are recognized for their work. Professional development activities are important because they reinforce geographers’ sense of positively contributing to their organizations, enhance interpersonal interactions, facilitate work on specific projects, and expand individuals’ knowledge and skills. Moreover, our findings suggest that nearly half of the reported workplace difficulties could potentially be reduced or eliminated as a result of more and better professional development. Nonetheless, many employers do not consistently provide opportunities for professional development to their employees. Based on our analysis, we contend that professional development is a beneficial investment for lifelong learning, from undergraduate and graduate education throughout the entire course of a professional career. 相似文献
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The recent (1950–1996) varve record from the proximal sediments in Nicolay Lake, Cornwall Island, Nunavut, Canada (77°46′ N,
94°40′ W) contains distinct subannual rhythmites. Deposition of these subannual rhythmites is due primarily to nival snow
melt, with additional sedimentary units resulting from major summer precipitation and subaqueous mass wasting events. In order
to evaluate the potential hydroclimatic signal contained in the varves from the unglacierized catchment, the nival deposition
record was estimated by delineating the initial subannual rhythmite within each varve. When the record is split into temporal
segments based on two phases that exhibit different sediment deposition patterns in the lake, the nival rhythmites are significantly
correlated to annual cumulative melting degree days (MDD) from the nearest weather station Isachsen (78°47′ N, 103°32′ W)
(1950–1962 AD and 1963–1977 AD with r = 0.55 and r = 0.82, respectively). A similar analysis with data from Resolute (74°43′ N,
94°59′ W) yields slightly weaker correlations (1950–1962 AD, r = 0.60; 1963–1994, r = 0.59). The strong positive correlation
with both the Isachsen and Resolute thermal records suggests that the paleoclimatic signal in the sediments reflects regional
climate conditions. Notably, the signal is strongest when the entire melt season is considered; weaker correlations with instrumental
weather records are associated with comparisons limited to the peak melt or early season melt periods. We attribute this to
the ongoing supply of snowmelt through the season in this polar region and the availability of sediment for transport throughout
the melt season. These results indicate that a high resolution hydroclimatic signal is present in the sediments from Nicolay
Lake and can be used for paleoclimate reconstruction provided sedimentary depositional controls are taken into account. 相似文献