"8.13"四川清平群发性泥石流灾害成因及其影响

汶川地震触发的大量崩塌滑坡改变了泥石流流域的物源条件,地震灾区震后泥石流活动呈现出愈加明显的高频率、群发性、大规模的特征.地处四川省绵竹市西北部的绵远河上游震后已多次暴发了泥石流.2010-08-13和08-18,在局地暴雨诱发作用下,绵远河上游的清平乡和天池乡境内的24条沟谷同时暴发了泥石流,冲出的固体物质高达1.08×107m3,其中仅清平乡附近,泥石流堆积扇规模就达到7.62×106m3,泥石流淤满河道形成了1.5 km2的堰塞体,致使14人死亡和失踪,清平乡境内大量震后重建的民房遭淤埋,泥石流多次中断九环线的重要支线--绵(竹)茂(县)公路汉旺-清平段,直接经济损失高达4.3亿元.此次群发性泥石流灾害剧烈的改变着震后局部的河流微地貌形态,对灾后恢复重建和发展规划也将产生深远影响.本研究从汶川地震对绵远河上游泥石流流域物源条件的影响分析入手,着眼于泥石流形成的基本条件,分析了2010-08-13(简称"8.13")特大群发性泥石流的成因:汶川地震后绵远河上游两侧支沟内积聚的巨最固体松散物源是此次泥石流形成的前提条件;1 h雨强达37 mm、累计达203.5mm的高强度暴雨是泥石流最直接的激发因素.泥石流物源区和堆积区的堆积物颗粒分析结果表明,泥石流以粘性泥石流活动为主.作为汶川地震后典型的次生山地灾害链过程,泥石流活动是自然地貌演化的必然结果,但此类远远超越常规规模和频率的泥石流灾害的影响将是一个长期的过程.因此,建议对危害居民点的重点沟谷提高泥石流治理标准,调整汛期的防洪方案.     

邛海北岸官坝河山洪泥石流灾害特征及发展趋势

官坝河为邛海流域最大支沟,近年来山洪泥石流频发,对邛海产生严重泥沙淤积灾害。本文在对官坝河1998年7月6日百年一遇泥石流灾害调查基础上,分析泥石流形成运动特征及其对邛海的淤积效应,揭示山洪泥石流暴发主要影响要素及发展趋势。研究表明:官坝河流域内物源丰富且形式多样,山洪泥石流暴发频率高且规模大;流域沟道长且比降大,沿途流速流量变化大且流态变换复杂;山洪泥石流对邛海泥沙淤积严重,大量泥沙不仅堆积在入湖口,还以浊流形式输移至湖心处;区域频繁地震活动、强降雨作用和不合理人类活动共同促进山洪泥石流暴发,预测山洪泥石流活动强度总体呈上升趋势。该成果可为官坝河流域规划管理和工程治理提供参考依据,有助于揭示区域山洪泥石流特征及其对邛海的泥沙淤积演化过程。     

震后泥石流活跃期的新认识——以四川汶川“8·20”灾害事件为例

受2019年8月19—20日强降雨影响,位于汶川地震灾区的都江堰和汶川地区(简称"都汶地区")暴发群发性山洪泥石流灾害(简称"8·20"灾害),造成12人遇难,26人失联,直接经济损失约36.26亿元。通过遥感解译、野外现场调查等手段,结合气象、地形、物源等数据分析,对本次岷江流域泥石流成因与特征有了初步认识:(1)汶川灾区泥石流活动性由震前低频非群发特征,在震后5年内,经历了高频、特大型、群发、粘性泥石流活动性发展阶段,在震后5～15年间,已经演化成低频、大中型、群发、粘-过渡性泥石流并伴生山洪,震后15～20年,汶川灾区泥石流将恢复或接近震前活动状态;(2)"8·20"灾害具有群发性特征,涉及沟谷多达23条,主要沿人类或工程活动相对集中的岷江河谷、都汶公路沿线呈条带状分布;(3)"8·20"灾害的激发雨强和有效降雨分别为24.2 mm/h和116.4 mm,高于震后初期激发雨强,但略低于震前泥石流激发雨强;(4)受控于主河水动力条件和泥石流体搬运能力,"8·20"灾害中泥石流以侵蚀作用和堆积作用两种方式形成危害,洪水表现为冲蚀破坏。"8·20"灾害活动是汶川"5·12"强震10年后出现的一次区域性山洪泥石流灾害,加强对此次灾害的认识,有助于为地震灾区灾害防治和减灾规划提供科学支撑。     

基于优化组合赋权法的都汶高速沿线泥石流危险度评价

2013-07-10,持续强降雨导致汶川地震灾区都(江堰)汶(川)高速公路沿线的桃关沟、七盘沟等多处暴发大规模群发性泥石流灾害(简称"7·10"灾害),大量泥沙冲毁或淤埋民居、工厂厂房和都汶高速公路,造成直接经济损失达数亿元。为了科学评价泥石流危害性,对"7·10"暴发的9条典型泥石流沟选取流域面积、流域切割密度、一次冲出规模、沟道纵坡坡降、流域内物源动储量、年平均降雨量、堵塞系数等7个影响因子,分别根据灰色关联度法、熵值法和二项系数法得出各自权重值,然后采用优化组合赋权法推算出各影响因子的组合权重值。在此基础上建立危险性评价数学模型,计算出各沟危险度,结果显示与泥石流的现状和发展趋势相吻合。     

强震区都江堰市龙池镇泥石流物源的遥感动态演变

"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。     

四川省安县千佛山景区震后泥石流灾害及其判识

汶川地震对千佛山风景区造成严重的影响,直接诱发滑坡10处,崩塌数十处,形成大小堵塞坝4座,由此形成的松散物质总量大于1 700×104m3。2008年雨季有5条支沟暴发泥石流。在泥石流成因分析的基础上,选择流域形状、流域发育程度、沟床纵比降、山坡平均坡降、地层岩性和距发震断层距离6个指标,利用潜在泥石流判识模型,对流域内其余9条支沟进行了判断。结果显示,大部分沟道都具备形成泥石流的潜在条件。2009年雨季研究区全面暴发的大规模泥石流,验证判识的可靠性,表明该模型可以用于灾区潜在泥石流的判识。     

汶川地震强震区映秀地区泥石流的危险性

汶川地震震中四川省汶川县映秀镇及附近于2010-08-14暴发群发性泥石流(简称"8.14"泥石流),造成巨大的人员伤亡和财产损失。地震灾区松散固体物源丰富,泥石流灾害相对活跃,估算未来不同降雨频率下泥石流的暴发规模并评价其危险性,是泥石流灾害风险管制的首要工作。在研究四川省部分地区的泥石流和对应降雨频率资料的基础上,得到泥石流规模和降雨频率之间的关系式。以映秀"8.14"泥石流的暴发规模和降雨频率为基础数据,通过泥石流规模和降雨频率之间的关系式推算得到映秀及附近岷江两岸13条泥石流沟在不同降雨频率下的泥石流规模。以泥石流在堆积扇上的平均堆积厚度(泥石流规模/堆积扇面积)、泥石流发生频率、流域面积、主沟长度、流域相对高度、流域切割密度和不稳定沟床比例为危险性判断因子,分别对映秀及邻近地区的13条泥石流沟在100 a、50 a、20 a、10 a和5 a一遇5种不同频率降雨条件下的泥石流危险性进行评价。结果表明:在5种降雨频率下,8条沟的泥石流危险性为高度,4条沟的为中度到高度,1条沟的为中度。     

5·12汶川地震诱发都江堰龙池镇干沟泥石流可能性地质分析

岷江一级支流龙溪河右岸次级支流干沟,位于四川省都江堰市龙池镇,沟口为5·12汶川地震后都江堰龙池镇主要过渡安置房集中居住区.根据流域地质地貌条件,5·12地震诱发崩塌、滑坡山地地质灾害特征及泥石流发育历史等方面,分析预测了干沟震后暴发大规模泥石流的可能性及其危害性.研究表明,干沟为一多期次泥石流沟,其中两次在沟口形成厂规模巨大的泥石流堆积扇;流域内5·12地震滑坡、崩塌极为发育,固体碎屑物质极为丰富,在持续强暴雨下有发生大规模泥石流的极大可能,将对沟口过渡安置房集中居住区带来严重危害.据此,提出了停建干沟沟口过渡安置房等建议.     

汶川震区北川县城魏家沟暴雨泥石流灾害调查分析

2008-09-24强降雨过程导致汶川震区北川县城魏家沟泥石流暴发,对老北川县城造成了严重的破坏.由于这场泥石流灾害发生在汶川地震高烈度区,是地震与降雨共同作用下的结果,研究其形成与成灾过程,对于进一步认识强震区泥石流发育特征具有萤要的意义.根据现场调查和高分辨率航空图像解译,分析了魏家沟泥石流流域特征,特别是地震条件下的泥石流物源特征,在此基础上讨论了泥石流起动过程和堆积过程.魏家沟泥石流典型实例表明了汶川震区泥石流已进入一个新的活跃期.因此,应该开展对汶川地震区的泥石流风险评估和监测、早期预警等研究,采取有效的工程措施控制泥石流的发生和危害.     

“4·20”芦山7.0级地震次生山地灾害活动特征与趋势

2013-04-20芦山县发生7.0级地震,震源深度13 km.截至4月29日地震共造成196人遇难,21人失踪,13484人受伤,200余万人受灾.地震发生后,我们立即开展了地震次生山地灾害的遥感解译、实地调查及危险性评估工作.作者定义了地震次生山地灾害,分析了次生山地灾害的活动特征、形成机制与模式以及发展趋势,并与汶川地震次生山地灾害进行了对比.初步查明芦山地震诱发了1460余处崩塌和滑坡,大量落石和4处堰塞湖.次生山地灾害具有规模小、群发性和高位破坏的特征.崩塌和落石成群发育于坚硬岩石形成的陡坡上,主要发育区段有:芦山县的宝盛乡金鸡峡、双石镇大岩峡以及省道S210线K317路段和灵关镇以北小关子段,对沿河公路及救援生命通道影响严重.滑坡数量较少,以中小规模为主,主要发生于砂岩、页岩和松散堆积层中,仅发现一处大型滑坡并转化为碎屑流.堰塞湖主要由崩塌、滑坡形成,均为低危险性小型堰塞湖.芦山地震次生灾害的主控因素为构造、岩性、结构面和地形,崩塌破坏主要表现为顺层滑动破坏型、切层倾倒破坏型和结构面控制破坏型3种模式.芦山地震诱发崩塌、滑坡的数量、分布范围和规模比汶川地震小得多,其数量仅为汶川地震的5.53％,造成的地表破坏面积(3.06 km2)仅为0.57％.芦山地震区两次地震扰动的叠加效应,大大降低坡体的稳定性,震后崩塌、滑坡和泥石流的活动性增加,增幅有限,活跃期也相对较短,但震区山地灾害的隐伏性和隐蔽性强,给隐患排查带来困难.     

Women,Politics, Elections,and Citizenship

Abstract

Significantly more women than men are registered voters in the United States, and a higher proportion of women voters actually cast ballots on election day. Yet the 106th Congress (1999-2001) includes only 56 women members, 12% of the total membership of the House and Senate. Likewise, women hold only 22% of the total seats in state legislatures. The purpose of this article is to examine this paradox. It first examines the history of the women's movement in the United States. It then turns to an evaluation of women's progress in gaining elected office. Finally it considers three primary obstacles to women gaining equitable representation: solidarity among women, political culture, and the single-member district system now employed in the United States.     

FANTASY,GEOGRAPHY, WAGNER,AND OPERA*

ABSTRACT. Wilhelm Richard Wagner fused fantasy based on epic and lore with seamless scores, using landscapes and urban images to forge spatial order on stage. As a footloose composer-conductor, Wagner was considered a globetrotter for his time, and from trans-European tours he drew inspiration for numerous stagings. Nine of his operas have rustic pastoral settings, with actors silhouetted against geological formations, forests, vistas of undulating terrain for pilgrimages, or raging seas, all visually believable scenery. Rienzi and Die Meistersinger von Nürnberg are urban in setting, whereas Die Feen and Das Liebesverbot are set in a castle-like format.     

Race,Gender, and Constrained Work Trips in Buffalo,NY, 1990

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.     

Race,Gender, and Constrained Work Trips in Buffalo,NY, 1990

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.     

Elevation, Age, Soil Development, and Chemical Weathering at Storbreen, Jotunheimen, Norway

Chemical weathering and associated soil development trends on glacial forelands are commonly assumed to exhibit increases with time elapsed since glaciation. However, this gross trend is complicated by several other factors including elevation, aspect, and microtopography. This paper demonstrates that on the glacial foreland at Storbreen, Jotunheimen, Norway, chemical weathering and associated soil development trends show significant elevational influences. We sampled soils at shallow depths (0–1, 1–5, and 15–20 cm) at two sites on a moraine dated to 1750 at its elevational extremes of 1155 m (site L) and 1385 m (site H). The two moraine sites also differed developmentally from an adjacent 9000-year-old surface (site T) at an intermediate elevation, 1205 m. Analyses were conducted on the fine-earth fractions. Extractable elemental composition exhibited detectable differences between the same-age soils at different elevations with the lower site L tending to have measured parameters intermediate between the high site H and the older site T. Weathering, as indicated by mineralogy, was more pronounced at the 9000-year-old site T and least evident at the high elevation site H. In addition, elevation under the conditions of the field research may inhibit pedogenesis as indicated by the chemical data. Site H, for example, showed little variation with depth and had in general, less organic matter accumulation, smaller C:N ratio, greater pH, and lesser amounts of the measured extractable elements than the soil at site L. Site T generally had smaller pH and larger levels of the measured elements than the other sites. It was concluded that elevation has a significant control on weathering and pedogenesis that may mask the effects of age in this cold and wet environment.     

Time,Action, Space

Postmetropolis deepens Edward Soja's engagement with the sociospatial dialectic, one of his major contributions to urban theory. It also represents an uncharacteristic foray into history. The objectives of my contribution are to probe his treatment of time and to extend his sociospatial dialectic into the realm of actor-network theory, thereby further situating the materiality of the city at the theoretical center of social thought.