Debris-flow susceptibility of upland catchments     

Mélanie Bertrand  Frédéric Liébault  Hervé Piégay 《Natural Hazards》2013,67(2):497-511

Over the last three decades, many regional studies in mountain ranges under temperate climate revealed that it is possible to discriminate debris-flow and fluvial fans from morphometric indicators measured at the scale of the catchment and the fan itself. The most commonly used indicators are the Melton index (R), a normalized index of the gravitational energy of the catchment, and the fan slope (S). A wide range of thresholds have been proposed for discriminating purpose, but these are generally based on a small population of catchments and may be highly influenced by ambiguous fans included in the data set. A database of 620 upland catchments from several mountain ranges under temperate climate was compiled from the literature to propose robust discriminant morphometric thresholds for debris-flow versus fluvial responses. Linear discriminant analysis (LDA) and logistic regression (LR) were performed using the whole data set, and a leave-one-out cross-validation was used to evaluate performances of the models. Sensitivity and specificity scores obtained for LDA and LR were 0.96 and 0.73, and 0.95 and 0.75, respectively. It is also shown that the channel slope above which debris-flow is observed decreases with the gravitational energy of the catchment. Limitations of the morphometric discrimination are discussed.  相似文献   

Ceilometer observations of the boundary layer over Warsaw,Poland     

Iwona S. Stachlewska  Michał Piądłowski  Szymon Migacz  Artur Szkop  Anna J. Zielińska  Paweł L. Swaczyna 《Acta Geophysica》2012,60(5):1386-1412

Jenoptik’s CHM 15k ceilometer was used to monitor the vertical structure of the atmospheric boundary layer (ABL) over Warsaw, from 2008 until 2011, on Mondays and Thursdays, in 24h periods. Hereby, we present an assessment of the signal-to-noise ratio along with a sensitivity study of signal smoothing methods developed in-house. With the proposed averaging, ceilometer attenuated-backscatter signals reached the high troposphere, which makes this sensor competitive to a single-wavelength elastic lidar. The smoothed signals were employed as an input for algorithms developed to automatically detect the ABL height, clouds, fog, and precipitation in the lower troposphere. The classification of weather conditions was validated by the METAR reports from the Warsaw Airport. The obtained ABL heights were compared to those assessed from radio-soundings from a nearby meteorological station WMO12374 in Legionowo. An inter-comparison of the ABL heights, derived by using the Jenoptik’s automated routine against the in-house developed algorithms, is in favor of the latter. The presented four annual cycles of the ABL height, obtained with various derivative-based methods, are the first such long-term results reported using the CHM 15k sensor in Eastern Europe.  相似文献   

Floods at the northern foothills of the Tatra Mountains — A Polish-Swiss research project   总被引：1，自引：1，他引：0  

Zbigniew W. Kundzewicz  Markus Stoffel  Ryszard J. Kaczka  Bartłomiej Wyżga  Tadeusz Niedźwiedź  Iwona Pińskwar  Virginia Ruiz-Villanueva  Ewa Łupikasza  Barbara Czajka  Juan Antonio Ballesteros-Canovas  Łukasz Małarzewski  Adam Choryński  Karolina Janecka  Paweł Mikuś 《Acta Geophysica》2014,62(3):620-641

The present paper introduces the topical area of the Polish-Swiss research project FLORIST (Flood risk on the northern foothills of the Tatra Mountains), informs on its objectives, and reports on initial results. The Tatra Mountains are the area of the highest precipitation in Poland and largely contribute to flood generation. The project is focused around four competence clusters: observation-based climatology, model-based climate change projections and impact assessment, dendrogeomorphology, and impact of large wood debris on fluvial processes. The knowledge generated in the FLORIST project is likely to have impact on understanding and interpretation of flood risk on the northern foothills of the Tatra Mountains, in the past, present, and future. It can help solving important practical problems related to flood risk reduction strategies and flood preparedness.  相似文献   

西班牙交通基础设施与城市体系建设     

Lois-GonzálezRubénC  Piñeira-MantiñánMJ  翟炜  顾朝林 《地理研究》2016,35(7):1353-1369

从社会和地方融合、均衡性与土地异质性、交通网等级体系和支路网与交通可持续性四个角度探讨西班牙交通基础设施网建设对土地开发和土地规划相关国家法规的影响。从城市地理学视角分析中央政府基于改善城市和区域连接度和可达性进行的高速公路网、高铁网、机场和港口等交通基础设施规划,通过1950年代以来土地开发和房价涨跌、新兴产业培育和交通状况改善刺激不同级别城市蔓延和分化的人口增长,重塑西班牙国家城市体系格局。随后,概括了蔓延的城市增长模式和房地产与交通投资泡沫破裂后带给区域增长中心的影响,对通过交通基础设施规划进行投机性投资政策进行了批评。最后建议中央政府应该避免投机投资行为,基于现有的城市体系层级改善核心城市和大城市周边的机动性,优化基础设施建设,建立新的城市与区域增长模式。  相似文献   

Temperature and precipitation fluctuations in the Czech Republic during the period of instrumental measurements   总被引：2，自引：0，他引：2  

Rudolf Brázdil  Pavel Zahradní?ek  Petr Pi?oft  Petr ?těpánek  Monika Bělínová  Petr Dobrovolny 《Theoretical and Applied Climatology》2012,110(1-2):17-34

The history of early meteorological observations using instruments in the Czech Lands is described (the longest temperature series for Prague-Klementinum starts in 1775, precipitation series for Brno in 1803). Using the PRODIGE method, long-term monthly temperature and precipitation series from selected secular stations were homogenised (for 10 and 12 stations, respectively). All the seasonal and annual temperature series for the common period 1882–2010 show a significant positive linear trend with accelerated warming from the 1970s onwards. No significant linear trends were disclosed in the series of seasonal and annual precipitation totals. Correlation coefficients between the Czech series analysed decrease as distances between measuring stations increase. A sharper decrease of correlations for precipitation totals displays much weaker spatial relationships than those for mean temperatures. The highest correlations between all stations appeared in 1921–1950, the lowest in 1891–1920 (temperature) and 1981–2010 (precipitation). Wavelet analysis reveals that very distinct annual cycles as well as the slightly weaker semi-annual ones are better expressed for temperature series than for precipitation. Statistically significant cycles longer than 1?year are temporally unstable and sporadic for precipitation, while in the temperature series cycles of 7.4–7.7 and 17.9–18.4?years were recorded as significant by all stations in 1882–2010 (quasi-biennial cycle of 2.1–2.2?years for half the stations). Czech homogenous temperature series correlate best with those of the Northern Hemisphere for annual, spring and summer values (with significant correlation coefficients between 0.60 and 0.70), but this relation is temporally unstable. Circulation indices, such as the North Atlantic Oscillation Index (NAOI) and the Central European Zonal Index (CEZI), may explain the greater part of Czech temperature variability, especially from December to March and for the winter; however, this relationship is much weaker, or even random, for precipitation series. Further, relationships with the Southern Oscillation Index (SOI) are weak and random. Relatively weak coincidences exist between statistically significant cycles in the Czech series and those detected in NAOI, CEZI and SOI series.  相似文献   

塔里木盆地克拉2气田白垩系储层沉积相   总被引：19，自引：6，他引：13  

贾进华  顾家裕  郭庆银  皮学军  王月华  邹义声 《古地理学报》2001,3(3):67-75

克拉2气田是我国陆上勘探发现的最大气田,它的发现奠定了塔里木盆地做为我国 “西气东输” 重要天然气基地的资源基础。克拉2气田产层主要为下白垩统巴什基奇克组砂岩、下第三系库姆格列木群底砂岩和白云岩,其中下白垩统巴什基奇克组砂岩储层厚度为220.3-285.2m,孔隙度为1.1-22.4%,平均12.83%;渗透率为0.004-1770.1×10-3μm2,平均51.46×10-3μm2。砂岩储层以剩余原生粒间孔为主。通过钻井和露头剖面沉积相对比,克拉2气田巴什基奇克组第三段为扇三角洲前缘沉积,主要微相有水下分流河道、水下重力流和浅湖泥等,岩性以砂砾岩、含砾砂岩和褐色泥岩为主;第二段为辫状河三角洲前缘沉积,主要有水下辫状河道、河口砂坝和分流间湾等微相,以棕褐色中细砂岩夹薄层泥岩为主;第一段为辫状河三角洲平原沉积,主要有远端辫状河道和分流间湾微相,以棕褐色中细砂岩为主。巴什基奇克组沉积时期,古气候以干旱炎热为主,北部发育多个扇体,在平面上相互连接、叠置形成多个物源出口,形成了一系列由辫状河道组成的辫状河三角洲,而非单一辫状河流形成的沉积体,从而形成大面积分布的稳定砂体。沉积微相对比表明,巴什基奇克组储层是由互相切割的多个辫状河道砂体叠置而成,各段微相在横向上分布十分稳定,各砂体互相连通、连续性好,泥岩夹层薄、不连续,空间上具有厚度大、分布广、连续性好、物性好和隔夹层少的特点,为一套优质天然气储层。  相似文献   

洞庭盆地第四纪沉积环境演变的初步分析   总被引：15，自引：2，他引：15  

皮建高  张国梁  梁杏  张人权 《地质科技情报》2001,20(2):6-10

利用水流能量指数，分析了洞庭盆地第四纪沉积环境的演变特征。得出洞庭盆地主要为河流－过流型湖泊相互消长的沉积环境。沉积环境的演变及主要水流方向，受差异性构造沉降的控制。历史时期，人为作用对盆地沉积环境影响很大，并且是近代洞庭湖区洪灾加剧的主要原因。  相似文献   

洞庭盆地第四纪构造活动特征   总被引：17，自引：0，他引：17  

梁杏  张人权  皮建高  张国梁  孙锡良 《地质科技情报》2001,20(2):11-14

利用沉积等厚线图，分析得出的洞庭盆地第四纪构造活动特征如下：北北东及近东西向两组断裂将盆地切割为一系列断块；盆地西部为箕状断块，东部为箕状凹陷、早、中更新世为盆地的断陷阶段，晚更新世以来进入坳陷阶段；第四纪以来构造沉降速率呈加速度增强；构造活动的时空变化控制着洞庭湖的演变。  相似文献   

MgO活性及其在MgCl2溶液中溶度的研究   总被引：6，自引：0，他引：6       下载免费PDF全文

朱黎霞  夏树屏  邢丕峰  高世扬 《盐湖研究》2002,10(2):18-23

测定了不同MgO的碘值和比表面积 ,给出了MgO活性与煅烧温度之间的关系式。研究了MgO活性、煅烧温度、溶解温度和MgCl2 浓度等对MgO溶解的影响。并讨论了活性MgO在含不同硼碱比 [n(B2 O3) :n(MgO) =n]的MgCl2 溶液中形成硼酸镁盐过饱和溶液与增溶的MgO关系。  相似文献   

模糊综合评判在洞庭湖区工程地质环境质量评价中的应用     

皮建高 《湖南地质》1992,11(2):157-162

基本地震烈度、饱和砂土振动液化的可能性、土体允许承载力和压缩模量及洪水威胁性等,是影响洞庭湖区工程地质环境质量的5个主要参评因子,据此本文运用模糊综合评判方法,对洞庭湖区的工程地质环境质量进行了综合评价。  相似文献