Combining suspended sediment monitoring and fingerprinting to determine the spatial origin of fine sediment in a mountainous river catchment

An excess of fine sediment (grain size <2 mm) supply to rivers leads to reservoir siltation, water contamination and operational problems for hydroelectric power plants in many catchments of the world, such as in the French Alps. These problems are exacerbated in mountainous environments characterized by large sediment exports during very short periods. This study combined river flow records, sediment geochemistry and associated radionuclide concentrations as input properties to a Monte Carlo mixing model to quantify the contribution of different geologic sources to river sediment. Overall, between 2007 and 2009, erosion rates reached 249 ± 75 t km^?2 yr^?1 at the outlet of the Bléone catchment, but this mean value masked important spatial variations of erosion intensity within the catchment (85–5000 t km^?2 yr^?1). Quantifying the contribution of different potential sources to river sediment required the application of sediment fingerprinting using a Monte Carlo mixing model. This model allowed the specific contributions of different geological sub‐types (i.e. black marls, marly limestones, conglomerates and Quaternary deposits) to be determined. Even though they generate locally very high erosion rates, black marls supplied only a minor fraction (5–20%) of the fine sediment collected on the riverbed in the vicinity of the 907 km² catchment outlet. The bulk of sediment was provided by Quaternary deposits (21–66%), conglomerates (3–44%) and limestones (9–27%). Even though bioengineering works conducted currently to stabilize gullies in black marl terrains are undoubtedly useful to limit sediment supply to the Bléone river, erosion generated by other substrate sources dominated between 2007 and 2009 in this catchment. Copyright © 2011 John Wiley & Sons, Ltd.     

对2008年汶川MS8.0地震沿龙门山后山出现地表破裂现象的讨论

介绍了汶川地震沿龙门山后山汶川-茂县断裂带11个点位出现的地表破裂现象.这些地表破裂点位南起汶川卧龙乡鱼丝洞,向北经耿达乡牛坪、草坡乡金波、漳排、足湾、绵虒乡高东山、玉龙乡岭岗、威州镇七盘沟到茂县壳壳寨、凤仪镇马良沟,长度达100 km.尽管这些地表破裂点位多数断续展布在高山山顶或山体一侧,与山体走向一致,但仍有少数地...     

Tree establishment on bars in low‐order gravel‐bed mountain streams

In many large alluvial rivers, trees often recruit and survive along laterally accreted sediments on bars. This produces a gradient of tree ages and composition with distance from the active channel. However, in low‐order, gravel‐bed mountain streams, such as the stream investigated in this study, it is suggested that vertical accretion results in sediment deposition patterns on bars that are often highly patchy. Consequently, tree species and ages are also heterogeneously distributed, rather than having distinct linear or arcuate banding patterns with distance from the channel. In addition, overall age patterns of trees on these bars follow the distribution of floods, with numerous young trees and few older trees. Recruitment is fairly continuous on these bars and is not correlated with high water years, suggesting that even flows close to bankfull levels are capable of transporting fine sediment to the bars on which trees establish. This pattern of sediment deposition/erosion and the resulting tree recruitment and survival seem to be a result of valley confinement and the lack of lateral accretion in these smaller, mountainous channels. Copyright © 2011 John Wiley & Sons, Ltd.     

汶川地震甘肃省文县地震地质灾害遥感分析

2008年汶川地震诱发了大量的次生山地灾害.本文以多源、多时相的遥感影像(TM、ASTER、SPOT)作为信息源,基于地学知识,采用图像增强、人机交互的方式对甘肃省文县地区汶川地震引发的次生山地灾害进行解译.以ArcGIS软件为处理平台,运用空间分析技术,将解译结果与海拔高度、坡度、植被覆盖度和地震烈度进行空间分析,获得了研究区次生山地灾害的分布规律,其特点为:文县境内的次生山地灾害主要分布在20°～60°的边坡;多发生在1 000～2 500m的海拔高程范围内;主要分布在地震烈度Ⅶ度及以上区域.     

雷达干涉测量技术获取多分辨率山区高程模型

利用一组间隔仅为一天的高分辨雷达卫星COSMO-Skymed影像获取西部某山区4个不同分辨率（4m、10m、20m、50m）的数字高程模型（DEM）。由于西部高山空白区缺乏实测资料,所以以航天飞机雷达地形测绘（SRTM）为参考数字高程模型（DEM）并从其中获取较为可靠的足量地面控制点,从图像中选取高坡度、低坡度、低相干性三个区域,分别从坡度、相干性、分辨率三个方面,比较、分析山区DEM的精度。研究表明：利用合成孔径雷达干涉（InSAR）技术获取的与SRTMDEM基本一致;低坡度区域比高坡度区域的精度更高;相比于低坡度地区,高坡度地区的高程差值对分辨率的变化更为敏感;DEM分辨率越高,与SRTMDEM的差值就越大,与SRTMDEM本身的分辨率较小有关;对于低相干区域,其可靠性有待商榷,即使其50m分辨率的DEM与SRTMDEM也存在较大差距。     

高精度三维地震勘探在八宝矿区的应用

以八宝矿区为例,针对山区存在的复杂浅表层地震地质条件,进行了高精度三维地震勘探,取得了准确率较高的成果。以往山区三维地震勘探漏掉解释小型构造和构造偏移较大的现象有了很大的改善,所以在山区地形高差大、浅表层地震条件复杂、深层地震条件一般、南部地层反转等特点下,开展高精度三维地震勘探具有重要的意义。     

山区下切河流地貌演变机理及其与河床结构的关系

为研究河床结构在下切性河流地貌演变过程中所起到的作用与影响机制,对中国典型下切性河流区域的地貌特征与河床结构发育进行了调查与统计分析.结果表明,当河流剧烈下切使得河谷边坡超过临界坡度后,易于失稳而发生大规模的崩塌滑坡现象,河流演变从而进入下切拓宽阶段.大量边坡物质进入河道,促进了河床结构的发育,能够维持较高的河道纵坡降...     

An Improved Method Based on Shallow Ice Approximation to Calculate Ice Thickness along Flow-Line and Volume of Mountain Glaciers

To evaluate the water storage and project the future evolution of glaciers, the ice-thickness of glaciers is an essential input. However, direct measurements of ice thickness are labo-rious, not feasible everywhere, and necessarily restricted to a small number of glaciers. In this article, we develop a simple method to estimate the ice-thickness along flow-line of mountain glaciers. Different from the traditional method based on shallow ice approximation (SIA), which gives a relationship be-tween ice thickn...     

江苏省地质环境区划评价指标体系初步研究

建立地质环境区划评价指标体系,评价地质环境质量,对有效保护地质环境、履行地质环境保护管理职能具有重要意义。笔者在充分分析研究江苏省地质环境资料及成果的基础上,以地质环境问题为导向,人地和谐统一的思路,基于地质环境安全、地质资源保障及社会需求的原则,从地质环境的自然属性和社会属性两方面考虑,建立了地质灾害(防治)、矿山地质环境(保护)、山体资源保护、地质遗迹保护、地下水污染防治和土壤污染防治等6个专项区划的评价指标体系,并提出一套由7个目标层、16个约束层和40项指标构成的江苏省地质环境综合区划评价指标体系,为合理评价江苏省地质环境提供科学依据。     

浅析大兴安岭中南段多金属成矿航磁异常特征

大兴安岭作为在古亚洲洋构造～成矿域基础上发展起来的北方造山带, 具有多块体拼合增生造山的典型特征,中生代、新生代又受到多种成矿地质作用的改造和叠加, 成矿条件十分优越,具备了大规模成矿的条件和潜力.这里在充分研究大兴安岭中南段地质构造、航磁特征的基础上,对航磁异常进行综合解释,寻找与成矿密切相关的中酸性岩体及其隐伏岩体...