Broad area mapping of monthly soil erosion risk using fuzzy decision tree approach: integration of multi-source data within GIS

Soil erosion poses a serious problem for sustainable agriculture and the environment. There is a need to develop a simple and practical approach for broad area mapping of soil erosion risk that uses the uncertain but available information as input data within the constraints of reasonable cost and time. In this work, a predictive approach for conducting analytical erosion risk assessment across broad areas is developed, which combines a fuzzy decision tree (FDT), remote sensing and Geographic Information System (GIS). This approach is applicable to situations with a limited amount of input data and can easily adjust assessment factors according to actual need. In this study, four dominating factors affecting soil erosion were considered: soil, topography, land cover and climate. GIS thematic layers of these factors were constructed followed by fuzzified analysis through trapezoidal shaped membership functions. Based on subdivided erosion response units (ERUs), an optimal FDT was determined to classify monthly soil erosion risk into five levels. High-risk and very high-risk soil erosion in the study area is mainly concentrated from June to August, with July and August showing the highest risk covering more than 80% of the study area. November to March is dominated by low risk over more than 90% of the study area, while medium risk is dominant in April, May, September and October. Compared with field survey data, the fuzzy decision erosion risk assessment approach was shown to be applicable and economical for rapidly identifying and locating soil erosion risk with limited input data by means of remote sensing and GIS.     

湖南省地形地貌与地质灾害分布关系分析

湖南是我国地质灾害比较严重的省份之一,属地质灾害高易发区,地质灾害分布和发育程度具有一定的地域性,地形地貌对地质灾害的发生起着主控作用。本文根据湖南省地形地貌特点,结合全省1∶10万县市地质灾害调查数据,从区域上研究了不同地貌特征对不同地质灾害的影响,并选取了典型地形地貌进行分析。     

南海西南次海盆被动陆缘构造单元划分及伸展演化过程

南海西南次海盆被动陆缘洋陆转换带位于陆缘强烈伸展区,蕴含着岩石圈临界伸展破裂和洋盆扩张过程的丰富信息。本文利用多道地震剖面和重力异常数据,对西南次海盆被动陆缘构造单元进行划分,研究陆缘南、北部洋陆转换带结构构造特征,探讨陆缘伸展演化过程。多道地震剖面资料显示,北部洋陆转换带发育有裂陷期断陷和向海倾斜的掀斜断块;南部发育有低角度正断层控制的裂陷期断陷、海底火山以及局部隆起;从陆到洋方向,重力异常值变化明显。根据上述结果南海西南次海盆被动陆缘划分为近端带、洋陆转换带和洋盆三个构造单元,分别对应了其伸展演化过程的三个阶段：前裂谷阶段、陆缘裂陷阶段和海底扩张阶段。     

Physical properties of Mesozoic sedimentary rocks from the Perth Basin,Western Australia

The Perth Basin (PB) hosts important aquifers within the Yarragadee Formation and adjacent geological formations with potential for economic exploitation by both geothermal energy and carbon capture and sequestration. Published studies on the reservoir quality of the sedimentary units of the PB are very few. This study reports some petrophysical and lithological characteristics of the sedimentary units of interest for geothermal and geosequestration scenarios and help interpolation toward non-sampled intervals. A new fluvial-dominated lithofacies scheme was developed for the Mesozoic stratigraphy from four wells drilled in the central PB (Pinjarra-1, Cockburn-1, Gingin-1 and Gingin-2) based on grainsize, sorting, sedimentary structures and colour that relate to the environment of deposition. Systematic laboratory measurements of permeability, porosity, and thermal conductivity were conducted on core samples to investigate a variety of lithofacies and depths from these wells. Empirical correlations are established among the different physical properties, indicating encouraging relationships for full PB basin interpolation such as between porosity and permeability, when the samples are grouped into ‘hydraulic units’ defined by a ‘flow zone indicator’ parameter. The common principal controls on the PB thermal conductivity are the pore space arrangement and mineralogical content, which are strongly lithofacies-specific. Therefore, the lithofacies type could be a good first-order discriminator for describing spatial variations of thermal conductivity and then estimate their flow zone indicator.     

The Ligurian Units of Western Tuscany (Northern Apennines): insight on the influence of pre-existing weakness zones during ocean closure

Most of the tectonic units cropping out in Western Tuscany are fragments of the Jurassic oceanic crust, ophiolitic successions, overlaid diachronously by Upper Cretaceous-middle Eocene carbonate and siliciclastic flysch successions with their Cenomanian-lower Eocene shalycalcareous basal complexes. These units, so called Ligurian, have been emplaced during the closure of the Ligurian-Piedmont Ocean. Ophiolite bearing debris flows are common in the flysch basins and their relationship with ophiolitic tectonic slices points to a strong relation between tectonics and sedimentation from the early compressive events of the Late Cretaceous. The tectonic activity reflects in a rough morphology of the ocean floor. It progressively influences the distribution and sedimentology of the turbidites. During middle Eocene this relationship begun very important and a paleogeographic reconstruction with prominent linear ophiolitic reliefs that bounded some turbiditic basins can be done. In our reconstruction the sedimentary and structural evolution can be framed in the context of strain partitioning, developed during the ocean closure, between subduction processes and ancient weakness zones crosscutting both the ocean and the Adria continental margin and reactivated in compressive regime. These weakness zones can be interpreted as transform faults of the Ligurian-Piedmont Ocean with prolongations in the Adria passive margin.

The weakness zones crosscut the oceanic lithosphere and the Adria continental margin and interfered with the subduction processes. The activity of the weakness zones is reflected in the Ligurian Units architecture where two main structural strike trends of thrusts and folds axial planes occur. The first trend is WSW-ENE oriented and it is connected with the reactivation of the weaknesses zones. This first orientation developed progressively from Late Cretaceous to Pliocene, from oceanic to ensialic convergence (D1, D2, and D4 deformation phases). The second trend is NNE-SSW oriented and is related to the late Eocene continental collision and the subsequent translation to the NE of the oceanic units onto the Adria continental margin (D3 deformation phase).     

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锦45块储层流动单元

正确地划分储层流动单元,对预测剩余油分布、调整开发方案、提高采收率都具有重要意义。采用多参数的聚类分析和模糊综合评价相结合的方法进行储层流动单元的划分,在此基础上应用BP网络技术对流动单元进行预测。研究表明,本区储层可以划分为Ⅰ、Ⅱ、Ⅲ、Ⅳ 4类流动单元:其中Ⅰ类是该区储集性能最好的储层流动单元,虽然开发程度较高,大部分井已经关闭,但个别井目前仍具有一定的生产能力;Ⅱ类是该区储集性能较好的储层流动单元,水淹的程度较低,还存有一定的剩余油,是目前油田生产的主要区域;Ⅲ类是该区储集性能较差的流动单元,开发效果一般,动用程度较差,所以是油田进一步挖潜的区域;Ⅳ类是该区储集性能最差的流动单元,原始含油性很差,因此不是剩余油分布的主要区域。对各类流动单元特征进行了精细的分析,为油田综合治理提供了详细的地质依据。     

盐胁迫对霸王水势的影响

2007年8月采用PSYPRO水势仪,测定了青海省农林科学院林业所试验基地盆栽霸王的叶水势、土壤水势及大气水势,并对霸王叶水势在不同土壤盐胁迫下的日变化进行了动态观测,分析了不同土壤盐胁迫条件下影响霸王叶水势变化的主要影响因子。结果表明,在土壤水分充足的条件下,霸王能在盐分浓度为1.5%的土壤中生长,此时叶水势值大小的比较为0>0.5%>1.5%;叶水势与土壤水势相关性的比较为0>0.5%>1.5%,与大气水势相关性的比较为0.5%>0>1.5%。     

Delineating floodplain and upland areas for hydrologic models: a comparison of methods

A spatially distributed representation of basin hydrology and transport processes in hydrologic models facilitates the identification of critical source areas and the placement of management and conservation measures. Floodplains are critical landscape features that differ from neighbouring uplands in terms of their hydrological processes and functions. Accordingly, an important step in watershed modelling is the representation of floodplain and upland areas within a watershed. The aim of this study is (1) to evaluate four floodplain–upland delineation methods that use readily available topographic data (topographic wetness index, slope position, uniform flood stage, and variable flood stage) with regard to their suitability for hydrological models and (2) to introduce an evaluation scheme for the delineated landscape units. The methods are tested in three U.S. watersheds ranging in size from 334 to 629 km² with different climatic, hydrological, and geomorphological characteristics. Evaluation of the landscape delineation methods includes visual comparisons, error matrices (i.e. cross‐tabulations of delineated vs reference data), and geometric accuracy metrics. Reference data were obtained from the Soil Survey Geographic (SSURGO) database and Federal Emergency Management Agency (FEMA) flood maps. Results suggest that the slope position and the variable flood stage method work very well in all three watersheds. Overall percentages of floodplain and upland areas allocated correctly were obtained by comparing delineated and reference data. Values range from 83 to 93% for the slope position and from 80 to 95% for the variable flood stage method. Future studies will incorporate these two floodplain–upland delineation methods into the subwatershed‐based hydrologic model Soil and Water Assessment Tool (SWAT) to improve the representation of hydrological processes within floodplain and upland areas. Copyright © 2016 John Wiley & Sons, Ltd.     

基于地层结构组合的第四纪地质单元划分研究——以皖江经济带沿江丘陵平原区为例

为支撑地质条件复杂地区的水文地质、工程地质和环境地质调查研究,在皖江经济带沿江丘陵平原区通过系统分析第四纪地层的岩性、结构、构造等组合,以地貌以及第四系成因、沉积相和沉积物物源为指标,结合已有区域第四纪研究成果以及年代地层和岩石地层划分标准,进行皖江沿江丘陵平原区“第四纪地质单元”划分,共划分出冲积-湖积平原地质单元、洪积-坡积岗地地质单元和残积-剥蚀丘陵地质单元3个一级地质单元,总结了7种类型第四纪地层结构组合及其特征,为区域水文地质和工程地质调查与研究奠定了基础。