Relationships between rainfall and landsliding in the Middle Hills,Nepal     

《Norsk geografisk tidsskrift. Norwegian journal of geography》2012,66(2):74-81

Many studies have documented major landslide events in mountain areas following heavy rainfall amounts. In the Himalaya, landslides occur during every monsoon period, but the role of rainfall in triggering these failures is not clear. This paper reports the results of a three-year study (1991-1993) into landsliding in the Likhu Khola drainage basin, Middle Hills, Nepal. Considerable annual variability in numbers, types and sizes of landslides was noted. Some of this variability can be explained by fluctuations in rainfall amounts and intensities, but many landslides were explained more easily by other controlling factors. In situations where slopes are extensively terraced for agriculture, with some terraces being intensely irrigated and others not, relationships between landsliding and rainfall amounts are complex and no simple explanations can be made.  相似文献   

基于空间索引的规则格网DTM内插算法研究   总被引：2，自引：0，他引：2  

吴焕萍  潘懋  胡金星  马照亭  宋杨 《地理与地理信息科学》2004,20(1):43-46

从离散点内插规则格网数字地形模型(DTM)方法的关键是如何提高待插点周围数据的搜索效率。该文针对离散点的空间分布特性,给出了基于网格分块和KD-Tree两种空间索引技术的规则格网内插方法。实验表明,这两种索引方法能显著提高搜索速度,算法内插效率较高。最后,在算法效率分析的基础上,对两种索引方法所适应的条件进行了讨论。  相似文献   

Field study on drainage densities and rescaled width functions in a high‐altitude alpine catchment          下载免费PDF全文

Raphaël Mutzner  Paolo Tarolli  Giulia Sofia  Marc B. Parlange  Andrea Rinaldo 《水文研究》2016,30(13):2138-2152

This paper addresses the effect of accurately mapping spatially heterogeneous drainage densities in high‐altitude alpine basins on Rescaled Width Functions (RWFs), used in some applications as a minimalist model of the hydrologic response. The channel network and 373 of its channel heads were mapped in the field in a high mountain catchment in the Swiss Alps. The mapped channel network is characterized by highly uneven drainage density, here described by the distribution of the length to the first channelized site computed along steepest descent from any unchannelled site. Various channel networks were extracted from a 1 m lidar‐derived digital terrain model and compared with the field‐mapped channel network using geomorphologic parameters, hillslope‐to‐channel distance and RWFs. Our results show that the channel network derived by statistical analysis of surface morphology is consistent with the field‐mapped network. Larger discrepancies were observed when the channel network was obtained with classical threshold‐based approaches relying on cumulative drainage area and local slope. The actual arrangement of the drainage densities has a significant impact on the RWFs. The discrepancy was largest between RWFs derived from classical extraction methods and RWFs derived with the field‐mapped network, indicating an inappropriate extraction of the channelled portion of the high‐altitude catchment that is a reflection of the variety of channel initiation processes. Our results suggest that spatial heterogeneity of the drainage density might play an important role in modelling streamflow generation. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

数字地面模型在土地整治中的应用研究     

王云帆  王庆 《国土资源信息化》2011,(5):46-48,31

DTM作为地理空间定位的数字数据的集合,在GIS空间数据库中,能够反映地理基础、社会经济、资源与环境和地形等多方面的信息。本文在综述数字地面模型的建立方法的基础上,应用DTM进行坡度分级和区域设计模型叠加模式,探讨了三维地表模型在土地整治中应用。  相似文献   

Digital terrain modelling using Corona and ALOS PRISM data to investigate the distal part of Imja Glacier, Khumbu Himal, Nepal   总被引：2，自引：2，他引：0  

LAMSAL Damodar  SAWAGAKI Takanobu  WATANABE Teiji 《山地科学学报》2011,8(3):390-402

This study used Corona KH-4A and Advanced Land Observing Satellite (ALOS) PRISM images to generate digital terrain models (DTMs) of the distal part of Imja Glacier,where a few supraglacial ponds (～0.07 km 2) expanded into the large Imja Glacier Lake (Imja Tsho,～0.91 km 2) between 1964 and 2006.DTMs and subsequently derived topographical maps with contour intervals of 1 m were created from the high-resolution images (Corona in 1964 and ALOS in 2006) in the Leica Photogrammetric Suite (LPS) platform.The DTMs and topographic maps provided excellent representation of the elevation and micro-topography of the glacier surface,such as its supra-glacial ponds/lake,surface depressions,and moraine ridges,with an error of about +/-4 m (maximum).The DTMs produced from the Corona and ALOS PRISM images are suitable for use in studies of the surface change of glaciers.The topographical maps produced from the Corona data (1964) showed that part of the dead ice in the down-glacier area was even higher than the top of the lateral moraine ridges,while the glacier surface in the up-glacier area was noticeably lower than the moraine crests.This suggests more extensive melting of glacier ice in the up-glacier area before 1964.The average lowering of the glacier surface from 1964 to 2006 was 16.9 m for the dead-ice area west of the lake and 47.4 m for the glacier surface east of the lake;between 1964 and 2002,the lake surface lowered by 82.3 m.These figures represent average lowering rates of 0.4,1.1,and 2.2 m/year for the respective areas.  相似文献   

基于多尺度DTM的坡式梯田三维可视化研究     

周春寅  赵卫东  钱家忠 《地理与地理信息科学》2011,27(6)

针对黄土高原梯田可视化问题,以往的相关研究基本解决了水平梯田的三维可视化,但关于坡式梯田的研究尚为空白。坡式梯田因其具备更加突出的人工微地形特性,难以通过传统的DEM可视化方法实现其三维可视化。该文提出了多尺度DTM叠加法,利用偏移线法、高程增量法等方法提取田埂坡度特征,将研究区的低分辨率格网DEM(G-DEM)、坡式梯田分布区的高分辨率坡度DTM及G-DEM融合为一体,对坡式梯田进行三维叠加可视化。与传统G-DEM可视化方法相比,多尺度DTM叠加可视化法不仅所需数据存储量更小,而且具备更加逼真的坡式梯田三维可视化效果,能够有效显示坡式梯田的平坦田面和陡直田埂,是对基于DEM的梯田地形三维可视化的有益探索。  相似文献   

Use of fused airborne scanning laser altimetry and digital map data for urban flood modelling     

David C. Mason  Matthew S. Horritt  Neil M. Hunter  Paul D. Bates 《水文研究》2007,21(11):1436-1447

Flood modelling of urban areas is still at an early stage, partly because until recently topographic data of sufficiently high resolution and accuracy have been lacking in urban areas. However, digital surface models (DSMs) generated from airborne scanning laser altimetry (LiDAR) having sub‐metre spatial resolution have now become available, and these are able to represent the complexities of urban topography. This paper describes the development of a LiDAR post‐processor for urban flood modelling based on the fusion of LiDAR and digital map data. The map data are used in conjunction with LiDAR data to identify different object types in urban areas, though pattern recognition techniques are also employed. Post‐processing produces a digital terrain model (DTM) for use as model bathymetry, and also a friction parameter map for use in estimating spatially distributed friction coefficients. In vegetated areas, friction is estimated from LiDAR‐derived vegetation height, and (unlike most vegetation removal software) the method copes with short vegetation less than ～1 m high, which may occupy a substantial fraction of even an urban floodplain. The DTM and friction parameter map may also be used to help to generate an unstructured mesh of a vegetated urban floodplain for use by a two‐dimensional finite element model. The mesh is decomposed to reflect floodplain features having different frictional properties to their surroundings, including urban features (such as buildings and roads) and taller vegetation features (such as trees and hedges). This allows a more accurate estimation of local friction. The method produces a substantial node density due to the small dimensions of many urban features. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

三角网结构DTM的土方计算及应用   总被引：17，自引：0，他引：17  

慕永峰  朱昌勇  李建 《测绘工程》2000,9(1):52-56

由离散高程点建立的三角网ＤＴＭ,能够在多方面应用。如生成等高线、建立地面模型、计算工方量等。文中就其在地面整平（切割面水平或有一定坡度）、河道（或水渠）开挖及筑堤中的土方量计算和水域容积中的体积计算方面介绍三角网ＤＴＭ的应用。  相似文献   

土地整治中土方量计算方法的研究及精度分析     

崔丽丽  全斌  潘瑜春  李淑华  吴丹 《测绘与空间地理信息》2014,(9)

主要介绍了方格网法、断面法、等高线法、DTM法四种土方计算方法的计算原理,利用CASS 7.0软件的土方计算辅助计算模块中提供的方格网法、断面法、等高线法、DTM法进行计算实现,在算例分析的基础上,对四种方法的计算精度、适用范围、优缺点进行分析比较,并对土方计算的发展前景进行展望。  相似文献   

基于机载三维成像仪快速获取数字地面模型     

尤红建  刘彤  李树楷 《测绘工程》2003,12(2):14-16,33

机载三维成像仪是集成GPS、姿态测量装置、激光测距仪和光谱成像仪的新型航空遥感系统，它能同步获取地面目标的定位、定性数据。本文简要介绍了机载三维成像仪系统，在计算出扫描激光测距点三维坐标的基础上，着重分析了DTM快速生成算法，包括DTM的快速内插和航带间的自动无缝拼接。  相似文献