Simulated effect of a forest road on near‐surface hydrologic response and slope stability

Forest management practices often result in significant changes to hydrologic and geomorphic responses at or near the earth's surface. A well‐known, but not fully tested, hypothesis in hillslope hydrology[sol ]geomorphology is that a near‐surface permeability contrast, caused by the surface compaction associated with forest roads, can result in diverted subsurface flow paths that produce increased up‐slope pore pressures and slope failure. The forest road focused on in this study is located in a steep forested, zero‐order catchment within the H. J. Andrews Experimental Forest (Oregon). A three‐phase modelling effort was employed to test the aforementioned hypothesis: (i) two‐dimensional (vertical slice), steady‐state, heterogeneous, saturated subsurface flow simulations at the watershed scale for establishing the boundary conditions for the catchment‐scale boundary‐value problem in (ii); (ii) two‐dimensional (vertical slice), transient, heterogeneous, variably saturated subsurface flow simulations at the catchment scale for estimating near‐surface hydrologic response and pore pressure distributions; and (iii) slope stability analyses, using the infinite slope approach, driven by the pore pressure distributions simulated in (ii), for assessing the impact of the forest road. Both observed and hypothetical rainfall events are used to drive the catchment‐scale simulations. The results reported here support the hypothesis that a forest road can have an effect on slope stability. The permeability contrast associated with the forest road in this study led to a simulated altering of slope‐parallel subsurface flow with increased pore pressures up‐slope of the road and, for a large rainfall event, a slope failure prediction. Copyright © 2005 John Wiley & Sons, Ltd.     

红外测距仪在城市道路放线测量中的应用

在城市道路放线测量中，碰到障碍物是司空见惯的．障碍物的存在，阻挡了视线的近视；这时测量工作者必须想方设法绕过或跨越障碍物，在实地标定出位于障碍物另一端视线“盲区”内的中线桩的点位．当障碍物比较多而且比较复杂时，通常的做法先有设经纬仪导线，再由邻近的导线点在实地标定出上述中桩点的位置．这种方法既费时又费力，在时间紧、任务重的场合不大适用．本文介绍一种使用红外测距仪快速跨越障碍物的作业方案，既省时又省力，可以大大缩短工期，极大地提高放线测量的工作效率．     

基于GIS的城市道路网无级比例尺信息提取

阐述了无级比例尺矢量数据信息处理技术的基本原理、流程与方法,研究了城市道路网信息提取的实现方法,概括了无级比例尺信息提取过程中要素选取的“取舍”原则,提出了面向对象的城市道路网分类体系,并运用层次分析法对同级别城市道路进行重要性排序,从而实现了将各级别城市道路的重要性进行总体排序,为城市道路网无级比例尺信息的内容选取提供了前提。     

BOOK REVIEWS

Book Reviewed in this article: Rabat: Urban Apartheid in Morocco . Janet Abu -Lughod . Marketplaces in a Developing Country: The Case of Western Nigeria . Isaac Ayinde Adalemo . Farming Development and Space: A World Agricultural Geography . Bernd Andreae . Section and Party: A Political Geography of American Presidential Elections, from Andrew Jackson to Ronald Reagan . J. Clark Archer and Peter J. Taylor . Women and Space: Ground Rules and Social Maps . Shirley Ardener , ed. European Progress in Spatial Analysis . R. J. Bennett , ed. The Origins of Academic Geography in the United States . Brian W. Blouet Geographic Perspectives on Global Problems . Ronald Reed Boyce . Seasonal Dimensions to Rural Poverty . Robert Chambers , Richard Longhurst and Arnold Pacey eds. The New Nationalism and the Use of Common Spaces: Issues in Marine Pollution and the Exploitation of Antarctica . Jonathan I. Charney , ed. Communications Tomorrow: The Coming of the Information Society . Edward Cornish , ed. The Design of Suburbia . Arthur Edwards . Explorer on the Northern Plains: Lieutenant Gouverneur K. Warren's Preliminary Report of Explorations in Nebraska and Dakota in the Years 1855–56–57. With an Introduction by Frank N. Schubert . The Changing Climate: Responses of the Natural Flora and Fauna . Michael J. Ford . Essentials of Physical Geography . Robert E. Gabler , Robert J. Sager , Sheila Brazier , and Daniel L. Wise. The Road to Jaramillo . William Glen . Valued Environments . John R. Gold and Jacquelin Burgess , eds. Proximity and Preference: Problems in the Multidimensional Analysis of Large Data Sets . Reginald G. Golledge and John N. Rayner , eds. A Search for Common Ground . Peter Gould and Gunnar Olsson , eds. Geography: Its History and Concepts . Arild Holt -Jensen . A Population Geography . Huw R. Jones . The Human Mosaic: A Thematic Introduction to Cultural Geography, 3rd ed. Terry G. Jordan and Lester Rowntree . Urban Social Geography: An Introduction . Paul Knox . The Anatomy of Job Loss: The How, Why and Where of Employment Decline . Doreen Massey and Richard Meegan . The Information Society as Post-Industial Society . Yoneji Masuda . Map Librarianship, 2nd ed. Harold Nichols . India: Cultural Patterns and Processes . Allen G. Noble and Ashok K. Dutt , eds. The God that Limps: Science and Technology in the Eighties . Colin Norman . Geography: An Introductory Perspective . Robert E. Norris , Keith D. Harries and John D. Vitek . The Politics of Technology Assessment . David M. O'Brien and Donald A. Marchand . Ethnic Segregation in Cities . Ceri Peach , Vaughan Robinson and Susan Smith , eds. Churches and Church Membership in the United States, 1980 . Bernard Quinn , Herman Anderson , Martin Bradley , Paul Goetting and Peggy Shriver . Energy in Australia: Politics and Economics . Hugh Saddler . Development from Above or Below? The Dialectics of Regional Planning in Developing Countries . Walter B. Stóuhr and D. R. Fraser Taylor , eds. Human Impact on the Ecosystem . Joy Tivy and Greg O'Hare . Plants and People: Vegetation Change in North America . Thomas R. Vale . The Mapmakers: The Story of the Great Pioneers in Cartography from Antiquity to the Space Age . John Noble Wilford .     

面向对象的高空间分辨率遥感影像道路信息的提取

遥感影像的道路信息提取是构建及更新地理空间数据库的一个重要组成部分。针对高空间分辨率遥感影像丰富的地物细节信息和突出的结构、纹理信息的特点,采用一种面向对象技术,实现了高空间分辨率影像道路信息提取。首先,利用面向对象的影像分割技术得到道路均值对象,然后挖掘高空间分辨率遥感影像中描述道路的光谱特征、几何特征及纹理特征,构建道路对象的知识库,实现了城郊重要道路信息的提取。与最大似然法相比,提取结果充分利用道路形状和纹理信息,能克服光谱特征的噪声现象,提取道路准确率高,为高空间分辨率遥感影像道路信息提取提供了一种新的途径。     

南通市高等级公路冬季路面打滑情况分析

本文首先介绍了Norrman提出的冬季路面打滑分类专家系统（ESCSR），在此基础上利用南通市气象台37个冬季的有关气象要素，分析了该市冬季降水条件下的路面打滑情况，为做好冬季公路气象服务及公路工程设计提供依据。     

谈旅游产品开发规划的理念和途径

旅游产品开发是旅游规划与开发的核心内容.只有树立正确的理念,遵循正确的途径和方法,才能设计出好的旅游产品.作者以此为出发点,首先阐述了当前旅游产品开发规划中应树立的几个理念,即大旅游、大开发理念,市场化、企业化理念,特色化、品牌化理念,绿色化、生态化理念,多层次、多样化理念,整合创新理念;其次,提出了旅游产品开发规划应遵循的几条途径,即综合导向、三维开发、跟踪趋势、创意构思等.     

Spatial simulation of forest road effects on hydrology and soil erosion after a wildfire

Post-fire catchment and water utility managers throughout the world use predictive models to estimate potential erosion risks to aid in evaluating downstream impacts of increased runoff and erosion, and to target critical areas within a fire for applying mitigation practices. Erosion prediction can be complicated by forest road networks. Using novel GIS technology and soil erosion modelling, this study evaluated the effect of roads on surface runoff, erosion and sediment yields following a wildfire and determined that the predictive models were providing reasonable results. The GeoWEPP model was used to simulate onsite erosion and offsite sediment delivery before and after fire disturbance using a 2-m resolution DEM as the terrain layer. Erosion rates in excess of 4 Mg ha⁻¹ year⁻¹ were predicted mainly from steep moderate and high severity burn areas. Roads influenced surface runoff flow path distributions and sub-catchment delineations, affecting the spatial distribution of sediment detachment and transport. Roads tended to reduce estimated erosion on slopes below the roads but increases in erosion rates were estimated for road fillslopes. Estimated deposition amounts on roads and in sediment basins were similar to measured amounts. The results confirm that road prisms, culverts and road ditches influence sedimentation processes after wildfire, and they present opportunities to detain eroded sediments.     

Characteristics of grassland degradation and driving forces in the source region of the Yellow River from 1985 to 2000*

The source region of the Yellow River is located in the middle east of the Tibetan Plateau in northwest China. The total area is about 51,700 km2, mainly covered by grassland (79%), unused land (16%) and water (4%). The increasing land utilization in this area has increased the risk of environmental degradation. The land use/cover data (1985 and 2000) provided by the Data Center of Resources and Environment in the Chinese Academy of Sciences were used to analyze the land cover change in the source region of the Yellow River. DEM (1:250,000) data, roads and settlement data were used to analyze the spatial characteristics of grasslands degradation. The ArcGIS 9 software was used to convert data types and do the overlay, reclassification and zonal statistic analysis. Results show that grassland degradation is the most important land cover change in the study area, which occupied 8.24% of the region’s total area. Human activities are the main causes of the grassland degradation in the source region of the Yellow River: 1) the degradation rate is higher on the sunny slope than on the shady slope; 2) the grassland degradation rate decreases with an increase in the elevation, and it has a correlation coefficient of -0.93; 3) the nearer to the settlements the grassland is, the higher the degradation rate. Especially within a distance range of 12 km to the settlements, the grassland degradation rate is highly related with the distance, with a coefficient of -0.99; and 4) in the range of 4 km, the degradation rate decreases with the increase of distance to the roads, with a correlation coefficient of -0.98. Besides some physical factors, human activities have been the most important driving forces of the grassland degradation in the source region of the Yellow River since 1985. To resolve the degradation problems, population control is essential, and therefore, it can reduce the social demand of livestock products from the grassland. To achieve sustainable development, it needs to improve the management of grassland ecosystem.     

基于GIS的福建省公路网络体系可达性分析

以福建省公路交通情况为基本资料,通过运用ArcGIS的网络分析功能,从时间距离的角度,采用加权平均旅行时间的指标,对福建省公路交通网络体系的可达性情况进行计算、分析,得出福建省公路交通网络体系可达性的区域等级情况,在此基础上分别对第一、二、三阶梯的可达性成因进行分析,并对福建省不同地区的交通可达性进行了比较.