共查询到20条相似文献，搜索用时 31 毫秒
1.
Maria Salonen Tuuli ToivonenJean-Michel Cohalan Oliver T. Coomes 《Applied geography (Sevenoaks, England)》2012,32(2):501-513
Quantitative measures of accessibility are increasingly used in land cover change modeling and in assessing human pressure on the environment. In riverine Amazonia the significance of physical accessibility for biodiversity, land use patterns and economic livelihoods is widely acknowledged, but attempts to quantify accessibility in practice have been few in number. In this study we compare different distance- and frequency-based measures of spatial accessibility and develop a quantitative model of accessibility patterns for the north-eastern Peruvian Amazonia where rivers form the core of the transportation network. We model accessibility between the rural areas of the Loreto region and the capital city of Iquitos, using different distance algorithms in a geographic information system, and complement the distance model with information on river boat frequencies and transport capacities. Patterns of accessibility are visualized in terms of potential production zones for different types of agricultural and non-timber forest products.This study demonstrates how results from different accessibility measures vary considerably. The mean Euclidean distance to Iquitos is almost 270 km, the mean network distance nearly 760 km and the mean travel time 70 h. Observed network distances from validation points to Iquitos are on average 1.6 times longer than Euclidean distances, and for the whole study area, the average ratio between modeled network distances and Euclidean distances is 3.1. The correlation between network distances and time distances is very strong, but time distances are relatively shorter along the major channels where boat traffic is considerably faster than along narrow, tightly meandering rivers. Measures of boat frequency and transport capacity show that availability of transport possibilities is highly varying across the region. These measures provide insights into the ’thickness’ of trade, indicating the level of market integration for riverine settlements. We conclude that quantifying accessibility in an environment like Peruvian Amazonia requires measures that take into account the spatial structure and dynamic nature of the riverine transportation network. Time as a unit of distance provides the most relevant measure of accessibility in the Amazonian context, where many human actions and traditional livelihoods are controlled by travel times between the regional core and the hinterland. 相似文献
2.
Railroads, roads and lateral disconnection in the river landscapes of the continental United States 总被引：1，自引：0，他引：1
Railroads and roads are ubiquitous features in the river corridors of the United States. However, their impact on hydrologic, geomorphic, and ecological processes in fluvial and riparian landscapes has not been systematically explored at regional or continental extents. This study documents the geographic distribution of roads and railroads in the alluvial floodplains of the continental United States and the regional variability of their potential impacts on lateral connectivity and resultant channel and floodplain structure and function. We use national scale data sets and GIS analysis to derive data on stream–transportation network interactions in two broad categories: (1) crossing impacts, such as bridges and culverts, and (2) impacts where transportation infrastructure acts as a longitudinal dam along the stream channel, causing lateral floodplain disconnection. Potential stream crossing impacts are greatest in regions with long histories of road and railroad development and relatively low relief, such as the Mid-Atlantic, New England, and the Lower Mississippi and Ohio Valleys. Potential lateral disconnections are more prevalent in rugged regions such as the Western U.S. and Appalachians where transportation routes follow river corridors along valley bottoms. Based on these results, we develop a conceptual model that suggests that the area of lateral disconnection due to transportation infrastructure should be most extensive in mid-sized alluvial valleys in relatively rugged settings. The result of this disconnection is the disruption of the long-term, cut-and-fill alluviation and of the shorter-term flood and flow pulse processes that create and maintain ecosystem function in river landscapes. The tremendous extent of transportation infrastructure in alluvial valleys documented in this study suggests a revision to H.B.N. Hynes' statement that the valley rules the stream. Instead, it appears that in modern landscapes of the U.S. the valley rules the transportation network — and the transportation network rules the stream. 相似文献
3.
Quaternary catchments in the south of the Sorbas Basin, SE Spain have been affected by two regionally significant river captures. The river captures were triggered by changes in regional gradients associated with sustained Quaternary uplift in the region of 160 m Ma−1. The first capture occurred in the early Pleistocene and re-routed 15% of the original Sorbas Basin drainage into the Carboneras Basin to the south. The second occurred in the late Pleistocene and re-routed 73% of the original Sorbas Basin drainage to the east. This latter capture had dramatic consequences for base-level in the Sorbas Basin master drainage. Local base-level was lowered by 90 m at the capture site, 50 m at 7 km upstream and 25 m at 13 km upstream of the site. The base-level change instigated a complex re-organisation of the drainage networks in systems tributary to the master drainage over the ensuing period (some 100 ka). After the capture, drainage systems closer to the capture site experienced a tenfold increase in incision rates over most of their network. Those located some 13 km upstream of the capture site experienced a fivefold increase in incision, although in this instance, the changes do not appear to have propagated to the headwater regions of the drainage nets. The sensitivity of individual catchments was largely governed by geological controls (structure and lithology). The detailed network evolution in the most sensitive areas can be traced by reconstructing former drainage pathways using abandoned drainage cols and the alignment and degree of incision of the drainage networks. Three main stages of evolution can be identified which record the progressive spread of base-level changes from the master drainage. These are Stage 1 (pre-capture): original south-to-north consequent drainage; Stage 2 (early stage, post capture): aggressive subsequent southwest-to-northeast and east–west drainage developed along structural lineaments first in the east of the area (Stage 2a), and later in the west of the area (Stage 2b); and Stage 3 (late stage, post capture): obsequent drainage developing on the topography of the Stage 2 drainage. All stages of the network evolution are associated with drainage re-routing as a function of river capture at a variety of scales. The results highlight the complex response of the fluvial system, and the very different geomorphological histories of adjacent catchments, emphasising the need for regional approaches for examining long-term changes in fluvial systems. 相似文献
4.
Hui Yuan Qingquan Li Shih-Lung Shaw William H. K. Lam 《International journal of geographical information science》2018,32(6):1211-1246
Spatiotemporal proximity analysis to determine spatiotemporal proximal paths is a critical step for many movement analysis methods. However, few effective methods have been developed in the literature for spatiotemporal proximity analysis of movement data. Therefore, this study proposes a space-time-integrated approach for spatiotemporal proximal analysis considering space and time dimensions simultaneously. The proposed approach is based on space-time buffering, which is a natural extension of conventional spatial buffering operation to space and time dimensions. Given a space-time path and spatial tolerance, space-time buffering constructs a space-time region by continuously generating spatial buffers for any location along the space-time path. The constructed space-time region can delimit all space-time locations whose spatial distances to the target trajectory are less than a given tolerance. Five space-time overlapping operations based on this space-time buffering are proposed to retrieve all spatiotemporal proximal trajectories to the target space-time path, in terms of different spatiotemporal proximity metrics of space-time paths, such as Fréchet distance and longest common subsequence. The proposed approach is extended to analyze space-time paths constrained in road networks. The compressed linear reference technique is adopted to implement the proposed approach for spatiotemporal proximity analysis in large movement datasets. A case study using real-world movement data verifies that the proposed approach can efficiently retrieve spatiotemporal proximal paths constrained in road networks from a large movement database, and has significant computational advantage over conventional space-time separated approaches. 相似文献
5.
《自然地理学》2013,34(5):453-478
This paper presents results of the geomorphological study of river elements for a morphostructural characterization of Hispaniola. The fluvial system and its primary and secondary drainage divides were delimited using a specially developed methodology. More than 120 fluvial basins were studied. The largest rivers are the sixth-order Yaque del Norte and Yaque del Sur. The fluvial density is in the range of 0.08-4.0 km/km2, with highest values in the Cordillera Central. There are two large hydrological regions, the Western and the Eastern, with a northeastern transverse diagonal boundary, coinciding with the direction of the Beata Escarpment. Using quantitative data to characterize the morphostructure of the fluvial network in Hispaniola enabled us to make comparisons with a Cuban network. As is shown, the river pattern in Hispaniola is basically tectonic, with a remarkable directional diversity in the main first-order drainage divide. In the Caribbean area, Eastern Cuba is the only other location with this pattern. 相似文献
6.
ABSTRACT Fluvial megafans chronicle the evolution of large mountainous drainage networks, providing a record of erosional denudation in adjacent mountain belts. An actualistic investigation of the development of fluvial megafans is presented here by comparing active fluvial megafans in the proximal foreland basin of the central Andes to Tertiary foreland‐basin deposits exposed in the interior of the mountain belt. Modern fluvial megafans of the Chaco Plain of southern Bolivia are large (5800–22 600 km2), fan‐shaped masses of dominantly sand and mud deposited by major transverse rivers (Rio Grande, Rio Parapeti, and Rio Pilcomayo) emanating from the central Andes. The rivers exit the mountain belt and debouch onto the low‐relief Chaco Plain at fixed points along the mountain front. On each fluvial megafan, the presently active channel is straight in plan view and dominated by deposition of mid‐channel and bank‐attached sand bars. Overbank areas are characterized by crevasse‐splay and paludal deposition with minor soil development. However, overbank areas also contain numerous relicts of recently abandoned divergent channels, suggesting a long‐term distributary drainage pattern and frequent channel avulsions. The position of the primary channel on each megafan is highly unstable over short time scales. Fluvial megafans of the Chaco Plain provide a modern analogue for a coarsening‐upward, > 2‐km‐thick succession of Tertiary strata exposed along the Camargo syncline in the Eastern Cordillera of the central Andean fold‐thrust belt, about 200 km west of the modern megafans. Lithofacies of the mid‐Tertiary Camargo Formation include: (1) large channel and small channel deposits interpreted, respectively, as the main river stem on the proximal megafan and distributary channels on the distal megafan; and (2) crevasse‐splay, paludal and palaeosol deposits attributed to sedimentation in overbank areas. A reversal in palaeocurrents in the lowermost Camargo succession and an overall upward coarsening and thickening trend are best explained by progradation of a fluvial megafan during eastward advance of the fold‐thrust belt. In addition, the present‐day drainage network in this area of the Eastern Cordillera is focused into a single outlet point that coincides with the location of the coarsest and thickest strata of the Camargo succession. Thus, the modern drainage network may be inherited from an ancestral mid‐Tertiary drainage network. Persistence and expansion of Andean drainage networks provides the basis for a geometric model of the evolution of drainage networks in advancing fold‐thrust belts and the origin and development of fluvial megafans. The model suggests that fluvial megafans may only develop once a drainage network has reached a particular size, roughly 104 km2– a value based on a review of active fluvial megafans that would be affected by the tectonic, climatic and geomorphologic processes operating in a given mountain belt. Furthermore, once a drainage network has achieved this critical size, the river may have sufficient stream power to prove relatively insensitive to possible geometric changes imparted by growing frontal structures in the fold‐thrust belt. 相似文献
7.
肯尼亚交通优势度及其空间分异格局分析 总被引：1，自引：0，他引：1
基于2018年肯尼亚铁路、公路、机场、港口等交通基础设施数据，设定交通优势度指数及交通网络连接度指数和交通对外通达度指数2个分指数，采用探索性数据分析法对肯尼亚交通优势度及其空间分异格局进行分析，并对其影响因素进行探讨。研究发现：① 肯尼亚交通优势度空间差异十分显著，以内罗毕、蒙巴萨和基苏木为主要交通节点的铁路沿线地区交通优势度水平明显高于其他地区；② 肯尼亚交通优势度空间分异格局总体上呈现出较强的非均衡性，交通网络连接度呈现出以内罗毕为核心，以铁路沿线为轴带呈圈层状向四周递减的空间分异格局，而交通对外通达度呈现出北部和西北部较低而南部和东南部较高的空间分异格局。③ 地形地貌、气候、水文、人口集聚、经济发展等是形成肯尼亚交通优势度空间分异的主要影响因素。对交通基础设施空间分布进行优化调整，积极引导经济空间合理布局，是推动肯尼亚经济健康持续发展的重要途经。 相似文献
8.
The fluvial geomorphological development of the Tagliamento River and its flooding history is analysed using historical documents and maps, remote-sensed data and hydrological information. The river has been building a complex alluvial fan starting from the middle part of its alluvial course in the Venetia–Friuli alluvial plain. The riverbed is aggrading over its entire braided length. The transition from braiding to meandering near Madrisio has shifted downstream where the river width determined by the dikes becomes narrower, causing major problems. The flood hazard concentrates at those places and zones where flooding occurred during historical times. Prior to the agrarian and industrial revolution, land use was adjusted to the flooding regime of the river. Subsequent land-use pressure led to a confinement of the river by dikes to such an extent that the flood risk in the floodplain downstream of Madrisio has increased consistently, and represents nowadays a major territorial planning issue. The planned retention basins upstream of the middle Tagliamento will alleviate the problem, but not solve it in the medium and long term. Therefore, fluvial corridors in the lower-middle parts (from Pinzano to the sea) have been identified on the basis of the flooding history in relation to fluvial development during historical times. The result should be used for hydraulic simulation studies and land-use planning. 相似文献
9.
中国交通通达度评价:从分县到分省 总被引：15，自引：3，他引：12
从自身交通设施保障程度和与外界交流联系便利程度两方面,采用公路密度、铁路密度、与公路距离等8个指标,构建了交通通达指数模型;运用GIS技术,以2005年为例,定量计算中国分县通达指数,集成中国分省通达指数,从分县和分省两个尺度评价了中国交通通达水平。结果表明:⑴ 从分县尺度看,中国县域交通通达水平高低两端差异悬殊,呈明显"纺锤形"结构,呈现由沿海逐渐向内陆递减趋势,贫困地区与城市化地区交通密度差距显著;⑵ 从分省尺度看,中国分省交通通达水平差异显著,地域分布呈现"东高西低"的空间格局;不同等级水平间通达指数差距明显,西部省份交通支撑能力和保障水平偏低。因此,应大力加快西部地区交通基础设施发展,实现地区间和谐发展。 相似文献
10.
马六甲海峡、苏伊士运河、巴拿马运河三大主航道在全球集装箱海洋运输中发挥着核心作用。本文基于全球集装箱运输船舶AIS轨迹数据构建了无向加权网络,采用网络平均度、聚类系数、平均最短路径长度等指标,从地理空间的视角,度量了全球集装箱海洋运输对三大航道的依赖性。结果表明：① 海上主航道受阻对不同区域的影响程度存在显著性差异,对国家中转功能及可达性的影响以航道为中心向外呈距离衰减效应;② 集装箱海运网络对航道的依赖性由高到低依次为马六甲海峡、苏伊士运河、巴拿马运河;③ 从区域角度看,东南亚、中东及地中海等区域国家对航道的依赖性远高于其他国家;④ 三大航道受阻导致集装箱海运网络结构特征发生变化,对海运大国中转功能及可达性产生中等级别影响,绝大部分海运国家的变幅在中等及以下级别。研究成果对全球集装箱运输网络重点航线保护及航线优化具有参考价值。 相似文献
11.
Hassan A. Karimi Piyawan Kasemsuppakorn 《International journal of geographical information science》2013,27(5):947-962
With the advanced capabilities of mobile devices and the success of car navigation systems, interest in pedestrian navigation systems is on the rise. A critical component of any navigation system is a map database, which represents a network (e.g., road networks for car navigation) and supports key functionality such as map display, geocoding, and routing. Road networks, mainly due to the popularity of car navigation systems, are well defined and publicly available. However, in pedestrian navigation systems, as well as other applications including urban planning and physical activity studies, road networks do not adequately represent the paths that pedestrians usually travel. Currently, there is a void in literatures discussing the challenges, methods, and best practices for pedestrian network map generation. This coupled with the increased demand for pedestrian networks is the prime motivation for development of new approaches and algorithms to automatically generating pedestrian networks. Three approaches, network buffering, using existing road networks, collaborative mapping, using Global Positioning System (GPS) traces collected by volunteers, and image processing, using high-resolution satellite and laser imageries, were implemented and evaluated with a pedestrian network baseline as a ground truth. The results of the experiments indicate that these three approaches, while differing in complexity and outcome, are viable for automatic pedestrian network map generation. The recommendation of a suitable approach for generating pedestrian networks for a given set of sources and requirements is provided. 相似文献
12.
武汉都市圈路网空间通达性分析 总被引：20，自引：1，他引：19
以武汉都市圈为例.通过距离算法、拓扑算法和空间句法模型,构建系列通达性数理模型.定量分析武汉都市圈路网发育的空间结构性规律:武汉都市圈路网整体发育水平和通达性格局保持高度相关性和一致性.空间差异显著;通达性遵循距离衰减律,空间收敛整体效应明显.呈现三大等级圈层和"中心-外围"结构:高等级路网发育不均衡.引起时空距离通达性圈发生"摄动"变形,呈西北-东南向倾斜的"Y"字形结构:拓扑连接等通达性圈更是出现"破碎化",交通轴线网络呈"轴一辐"式和"鱼骨刺"状空间伸展序:同时,路网发育的等级差异性也导致整个网络伺服效率和应对"拥堵"能力的低下,并形成沿长江东西向、沿京广南北向两条带状集成核.成为整个路网的第一等级交通轴线,控制整个都市圈网络连接性,强化交通轴线交汇处-武汉市的中心性优势:路网通达性这种等级空间格局与圈域城镇体系、交通设施和社会经济发展状况密切相关.尤其是与高速公路为代表的高等级路网发育水平,表现出复杂的共轭协调关系. 相似文献
13.
14.
武汉城市圈城乡道路网的空间结构复杂性 总被引：6，自引：1，他引：5
以武汉城市圈为研究区,借助ArcGIS9.3、Pajek2.7和SPSS16.0等软件,从节点重要性、可达性、集聚性3个方面定量揭示了复杂城乡道路网的空间异质性:①高度节点重要性呈幂律分布,表现出无标度性,低度节点重要性则基本呈钟型泊松分布,呈现一定的随机性,导致整个圈域节点的重要性分布曲线既不遵循钟型泊松分布也不遵循幂律分布,出现"涌现"性;节点度值空间分布较均匀,呈现点状特征和弱集聚性,具有明显间断性和跳跃性,表现出一定的"中心-边缘"和"等级圈层"的复合结构;②节点的可达性主要由网络平均路径长度、紧密度和介数指标表达,其中道路网平均路径长度较大,节点交通联系呈线状组织,遵循距离衰减律,成等级圈层分异,但受快速干道影响明显,空间收敛减慢,发生"摄动"变形,形成两条以南北京珠高速和东西宜黄高速为轴的城市交通走廊;节点的紧密度系数较随机网络小,但高紧密度节点在空间分布上较为集中,呈现出一定的"中心-边缘"空间格局;节点的介数指标相对较高,呈现指数分布,空间分布较均匀,但仍呈现出一定的"等级圈层"分异;③网络的集聚性空间差异显著,形成多个大型网络社团,网络的聚类系数近似为零,局部呈现耦合性质,高聚类系数节点集聚成"半月形"展布,低聚类系数节点分布较为离散。 相似文献
15.
基于社会网络分析方法,利用国家交通运输物流公共信息平台2018年全国地级及以上城市的公路零担专线数据,从城市节点、城际联系、子网络3个层面对中国城市网络结构特征进行识别,结果表明：1）上海、天津、郑州、广州、杭州在网络中处于主导性地位,根据货流组织系数,可将城市节点划分为强中心、次强中心、弱中心、从属型4种类型。2）在首位联系总量排名前十的城市中,输出型城市和输入型城市的比例为4∶1,反映货流流向的不均衡性。由公路零担专线数据刻画的网络空间呈现显著的距离衰减规律,集中在500 km的专线数量占比为41.9%。3）公路零担专线网络形成东北―冀鲁蒙社区、中原社区、关中社区、江淮社区、泛珠三角―长三角社区、长株潭社区6个具有显著地域特征的城市社区,社区结构表现出明显的空间集聚和跨行政区特征。最后,提出以下建议：增强成渝城市群公路零担专线服务能力,发挥核心城市产业集聚和带动作用;优化边缘城市产业结构,加强交通与产业融合;积极引导无车承运人平台发挥网络规模化效应,提高公路货运组织效率。 相似文献
16.
本文运用景观生态学原理,借助ArcGIS技术,选择中国北方10个流域及其12个沙漠/沙地,并以西部的和田河和东部的西辽河为典型研究区,在流域与沙区、河道与沙丘两个尺度上,选取景观破碎度指数、景观多样性指数等指标,探讨中国北方干旱、半干旱区沙漠/沙地景观与廊道景观(河流)的空间镶嵌格局特征。结果表明：在流域与沙区尺度上,内流区较外流区沙区景观类型复杂,景观破碎度较小,外流区沙区景观结构较为相似;内流区沙区景观指数自西向东呈现出“景观破碎度递增、景观结构复杂性递减”的规律。在河道与沙丘尺度上,在缓冲带范围内,和田河较西辽河沙丘景观类型复杂,景观破碎度较小;景观指数随河道距离的变化呈现出“景观破碎度随距河道距离的加大而逐渐递减,丰富度指数随距河道距离的加大而呈阶梯状递增”的规律;从沙丘斑块类型景观指数上看,西辽河以固定、半固定的简单型沙丘为主,和田河以流动的综合型沙丘为主。主导的沙丘类型景观距离河道越远,面积比例越小,不同沙丘类型的水平景观破碎度随河道距离递减。 相似文献
17.
运用Hicks-Moorsteen TFP指数法对中国公路运输业全要素生产率进行测度和演化分析。结果发现：2009~2012年中国公路全要素生产率实现了增长,2013~2015年出现下降。2009年来技术进步推动了东部地区公路运输全要素生产率的增长,而运营效率提升则在推动中西部地区公路运输全要素生产率增长时起到了关键作用。中西部地区公路运输效率增长优于东部地区。东部地区在引领技术进步的同时,应注重公路运输效率的提升;中西部地区应注意加大先进技术的引进。政府和主管部门对中西部公路运输应推出持续性支持政策。 相似文献
18.
The use of multi-perspective and multi-scalar city networks has gradually developed into a range of critical approaches to understand spatial interactions and linkages. In particular, road linkages represent key characteristics of spatial dependence and distance decay, and are of great significance in depicting spatial relationships at the regional scale. Therefore, based on highway passenger flow data between prefecture-level administrative units, this paper attempted to identify the functional structures and regional impacts of city networks in China, and to further explore the spatial organization patterns of the existing functional regions, aiming to deepen our understanding of city network structures and to provide new cognitive perspectives for ongoing research. The research results lead to four key conclusions. First, city networks that are based on highway flows exhibit strong spatial dependence and hierarchical characteristics, to a large extent spatially coupled with the distributions of major megaregions in China. These phenomena are a reflection of spatial relationships at regional scales as well as core-periphery structure. Second, 19 communities that belong to an important type of spatial configuration are identified through community detection algorithm, and we suggest they are correspondingly urban economic regions within urban China. Their spatial metaphors include the administrative region economy, spatial spillover effects of megaregions, and core-periphery structure. Third, each community possesses a specific city network system and exhibits strong spatial dependence and various spatial organization patterns. Regional patterns have emerged as the result of multi-level, dynamic, and networked characteristics. Fourth, adopting a morphology-based perspective, the regional city network systems can be basically divided into monocentric, dual-nuclei, polycentric, and low-level equilibration spatial structures, while most are developing monocentrically. 相似文献
19.
20.
Xue Yang Kathleen Stewart Zhen Dong Xia Zhang Qingquan Li 《International journal of geographical information science》2018,32(3):601-621
Lane-level road network updating is crucial for urban traffic applications that use geographic information systems contributing to, for example, intelligent driving, route planning and traffic control. Researchers have developed various algorithms to update road networks using sensor data, such as high-definition images or GPS data; however, approaches that involve change detection for road networks at lane level using GPS data are less common. This paper presents a novel method for automatic change detection of lane-level road networks based on GPS trajectories of vehicles. The proposed method includes two steps: map matching at lane level and lane-level change recognition. To integrate the most up-to-date GPS data with a lane-level road network, this research uses a fuzzy logic road network matching method. The proposed map-matching method starts with a confirmation of candidate lane-level road segments that use error ellipses derived from the GPS data, and then computes the membership degree between GPS data and candidate lane-level segments. The GPS trajectory data is classified into successful or unsuccessful matches using a set of defuzzification rules. Any topological and geometrical changes to road networks are detected by analysing the two kinds of matching results and comparing their relationships with the original road network. Change detection results for road networks in Wuhan, China using collected GPS trajectories show that these methods can be successfully applied to detect lane-level road changes including added lanes, closed lanes and lane-changing and turning rules, while achieving a robust detection precision of above 80%. 相似文献