地学雑誌
Online ISSN : 1884-0884
Print ISSN : 0022-135X
ISSN-L : 0022-135X
117 巻 , 2 号
選択された号の論文の28件中1~28を表示しています
表紙
  • 2008 年 117 巻 2 号 p. Cover02_1-Cover02_2
    発行日: 2008/04/25
    公開日: 2010/06/02
    ジャーナル フリー
     最近の探査により,火星に関する各種データの量が飛躍的に増加し,データの質も改善されてきている.この状況に対応して,惑星科学者たちはGISを火星の地形研究において重要なツールとして使用するようになってきた.
     この俯瞰図は,アメリカ航空宇宙局が打ち上げたマース・グローバル・サーベイヤー探査機搭載のMOLAと呼ばれるレーザー高度計のデータをもとに,GIS上で作成した.高度の誇張度は8である.タルシス高地は火成作用や構造運動,さらには過去に地表に多く存在したとされる水の証拠が豊富である.また,火星の地表のなかでも若い地質年代に区分される.太陽系で最大級の火山群やヴァリスマリネリスと呼ばれる巨大な谷,巨大洪水による侵食でできたとされるアウトフローチャンネル群などが,この俯瞰図でわかりやすく表示されている.手前に見えるアラビア高地は衝突クレーターが多数存在し,地質年代が古いと考えられている.
     アメリカ合衆国地質調査所,トレント・ハレ氏提供.
    (文:小松吾郎)
特集号:GIS
I.GISの発展,理論,教育,データ整備
総説
  • 岡部 篤行
    2008 年 117 巻 2 号 p. 312-323
    発行日: 2008/04/25
    公開日: 2010/06/02
    ジャーナル フリー
     This paper reports the history of GIS developments in the 1970s and 1980s in Japan. The paper outlines ten GIS development projects: Small Area Information Systems, UIS-I, Geographic Information Processing System and Overlay Mapping Technique, Computer Graphic Systems for City Planning, ISLAND, TUMSY, Local Government GIS, Geographical Information Processing, TOGIS, and UIS-II.
  • 奥貫 圭一
    2008 年 117 巻 2 号 p. 324-340
    発行日: 2008/04/25
    公開日: 2010/06/02
    ジャーナル フリー
     This paper discusses spatial analysis and applicable tools available in GIS environments. Since the 1990s, organizations conducting research in the field of Geographic Information Science (GISci) have been developing software packages and extension toolboxes for spatial analysis. Many researchers dealing with spatial phenomena have little knowledge of the wide selection of GISci applications that can be applied to spatial analysis in their research. They can benefit from information and direction on valuable computational resources that can be applied to their specific research problems. FreeSAT, an online portal, has been constructed to provide researchers with information on spatial analysis tools. The FreeSAT website provides links to a wide variety of spatial analysis tools and information on specific research problems to which these tools can be applied.
     This paper also discusses various computational methods for spatial analysis, such as the nearest neighbor distance, K-function, Voronoi's tessellation, and Huff-based marketing methods, which are all found at the FreeSAT site. It also provides detailed discussions on the application of Spatial Data Analysis Machine (SDAM) and Spatial Analysis on a NETwork (SANET) toolboxes to spatial analysis. While most toolboxes of this type are developed by organizations in the United States or Europe, both SDAM and SANET were developed by organizations in Japan.
論説
  • 湯田 ミノリ, 伊藤 悟, 内田 均, 木津 吉永, 伊東 純也
    2008 年 117 巻 2 号 p. 341-353
    発行日: 2008/04/25
    公開日: 2010/06/02
    ジャーナル フリー
     The use of GIS in education in Japan has not yet been widely diffused, although the computer and network environments of schools have been improved, and teachers have already recognized the characteristics and advantages of this tool in education.
     Nowadays, GIS has been intergraded into many aspects of our lives. Mobile phones are also basic tools in our daily lives. A GIS application that runs on cellular phones would be helpful in school education.
     From this point of view, the authors have developed a system called Cellular Phone GIS including a GIS application for mobile phone (hereinafter Cell Phone GIS Application) and its web-based GIS viewer application for PC using Google maps (hereinafter PC viewer), and carried out fieldwork at an upper secondary school using these tools. Data can be input and edited outdoors with the Cell Phone GIS Application. These data can be viewed on both cellular phones and personal computers via the Internet. Students carried out a land use survey in the area around the school with the Cell Phone GIS Application, and examined and presented the results using the PC viewer in class.
     Students participated actively in the fieldwork with the cellular phone. Through experience of the survey with the tool, they found many new things and learned to adopt multi-dimensional points of view and ways of thinking. Also, this project generated more interest among students in geography classes.
     The Cell Phone GIS Application provided high school students with a feeling of accomplishment from the fieldwork. Meanwhile, this tool and PC viewer minimized work after fieldwork because users do not have to input and aggregate data again. Therefore, teachers and students can use course hours efficiently. The Cellular Phone GIS can provide an environment in which students are able to receive educational effects from fieldwork.
  • 高橋 昭子, 岡部 篤行
    2008 年 117 巻 2 号 p. 354-369
    発行日: 2008/04/25
    公開日: 2010/06/02
    ジャーナル フリー
     This paper analyzes an evaluation of students taking a GIS laboratory teaching course that uses an online learning system. First, a factor analysis is applied to evaluation data on students. Second, a cluster analysis is applied to the factor score of each student. As a result, three groups of students are obtained. A multiple comparison method is applied to compare the three groups with respect to factor loading, evaluation, test scores and total access time. The characteristics of the three groups are as follows. Students in the first group heavily depend on teachers. They hesitate to ask other students even if they have questions. They cannot set the pace of their studies in the class. Support from teachers is needed until they get used to the online learning system. Students in the second group are satisfied with laboratory teaching. They can study at their own pace with the system. They also have high expectations about future online learning systems. However, they do not study positively with the system. Teachers need to encourage students in the second group to study more with the system. Students in the third group actively use the system, but level of their satisfaction of laboratory teaching is low. They do not have high expectations for future online systems. Teaching methods should be improved to take advantage of the system.
  • 渡邉 敬逸, 村山 祐司, 藤田 和史
    2008 年 117 巻 2 号 p. 370-386
    発行日: 2008/04/25
    公開日: 2010/06/02
    ジャーナル フリー
     Enormous amounts of statistics have been published since the start of the Japanese modern era. Among all of these statistics, modern statistics published in the Meiji era are fundamental for grasping the historical geography of Japan. GIS can be powerful analytical tool for applying such modern statistics to historical regional analyses.
     Although GIS has potential for historical regional analyses using modern Japanese statistics, studies are not making significant progress at the present time. A background factor is that municipal polygon data and digitized statistics in the Japanese modern era are not available to the public. As a result, in 2004, the authors established the open web-based database titled “Historical regional statistics,” which contains a variety of municipal polygon data and digitized statistics from the modern era. The purpose of this study is to review some digitized statistics and municipal polygon data contained in “Historical regional statistics,” and discus their availability through a case study.
     “Historical regional statistics” contains eight groups of statistics (39 statistics) and four groups of municipal maps (213 maps). Among these data, military statistics, “Meiji 24 Nen Chohatsu Bukken Ichiranhyo (Requisition Order List in 1891)”, “Fuken Tokei Hyo (Prefectural Statistics)” and “Consolidation of municipalities database” are available and provide versatility. The case study, which analyzes the regional structure of central Japan in the mid-Meiji era, applies the 1890 “Consolidation of municipalities database” and military statistics, “Meiji 24 nen Chohatsu Bukken Ichiranhyo (Requisition order list in 1891)”. Factor and cluster analyses are applied to explain the regional structure. In the factor analysis, eight factors are abstracted from 35 variables. Then, by applying the cluster analysis to the factor matrix, central Japan is classified into six regional types.
     Complicated research processes for handling or building of data are reduced by digitized statistics and municipal polygons. The regional structure analyzed in the case study can be understood from existing findings of historical geography in Japan. These points show the possible availability of “Historical regional statistics” for historical regional analyses with GIS. On the other hand, it is shown that data used in the case study contain some errors. This point is common to other data in “Historical regional statistics,” and needs to be corrected with the user's cooperation.
資料
  • 宇根 寛
    2008 年 117 巻 2 号 p. 387-400
    発行日: 2008/04/25
    公開日: 2010/06/02
    ジャーナル フリー
     Recently, the circumstances of the world's national mapping organizations have changed due to various factors such as the computerization of mapping technologies, development of GIS and the Internet, global environmental problems and government restructuring. The new roles of national mapping organizations in the era of GIS should be to: 1) provide and maintain a unique framework for exchanging and sharing geo-spatial data as a social infrastructure and 2) contribute to sustainable development by providing accurate, current geographic information on the global environment. The Geographical Survey Institute (GSI), the national mapping organization of the Japanese Government, has adopted such roles by promoting the Digital Japan Project and the Global Mapping Project. GSI developed the Denshi Kokudo Web System to provide a platform for various geo-spatial data applying web-mapping technologies to realize the Digital Japan concept. This system enables users to dispatch original geographic information without having to prepare background map data. GSI also acts as the secretariat of the International Steering Committee for Global Mapping. The Global Mapping Project develops digital geographic information covering the earth's surface at 1km resolution with standardized specifications available to all through cooperation among national mapping organizations around the world. This paper outlines the background, history and current status of these projects.
II.自然地理学分野
総説
  • 小松 吾郎
    2008 年 117 巻 2 号 p. 401-411
    発行日: 2008/04/25
    公開日: 2010/06/02
    ジャーナル フリー
     In planetary geomorphology, the use of printed images and topographic maps was standard practice until the late 1980s, but the availability of low-cost computers stimulated the propagation of digital data analyses in the 1990s. In the present-day research environment, Geographic Information Systems (GIS) are becoming increasingly important. This is due in large part to the explosive increase of data sent by an armada of spacecraft observing Mars. The future development of GIS in research on planetary surfaces might involve more extensive use of the Internet and introduction of virtual reality technology.
  • 山野 博哉
    2008 年 117 巻 2 号 p. 412-423
    発行日: 2008/04/25
    公開日: 2010/06/02
    ジャーナル フリー
     Although much attention has been paid to low-lying atoll reef islands as the first victims of a sea-level rise caused by global warming, they usually are not mapped (e.g., shoreline positions, elevation, and land-use/cover), thus a quantitative evaluation of the impact of global warming is not feasible. In this paper, recent advances in remote-sensing technology are described, including the current status of the mapping of shoreline positions, elevation, and land-use/cover of atoll reef islands. Then, the effectiveness of historical reconstruction based on the maps produced from archived past images, as well as archaeological human settlement data and socioeconomic data, is shown to examine the nature of the vulnerability of atoll reef islands to global warming. Overall, geographic information generated by remote sensing could be of great help for assessing and understanding the vulnerability of atoll reef islands.
論説
  • 中山 大地, 森永 大介, 松山 洋
    2008 年 117 巻 2 号 p. 424-438
    発行日: 2008/04/25
    公開日: 2010/06/02
    ジャーナル フリー
     This study analyzes runoff and inundation flow to reproduce the condition of the August 1993 flood that occurred in the upper reaches of Sendai River in the northern part of Kagoshima prefecture, and determines model parameters. Besides, the case of situation more serious than the past floods were assumed, and it is estimated whether the inhabitants could take refuge by traveling on foot on flooded roads to evacuation centers.
     In the runoff analysis, the distributed runoff model based on the kinematic wave model was used. A Gridded Digital Elevation Model (DEM), 50 m resolution was used to provide terrain data and flood runoff was calculated with the Drainage Direction Matrix (DDM) extracted from DEM. Past discharge hydrographs were fairly well reproduced by the runoff analysis. In the inundation flow analysis, a 2-dimensional unsteady flow model based on the dynamic wave model was used to calculate the expansion of the inundation flow. In the inundation flow analysis, the order of water depth was reproduced well in comparison to actual inundation, however, the estimated inundation area was smaller than the actual one.
     Next, runoff and inundation flow analyses were carried out with the modeled rainfall, which was more serious than that of past floods, using the model parameters determined above. The simulated flooded areas were almost the same as those caused by torrential rain in August 1993, however, the water was deeper. The current velocity was high just after the area flooded, but it slowed after 1 to 2 hours to about 0.05 m/sec in most of the flooded areas.
     From a viewpoint of the relations among water depth, height of a person and current velocity, it was quantitatively estimated whether the inhabitants could take refuge or not by traveling on foot on the flooded roads to evacuation centers. Some evacuation centers were located in the flooded areas, so inhabitants could not take refuge there on foot unless they took refuge at early stage of the flood. Whether or not inhabitants could take refuge safely on foot largely depended on their height, and the areas where they could walk safely was limited by their height.
  • 小荒井 衛
    2008 年 117 巻 2 号 p. 439-454
    発行日: 2008/04/25
    公開日: 2010/06/02
    ジャーナル フリー
     This paper analyzes a volcanic hazard map using grid DEMs and vector GIS data, such as landform classification polygons shown on the Land Condition Map of Bandai Volcano which was published by the Geographical Survey Institute. The hazard areas described on the hazard map of Bandai Volcano, landform classification on a land condition map and morphometric data derived from 50-m and 10-m grid DEMs were overlaid using GIS. The results indicate that the expected hazard areas on the hazard map correspond to the past hazard areas shown on the land condition map. Because large-scale collapses of the volcanic body occurred many times as major processes of landform evolution, the areas underlain by past debris avalanche deposits shown on the land condition map are important for discussing disaster prevention. The result of the landform analysis using the 50-m DEM corresponds to a rough landform classification, whereas the result using the 10-m DEM reflects micro-scale landforms.
III.人文地理学分野
総説
  • 高阪 宏行, 関根 智子
    2008 年 117 巻 2 号 p. 455-463
    発行日: 2008/04/25
    公開日: 2010/06/02
    ジャーナル フリー
     The aim of this paper is to review the present situation of business Geographic Information Systems (GIS) in Japan. This paper especially focuses on various geographic information services produced by geographic information technology. Geographic information is defined as attribute data with location and geographic information technology is considered in the second section in terms of software and hardware for manipulating geographic information. The third section reviews location-based services (LBS), which trace positions in real-time using location sensor technology. LBS are classified into six types of service: provision of information specified for a position, tracing service for people, tracing service for vehicles and ships, tracing service for luggage and goods, proximity-based notification, and proximity-based actuation. Spatial analysis on GIS has been applied in business tools to assist sales promotion activities and the posting of handbills in shops and offices. The fourth section presents trade area analysis used to perform effective sales promotion activities. Rating methods and spatial interaction models are also used for location assessments of sites proposed for new shops. The fifth section considers geodemographics as an area marketing tool. The last section presents the outlook for business GIS in Japan.
  • 矢野 桂司, 中谷 友樹, 磯田 弦, 高瀬 裕, 河角 龍典, 松岡 恵悟, 瀬戸 寿一, 河原 大, 塚本 章宏, 井上 学, 桐村 喬
    2008 年 117 巻 2 号 p. 464-478
    発行日: 2008/04/25
    公開日: 2010/06/02
    ジャーナル フリー
     バーチャル京都は,歴史都市京都の過去,現在,未来を探求することを目的に,コンピュータ上に構築されたバーチャル時・空間である。本研究では,最先端のGISとVR技術を用いて,複数の時間スライスの3次元GISからなる4次元GISとしてのバーチャル京都を構築する。本研究は,まず,現在の京都の都市景観を構築し,過去にさかのぼる形で,昭和期,明治・大正期,江戸期,そして,京都に都ができた平安期までの都市景観を復原する。
     バーチャル京都を構築するためには以下のようなプロジェクトが行われた。a)京都にかかわる,現在のデジタル地図,旧版地形図,地籍図,空中写真,絵図,景観写真,絵画,考古学資料,歴史資料など位置参照可能な史・資料のGIS データの作成,b)京町家,近代建築,文化遺産を含む社寺など,現存するすべての建築物のデータベースおよびGISデータの作成,c)上記建築物の3次元VRモデルの構築,d)上記GISデータを用いた対象期間を通しての土地利用や都市景観の復原やシミュレーション。
     バーチャル京都は,京都に関連する様々なデジタル・アーカイブされたデータを配置したり,京都の繊細で洗練された文化・芸術を世界に発信したりするためのインフラストラクチャーである。そして,Webでのバーチャル京都は,歴史的な景観をもつ京都の地理学的文脈の中で,文化・芸術の歴史的データを探求するためのインターフェイスを提供する。さらに,バーチャル京都は,京都の景観計画を支援し,インターネットを介して世界に向けての京都の豊富な情報を配信するといった重要な役割を担うことになる。
論説
  • 田中 耕市
    2008 年 117 巻 2 号 p. 479-490
    発行日: 2008/04/25
    公開日: 2010/06/02
    ジャーナル フリー
     The purpose of this study is to clarify, from a macro-scale viewpoint, the characteristics of urban density growth and patterns of land use change in Tokyo 23 wards from 1991 to 2001, which corresponds to a period of recession. The changes in urban density and former land use where office buildings and multiple dwelling units (MDUs) were located are measured quantitatively. The number of office buildings increased while the number of MDUs hardly changed. However, due to mass construction of high-rise buildings, both the density surfaces of urban office buildings and MDUs developed significantly during the decade. The highest density of office buildings was observed in three wards of central Tokyo. Because numerous office buildings were constructed in those areas, the accumulation of office buildings shows a growing tendency. Construction of many MDUs in commercial and business areas became a factor enhancing population inflows to central Tokyo. The characteristics of the former land use of MDUs differ by area. Some of the highest density spots for the total floor space of MDUs in 2001 are found in the eastern part of Tokyo because high-rise MDUs accumulated in empty lots where factories or warehouses had been located. The former land use was closely related to areal differences in increasing urban density caused by the City Planning Law or the Building Standard Law.
  • 橋本 雄一
    2008 年 117 巻 2 号 p. 491-505
    発行日: 2008/04/25
    公開日: 2010/06/02
    ジャーナル フリー
     This study clarifies the spatio-temporal structure of buildings in Sapporo City and the reconcentration of dwelling space in the central area. The data used in the analysis are gross floor area ratio (gross floor area of each building use [m2]/district area [m2]), and the data sources are the basic survey data for city planning of Sapporo City in 1980, 1986, 1991, 1996 and 2001. First, this research applies the quasi three-mode factor analysis to a three-dimensional matrix (3,934 districts×14 building uses×5 years), and considers the spatio-temporal structure of the buildings in Sapporo City. Next, it analyzes the locations of houses, apartments, and commercial establishments by direction from the central area, and accessibility to railroad and subway stations. The main results are as follows. Regarding the spatio-temporal structure of buildings in Sapporo City, commercial establishments predominate in the central area, and houses and apartment houses occupy most of the surrounding area. The density of buildings is greater along the subway line. Apartment houses increase in density as opposed to commercial establishments or houses near stations around the central area. It is thought that reconcentration of this dwelling space in the central area is a phenomenon observed during the period of this research, and accelerated from the second half of the 1990s. Moreover, GIS is a useful tool for creating map data with a new boundary line, as well for calculating attribute data accompanying boundary changes in the analyses.
  • 中谷 友樹, 矢野 桂司
    2008 年 117 巻 2 号 p. 506-521
    発行日: 2008/04/25
    公開日: 2010/06/02
    ジャーナル フリー
     To detect spatio-temporal pattern of crime clusters/hotspots, the possibilities of three-dimensional mapping methodologies for crime event data are explored using two approaches: three dimensional kernel-density mapping using a volume rendering technique and visualisation of cylindrical significant clusters that can be detected by space-time scan statistics. Both approaches are intended to visualise spatio-temporal domains with high densities of crime in a three-dimensional space composed of two geographical dimensions and one time dimension. The proposed three-dimensional mapping methodologies are evaluated through application to a dataset of snatch-and-run offences in Kyoto City during the period 2003-2004. The results are summarized as follows:
     (a) Three-dimensional crime mapping enables effective visualisation of the geographical extents and duration of crime hotspots simultaneously. This method is particularly useful to identify geographical diffusion and movements of crime clusters/hotspots compared to traditional dynamic analyses of crime mapping using cross-sectional maps with arbitrary time intervals.
     (b) In practice, the roles of three-dimensional kernel mapping and space-time scan statistics should be complementary. Space-time scan statistics provide clear-cut domains of crime clusters/hotspots that can be used for secondary analyses, such as evaluation of socio-environmental and temporal characteristics focusing on detected domains. However, we should note that the method assumes cylindrical geometrical-constrains of space-time domains. Three-dimensional kernel density mapping provides fuzzy domains with high densities of crime and a useful basis to assess the validity of the assumption of spatial scan statistics and to investigate detailed space-time sequences of crime clusters/hotspots.
     (c) Empirical analyses of the snatch-and-run offence dataset in Kyoto City revealed constant clusters/hotspots during the study period in central Kyoto and around Kyoto Station as well as transient clusters/hotspots around several railway stations in the suburbs. Temporal differences of transient clusters show geographical movements of hotspots from the north to the south via the west. We also identified that outbreaks of snatch-and-run offences alternated between a pair of cluster areas. These results suggesting so-called displacement phenomena indicate the need to monitor crime events and effects of crime-preventive actions in a widespread space-time context.
短報
  • 鈴木 晃志郎, 若林 芳樹
    2008 年 117 巻 2 号 p. 522-533
    発行日: 2008/04/25
    公開日: 2010/06/02
    ジャーナル フリー
     Geographers have made a variety of studies using guidebooks to clarify the meaning and distribution of tourist sites in cities. Nevertheless, few studies quantitatively examine the spatial distribution of tourism sites in detail. In addition, little is known about differences among attractions in terms of the cultural backgrounds of tourists. Hence, this study made a spatial analysis of tourist attractions described in guidebooks written for Japanese and English-speaking readers. Applying kernel density estimation and raster operation method with GIS, this study clarifies that tourism attractions in guidebooks differ between Japanese and Anglophone countries. English guidebooks recommend readers to visit not only cultural sites (e.g., historic places, museums, and theatres) but also sites for nightlife (e.g., bars and taverns). In contrast, Japanese guidebooks show less interest in these types of attraction, and tend to focus more on shopping and eating. The spatial distribution of the tourism attractions also indicates some differences between Japanese and Anglophone guidebooks. Specifically, the spatial extent of tourist attractions in English guidebooks is smaller than that in Japanese guidebooks, being located close to railway stations along Yamanote Line. English guidebooks are also characterized by tourist sites for nightlife, centering on the Roppongi district. Thus, attractions listed in guidebooks are regarded as a reflection of the interests and behavior patterns of tourists.
IV.環境・地域研究への応用
論説
  • 王尾 和寿
    2008 年 117 巻 2 号 p. 534-552
    発行日: 2008/04/25
    公開日: 2010/06/02
    ジャーナル フリー
     Over the last 100 years, regional landscapes in Japan have undergone major changes in land cover and land use, and the relationships between human society and river have also changed dramatically. The purpose of this study is to investigate the characteristics of landscape changes over a 100-year period related to the river systems in four main watersheds—Nakagawa, Kasumigaura, Kinugawa, and Kokaigawa watersheds—in the North Kanto Region. The four watersheds are divided into 801 subwatersheds. Landscape attributes such as recent land use, landform, geology, and soil are obtained from digital national land information provided by the Ministry of Land, Infrastructure and Transport of Japan, and land use maps of the Meiji era were retrieved from old edition topographic maps of the Geographic Survey Institute. Data are aggregated at the subwatershed level, followed by GIS and multivariate analysis. First, the composite properties of the physical environment are examined by a principal component analysis, resulting in nine major components. The subwatersheds are classified into five groups by a cluster analysis using the major component scores as variables. Each group shows its unique characteristics of landform, geology, and soil. Next, the relationships between land use patterns and physical environment in the Meiji era and the present in each classified group are illustrated with the stream order proposed by Strahler. Finally, the steady tendency of landscape change in relation to the stream order of river in the four watersheds is identified. The results suggest that: (1) Each classified group in terms of physical environment has a unique land use pattern and direction of change. (2) There is a strong relationship between stream order and landscape characteristics. (3) In the Nakagawa watershed, development of the Nasunogahara area in the Meiji era had a great impact on the distribution of paddy fields. (4) Major changes of land use from forest to dry field on the tephra-covered terraces are observed in the Kasumigaura watershed. (5) Kinugawa and Kokaigawa watersheds are characterized by a paddy field landscape molded along the river, which was inherited from the Meiji era. (6) Rapid urbanization of the terraces and natural levees are observed in all watersheds.
  • 木村 園子ドロテア, 岡崎 正規
    2008 年 117 巻 2 号 p. 553-560
    発行日: 2008/04/25
    公開日: 2010/06/02
    ジャーナル フリー
     To optimize the reactive nitrogen cycle in an ecosystem, technologies to increase nitrogen use efficiency and reduce emissions of nitrogen must be developed. In a watershed-ecosystem, land uses with purification abilities can be a powerful tool to mitigate nitrogen loads from non-point sources. This study analyzes the influence of land use on nitrate concentration in the watershed of the Tama River, a typical urban river in Japan. The upstream area is occupied by forest, while the downstream area is dominated by urban land use. In the Tama River watershed, 59% of the total land use is forest; 23% is urban area; and, only 5% is occupied by agricultural land. Urban areas are distributed downstream from the middle reaches. The average nitrate nitrogen (NO3--N) concentration in 2004 increased from upstream to downstream: it was 0.7 mg N L-1 in the upstream area, while it rose to 6.0 mg NO3--N L-1 in the downstream area. The river water NO3--N concentration showed a positive correlation with the proportion of urban land use, while it showed a negative correlation with the proportion of forest. However, some small sub-watersheds have low values for NO3--N concentration despite highly urbanized land use. These sub-watersheds are characterized by higher proportions of paddy rice fields to the total area, ranging from 0.3 to 3.0%, and higher proportions of water body areas, ranging from 8.3 to 30.6%, compared to other sub-watersheds. This might indicate the purification ability of the water bodies and paddy rice fields. Land use within 0 to 50 m from the river water surface influenced water quality and forest and other water bodies reduced nitrate concentration. Construction of artificial wetlands or riparian forests would decrease the N load into the river.
短報
  • 浅田 晴久, 松本 淳, 林 舟, 小口 高
    2008 年 117 巻 2 号 p. 561-567
    発行日: 2008/04/25
    公開日: 2010/06/02
    ジャーナル フリー
     Nepal is a mountainous country located between India and China, and has a large elevation difference in a north-south direction. The elevation difference accounts for physical and social diversities in the country. This study examines the relationship between topographic factors and distribution of residential areas in the Sagarmatha zone of eastern Nepal using information derived from topographical maps including a high-resolution digital elevation model (DEM). Residential areas in the study area are distributed from 400 to 5,200 m in altitude. More than 80% of them are concentrated from 1,000 to 2,500 m, and 2% are located above 3,000 m. Residential areas below 3,500 m tend to occur on relatively steep ridges, and those below 2,500 m tend to occur on north-facing slopes. Residential areas above 3,500 m tend to occur on relatively gentle valley sides and south-facing slopes. These differences in the residential environment by elevation are attributed to differences in topographic and climatic condition. This study suggests that GIS technology and digital data can provide basic information at a macro scale to solve regional problems in Nepal.
  • 西村 雄一郎, 岡本 耕平, ソムキット ブリダム
    2008 年 117 巻 2 号 p. 568-581
    発行日: 2008/04/25
    公開日: 2010/06/02
    ジャーナル フリー
     Many time-allocation studies have adopted questionnaires (activity diaries) or direct observation of informants. However, it is difficult to use questionnaires in rural areas of developing countries due to problems such as illiteracy, the fact that few people possess a watch, and the lack of place names in many rural and wild areas. Direct observation also has limitations because it is not possible to obtain information from many informants simultaneously. We developed a new survey method combining interviews with the use of GPS and GIS. The procedures are as follows. (1) Each informant is asked to carry a wristband GPS receiver for an entire day. The GPS unit records information related to the spatio-temporal aspects of the informant's activities. (2) After 24 hours of GPS, recording is completed; then the data are stored and represented visually using GIS software (ArcView 9.1). The investigator works out the shape of the spatio-temporal path of each informant by mapping tracking points with time information. (3) Subsequently, as GPS data reveals almost nothing about the content of activities, the investigator interviews each informant to clarify details of activities: what activity was carried out, at what time, where, and with whom.
     We conducted the survey in Dongkhuwaai Village, which is located about 30km from Vientiane, the capital of Laos. The daily activities of villagers consist mainly of a combination of subsistence agriculture, fishing, hunting, and gathering. By carrying out this survey, in which 138 villagers participated, it was verified that the new survey method has the following merits. (1) Using GPS improves the accuracy of spatio-temporal data. (2) GPS data can be easily correlated with satellite images and map data, which enables us to consider people's daily activities in combination with various geographical phenomena. (3) Investigators can obtain information outlining an informant's activities from GPS data before conducting interviews, thereby improving the efficiency of interviews.
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