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GIS APPROACH TO LANDSCAPE EVALUATION BASED 
ON SMALL WATERSHED UNITS 
3 a; ben sid . i : : i 
Tetsuo Masuyama* ", Toshiharu Yamamoto", Keitarou Hara*& Yoshizumi Yasuda® 
a: Graduate School of Business Administration and Information Science, Tokyo University of Information Sciences, 
1200-2 Yatoh-cho, Wakaba-ku, Chiba, 265-8501 JAPAN - hara@rsch.tuis.ac.jp 
b: Pacific Consultants Co. Ltd, Shinjuku, Daiichi-seimei Building, 2-7-1 Nishi-shinjuku, Shinjuku-ku, Tokyo, 163-0730 JAPAN - 
tetsuo.masuyama@tk.pacific.co.jp 
Commission VII, WG VII/3 
KEY WORDS: GIS, Ecosystem, Landscape, Land Use, Vegetation 
ABSTRACT: 
This research was implemented in Miyagi Prefecture, northeastern Japan. In recent years, the rich biodiversity of this prefecture has 
been decreasing rapidly due to loss of forest and traditional countryside landscape habitat. On the other hand, Japan has recently 
strengthened regulations for preservation of biodiversity and implementation of environmental impact assessments, with a strong 
emphasis on ecosystems. To help preserve biodiversity, a simple but effective method for environmental evaluation is required. In 
this research, GIS based landscape evaluation methods were applied to landscape evaluation in northeastern Japan. The study area 
was divided into 828 small watershed units, and four GIS indices; Natural Vegetation Cover, Extent of Forest Cover, Road Density 
and Land Modification Rate, were used to evaluate each watershed unit. The scores on these four categories were then used to 
calculate and overall score, called the Degree of Natural Symbiosis, for each unit. 
In addition, Interspersion and Juxtaposition spatial indices were analyzed for watershed units and also for polygons. The results of 
the evaluation were compared against known data on biodiversity and plant communities for the watershed units. The results of this 
comparison showed that the evaluation techniques adopted here provide an easily implemented but reliable tool for spatial 
environmental evaluation, and is suitable for application to various environmental planning efforts, such as regional development 
master plans, project- specific environmental impact assessment, species management plans and biodiversity conservation plans. 
1. BACKGROUND research. Masuyama et al. (2003) have identified several 
problems involved in small watershed evaluation implemented 
In recent years, land use in Japan has been affected by simply by superimposing indices rather than actually 
intensive development, and concern with ecological comparing the watersheds. In addition, this sort of evaluation 
preservation is increasing. At the national level, the Natural does not consider boundaries between abutting small 
Strategy for Biodiversity is under review, and a new law watersheds. Evaluation of connectivity between the small 
governing environmental impact assessment was promulgated watersheds is thus considered essential for meeting the goals of 
in June of 1997. this research. 
Under the new law, environmental criteria are evaluated at not 
only the national level, but also the prefectural, county and 3. METHODS 
municipal levels. The law calls for environmental disruption to 
be avoided whenever possible, and to be reduced or 3.1 Study Area 
compensated for in cases when avoidance is impossible or 
impractical. In addition, the previous system did not focus on Miyagi Prefecture faces the Pacific Ocean, in the Tohoku 
ecosystems, but under the new system, the concept of district of northern Honshu. The prefecture has an area of 
ecosystem has become a major focal point. The Natural approximately 7300km? and is endowed with a great variety 
Strategy for Biodiversity was based on the Convention on of rich natural habitats, including mountain ranges, such as Mt. 
Biological Diversity, to which Japan became the 18° Zao (1,841m) and Mt. Kurikoma (1,628m), hilly areas such as 
Contracting country in October 1995. Under this strategy, Mt. Tokura, lakes and marshes such as Izunuma and Uchinuma, 
which was revised in 2002, species of fauna and flora, as well and abundant beaches and indented rocky coasts. In addition, 
as vital habitats, are protected. Nevertheless, as of January, there are numerous biodiverse countryside habitats centering 
2002, about 20% of about Japan’s 240 species of mammal, on irrigated rice paddies, which function ecologically as 
13% of about 700 species of birds, and 19% of about 8800 seasonal wetlands. However, in recent years this rich natural 
species of vascular plants are listed as being in danger of heritage is facing a severe crisis in biodiversity. According to 
extinction in the nation’s Red Data Book. the March, 2001 issue of the “Prefectural Red Data Book, 20 
species of formerly present plants and animals are now extinct, 
2. AIMS 551 species are endangered, and 233 species are threatened. 
Under these conditions, Japan requires a fast and reliable 3.2 Ecosystem Analysis 
system for evaluation of ecosystems at the macro level. This 
research focuses on small watersheds as a unit of evaluation, To begin with, the entire prefecture was divided into small 
and utilizes four indicators to evaluate the value of these units watershed units. Each unit was then evaluated using four 
as natural habitats for plants and animals. In addition, spatial indices derived from geographic information system (GIS) data. 
analyses using both the watershed units and polygons are The scores on these indices were then summed and employed 
employed to measure connectivity. to rate each unit into four levels in terms of degree of natural 
Inclusion of connectivity is of great importance to the 
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