| Budget Amount *help |
¥2,500,000 (Direct Cost: ¥2,500,000)
Fiscal Year 2003: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2002: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2001: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Research Abstract |
The postglacial dissection front is a ditch-like topography on a hillslope formed in response to abrupt increase in rainfall intensity during the Pleistocene-Holocene transition in Japan. The front has been retreating throughout the Holocene. Therefore, the front can be regarded as an important indicator for hillslope classification, estimation of hillslope sediment supply, and prediction of slope failure in the near future. Because identification of the front has been performed based on airphoto interpretation, the results may differ depending on personal factors. Therefore, this study attempts the automatic identification of the front using high-resolution digital elevation models (DEMs), whose availability has been increasing in recent years. The identification of the front requires accurate derivation of stream-nets and their properties, extraction of longitudinal profiles of master streams, identification of relatively steep river segments, and analysis of watershed transverse pro
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files. As these types of basic research is indispensable to reach the final aim, automatic identification of the postglacial dissection front, this study spent a long time and lots of efforts for basic research including the development of methodologies. Then the newly developed methods were applied to three Japanese barelands (Usu, Kusatsu-Shirane and Aka-Kuzure) and three broad hilly lands and mountains (Tama, Hamada and Shiojiri regions). DEM-based terrain analysis was also applied to some geomorphologically important issues even if they are not directly related to the postglacial dissection front. In addition, existing relevant studies were reviewed at the early stage of the research project. Although some basic methods of terrain analysis using DEMs, such as derivation of hillslope angles and curvature have been established, previous studies have rarely dealt with complex topographic elements as examined in this study. Therefore, basic trials in this study to provide some universal methods for geomorphological analyses seem to be meaningful. Less
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