Knowledge-based Classification of Land Use and Landform for Disaster Risk Assessment

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The knowledge about the condition of the ground is a crucial factor that controls damage due to natural disasters. However, to collect information on the ground condition over a wide area is not an easy task. In order to solve this issue, the following topics have been discussed in this research :1. Land use classificationBy combining land use data digitized from maps in the old times and those obtained from satellite data in the present time, a land use database has been constructed on a geographical information system (GIS). In this study, the satellite image classification is based on image objects rather than individual pixels.2. Landform classificationBased on the land use and its change, landform classification has been obtained by applying inference rules. These inference rules are the relationship between the two classifications and was constructed based on the knowledge about geomorphology.3. Surface soil structureA number of boring logs have been collected to construct a boring log database. Based on this database together with the landform classification, typical soil profiles have been selected for each landform classification. This set of soil profiles can be considered to represent a surface soil structure in the target area in this research (Chiba city).4. Seismic risk assessmentBased on this surface soil model, seismic risk assessment has been conducted. In addition, a series of microtremor measurement and also earthquake observation have been carried out. According to these studies, it was found that dynamic properties of the ground and hence the seismic risk are strongly affected by local land form and soil conditions.