The western part of Chiba Prefecture, as called Katsunan area, to the east of Tokyo, has suffered land subsidence for ten years. Total amount of ground surface lowering ranges from 30cm to 150cm in various sites. Such a lowering is one of the main causes of landuse change in the lowland in this area.
The author tried to clarified the relationship between physical conditions of land, land sbsidence and change of landuse. The relationship between physical conditions and landuse is shown in Table 2.
Changepattern of landuse is related to several factors (Tables 4 and 5), and it is classified into 4 main types and some subtypes as follows:
Type A (A
1, A
2): Natural Landuse is changed only by land subsidence.
Type B (B
1, B
2): Mixed Landuse is changed by land subsidence and human impact.
Type C: Artificial Landuse is changed by prominent human impact and land subsidence.
Type D: Built-up area Built-up area formed before land subsidence, wihout landuse change.
Total depth of land subisdence decides grades of landuse change (paddy fields to stagnant water, paddy fields to reclaimed land by landfill etc.). Types of landuse change (natural, mixed or artificial etc.) are decided by other factors like distance from Tokyo or starting time of new housing area construction.
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