HR: 1340h
AN: GC13A-0941    [Abstracts]
TI: Relationship Between Land Subsidence and the Earth Surface Environment at Kujukuri Plain in Chiba Prefecture, Japan
AU: * OBANAWA, H
EM: obanawa@geoenv.k.u-tokyo.ac.jp
AF: Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8563, Japan
AU: TOKUNAGA, T
EM: tokunaga@k.u-tokyo.ac.jp
AF: Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8563, Japan
AB: This study investigated a long-term spatio-temporal change of land subsidence at Chiba prefecture, Japan, and compared with temporal change of the earth surface environment. Land subsidence has occurred across the wide area of Chiba Prefecture. It is concerned that continuous land subsidence may increase possibilities of environmental changes such as stream regime, increase of floods, and saltwater intrusion. Precise prediction and appropriate management of the environmental changes in the future require better understandings of temporal change and spatial distribution of land subsidence in detail and evaluating of their impact to the natural environment. Previous studies have mainly dealt with the subsidence data during recent 40 years. Thus firstly, we investigated older data of first order leveling survey carried out by Geographical Survey Institute in Japan and integrated those data into recent results. The integrated data revealed the temporal change of land subsidence for past 100 years; for example, subsidence has generally started from the early 1960s in the study area. Then, spatial distribution of land subsidence was examined by data processing with a GIS software. Secondly, we compared the settlement values with natural and artificial settings including altitude, slope angle, geologic age, geomorphologic classification, and land use to examine what kind of locations are susceptible to subsidence. As a result, we found that valley bottom or lowland, i.e., locations with low-altitude, low-slope angle and new geologic age, are susceptible to subsidence. Finally, temporal change of land cover was revealed using old topographic maps. Then, we compared the temporal change of land cover with ground level and discussed their relationships.
DE: 0478 Pollution: urban, regional and global (0345, 4251)
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting