Monitoring of land subsidence and estimation of social capital loss

Land subsidences in wide area due to the pumping up of groundwater have been occurring in some alluvial plains in Japan, and it has become a social problem. To address the subject of how to regulate the pumping up of groundwater, survey of land subsidence, observation of groundwater, and monitoring of pumping-up water quantities have been conducted to date. Presented in this paper is a method to grasp in details the situation of the wide-area land subsidence by using aerial photographs. With an analytical plotter system, this method transforms analog data obtained from photographs into wide-area three-dimensional coordinate data. In this study, to grasp the situation of the land subsidence, the distribution of land subsidence in the 21 years in Shiroishi plain, Saga Prefecture, was analyzed based on survey results of 1973 and aerial photographs taken in 1994. Then, the loss in social capital due to the land subsidence was roughly estimated to make clear the importance of regulating the pumping up of groundwater.