Combination GM(1,1) and Stochastic Poroelastic Theory to Prediction the Land Subsidence in Yunlin and Jiayi Area, Taiwan

Abstract

In this study, the grey system GM(1,1) and the geostatistical method are initially used to predict the land subsidence of the Yunlin area in the next five years. The Yunlin County Yuanchang Element School is taken as the site example when the stochastic poroelastic model is used in the study because there is a lack of data related to land subsidence. The verification results and prediction data of the stochastic poroelastic model and the grey system are displayed. The results show that the land subsidence in the next five years as calculated based on the data obtained from the monitoring wells is 0.3 m, while 0.31 m and 0.33 m are the prediction results from the stochastic poroelastic model and grey system model, respectively. This indicates the high precision of both models in predicting land subsidence. In order to simulate the effect of climate change on territorial planning, a prediction is made on the possible land subsidence for 2030, in this study. The prediction results are shows that by 25 January 2030, the stochastic poroelastic model shows a land subsidence of 1.01 m, while it is 1.68 m for the Grey System model. Because only the Changyuan Element School is taken as an observation station for the stochastic poroelastic model, the Grey System model is used to predict land subsidence for 2007 by the geostatistical method. The results show that land subsidence will mainly occur in the mid-western area of Yunlin and the western coastal area of Jianyi. To simulate the possible situations in the year 2030, four scene simulation models are proposed in this research, that is, adding 10% discharge, adding 20% discharge, subtracting 10% discharge, and subtracting 20% discharge. The results show the prediction on land subsidence for the year 2003 when add 10% discharge, subtract 10% discharge, add 20% discharge, and subtract 20% discharge, respectively. Land subsidence will occur mainly in the mid-western area of Yunlin and the western coastal area of Jiayi. The maximum land subsidence could reach up to 150 cm or so.