ABSTRACT

A risk assessment of land subsidence with spatial and temporal variability of groundwater level variations in Yunlin County, Taiwan is developed. The geoprocessing tools in geographic information system (GIS) are utilized to establish several thematic maps. The principal component analysis (PCA) is then adopted to determine the weighting of factors. From the results, spatial characterization of land subsidence with spatial variability is investigated. Results obtained illustrate that building resilience may be effective for land subsidence risk reduction and sustainable development of the coastal land area of Yunlin County. Furthermore, it appears that the PCA has the advantage of improving the discrimination of analysis results.

INTRODUCTION

Land subsidence problem is one of the most important, complex, and controversial topics in geotechnical engineering. The land subsidence is gradually occurred in excessive pumping areas. It may increase flooding and cause groundwater salinization, damage infrastructure, wetland and coastal marsh ecosystem. In particular, global climate changes have increased the frequency of extreme weather in Taiwan (Lee, Tung and Lin, 2019; Pörtner et al., 2022). Additionally, land subsidence may contribute to the relative sea-level rise (Bagheri-Gavkosh et al., 2021; El Shinawi, 2022). The sea-level rise and land subsidence may increase the risk of coastal flooding and contribute to shoreline retreat.

Since 1960's, the land subsidence in the southwestern coastal area in Taiwan gradually occurred in over-pumping areas. Most of the western coastal areas of Taiwan are alluvial plains, and the terrain decreases from the central mountain range in the east to the west. Because of the advantage of flat terrain, low land cost and convenient transportation, the western coastal areas became one of the more prosperous regions in Taiwan in the 1960's. Most of the structure and land use are based on industrial infrastructure, aquaculture fishery and agricultural land. As the aquaculture fishery began to prosper, most farmers in the western coastal area gave up agriculture and turned to aquaculture fishery, and a large amount of farmland was also converted to aquaculture fishery land. According to the Council of Agriculture, Executive Yuan, the current area of fish farms in the coastal area of Yunlin County covers an area of more than 3,600 hectares.

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