Impacts of Climate Change and Land Subsidence on Inundation Risk

Abstract

In this study, a physiographic drainage-inundation model was used to analyse the impacts of land subsidence and climate change on inundation disaster and risk in a land subsidence area. The results indicated that for land subsidence and land subsidence combined with climate change, inundation area, and volume increased under one-and two-day storms for 2-, 5-, 10-, 25-, 50-, 100-, and 200-year return periods. Moreover, locations that originally had high inundation depth showed even greater inundated areas and volumes in the presence of land subsidence. The inundation phenomenon under the combination of land subsidence and climate change proved to be severe, compared to that of land subsidence alone. Land subsidence increased not only inundation depth but also inundation duration. Given land subsidence and climate change, the average inundation duration for each return period increased. The average flooding duration for each return period post land subsidence was found to be 1.05-1.1 times greater than that preceding it. Under the combination of land subsidence and climate change, the average flooding duration for each return period post land subsidence was about 1.13-1.27 times greater than that before it. Furthermore, by assessing inundation risk with inundation depth index, inundation duration index, and damage index from different land uses, it was found that after land subsidence, inundation risk showed an increase, which was amplified in the presence of land subsidence combined with climate change. must inevitably lead to abnormal global climate and extreme hydrological phenomena, which will subsequently result in the frequent arrival of natural disasters, such as floods and droughts. Taiwan is situated in a region that is highly vulnerable to climate change. According to statistical data [4], climate change has been increasing the frequency and volume of precipitation and has caused the sea level to rise. For instance, the average rate of sea-level rise for oceans near Taiwan has reached 2.4 mm/year [5], which is approximately 1.3 times higher than the corresponding rate worldwide (1.8 mm/year). In Taiwan's Southwestern coastal areas, the rate has surged to a maximum of 7.89 mm/year. Therefore, it is apparent that the combined effects of climate change and land subsidence are among the greatest environmental hazards faced by Taiwan, leading to the worst ever inundation and sea-level rise, causing serious harm to the sustainable development of the economy and society [4].Situations with similar inundation potentials do not necessarily generate the same inundation disaster. The occurrence of a disaster and its degree are typically influenced by the target, time, space of concern, and land utilization conditions. For example, several inundations of identical depth, occurring at different times, locations, and land utilization conditions, cause disasters of different severities. Uitto [6] proposed that the occurrence and severity of a disaster is determined by three basic variables:(1) hazard (natural phenomena ...

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