為解決台灣西部沿海地區近年來因地層下陷所造成的淹水問題,本研究企圖由改善地層下陷的源頭角度出發,並在考量抽取地下水所造成的外部性後,建立一固定型補貼模型來鼓勵養殖漁業進行休養。在實證上,我們以彰化縣大城鄉之養殖漁業為例,探討當政府以補貼政策並輔以各種不同的地下水與地層下陷管制情境時,政府的總補貼支出、各區域之地下水減抽量以及地層下陷減緩量情形為何?又這些管制在減緩下陷後,於未來所能避免掉總經濟損害(主要為淹水損害)的貨幣價值又為何?透過補貼支出與總經濟損害數值比對,本研究進一步將模擬結果與政府目前正在推行之「易淹水地區水患治理計畫」進行比較,探討相關政策之優劣。模擬結果發現,本研究以補貼為基礎的所有管制情境之益本比,皆較「易淹水地區水患治理計畫」為高,且當政府將地層下陷幅度以大城鄉總量而非以該鄉個別區域來進行管制時,所能帶來的益本比值最高,此顯示政府在採取治水計畫時,若能由淹水源頭並搭配較為彈性的管制機制時,可發揮更大的成效。
In order to solve the flooding problem caused by severe land subsidence in south-west coast of Taiwan, this research proposes a subsidy model to encourage the aquaculture farmers fallow their land. By taking the externality induced by pumping groundwater into consideration and using Da-cheng Township in Changhua Country as an example, our study tries to investigate how the subsidy policy might affect the amount of groundwater use, the land subsidence levels, the total government subsidy payment and the avoided damage costs in this area. The simulation results indicate that the benefit-cost ratios generated by our subsidy policies are all higher than that of “Regulation Project of Flood-Prone Areas” . We also find out the benefit-cost ratio will be the highest when the regulation of land subsidence is imposed on the amount of whole town instead of each area. This implies that if the government can solve the land subsidence problem from its very beginning with more flexibility, it can enhance the flood control efficiency.