Assessment of the Economic Losses Induced by Land Subsidence in Tianjin Binhai New Area

Different from sudden disasters,land subsidence is a slow-onset geohazard and accumulated over years.In terms of the main causing factor,the numerical model of land subsidence was established.With three groundwater extraction scenarios,the computer program was compiled to predict the land subsidence in the process of dynamic changes of groundwater level.Maintaining the same condition of groundwater exploitation in 2007(Scenario 1),from 2007 to 2020,the maximum accumulative subsidence in Tianjin Binhai New Area(TBNA) will be 640mm and the average accumulative subsidence will be 268mm.With 2% decrease in groundwater exploitation year by year(Scenario 2),the maximum accumulative subsidence will be 520mm and the average accumulative subsidence will be 177mm.With the water from South-to-North Water Transfer Project replacing groundwater exploitation completely(Scenario 3),the maximum accumulative subsidence will be 150mm and the average accumulative subsidence will be 95mm.The economic losses caused by land subsidence were sorted into 23 classifications.From 2007-2020,the economic losses in TBNA were evaluated according to the evaluating methods of future value method,engineering cost method,shadow engineering method,replacement cost method,disaster comparison method,proportional method of indirect and direct comparison,and weight method,etc.As the result of the evaluation,the loss induced by land subsidence under Scenario 1,Scenario 2 and Scenario 3 will be 122.21×108 yuan RMB,80.71×108 yuan RMB,and 43.32×108 yuan RMB respectively.