Prioritizing countermeasures for reducing seawater-intrusion area by considering regional characteristics using SEAWAT and a multicriteria decision-making method

Coastal areas are being increasingly damaged by the expansion of seawater-intrusion areas. This study suggested a three-step method to prioritize the countermeasures adopted to reduce the areas affected by seawater intrusion. First, the most vulnerable area to damage from seawater intrusion was selected among 25 areas on the western coast of the Republic of Korea using three multicriteria decision-making (MCDM) methods. As a result, Taean-gun was selected as the most vulnerable area for seawater intrusion. Second, a numerical model called SEAWAT was configured to predict the areas where seawater intrusion could potentially occur. For future scenarios, Representative Concentration Pathways (RCPs) 4.5 and 8.5 were used as the sea-level rise scenarios. To predict the future use of groundwater, the future groundwater extraction rate was predicted using a linear regression of the groundwater-use data over the past 10 years. As a result, it was predicted that 68.5% of the total Taean-gun area would be affected by seawater intrusion for RCP 8.5 and current trends in groundwater use. Third, the effectiveness of the measures adopted for the reduction of seawater-intrusion areas were analysed by considering the projected future scenario and the local characteristics (including the total population, population density, groundwater-level distribution, salinity distribution, groundwater-use characteristics, and ground-elevation distribution) of the Taean-gun district. After considering the effects of the countermeasures adopted for the different locations in Taean-gun and the data related to seawater intrusion, the priority areas for applying countermeasures against seawater intrusion were determined using three MCDM methods. It was concluded that the Taean-myeon is a priority area for applying countermeasures.