Developing a salt-removal plan to remedy tsunami-caused salinity damage to farmlands: Case study for an area in southern Thailand

We developed a salt-removal plan to reduce tsunami salinity damage based on the results of field surveys of soil salinity levels in southern Thailand after the 2004 Indian Ocean tsunami. Although salinity greatly exceeded the maximum for crop growth (4 dS/m) immediately after the tsunami, the soil's electrical conductivity was high only in the surface layer (1 to 2 cm deep) and decreased sharply in lower layers, rapidly falling below 4 dS/m. Long-term field surveys indicate that the soil's salinity was removed almost completely by rainfall during the rainy season, but that salinity had long-term effects on local crops. We propose a simple method for estimating the risk of salt damage based on meteorological observations and develop a method for calculating the amount of water required to reduce salinity based on the amount of salinity invasion for an argillaceous soil. Stripping the salinized surface soil so that the surface salt can be flushed out through drainage canals by rainfall or irrigation is an effective salt-removal measure that farmers can implement. Based on our results, we describe a plan farmers can use to rehabilitate their farmland and that can be modified for use elsewhere.