抄録
We investigated the relation between salt damage persistence and the restoration of farmland and drainage systems in the coastal parts of the Miyagi Sendai Plain that were extensively inundated by flows from the 11 March 2011 tsunami. We found that drainage pump stations near the sea could not be operated to prevent invasion by sea water, and flooding of the farmland continued for an extended period . The salinity concentrations in water in the drainage canals near the sea were also high because of sea water intrusion. The high concentrations of salt in the farmland soil immediately after the tsunami were removed mostly by natural rainfall. As a measure for the future, the water level of farm drains should be kept below the position of drainage pipes to aid the removal of residual salts. To prevent saltwater intrusion from the sea, an effective strategy is to keep the water level high in drainage canals that are connected to the sea.
