3 Post-tsunami assessment and restoration of soil and water
- The level of salinity in tsunami-affected soils in Aceh and the rate of salt leaching was influenced by:
- the length of time that land was inundated by sea water
- soil moisture levels at the time of the tsunami
- soil type—salt leaches faster from sandy and peat soils than from clay soils
- the depth and type of sediment deposited by the tsunami
- drainage in fields and the local catchment
- access to irrigation water to flush salt from fields
- rainfall after the tsunami.
- Salt can leach vertically through the soil profile and laterally across fields with surface waters.
- Three years after the tsunami, high salinity readings were still measured in Aceh, mainly linked to poor drainage.
- Construct in-field drainage to accelerate the salt leaching process.
- Assess results from soil salinity surveys carefully to avoid misinterpretation.
- Incorporate shallow sediments (<20 cm) that are not highly saline into the topsoil.
- Remove deeper or highly saline sediments from fields.
Tsunamis can have a number of effects on coastal soils: increased soil salinity and sodicity, sediment deposition, and scouring and erosion of topsoil. The physical and chemical properties of tsunami-affected soils in Aceh are discussed in Agus et al. (2008), Hulugalle et al. (2009) and McLeod et al. (2010).
Particular requirements for the recovery of agriculture in Aceh included:
- assessing and managing soil salinity and other soil issues
- managing the sediments deposited by the tsunami
- assessing and managing water quality
- repairing drainage and irrigation structures.
This section includes:
- methods of salinity assessment
- soil salinity impacts
- soil and crop rehabilitation related to the commonly experienced post-tsunami problems
- observations of the physical and chemical impacts of the tsunami.