Proceedings - Balai Penelitian Tanah

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McLeod et al.
fields after the tsunami. When the surface drainage systems were
damaged by the tsunami, both the vertical and horizontal leaching of
salts was restricted. On the other hand, the coarser soil in dryland
fields is more permeable, hence more conducive to leaching.
Figure 3. Areas that were flooded for a longer period are more saline,
EM38 data from Lho Nga in August 2005 (left) and from a
cluster of sites in Pidie District in October 2005 (right)
In rice fields, good irrigation, water availability and water circulation
affected the level and persistence of soil salinity problems. Rice fields
that were under irrigation at the time of the tsunami event tended to be
less saline than those fields that were dry. This suggests that
seawater did not infiltrate into the already flooded soil, but most likely
moved horizontally at the soil surface.
The availability of fresh irrigation water and good drainage systems
continued to be important after the tsunami. Both transects in site 5
(Figure 3) were flooded with seawater for more than three days after
the tsunami. The owner of the paddock in site 5-2 was able to pump
the saline water out while the farmer in site 5-1 could not. A good rice
crop was observed in transect 5-2 in October 2005, while the crops in
site 5-1 all died. However, after irrigation water became available in
2008 both sites had good rice crops.
In some areas, agricultural lands have been exposed to tidal
movements due to the loss of sand dunes. These areas will remain
saline and unsuitable for normal cropping until new sand dunes or
other protection from sea water is in place.
CONCLUSION
Electromagnetic induction technology, using the EM38 equipment has
allowed rapid assessment of soil salinity in tsunami affected areas in
Aceh. It allows monitoring of saline sites over time to assess their
suitability for cropping after a tsunami.
International Workshop on Post Tsunami Soil Management, 1-2 July 2008 in Bogor, Indonesia