3057
Geoenvironmental Approach to Restoration of Agricultural Land Damaged by
Tsunami
Approche géo-environnementale de la restauration de terres agricoles endommagées par Tsunami
Omine K.
Nagasaki University
Moqsud M.A.
Yamaguchi University
Hazarika H.
Kyushu University
ABSTRACT: In this study a geo-environmental approach was used for the restoration of the farmed land which was damaged by
salinity, due to tsunami water water in the pacific coast of Tohoku region in Japan. The mega earth quake that hit on 11th March,
2011 has triggered a Tsunami in the coastal areas of Tohoku region. The huge water severely affected various environmental and geo-
environmental parameters in that area. Soil salinity in the agricultural land has become a great concern for the after disaster geo-
environmental restoration. Various approaches are being tried to get rid of the salinity problem of the agricultural land. In this study,
major chemical properties (pH, electrical conductivity) of soil in Rikuzentakata city (one of the most affected areas due to tsunami)
were measured in the field test during May and June, 2011. An innovative approach by using compost containing Halo bacteria/salt
tolerance bacteria in this area was tested to restore the saline soil. This method can be useful for reducing the excessive salts from the
soil. The compost can also provide necessary nutrients to the soil and plant.
RÉSUMÉ : Dans cette étude une approche géo-environnementale a été appliquée à la restauration de terres cultivées qui ont été
endommagées par l'eau saline amenée par un tsunami dans la région côtière de Tohoku au Japon. Le méga tremblement de terre qui a
frappé le 11 mars 2011 a déclenché un tsunami dans cette région. Cette énorme quantité d’eau de mer a affecté fortement les
caractéristiques environnementales et géo-environnementales de la zone. La salinité de la terre agricole notamment est devenue une
préoccupation majeure. Plusieurs approches sont expérimentées afin de se débarrasser du problème de la salinité de la terre agricole.
Dans cette étude, les propriétés chimiques majeures du sol (pH, conductivité electrique) dans la ville de Rikuzentakata (une des
régions les plus affectées par le tsunami) ont été mesurées in situ durant les mois de mai et juin 2011. Une approche novatrice a été
mise en œuvre pour restaurer le sol salin ; elle utilise un compost qui contient des bactéries de type archées halophiles. Les bactéries
de ce type peuvent utiliser les sels excédants du sol et par conséquent réduire le taux de salinité. Ce compost peut fournir aussi des
éléments nutritifs nécessaires au sol et aux plantes.
KEYWORDS: salt damage, agricultural land, restoration, microorganism
1 INTRODUCTION
A disaster is the tragedy of a natural or man-made hazard (a
hazard is a situation, which poses a level of threat to life, health,
property, or environment) that negatively affects society or
environment. A natural disaster is a consequence when a natural
hazard (e.g., volcanic eruption or earthquake) affects humans.
Tsunamis and earthquakes are two of the most dangerous, and
yet the most common, hazards to affect population centres and
economic infrastructures worldwide. Generally, tsunami
flooding results from a train of long-period waves that can
rapidly travel long distances from where they were generated by
deep-ocean earthquakes, submarine landslides, volcanic
eruptions, or asteroid impacts (Morton et al. 2007). Due to
tsunami, the sea water carries sediments and salt. There have
been many studies on recent (Nishimura and Miyaji 1995) and
ancient tsunami deposits (Minoura et al. 1996, Bourgeois et al.
1988). These include descriptions of tsunami deposits in coastal
lake, estuary, lagoon, bay floor and shelf environments, and
even the farmland (Shiki and Yamazaki 1996). The mega
earthquake and consequent tsunami caused a great damage to,
not only human life and infrastructure, but also the agricultural
land and crops in Tohoku region, Japan. The after math of the
tsunami has created many problems to environment and geo-
environment of the affected areas. Soil pollution with high
salinity, which made the farmland unusable for cultivation, is
one of the major geo-environmental problems. The objective of
this study is to know the extent of change of soil chemical
properties due to tsunami and to apply an innovative approach
to control the salinity of the agricultural land (Omine 2012).
2 TOHOKU REGION PACIFIC COAST EARTHQUAKE
The great east Japan Earthquake (Higashi Nihon Daishinsai in
Japanese) of magnitude 9.0 was an undersea mega thrust
earthquake off the coast of Japan that occurred at 14:46:23 JST
on Friday, 11 March 2011. The location of the epicentre
(38.3220 N, 142.3690 E) of this earthquake was 70 kilometres
east of the Oshika Peninsula of Tohoku and the hypocenter at an
underwater depth of approximately 32 km. It was the most
powerful known earthquake to have hit Japan, and one of the
five most powerful earthquakes in the world since modern
record-keeping began in 1900. The earthquake triggered
extremely destructive tsunami waves of around 40 m in height
in Miyako, Iwate and Tohoku, in some cases traveling up to 10
km inland. In addition to loss of life and destruction of
infrastructure, the tsunami caused a number of nuclear accidents
in the power plant in Fukushima that caused evacuation zones
affecting hundreds of thousands of residents. The sea water
inundated large areas of agricultural land and turned soil saline.
3 SOIL INVESTIGATION
Field test was conducted in Rikuzentakata city of Iwate
prefecture to determine chemical properties of soil. Figure 1
shows the damaged area in Rikuzentakata city. This city was
