out in the southern part of Cuddalore
district and northern portion of
Nagapattinam district, which were
the worst affected areas of 2004
tsunami. The coastal vegetation of
southern Cuddalore district consists
mainly of mangroves (Pichavaram)
whereas Nagapattinam study area
is characterized by the presence of
large casuarina shelterbelt (nonmangrove bioshield) plantations
raised by the Tamil Nadu Forest
Department since 1970s. The total
length of the coast covered in this
study was about 20 km and the land
up to 1 km from the shoreline was
taken up for the assessment. The
height of the tsunami that hit these
coastal areas was about 4.5m. Using
Quick Bird satellite imagery of May
2003 (pre-tsunami), the study area
was divided into three categories
namely, i) dense tree vegetation,
ii) open tree vegetation and iii) no
tree vegetation. Mangrove forest
with dense trees and thick casuarina
shelterbelt areas were included in
the dense tree vegetation category.
All other woody vegetation,
including degraded mangroves
and gaps in plantations, were
considered open vegetation. For
post-tsunami damage assessment,
IKONOS satellite imageries of
December 29, 2004 (3 days after
the tsunami) were used. Damages
due to tsunami were divided
into three categories namely, i)
damaged (areas where all or most
of the physical structures had been
destroyed, removed or damaged),
ii) partially damaged (some damage
but most of the physical structures
remain intact) and iii) undamaged
(no damage visible on the ground
or in the satellite imageries). A
comparison was then made between
the tree vegetation categories and
the tsunami damage using chisquare tests. The results showed
that within 1 km from the shore,
there was statistically significant
YOJANA March 2012
correlation between tsunami-caused
damage categories and different
tree vegetation densities: (χ42 = 5.15
x 102, P<0.01), in particular, dense
trees vegetation associated with
undamaged areas and dissociated
with damaged areas (Danielsen et
al, 2005).
Approach 2: In this approach,
two pairs of villages, one pair in
mangrove situation and another
pair in shelterbelt (non-mangrove
vegetation) plantation area, were
selected for the study. These
villages were located more or less
equidistance from the sea and at
similar elevation. However, one
village is protected by vegetation either mangrove or shelterbelt - and
another village is unprotected by
such vegetation. Impact of tsunami
on the villages is related to loss
of lives, damages to houses and
household properties, loss of boats
and nets, etc. Some of the damages,
for example, loss of boats and nets
mostly happened in the boatyards
and neither mangroves nor any
other coastal vegetation cover these
boatyards. Hence, loss of boats and
nets was common to both protected
and unprotected villages and thus,
could not be taken as an indicator to
assess if mangroves and shelterbelts
lessened the impact of tsunami.
Such a kind of misunderstanding
was also encountered when total
loss of human lives was taken as
one of the indicators. Total loss
of human lives in a village could
not be considered as an indicator
because some of them died while
in the boatyards. Others lost their
lives due to forceful entry of water
into the villages. In order to solve
these confusions and also to find
out suitable indicators a series of
discussions was held in the selected
villages. On the basis of the inputs
obtained the following indicators
were selected: i) loss of lives within
the village due to forceful entry of
the tsunami waves, ii) number of
houses damaged, either fully or
partially and type of houses, iii)
height of the water inundating the
villages (identified as lines in the
walls of the houses).
The results indicates that in
the mangrove protected village
of T.S.Pettai the loss of life and
damage to houses was nil whereas
in the mangrove-unprotected
village namely, Muzhukkuthurai,
11 (2 percent) people died and 89
percent of the houses damaged due
to forceful entry of tsunami water.
In the case of casuarina shelterbelt
plantation, 58 people died in the
unprotected village and more than
50 percent of the houses were
also damaged. In the shelterbelt
protected village of Madavamedu,
13 people died and only 21 percent
of the houses damaged (MSSRF,
2006).
Table 1 Distribution of tsunami damaged area with reference to tree
vegetation cover (numbers in parenthesis indicate %)
Damage category/
tree cover
Damaged
area (ha)
Partially
damaged
area (ha)
Undamaged
area (ha)
Total
(ha)
Dense tree
vegetation
2.2 (0.5)
15.7 (3.5)
437.1 (96.1)
455.0
Open tree
vegetation
30.9 (15.4)
84.4 (41.9)
86 (42.7)
201.3
502.9 (35.1)
384.2 (26.8)
No tree vegetation
547.0 (38.1) 1434.1
53