|
Statement
attributed to Dr. Tad Murty,Canadian Tsunami Expert on
Sethusamudram Ship
Channel Project.
The Indian Express dt.18.1.2005 has quoted Dr.Murthy as
saying, "My fear is that this is a deep ocean route, a
tsunami will enter the channel and cause devastation in Southern
Kerala. A slight
reorientation will help deflecting the energy back to the
ocean."
2.
Tuticorin Port Trust has searched the web for the email id
of Dr.Murthy to obtain his detailed comments on the SSCP with the
twin objectives of
seeking the views of experts on his comments and drawing
upon his undoubtedly
vast experience in
Tsunami early warning systems.
It has not been successful so far.
3.The
aforesaid statement attributed to him has the following
observations.
i.
SSCP is a deep ocean route.
ii.
The orientation is such that
a tsunami will enter the channel.
iii.
The entry of tsunami into the channel will cause devastation in Southern
Kerala
iv.
A slight reorientation
will help to deflect the tsunami back to the ocean.
Top
4.
The final layout of the channel suggested in the DPR
is enclosed. The
choice of the lay-out
has been dictated by sound reasons listed below:
(a)
The length of the channel should be the shortest to optimise
capital and maintenance dredging.
(b)
Channel should be, as far as possible, straight with minimum
bends.
(c)
If turning is required, straight segments are preferred over
curved alignments.
(d)
The straight segments should
be of length not less than 5 times of length of design vessels.
(e)
Orientation
of alignment should be, as far as possible,
along the principal wind,
wave and current
directions; it is
preferable to have the prevailing
currents aligned with the channel alignment to minimise the
effects of Cross
currents.
(f)
Straight legs of
alignment should be connected by smooth bends and not abrupt
angles.
(g)
Channel alignment
should be such that accretion of silt is avoided as much as
possible so as minimise maintenance dredging.
(h)
The alignment should be within the Indian Waters, i.e. West of the
Indo-Srilankan Maritime Boundary.
(i)
It should be as far as
possible from the environmentally
sensitive marine parks.
Top
5.
The Sethusamudram Ship Channel Project envisages a 300m
wide and (-) 12 m(i) deep
shipping channel connecting the Bay of Bengal and the Gulf of
Mannar through the Palk Strait, Palk Bay and Adam's Bridge.
While the Gulf of Mannar Marine National Park south of
Adam's Bridge is ecologically sensitive,
Point Calimere Wild Life Sanctuary
and Muthupet Mangrove forests adjoining Palk Bay/Palk
Strait are also vital from the ecology point of view.
While choosing the present alignment, therefore, the
following major considerations were decisive:
i.
The channel, though of only 300m width, should be as far away from
the ecologically sensitive areas along the coast to eliminate the
possibility of any damage to such areas.
ii.
The area available for fishing
activities, this area, continuing 75 to 80% of the total
fishing in Tamilnadu, should not be affected significantly, which
is possible if the channel is aligned near the international
maritime boundary, as close to it as possible, but maintaining a
safe distance from the boundary.
iii.
Capital dredging should be optimal.
The bathymetric studies in the area by National
Hydrographic organization and the National Institute of Ocean
Technology have already shown that the depth on the western side
of the proposed alignment is shallower than on the eastern side.
There is also a possibility of
harder material being encountered if the alignment is shifted
towards the shore.
iv.
Maintenance dredging requirements should be minimised.
Earlier investigations, including Tracer study, had
confirmed that in the
Palk Strait and Palk Bay legs of the channel, current and,
therefore, sedimentation movement is along the channel alignment.
This would reduce the quantity of maintenance dredging.
Hydrodynamic modelling studies recently carried out
by the Port Trust with the involvement of a renowned Dutch
firm have also shown that with
the chosen alignment, there
will be virutally no maintenance dredging in Palk Strait /Palk
Bay.
v.
The Navigational requirements area also complied with by the chosen alignment as no major issues have been thrown
up by the recently concluded Ship Manoeuvering
Studies.
6.
In the case of December, 26, 2004 tsunami, the conversion
of tsunami energy into higher tsunami wave heights due to
shallower depths could have caused the over passage and
dissipation of tsunami energy at Palk Strait and Adam's Bridge.
This could have caused turbulence causing the loss of tsunami wave
energy and redistribution of
bed sediments in the Palk Bay for absorbing the wave energy.
If shipping canal has been present, the view has been
expressed that these sediments would also have reached the channel
as a part of instantaneous process.
However, the animation models of the tsunami of 26.12.2004
available with the
Port Trust indicates that tsunami waves would have entered the
channel at its mouth near the Bay of Bengal after being
refracted by the north eastern and northern Srilanka,
irrespective of where the mouth lay- towards the north-east
or north. Reorienting
the channel entrance to the north-west
could be a better alternative but for the reasons listed in
para 5 [(a) to (b)], as
this alternative would
increase the capital cost significantly, take the alignment
closer to the Indian coast and, therefore, the ecologically
sensitive Point Calimere Wild Life Sanctuary and Muthupet
mangroves, besides reducing or virtually bisecting the fishing
grounds, and could result in increased maintenance
dredging because of cross
currents.
Top
7.
The Sethusamudram Ship Channel is
akin to a port entrance or approach channel though much
longer. The experience of Chennai and Tuticorin Port which felt the
impact of tsunami wave energy significantly, shows that the
approach channel per se plays an insignificant role in reducing or
increasing the impact of tsunami energy.
8.To
summarise, the views of Tuticorin Port Trust on the apprehensions
expressed by Dr.Murthy are: -
i.
SSCP will have a channel of only 300m width at the entrance to
Palk Strait, which already has a natural depth of more than 8 m
app. at all
points on the channel.
The proposal is
to dredge the channel, in this leg to (-) 12m CD only. Palk Bay
adjoining Palk Strait has natural depth of 12m or above and
therefore, no dredging is envisaged in Palk Bay. Palk Bay south
of Adam's Bridge and Adam's Bridge, where the natural depth is
less than 12m will be dredged to -12m CD.
Therefore, the
channel will have two dredged legs connected by a natural water
body and can hardly be termed as a deep ocean route.
The hydrodynamics could have been more complex in the
post channel period if Palk Bay were
are also to be dredged.
ii.
Irrespective of orientation in its present form or toward the
north (as possibility suggested by Dr. Murthy), tsunami wave
energy from Andaman Bay or Sumatra (the high risk areas where
tsunami can originate) could
enter Palk Strait and Palk Bay.
Orientation towards the northwest may not be feasible
economically, socially and environmentally.
The
entry of tsunami into the channel will be dissipated by Adam's
Bridge and later absorbed by the Gulf of Mannar.
Therefore, the apprehension of devastation in Southern
Kerala is not realistic. Hydrodynamic modelling studies recently carried out have
confirmed the earlier findings that increase
in magnitude of
the current in the post-channel era will be only along the channel
in Adam's Bridge with no change in current status alongside the
channel and the increase in current magnitude will be absorbed
immediately after existing from the channel caused by tsunami
wave energy parallel
to the Indian and Srilankan coasts, diverting the wave energy from
the coasts. It escapes imagination as to how Southern Kerala could be
impacted by tsunami travelling from Adam's Bridge towards the
Indian ocean.
|
