30 Sep VIZHINJAM HARBOUR STUDY:CRUISE IN THE SEA OFF TRIVANDRUM.
THRIVIKRAMJI: WORK STORY – 8
VIZHINJAM HARBOUR SILTATION STUDY -THRIVIKRAMJI &TEAM, CESS, INDIA
My boss (during 1980-82), Prof. C. Karunakaran (founder Director, CESS, Trivandrum), quite often made it a point, to query me if and when I was readying my team in MSD (Marine Sciences Div.) to go for sea-work. Prof. CK had a knack of making this poser to me, especially in the Heads of Divisions meeting routinely held once a month in his office.
Well, luck played a very interesting role in this respect, when the Harbour Engineering Department of the GoK came to CESS (in third quarter of 1980) to explore whether or not CESS could offer some scientific help in respect of abating the severe siltation in the mooring basin of the Vizhinjam Harbor (VH), south of Kovalam, near Trivandrum.
At the end of the first meeting itself, I made an offer to help answer the questions in respect of the current pattern and sediment sources. Based on this, the MSD wrote up a study plan for funding and implementation by the Harbour Engineering Department, GoK. In fact, I was hoping for a chance to launch the sea based work, and considered the VH study as a Launchpad.
The modern VH is set in a relatively small bay sheltered by a PC crystalline rock headland to the west and north while on the eastern side, what we notice is coastal cliffs of Tertiary Warkallis, overlying the crystalline rocks. A lower order stream originating in the east but on the west side of NH47, empties into the bay literally separates the crystalline rock territory from the sedimentary terrain to the south.
In plan view, the water-spread area or the shoreline of the harbor of the harbor makes a 2/3 U or sort of a J-shape with its longer arm pointing southerly. The shorter arm is (rocky crystalline) and is the abutment of the first N-S oriented breakwater armoured with a thick cladding of giant-reinforced-concrete tetrapods.
Soon after the completion of this breakwater, siltation that began during its construction continued unabated leading to the shrinkage of the water-covered area of the VH. Based on model studies, it was decided to construct the second breakwater (completely made of blocks of rock), roughly oriented along EW, but leaving a ship channel between the breakwaters. However, the completion of the second breakwater to a great extent diminished the rate of siltation. In fact, the CESS study was perhaps the reason to initiate the design and construction of the second breakwater. In fact, this study was very significant locally as this happened to be the first of its type as far as the organization was concerned.
I led the team of M/s Suchindan, Terry Machado, (late) Vasudevan et al to be in direct charge of the project. We had the services of two marine surveyors and sextants on loan from the Harbour’s department.
The workhorse was S/V.Rocket with the crew and owned by the ISRO, Trivandrum. This small 18 ft. single engine boat had no navigation or communication system (boat to shore) to speak of. The primary purpose of this craft was to work in the coastal waters to warn and caution the population engaged in the fisheries related activities to stay away from a certain area in the sea when rockets were test fired by the TERLS of ISRO.
Sextants and surveyors enabled position (and course) fixing in the sea. And S/V Rocket had no sea to shore communication system. Our own boat driver was asked to join the cruise as he would be of help chiefly in the deck work, like casting the devices and retrieving the samples. We had a van Veen grab for collecting seabed sediment. We also retrofitted the boat with a fish finder category of echo sounder. In fact we were all set to go off land on the cruise.
Then, we based on an approved project, went into the coastal sea to collect bottom profile data as well as seabed samples at certain fixed intervals with the intention of profiling the sea bed sediment of the inner-shelf and what they meant geologically. Our cruises did not involve overnight stay in the ocean as the S/V Rocket is seaworthy during daytime only. It was in fact early January when we went for sea-work.
However, on our way back to shore after work, sea became indeed choppy with white caps and the boat was pitching and rolling mildly, but quite sufficient enough to upset the stomach of one or two members of the party. However, on that account no one went for a leave of absence. The cruise covered six shore perpendicular tracks (water depths of up to 60 to 70 m and 12-16 km from the shoreline), between Poovar and Varkala.
One of the important outcomes of the study was reported in the Indian Journal of Marine Sciences, on the find of “ capsule shaped (fecal) pellets of Glauconite” in the relict sediment at the seabed off Trivandrum. The identification was purely based on the morphology of the particles of grass green grains in the medium sand fraction of the sediment. Some of the organismic casts (which we called micro-pelecypods and micro-gastropods) were re-designated as pterapods by Singh (CUSAT). Further, Rao (NIO), basing the results of his mineralogical investigations re-identified the capsule shaped pellets as a verdine.
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