Sunday, January 25, 2009

Flocculated in the Mississippi

After a few pleasant days at anchor in Venezuela and an uneventful voyage up
the Caribbean, I find myself again going up my favorite river, the
Mississippi. There was a possibility that I might have been heading off home
from the vessel, and it would have been great to spend a couple of days out
in New Orleans. But as it turns out, I still have a few turns of the log to
do out here.

As we came up the South west pass, it was dusk and the banks of the
Mississippi were actually steaming. I kid you not. There is a wicked cold
front out in New Orleans and the whole day a moist southerly wind was
trickling up the shore. As it came in contact with the cold waters of the
river, I could see the vapors forming on the surface. The effect was great.
Sadly it was quite dark to take a good picture. Going up the Mississippi in
the night is such a pity. Dawns and dusks are brilliant out in the river and
hopefully I'll catch another one going out of here.

A new thing I learnt on the river today is "Flocculation". Its called
locally as "Slush", primararily I suspect because Flocculation sounds so
indecent. The US Coast pilot Volume 5, Chapter 8, describes Flocculation as,

" ... A living mass of jellied material or muck, deposited in the lower part
of the Mississippi, during low stages of the river. It consists of the
suspended material which after being carried downstream by the current,
comes into contact with the relatively still water which breaks into the
passes. This muck has been observed to be as much as 10 to 15 feet deep. It
remains where deposited untill flushed out during high water stages of the
river. Although slowed down by this muck, deep draft vessels are able to
pass through it. Accordingly and because it will be flushed out eventually,
the corps of Engineers do not consider it necessary to remove the material
during low stages."

What the US Coast pilot Volume 5, Chapter 8 does not mention is how the
master of a deep draft vessel feels when his ship is Flocculated (I do like
this word :) ). The effect is very much like running aground. Your ship, one
moment humming its way up the muddy river is suddenly straining and
shuddering as if its stuck in jelly. The speed drops from a nice 10 knots to
something like two knots. The pilot was telling me that once they managed
to move only about 300 meters in four hours through this muck. Its not a
nice thing to experience and I'm not really keen to repeat the experience.

It seems that this happens only in Amazon other then this river, so even if
I can't say I enjoyed it, at least I can say that I was Flocculated!

(Since I couldn't take any pictures of the river tonight, Have put in a
picture of the chaps greasing the crane wire back in Venezuela. I am
personally afraid of heights and now as a Captain, I feel scared when even
others go up those chairs and stages!)

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Sanjay Varma said...

Thanks for sharing your experience. I am interested to know how did "Flocculation" effect the vessel's sea suctions, for cooling water. Was it sufficient to change over to high suction to avoid any chocking?

Velu said...

Hi Sanjay,

Thanks for posting here. Usually as we used to go up the Mississippi in a loaded condition, we would anyways be on an higher sea suction as SOP.

The cooling water was not affected due to the flocculation. As I understood from the pilot, the mass of jelly like substance is only at the bottom of the river and only will affect your ship if you are deepdraft going in the river.