DIR Ascent Protocol for Drift Dives in Heavy Current?

[Zieg]

You don't think that people who dive in strong currents all the time can not estimate them? Maybe you feel that divers can not estimate visibility without using a measuring tape?

Maybe you could do an experiment in the quarry?

I measure currents, visibility, and wave height for a living. Actually, I don't think most people can estimate currents at all. In fact, I know from experience that most people grossly overestimate current, visibility, and sea state. Numerous times I've stood on the deck of a workboat while measuring current and wave height, asked at least four different people what their estimates were and got at least four different wrong answers.

 

[shoredivr]

So you're telling me that in 6 seconds, you would drift 35ft away?

Jeff pretty well nails it for some of the wrecks like the Daryaw and the Lillie.

Now I'm interested. Last recorded dive I have for drifting along the Lillie wall, I went from the anchorage west of the wreck to the other end of Stovin Island (about 600 meters working from Google earth) in 27 minutes, take off 5 min for stopping at the wreck itself. That works out to 2.2 m/sec. or 4.2 knots REALLY roughly worked out. Tell you what, next time I do the Lillie I'll just count how many seconds it takes me to drift down its 130 ft length....the Lillie Parsons wall is more interesting than the wreck itself

Lilly Parsons
"LILLIE PARSONS DIVE NOTES

# Prepare for strong currents (2-3 knots). "

-- unless you've actually measured the current you can't say for sure how fast it is.

True, and it does vary. The St Lawrence River flow is controlled by locks to maintain the depth of both Lake Ontario, the river itself, and the erosion factor.

Best I can find right now is:

THE UNFOLDING STORY OF THE ZEBRA MUSSEL IN THE ST. LAWRENCE RIVER
"A colonization monitoring program set up in 1990, when the zebra mussel first appeared in the river, has demonstrated the effect of the current, using the navigational buoys set out along the fluvial stretch of the river between Cornwall and ŽÎle dðrlñÂns. The percentage of buoys colonized falls off sharply once current speed exceeds 0.75 m/s (Figure 3).
Figure 3
Colonization rate by zebra mussel as a function of current speed
Graphic Colonization rate by zebra mussel"

Dang, the graph didn't show up... but the values are <0.5 to >1.0 metres per second, or <.97 to >1.9 knots. Plus, the stretch of the river from Cornwall to Ile d'Orleans (Montreal) is wider than the stretch at the Brockville "Narrows" where the current can really pick up and is where we're talking about diving.

International St. Lawrence River Board of Control --- gives daily measurements of flow rates at Cornwall, again not the Brockville Narrows. Bests me what CMS is...cubic meters per second? or how to convert 7020 CMS to knots....

SparticleBrane, have you dived the St. Lawrence at Brockville? Come on up and give it a go.

Dam* I am such a dive nerd.

 

[SparticleBrane]

No, I have not -- need a drysuit first....

Thanks for all the research; at least someone is doing something besides pulling a number out of their @ss.

 

[shoredivr]

I measure currents, visibility, and wave height for a living.

Cool, then perhaps you have access to sites or studies that measure the St. Lawrence river flow near Brockville, Ontario. The flow is controlled for various reasons, ie shipping, lake and river water level, erosion, and its control is governed by an international body of Canadian and US interests, subject to international agreements on flow rates etc. The location's important since most of the stuff I Googled was for the tidal St Lawrence past Quebec City and into the Gulf of St. Lawrence...way different kettle of fish.

PS SparticleBrane, the August and September river temps are in the low 70's, this year it was 73 F in August, one could do it in a wetsuit....(though I dive it dry).

 

[JeffG]

There is a DIR Practitioners Forum for people who are already DIR, so if this forum is not for asking questions about DIR, what is its purpose? I'm sure it is more than just a place for "old hands" to mock people who ask simple questions about DIR practices?

You were given the answers. Just because you are unable to see them, is not our fault.

In any event, you and JeffG and Rainer have convinced me that asking questions about DIR here is not productive. This nuisance shall now cease.

Not productive for you anyways. There is that cotton saying that would be useful here.

 

[MonkSeal]

There is that cotton saying that would be useful here.

Are you refering to famous one about pulling out from ears and putting to mouth?

@OP: The answer really has been given. If you re-read the answers from people that have some GUE (or similar DIR training) you'll get the picture.

 

[Reg Braithwaite]

@OP: The answer really has been given. If you re-read the answers from people that have some GUE (or similar DIR training) you'll get the picture.

I'm quite happy with the quality of responses in the DIR forum, thank you all. And I agree with those that pointed out that there is no substitute for diving with experienced divers. I am reminded of something my music teacher said when I was badgering him about certain theory issues:

"Music theory is just a way we have of talking about music, but talking about music is not music."

 

[piikki]

What I'm saying is that many people who think they're diving in strong currents -- the current probably isn't as "strong" as they're saying.

Without actually measuring it, there's no way to know.

I agree, often numbers are for boasting but I don't need to know the numbers. When the captain says it's a ripping day I listen. When he says it might be a good day for everyone who can't make a hot drop to hold on to a rope when splashing, I listen. When I hold onto the line with a robust guy on the other end, and STILL end up flushed downstream 20ft before I get my crap together, I know it's ripping. When my arms are shaking pulling down the mooring line a mere 40ft, I know it definitely was ripping.

I have had dives on both Daryaw and Eastcliffe Hall that I would barely call recreational dives, and I am glad I did not do them with AOW + 15 dives. I definitely know it was ripping when divers are climbing up overwhelmed having aborted their dives at the mooring ball. Usually the mooring lines are designed so that it is easier to hang on the way up. If DIR is about looking beautiful this is not the place for it.

 

[Blackwood]

"Music theory is just a way we have of talking about music, but talking about music is not music."

a'ha

And as someone else (who may or may not choose to claim credit) once pointed out: "there are no DIR divers, only DIR dives."

 

[JeffG]

And as someone else (who may or may not choose to claim credit) once pointed out: "there are no DIR divers, only DIR dives."

only an idiot would say such a thing.