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Author Topic: The Lagoon as a Collection Basin  (Read 20726 times)

Ingo Prangenberg

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The Lagoon as a Collection Basin
« on: June 11, 2012, 06:51:30 PM »

Does anyone know if there will be further surveys undertaken in the northern lagoon area, especially in the main inlet where the "Wheel of Fortune" was spotted including the opposite side of the inlet where the school master and his daughter (separately) spotted large airplane parts?

Due to the currents, it appears as if, on numerous occasions, airplane parts have funneled into the main passage and into the northern lagoon areas. Although light aircraft materials can still be blown away during a torrential storm the lagoon should act as a sort colander, filtering out some light debris and depositing them in the northeastern/eastern lagoon coastline. What is blown away, might have been caught by the treeline, acting as its own filter for debris.

Budget wise, the lagoon is relatively shallow, thus making for an inexpensive search area compared to the deep. I wonder if a thorough search will be conducted again?

Does anybody have more information?
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Tom Bryant

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Re: The Lagoon as a Collection Basin
« Reply #1 on: June 11, 2012, 06:59:34 PM »

I think it would really be interesting to fly the same sort of geophysics surveys we do for mineral resources. Since the search for diamonds went into full swing new techniques of HRAM survey (HIgh Resolution AeroMag) have become pretty commonplace. New sensors including EM and approaches can coax some pretty small targets out of the low level chopper EM over Mag data. Not the small stuff certainly but certainly things like fuselage and bigger bits would likely stand out well. You could cover a lot of area fast and things like surface terrain, surf and tides would not be a factor. While not able to give definitive data it might narrow the search some. It has probably already been considered though and I have missed it in the data search so far.
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Martin X. Moleski, SJ

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Re: The Lagoon as a Collection Basin
« Reply #2 on: June 11, 2012, 07:00:22 PM »

Budget wise, the lagoon is relatively shallow, thus making for an inexpensive search area compared to the deep. I wonder if a thorough search will be conducted again?

I'm morally certain the answer is "not on Niku VII."

The big boat is meant to work in the open ocean.

I think that 95% of the effort will go into site mapping and spot-checking.

I would be very surprised if no one went ashore for a quick survey, but I doubt that there will be enough manpower and money to go back over the lagoon.

TIGHAR has done a lot with metal detectors and sonar in the lagoon itself and on the nearby shore.  Some stuff was found, but none that was likely to have been from NR16020.

The land searches that I have heard discussed are:
  • finish the work begun in "Rolling Thunder" at the Seven site.
  • Search the village thoroughly (not a trivial task--much larger and more complex than the Seven Site).
  • Search for Camp Zero (manageable for a 'regular' TIGHAR expedition)--if it is where TIGHAR speculates it should be.
LTM,

           Marty
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Tom Bryant

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Re: The Lagoon as a Collection Basin
« Reply #3 on: June 11, 2012, 09:07:56 PM »

One of the reasons I have become very partial to the HRAM surveys is how quick they are and how detailed they can be. The edge of the reef would be essentially an afternoon once setup is complete. Now it would not be able to tell you what the targets are  but depending on overall conditions some shapes are even able to be defined -ie if the large cross beam to wings structure was still intact. Won't be on this search but if something is found that proves the site it might be something to consider for down the road.
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Malcolm McKay

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Re: The Lagoon as a Collection Basin
« Reply #4 on: June 12, 2012, 04:24:40 AM »

... but depending on overall conditions some shapes are even able to be defined -ie if the large cross beam to wings structure was still intact.

My understanding is that magnetometers will not detect aluminium, so as the main wing spar is aluminium how will it be of assistance?
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Tom Swearengen

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Re: The Lagoon as a Collection Basin
« Reply #5 on: June 12, 2012, 06:57:48 AM »

To paraphrase Ric or Marty from sometime back, if someonw has the $$$ to donate to add these assets, I'm pretty sure that Ric will accomodate. Stuff like this is specialized, and can get expensive. Quite possibly with some planning it can be included in a future expedition.
Tom
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Ingo Prangenberg

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Re: The Lagoon as a Collection Basin
« Reply #6 on: June 12, 2012, 07:20:43 AM »

Regarding detecting aluminum, metal detectors and some magnetometers do have the ability, (such as those found at airports). If standard magnetometers do not detect them directly, a sizable chunk of aluminum should still "confuse" magnetometers and show up as an anomaly.

For more reading on specific magnetometers and their limitations look at: http://www.quantrosensing.com/  Price list included.

Besides it isn't so much the aluminum parts one would be looking for anyway. It is the accumulation of small bits of ferrous metal attached that cannot be replaced by an aluminum version. Those ferrous bits will add up and show a small scattered debris field.

« Last Edit: June 12, 2012, 07:35:15 AM by Ingo Prangenberg »
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Tom Bryant

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Re: The Lagoon as a Collection Basin
« Reply #7 on: June 12, 2012, 08:16:37 AM »

The survey system I mention is EM over Mag. Uses a dual sensor system to detect using magnetometer  and electromagnetic conductivity meter.
EM will detect metals other than iron and as pointed out large chunks of other metals can show up as well to magnetometer though I was thinking more on the EM side. Salt water could be an issue. I know that EM surveys are done over salt water but don't know the ins and outs of it.
Not as a sales pitch or anything but the systems are quite often mounted on a local chopper. Like Tighar's helpful aerial survey chopper. Rented with operator and interpretation if required. My experience with them is on larger targets (kimberlite and some narrow vein precious metals also some discussion with the contractor re UXO - un-exploded ordnance) but it is amazing to see the cultural features that can be spotted on a survey. Utilities lines and things like buried car doors for instance - old road signs - all sorts of junk shows up in the oddest places.
I have filed this under my "sure would be neat to try" file and will leave it at that.
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Andrew M McKenna

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Re: The Lagoon as a Collection Basin
« Reply #8 on: June 13, 2012, 02:39:19 AM »

Does anyone know if there will be further surveys undertaken in the northern lagoon area, especially in the main inlet where the "Wheel of Fortune" was spotted including the opposite side of the inlet where the school master and his daughter (separately) spotted large airplane parts?

Due to the currents, it appears as if, on numerous occasions, airplane parts have funneled into the main passage and into the northern lagoon areas. Although light aircraft materials can still be blown away during a torrential storm the lagoon should act as a sort colander, filtering out some light debris and depositing them in the northeastern/eastern lagoon coastline. What is blown away, might have been caught by the treeline, acting as its own filter for debris.

Budget wise, the lagoon is relatively shallow, thus making for an inexpensive search area compared to the deep. I wonder if a thorough search will be conducted again?

Does anybody have more information?

Your thought process is largely what drove the multiple searches of the lagoon over the years, particularly the 2001 and 2003 expeditions. 

In 2001 we looked at the changes in the Delta of sand on the lagoon side of the inlet and metal detected out there extensively thinking that stuff washed in would then be buried under the growing sand delta.  We actually brought a dredge with us, but never had enough reason to use it.  We visually inspected the area along the face of the delta, and most of the bottom of the NE end of the lagoon using divers towed on manta boards behind a skiff.  Everyone remembers where they were on 9/11, right?   Walt and I were at the bottom of the lagoon most of that day wondering to ourselves what had happened to humanity in this world.

We've walked with metal detectors most of the shoreline directly across from the inlet thinking that would be a good place for stuff to get deposited.  I am pretty confident that if there had been any large pieces of Electra out there, we would have noticed it, but I certainly can't be 100% sure.

The inlet has been extensively looked at with both eyeballs and metal detectors during the 2003 search for the "Wheel of Fortune".

The area of the lagoon just inside Baureke passage was searched with a magnetometer in 1999 (?)

Most of the lagoon was mapped by side scan sonar using an AUV during the 2010 expedition, and targets of interest were investigated by diving on them.

While we know that stuff can be flushed through the passage into the lagoon, as evidenced by a big tank from the NC that is on the lagoon shore, we've never been able to find any suspected L-10 related materials in the lagoon. 

The lagoon is actually pretty clear of man made stuff, including NC debris, except for the area just off shore of the colonial village where domestic junk was discarded, and several 55 gallon drums filled with concrete out in the lagoon center that were used to map out the landing channel for the PBYs that supplied the Coast Guard Station.

So, with that history, there is no lagoon survey planned for the upcoming trip.  Repeating any of that work would not seem productive given the other higher priority stuff that Marty mentions.

Andrew
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Martin X. Moleski, SJ

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Re: The Lagoon as a Collection Basin
« Reply #9 on: June 13, 2012, 07:18:37 AM »

To paraphrase Ric or Marty from sometime back, if someonw has the $$$ to donate to add these assets, I'm pretty sure that Ric will accommodate. Stuff like this is specialized, and can get expensive. Quite possibly with some planning it can be included in a future expedition.

I've said it several times, in different contexts: TIGHAR has the manpower, expertise, and permissions to carry out operations at Niku.  If there is a large benefactor who insists that a particular kind of search be done, I'm morally certain that TIGHAR will cooperate in organizing the mission.  If, instead, all that is being offered is friendly advice, TIGHAR will take it under consideration as such.  Opinions are like elbows--everybody has a couple of 'em.
LTM,

           Marty
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Andrew M McKenna

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Re: The Lagoon as a Collection Basin
« Reply #10 on: June 21, 2012, 10:24:19 AM »

Re-directed from the "stills from the ROV" thread

Not sure if this is the best place for this question but it is relevant to the ROV search.  Has any attempt been made to model the flow of water over and down the the reef?  In particular I am thinking about the outflow from the lagoon after storms or high tides. The "landing strip" area is not far from the main channel and that flow should move materials on the upper reef during periods of drainage.  I think the NC shelters the "landing strip" somewhat from the channel but it still may influence the distribution of debris down the reef face and may need to be taken into account in terms of the area to be searched.


Matt

Here is my impression.  See photos below.  Under normal tidal situation, the flow into the lagoon, highlighted as Green, comes through the Tatiaman passage and into the lagoon.  A lot of the flow goes straight in, and then makes the right hand turn as it rebounds of the far shoe of the lagoon, which is why Taria point, that promontory that sticks into the lagoon from the far side, is there.

The normal outflow, highlighted as Blue, draws from all of the lagoon towards the passage, and disperses it seaward of the channel in all directions  "north and south" along the reef flat.  Since the ocean level is lower than the lagoon level, the water simply goes downhill wherever it can toward the ocean.  The current can be pretty good right in the channel, but once it spreads out it isn't quite so strong.  You can still walk around on the reef flat during an outflowing tide, so it isn't like it will sweep you off your feet.  Also note that the water coming out of the lagoon is nearly 10° warmer than the surrounding ocean, so once it gets to the ocean, it is going to float on top of the colder ocean water rather than cascade down the reef face as you might imagine.

I don't see normal tidal flow as much of an agent of change with regards to moving big pieces of stuff around.  That would more likely be reserved for waves and storm events.

Most storms evidently come with wind, and therefore waves, out of the NW.  This "packs" water into the lagoon through the Tatiaman passage regardless of tidal condition.  Enough packing, and the bowl overflows so to speak, spilling out both Baureke Passage, and also we believe down by the end of the lagoon where the CG station was - see the red lines. 

You can clearly see that Baureke passage is open to flow in this 2007 sat photo, but it was high and dry in 2001, only marginally open in 2010, and evidently high and dry again in a sat photo taken most recently on 6/16/12, so it would seem that Baureke passage only once in a while serves a a relief valve for the lagoon.  Note the vegetation pattern around Baureke that has some areas devoid of bush, this I think is evidence of the occasional over wash in this area, leaving a scar on the landscape, if you will.

After a storm, all that water left in the lagoon would again flow out the main channel, perhaps in a stronger flow than normal, but generally in an orderly fashion, so to speak, downhill in all directions towards the ocean.  Again, I don't see this being an agent of change when it comes to moving big stuff around.

What moves big heavy stuff around on the reef are the waves and particularly storm related surf.  Large amounts of water with major momentum is where the energy is to be found, and it generally pushes stuff shoreward and southward along the western shoreline rather than dragging it out to sea.  See the second photo attached which shows the large blocks of coral, some as large as bulldozers, thrown up on the reef flat.  You can also see the area from which they came, the broken edge of the reef with the rectilinear lines vs the softer surf lines.  Note that the tide in this second photo is really low which is the only time that broken edge of the reef is above water.  We've seen it at extreme low tides where the water from the reef flat is cascading over this edge in a little waterfall into the ocean.

None of this probably answers your question.  I don't think we've modeled it beyond my description above as I don't think it was tidal outflow from the lagoon or a storm event that moved the Electra in our scenario.  I prefer to see the rising tide on the ocean side, combined with waves, eventually floating the aircraft, either largely intact or in big pieces - definitely buoyant in comparison to NC debris or coral blocks - to the edge of the reef and beyond.  After that, water infiltration, ocean current, "aquadynamics" (does an aircraft fly underwater?), and gravity do the rest.

The current off the edge of the reef generally heads to the NW along both sides of the island - see the Yellow lines, so if I were directing the deep water search I'd start N of the NC wreck, and work N to NW on the assumption that the aircraft, or big parts thereof, were floated off the reef by wave action and carried in that direction before hitting the bottom. 

How long or far before hitting the bottom is another question, and you can find lots of threads in the Forum asking how long the Electra would float, whether or not it would be relatively intact or in pieces, etc.  My personal thought is that it got floated off the reef mostly intact, perhaps without the landing gear and some of the skin, maybe some bigger parts torn off as indicated by the dado's coming ashore.  Ric I think is more on the side of the aircraft getting beat up pretty badly in the surf and therefore not floating away particularly far.

I hope that helps.

Andrew
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Jeff Victor Hayden

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Re: The Lagoon as a Collection Basin
« Reply #11 on: June 21, 2012, 11:00:31 AM »

Likeliest areas of initial structural failure, the thick black lines (apart from the landing gear being torn off).
These are the areas of the airframe that contain the highest percentage of void in comparison to airframe. Any forces acting upon the airframe, waves, tidal, storms etc... will have the most destructive effect upon the weakest part of the strusture, the part that contains the least airframe and most void.
These two areas contain the fuselage door opposite the skinned over window.
The two cockpit side windows plus the roof hatch.
Just my opinion


This must be the place
 
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Matt Revington

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Re: The Lagoon as a Collection Basin
« Reply #12 on: June 21, 2012, 12:55:56 PM »

Andrew thanks that is  very clear.  I was concerned because I was reading a report about the oceanography of the reefs in atolls in the Marshall Islands
http://www.sprep.org/att/IRC/eCOPIES/Countries/Marshall_Islands/30.pdf

and some of the reef faces were described as have very turbulent , difficult currents.  Of course none of those atolls matched the particulars of Niku but I see you all have been thorough and thought this through.
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Tom Swearengen

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Re: The Lagoon as a Collection Basin
« Reply #13 on: June 21, 2012, 01:26:44 PM »

Mee too---thanks andrew. Very informative from one that has been there. N-NW of the shipwreck----HUM----Probably where Ric will find the chunks of coral tht used to fly as NR16020---just trying to be positive! LOL
Tom
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Bill Mangus

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Re: The Lagoon as a Collection Basin
« Reply #14 on: June 21, 2012, 03:10:20 PM »

Andrew,

You make a reference to new satellite imagery of Nikumaroro on 16 Jun 12 in your post above.  Is there a link or source you can provide?
Bill Mangus
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