9/28/15 Report - Surge and Backwash and Cut Beach. Tropical Depression Eleven. Higher Waves.

Written by the TreasureGuide for the exclusive use of treasurebeachesreport.blogspot.com.

Illustration Showing Surge and Backwash On A Beach With A Cut

A few days ago I presented a couple of illustrations to show how coin lines were formed.   My intention was to continue on that subject, but I got on some other subjects.

The illustration in the previous post showed how the surge went up the slope and gradually decreased and then washed back down the hill.  When there is a cut, the surge can hit the face of the cut before the water slows.  When that happens the surge bounces off of the cut and washes back down the slope with greater force than if it had gradually slowed down on the slope.

The tide is important.  When a cut is created before high tide, as the tide increases, more and more water hits the cut as the tide comes in.  When the tide starts to go down, and if the waves are not big enough, the water will no longer be hitting the cut at all.

If the cut is created at low tide, the high tide can over-wash the cut and smooth it out if the water is hitting the beach straight on.

The main thing to notice is that when the water continues to hit a cut with force there is no gradual slowing of water as the surge slows and reverses.  Instead the water can hit the cut with force and bounce back sending the water back down the slope with force.

When the waves are hitting straight on, the backwash will be colliding with new surges.  If the wave period is small, that will happen frequently.

When the surge and backwash collides there will be a reduction in force at that point, and items can be dropped off.

Any items washing out of the cliff can be temporarily covered and protected by sand eroded from the cliff.

If the water is hitting at a angle from the north, then the water can wash up onto the beach and curve back down without losing as much force.  That can move a lot of sand and other items.  Of course if it is coming in at a good angle it can still carve away at the cut when the water is high enough.  You get more erosion when there is a good angle and high water.

High water washing directly up the beach will not cause nearly as much erosion as water washing in at an angle.

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Treasure Coast Beach This Afternoon

Last night we had a super moon and a lunar eclipse.  The tides were high, and I hear that in some areas there was flooding.  On the Treasure Coast the tide was about two feet higher than normal.  I didn't see any type of flooding.  In fact I thought the water was not any higher than yesterday.

Ida has finally disappeared.  We have Tropical Depression Eleven to the east of the Bahamas.  I expect it to stay out there and move north and not affect us much.  The waves were bigger though.  I thought in some places they looked like six to seven feet.  I saw a few surfers.

I found one cut that was close to two feet high.  I'm sure there were others around the Treasure Coast. I only looked at a couple of beaches.  One was mushy.  The other wasn't.

I wasn't finding anything old where I was.

There were some shells and fossil pieces.

We also have a disturbance in the Gulf.

The surf is supposed to be 3 to 5 feet until Wednesday when it is supposed to be up to 6 feet.

You might be able to find a good cut somewhere.  The waves are hitting directly from the East though.

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The history of money diggers article that I presented yesterday is a good read.  You might be able to pick up a few good clues from it.  In any case the folklore and history is interesting enough by itself.

Also check out the bibliography at the end.

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Happy hunting,
TreasureGuide@comcast.net

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9/22/15 Report - How Coin Lines Are Formed: The Basic Beach Dynamics. CSS Georgia Salvage.

Written by the TreasureGuide for the exclusive use of treasurebeachesreport.blogspot.com.

Yesterday I talked about finding coin lines.  Today I will attempt to illustrate the basics of how coin lines are formed.

The above illustration shows how the amount of water and force decreases as it goes up the slope of a beach.

The key concepts are those I've mentioned many times before.  First is the trigger point, which is the amount of force needed to pick up and move specific objects - in this case coins.

The force is greatest near the bottom of the slope and decreases as the water goes up the slope, sometimes eventually ceasing altogether.

At some point the water slows enough that it can no longer carry the objects and they settle out.  In my simple diagram that would be about at the number two.

That is the most simple scenario capable of creating a coin line.

However, not only does the water rush up the slope, very often there is a backwash.

In this illustration the red line shows the backwash.  If the water retreating back down the beach is strong enough to carry coins, it can carry coins back down the slope.

Remember, when the water slows to the critical "drop off" points, objects will be dropped.

But different objects have different "trigger points" as well as different "drop off" points.  Both the surge and the backwash can move coins and sand, or if not strong enough to move coins, it will just move the sand, leaving coins behind.

If the backwash has enough force it will carry coins back down the hill and also sand.  Sometimes it will have enough force to carry sand but not coins.  That applies to both the surge and backwash.

To additionally complicate matters, the coins can start out either in the water or in the sand.  They can be washed up or down.  They can be carried up the beach and dropped off at some point, or if they start out in the sand, they can be uncovered as the sand is washed away and washed down the slope.

A coin line can be very narrow when the surge is consistent or wide when you have a waves and a surge that varies more.

Once a coin gets covered by sand, it can be protected from the flow of water, which will flow over it without moving it until the sand is moved and it is uncovered.  If the water is moving enough to move the coin, of course it will also move the sand.

The backwash can be very strong in some cases, and in others virtually non-existent.  The balance between the two is important.  You'll often see the surge colliding with the backwash,

This is overly simplified, but I think it is still a decent illustration of the key concepts.

I'll possibly add to this in the future, considering things such angles, different sources and abrupt changes in beach profiles.

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Terry T. recently found these coins in a coin line.  You might remember that I mentioned that discolored coins are good signs or markers.  They have been out there long enough to have been sifted and sorted and dropped in a line.

Coins Recently Found In A Coin Line On The Treasure Coast.
Photo submitted by Terry T.

Here is what Terry said in response to yesterday's post about a coin line. ...All in the picture were found to the south of a public beach about 300 yards a few days ago. I had about an hour to detect. A cut approximately 3 ft ran for about 60 yards. 26 years ago people were able to park off of A1A on top the dune very close to the beach ( an old party spot). I have got stuck there many times in the sand. Only to come to the conclusion that a couple of 8 inch wide pieces of wood cut 3-4 feet in length stored inside my vehicle, and a little patience along with a small shovel (and a lot of sweat back in the day) would get me out of the situation. Now AAA will be called -lol. All are modern U.S. coins, but have been there for sometime ( I excluded the pop tabs - both modern and old school types from the picture). Not one fishing sinker was found - nor any gold, but this area has produced gold in the past along with other items. I went back 2 days later after digging the coins in the picture, and the cut was filled in. She hides it well.....

Thanks Terry.

The primary purpose of hunting a coin line is not to find modern coins, but they can also be made of old coins and sometimes even better things as well.  The thing about the coins is that they reveal a pattern that can then be exploited.

Any old green coin like those shown above can be a sign of a coin line or coin hole.

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Many artifacts and a 9,000 pound Dahlgren cannon has been recovered from the wreck site of the CSS Gerogia.

Here is that link.

https://www.dvidshub.net/news/176414/second-dahlgren-rifled-cannon-surprises-css-georgia-archaeologists#.VgBQ1t9Vikq

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It looks like Ida will fizzle out in the Atlantic.  There is a disturbance to the north of Florida that can be helping some of the states to the north of us.

The Treasure Coast is supposed to have a slowly increasing surf for the next week.  I'm not real hopeful.  We are getting into the Fall when typically we get some kind of storm.

Happy hunting,
TreasureGuide@comcast.net