2/26/20 Report - Reading the Water to Find the Treasure Holes. Test Your Detector. Beach Privatization.

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

Stairs at Seagrape Trail Saturday Morning.

Clipped form video submitted by DJ.

The posts at the bottom of the stairs at Seagrape Trail were getting washed out Saturday morning.  They had recently repaired them, but they were damaged again.  I was there that day but forgot to take photos.

Take a look at the stairs and the short posts sticking out of the sand in the photo below.  The posts are lower than the bottom step.  They weren't showing until the beach eroded.

Just To The North of the Seagrape Trail Access on 2/20

Clipped form video by DJ

Also notice the mass of water that is just below the stairs.  Just a few yards out is a wave surge behind that mass of water.  The surge will push the mass up the face of the slope, and the surge will rush up the slope towards the dunes.

Before I go much farther, I'd like to refer to what I think is the most important thing I've ever learned about beach dynamics.  The same principles apply to how things are moved in rivers and streams too, but for now I'm interested in these principles as they explain how sand and other items move on a beach.

Breaking it down, there is a certain amount of force needed to pick up different materials, including clay, silt, sand, pebbles, gravel and other items.  It takes more force to start an item moving than is required to keep the same item moving.

There is a certain amount of force required to suspend specific types of sand and other materials.  Generally it takes more water velocity and force to suspend clay than it takes to suspend sand, for example.  Even though the particles of clay are smaller, they are more cohesive so it takes more water force to pick it up.  And it takes more force to move pebbles than sand.  Things like the density of the objects, cohesiveness and even shape are important factors.  Pebbles are not more cohesive than sand, but they are more dense, so it takes more water velocity or force to get them moving.

There is also a certain amount of force required to keep an object moving once it is moving.  It takes less force to keep an object moving than it does to overcome the inertia and other factors that keep a particle or other object stationary.

The above chart shows velocity increasing from left to right on the horizontal axis, and particle size increasing from bottom to top on the vertical axis.  The right most red line shows that clay requires more force to suspend than sand, which requires less force to suspend than pebbles (or coins, rings, etc.).

Looking at the left most red line, you see that it takes little force to move already suspended clay or silt, but the force required to transport sand and pebbles or larger objects is greater.

Lets say you have enough water flow to get the sand moving, and enough to keep it moving, but then the force diminishes and the sand settles. The sand will be picked up where the force is relatively high, such as where the wave crashes, and carried up the slope until the water slows enough that the sand drops out of suspension.  If the water rushes back down the hill instead of slowly decreasing on the slope, sand can be carried down the hill, resulting in erosion.

The sand is moved when the force is great enough to pick it up and move it, and it is dropped when the force slows.  That part seems obvious enough, but there are other factors.  You have the tides and interacting multiple waves interacting.  Returning waves hit incoming waves, for example.  And there are irregularities in the surface of the beach.  And there is liquefaction.  (That is another topic for another time.)

There are different kinds of objects on the beach in addition to sand.  There are shells, and there might be coins and things.   Coins have their own peculiarities and methods of moving.  I once posted a number of ways that coins move.  But that is another discussion for another time.

Without getting into all the variables, sand will be moved differently than coins and things.  Different amounts of force are required to suspend and transport different objects.

Lets say you have just enough flow at the base of the slope to pick up and move sand.  It will be transported up the slope, and if the force slowly decreases, the sand will drop out and the sand will accumulate.   On the other hand, if the water picks up the sand and keeps it moving up the hill, and the water bounces off a cut or dune so the force is maintained at a high enough rate, the sand will wash down the hill again.  That is one way you get erosion.

Coins can be picked up if the force is great enough and carried up the hill along with the sand, but since it takes a greater amount of force to keep the denser objects moving, the water can slow enough to drop the coins while the sand continues to move out.  If the returning water force is great enough, the coins can be carried down the slope too.

You'll notice that when the water is bouncing off the face of a cut or off the dunes, the returning water can have a lot of force.  That means things will be carried down the slope until they drop out of suspension and settle in.

Different objects will settle at different places.  Like things will be dropped together.   As the water slows, coins and other things will drop out and settle before the sand.  That is how coin lines and coin holes are formed.   I've talked about that a lot in the past.

So what you are looking for is places where good targets have just been uncovered by eroding sand, or where those targets have been dropped.

After all of the fast moving water is over, slower water will move the grains of sand up the hill and drop the sand, building the beach and perhaps cover denser objects, such as any coins that were left behind.  Since you are interested in the areas where good targets are being uncovered or being dropped, you are looking for areas where the sand is being eroded or areas where the water has slowed enough to drop good targets.

It is all a beautiful balancing act.  Items are sifted and sorted like they are a gold pan, but on a beach the area is much bigger and there are a lot irregularities and complexities.  Still, I think you'll benefit if you get the ideas presented in the above chart.

...

PS: I lost the original source of the chart, so if anyone can find it I'd appreciate it.  I'd like to be able to credit the source.

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I received some questions and know that some of you might be wondering if your detector might not be working ok because you didn't find anything good last weekend.   Your metal detector is probably fine.  If you are not sure, test it on some small silver coins.  Maybe cut an old silver dime in half, take it to the beach and test your metal detector.  If you can detect a small piece of silver like that, you can detect a silver reale unless it is too deep or something is wrong with your sweep.  So pay attention to your sweep speed and height when you do your tests.   It never hurts to take some test targets to the beach to make sure.  But I'd bet that your detector is fine.  There is a lot of beach out there and you just have to put your coil over the right spot at the right time.   If you understand what I wrote above, that will help you.  Finding the spots is the main thing.

I know how it is.  When you don't get any hits, you start to wonder if you detector is working well.  Usually it is, but you can test it to make sure.

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Seems like there is some talk about beach privatization again.  I received the following emails from DJ.

Thought this bill died a couple years ago. 

https://www.tcpalm.com/story/news/newswire/2020/02/03/privatization-coming-beach-near-you-opinion/4643308002/?fbclid=IwAR3H3OMcGB98u3ZpMiBp3FHuUbF_5KtXjwu8EHnbrEWL-V13REygssrCgFg

HB 631 was approved and still on the books, lots of legaleaze

https://www.flsenate.gov/Committees/BillSummaries/2018/html/1888

These bills are filed to repeal 631 and protect beach access for the public (as far as I can tell)

House Bill 6063 (2020) - The Florida Senatewww.flsenate.gov › Session › Bill › 6063

Senate Bill 1680 (2020) - The Florida Senatewww.flsenate.gov › Session › 2020

I’ll try to get more current info, they don’t make it easy to understand.

Hope we don’t have to face this too.

We had a petition going on this back some time ago.   Somebody needs to stay on top of this.

There is also some proposed legislation for the Florida Keys that the Fisher organization is fighting.  I've been meaning to post what I received about that, but there has been so much local news lately that I didn't get around to it yet.

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The surf will be small this week.

Happy hunting,
Treasureguide@comcast.net

2/11/14 Report - Reading Beaches 101: Required Reading for Improved Beach Metal Detecting

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

Use link below for source of diagram and web site on sand movement.

An ancient philosopher named Heraclitus said something like "You can never step on the same beach twice."   He didn't say exactly that because he didn't speak English.  But that is what he meant.  He recognized how dynamic a beach really is.   

I have been thinking lately about doing a post on how things move on a beach, but I never got around to making the diagrams that I needed.  Well yesterday I found some diagrams that I can use for the purpose so I'll go ahead and address the topic.

You might wonder why you need this information.  You might think that all you have to do is get a metal detector and wander around on a beach and the detector will find things for you.  You can do that, but you won't find as much as quickly.  In order to increase increase your efficiency and increase the number of finds you make in the time you have available, you need to know how beaches work.  Otherwise you will be searching randomly, or at least less efficiently than you could.

There are miles and miles of beaches out there and treasure is not distributed purely randomly.  That is especially true of treasure that has not been dropped in the last few hours or days.  The trick is to find the hot spots where good things have accumulated.  This information will help you quickly find the most productive spots on the beach.

Many of the same things apply to shallow water, but for now I'm going to talk about beach detecting.

I found this diagram on a web site that you can access by using the following link.  It explains the movement of sand on a beach.  I'll use this diagram and others to show you how treasure moves too.

http://www.seafriends.org.nz/oceano/beach.htm

The sand is moved by wind and water.  I won't talk very much about the wind because its affect on detecting targets is negligible.

One area that is very important is the area between the two thin black horizontal lines just above and below the waves at the right side of the diagram, especially where those lines intersect with the beach.  That is petty much defines the area of wet sand on the front of the beach.

As the tide gets higher and the size of the swells and waves increases more of the beach is affected by the water and to show that the upper black line would be raised.  As the low tide decreases the lower black line would be dropped.

Going back to hurricane Sandy, on the Treasure Coast the water got all of the way up to the dunes or cliff at the back of most beaches.  Most of the time only the front of the beach is directly affected by the water.

A number of years ago I introduced and explained the terms "coin line" and "coin hole" in this blog.  Coin lines and holes are produced by water moving sand and other items, especially coins and some other items, and depositing them, sometimes in a coin line or coin hole.

If you know how to find and work coin lines and coin holes you will be able to dig a high number of items in a short amount of time. 

Coin lines and holes are do not always exist on any particular beach and will be difficult to find on beaches that have few targets.  They are much more apparent and easier to learn about on beaches that consistently have or have had a high number of visitors over a number of years.  On other beaches items move the same way, but it is not as easy to see the patterns simply because there are not enough data points.

Notice the blue arrows in the water going right to left in the diagram.  Those arrows show sand being moved from deeper water to shallow water and from the shallow water to up on the beach.

Other items besides sand, such as coins, also move up onto the beach in a similar manner, but not necessarily at the same time.  Items of different size, weight and shape are moved at different times.

It takes more water energy (generally bigger waves, swells and tides) to move coins than sand.  Other factors are involved too, but I won't overly complicate the basic factors now.

Sand accumulates on the front of the beach sometimes when coins and other items are not being moved onto the beach.  That creates poor detecting conditions, such as what we often see during the summer months, and in fact, the beginning of 2014.  That is when the beaches are building.

But there are arrows moving both directions - on to the beach AND from the beach into the water.  Notice the blue arrows going from left to right under the water.  

Normally there is a pretty good balance between the sand moving onto and off of the beach.  At other times the sand is moving more one way or the other.

Where items other than sand is dropped off depends on several factors including the size, weight and shape of the item plus the shape of the bottom, the tides, currents and where the waves are breaking.

Different objects drop out of the water at different times.  Sand will be moved and dropped off at one location, silt, mud, pebbles and other objects will be moved at different times and dropped off at different locations.  You've seen the results of that, I'm sure.   One time a sand bar will build up, or a shell pile be created or removed, for example.  That is the same way coin lines and holes are created. 

To get more specific, pebbles (defined as around 6 to 10 mm.) are dislodged when water speeds of 100 cm/s are reached, and settle out at around 20 cm/s.

Slower water will get sand moving, and it takes slower movement before the sand drops out and is deposited.

Silt and clay takes more speed to get it moving because it adheres, but once suspended takes very quiet water before it settles out.

The point is that different objects (including coins, rings, pebbles, shells, sand etc.) are picked up at different times depending upon flow of water and are deposited at different times. also depending largely on the amount of flow of water.

This is getting pretty long.  I'll have to cut it off here and pick continue with the topic later.


On the Treasure Coast we have a 1 to 2 foot surf.  It won't change for a few days, therefore expect continued poor beach detecting conditions.


Happy hunting,
TreasureGuide@comcast.net