Written by the TreasureGuide for the exclusive use of treasurebeachesreport.blogspot.com.
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Three Views of Same Beach Area Taken Different Days.
Photos captured from beach cams by Alberto s.
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Alberto S. sent me the above images along with the following email message.
… with some time available I went looking around the different beach cams online and a turtle nest on one of the places I checked looked to be partially on the slope so out of curiosity I looked back and found the day it was marked and it was showing the slope way in front and not as close. The image includes the dates I checked and it’s clear the slope changed over time, which seems some erosion has taken place even with conditions not favorable, but I suspect not enough. So in trying to learn about interpretation of beach conditions I was wondering if you could share your thoughts. Your help is always appreciated.
In case you can't see the dates very well, the top image is dated May30, 2019; the middle one is dated June 29, 2019; and last, July 29. 2019. Besides capturing each image, Alberto S. added a red line to highlight the berm.In each image, you can the turtle nest marker, highlighted by a white box. The turtle nest provides a reference point for estimating the movement of sand relative to the marked nest. A stable marker can give you a point of reference for more accurate readings. It appears that the berm was about the same distance away from the nest at the end of May and June, but in July, the berm is farther west and at the turtle nest.
That is an excellent way to watch beach movement in areas covered by a web cam. Thanks Alberto!
Movement of the berm definitely tells you something. If the berm is moving that tells you something, but there is more to it.
The beach can move back when it erodes, going from position 1 to 2, or sand can accumulate and the beach move
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| Illustration of three possible beach front slopes. |
That would be simple enough, and eroding beach would recede and an accumulating beach moves out into the water, but that is too simple. In the beach web cam images, it does not appear that the beach front changed much in slope or shape, however the slope of the beach can change, and that can be important too.
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| Three hypothetical beach front slopes. |
Lets say that 1 represents the normal or average slope. Line 2 shows a less steep slope. The berm moves back, but the foot of the slope is actually farther out into the water. A steeper slope could have the berm farther out towards the water while the foot of the slope is cut back.
All I'm illustrating here is that while the location of the berm is a decent indicator, there are other factors such as the slope and shape of the slope. For illustration purposes I drew a perfectly straight slope, but that does not happen in real life either.
Other things being equal, which, as I always say, they never are, from the first illustration, I'd most like to see a beach like slope number 2. The farther back the better.
From the second illustration, I most like number 3. The steeper the better, and a foot that is back from the normal water's edge. However, if the gradual slope cut into the back dunes that could be a good one also.
Of course, there are other factors. I'll perhaps get into those tomorrow or some other day, but knowing the history of the beach is important too. It can be helpful to know how the beach developed over time. If the erosion is cutting into newly accumulated sand rather than older layers, for example, it is not likely to produce much of anything old.
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The system shown on yesterday's National Hurricane Service map is giving us some rain but won't do much else.
The system out in the tropical Atlantic is not organized, but has plenty of time to develop. If it does, it could come our way.
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| TSource; nhc.noaa.gov |
The tides are nice and big but the surf is only about two feet.
Happy hunting,
TreasureGuide@comcast.net
