Where is the Water Going?!

[gordi]

Hi Mystic,

I think that his choice of words could have been a wee bit better in this one.
I suppose from the perspective of those on the land in and around that area it would look like the "water had gone" but in reality if the water had actually gone then the ocean/sea-level all the way along the coast would be affected (since all of the oceans are joined up in one big puddle!)

It looks like he's a little bit off in his assessment of what the video clip shows too. He seems to think that the area on the left of the bridge (the marina where the fishing boats are) is on the landward side? and that the area to the right (which looks like a canal or river) leads out to the ocean? I think it's the other way around. I think the marina on the left is on the ocean-side (you can see water running down right to left towards the ocean).

In fact, if you freeze-frame the video as it pans from the bottom of the footbridge steps, you can read some writing on the roof of a boat/barge moored there.... and it says:

"...RTO
...ARINA
...ARES
      DO
     SUL"

I did a little bit of searching on google maps and... I've found the exact location that is featured in the video!!

It's at the "PORTO MARINA MARES DO SUL"

....and HERE is the actual boat with the writing on the roof!



Now, if we pan out a little bit we can see...



...that the Marina is literally right by the beach! (On the coast!)
This means that the water levels in the marina will be VERY heavily influenced by the normal tides.

In a study of the coastal tides in the area:

HERE

It says:

Both    coastal  geometry  and  bottom  topography  
yield   to   a   considerable   amplification   of   the   tidal   
range,   from   the   mouth   to  the   interior   points...

...The   mean   depth  is  about  3  meters...
there  are  many  areas  of  low  depths  and  the  amount  of  
sediment  is  considerable....

...The  range  of  the  astronomical   tide   is  about  
1.7  m  in  the  mouth,  but   in  the  most  interior  areas  it  
may   reach   2.7   m...

In other words the mean (average) depth of the water there is about 3m and the normal astronomical tide (in the interior areas) change that value by up to 2.7m!
So.... pretty much all of the water in the marina areas (apart from about 30cm!!) will drain out of the marina with the normal tides.

I might be wrong, but I think this is a non-story.

There are loads of harbours/marinas, especially with soft sedimentary bottoms which drain out completely with every tide.
I think that the video may just have been someone documenting a low-tide when they were surprised to see so many boats lying in the mud, but I'm pretty sure that it happens there all the time.

kindest regards,

G