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Welcome to San Stefanos (NW Corfu) => San Stefanos news and views => Topic started by: Jimbo on October 17, 2015, 01:30:27 AM

Title: Beach - a hypothesis
Post by: Jimbo on October 17, 2015, 01:30:27 AM
A distinguished local who cannot be named said to me that he/she thought that the extreme narrowing of the beach at the Havana/Mango point was a result of construction work there - extensions to Mango and Delfino Blu.

I could not see how this could happen, but many of us remember the wide beach there, the football pitch below Havana, even the cabana on the beach. The beach is not (to my recollection) significantly narrower anywhere else, and was almost visibly widening at the other ends this autumn.

So I've been pondering this. Why would the tides attack this sector more than the others? Variations in the tidal drift could perhaps do it, and that was the theory presented to me. But we would expect those to be random and on average cause a small coming and going. What we are seeing is consistent erosion in one "hot spot." What mechanism could consistently produce this effect?

The beach, as we all know, at Agios Stefanos is very flat, with a low tidal range. Low points on the land side of the beach will be more vulnerable to inundation.  Even a 0.5 centimeter lowering of a region could cause more aggressive tidal influx and hence more erosion.

Concrete weighs a lot. The geology there is sandstone. I'm not a geologist, but I can imagine that sandstone may be subject to compression. Is it possible that several tons of concrete close to the beach could be lowering the beach level just enough to permit attack?

If anybody knows a geologist or structural engineer, please pose this question. Meanwhile, I will send it to New Scientist - that's a free way of getting expert advice.

Should this theory be correct, that sector of the beach will not recover. It may be rubbish, of course. But there has to be a rational explanation.
Title: Re: Beach - a hypothesis
Post by: Gillywoo on October 17, 2015, 06:45:45 PM
Sounds very plausible to me!

We stood on the steps above the Havana Bar, watching the waves rolling in and out.

Large rocks have now been placed on the sand in this area - I think they were placed there last winter.

When you watched the waves, as they hit the rocks they became distorted and ebbed at an angle instead of flowing back and forth. So no doubt the sand below was being pulled away in a different direction to the rest of the beach.

I wonder if this may also be an added reason?
Title: Re: Beach - a hypothesis
Post by: Lesley on October 17, 2015, 07:13:06 PM
Or another subject is the new harbour responsible??????
Title: Re: Beach - a hypothesis
Post by: Jimbo on October 18, 2015, 02:31:21 AM
I've hear the "new harbour" argument, but I don't see how that could affect the small zone in front of Havana/Mango. It would be interesting to hear a reasoned analysis.
Title: Re: Beach - a hypothesis
Post by: abbo on October 18, 2015, 01:32:12 PM
hmm, i've stood there too a few times this year mulling over it. the thing that fascinates me is the drop in height over, say, 5 years. the Havana was never that "high" then. The football pitch was maybe 2 feet up, its dropped 5/6 feet.

There has to be a cause, the building work seems a logical cause given the pinpoint area, but why is bemusing. Logically you'd think any erosion would be at the Manthos end, but that end was in good nick this year.

Title: Re: Beach - a hypothesis
Post by: Jimbo on October 18, 2015, 04:54:25 PM
There hasn't been much building at the southern end of the beach for years. What is there is way back from the beach, and not very heavy construction apart from Nafsika, which has been there a very long time.

Construction higher up - like Vicky - is almost certainly on a reasonable chunk of sandstone. The central zone is lower and marshy. Athina is set well back, so not likely to influence the beach.

Beaches at the nudist end onward and at Waves end have ebbed and flowed in quite a natural way. The situation in the centre is of steady erosion. It's like a target. It shows no signs of natural repair.

A swimming pool full of water can weigh over 1,000 tons. That's a lot of pressure on an unstable substrate!
Title: Re: Beach - a hypothesis
Post by: Dupnica on October 18, 2015, 10:07:39 PM
 I have been puzzling over this for some time.When you look at the aerial photos from a few years ago you'll see a couple of rows of sunbeds at the water's edge and behind them a very wide expanse of sand.How could things have changed so dramatically in just a year?
 I don't believe it has occurred naturally by tides or storms or even the dreaded Longshore Drift.

I've had a look at the Beachapedia website and have discovered this--

 "Beaches are dynamic and natural.Buildings bridges and roads are static.The problem occurs when there is a static structure built on a dynamic,moving beach.
 If buildings and roads were not built close to the shore,we would not have to worry about shoreline structure or sand erosion"

 Makes you wonder how Delfino Blu and the others ever got planning permission in the first place.Guess we'll all have to wait and see what happens next.They may all crumble into the sea in a few years time.

 
 
Title: Re: Beach - a hypothesis
Post by: Jimbo on October 19, 2015, 12:35:04 AM
Thanks very much for locating that. Havana Bar is quite a light structure. Delfino Blu is not, and the Mango Bar extension is even more concrete bridging the gap between the two.

We need a kindly structural engineer to advise further.

The bad news is that, if this hypothesis is true, the steady erosion of that section of the beach over the last few years is not going to go away.
Title: Re: Beach - a hypothesis
Post by: Jimbo on October 19, 2015, 03:50:15 PM
I have just sent this email to the Faculty of Geology and Geoenvironment at the University of Athens:

"Kalimerasas,
 
I would be grateful for this to passed on to somebody who might be interested! Apologies for writing in English.
 
Agios Stefanos (Avliotes) in NW Kerkyra has for a very long time had a long and wide beach. But over very recent years a specific “hot spot” on the beach line has seen dramatic erosion.
 
This spot corresponds to the position of the two main beach bar/tavernas in the centre of the beach, one of which has made a substantial expansion.
 
There has been much discussion in forums of the possible causes: longshore drift, the new harbour to the south, chaotic factors arising from storms, beach sinking caused by construction etc.
 
What was a 30/40 metre beach expanse is now effectively zero (but only in this region) at high tide. This has significant impact for tourism in the village.
 
I believe that this would be a useful and interesting study for a graduate student, and might suggest what, if any, action might give a reasonable scenario of repair for what was a wide and beautiful beach.
 
Several thousand people will be pleased to hear what you may have to say!
 
Best wishes
 
Jim Hawkins"
Title: Re: Beach - a hypothesis
Post by: rilo57 on October 19, 2015, 06:06:58 PM
Should be interesting to see what reaction it receives...
Title: Re: Beach - a hypothesis
Post by: Dupnica on October 19, 2015, 08:07:43 PM
 Top marks Jim! That will be an interesting project for someone.

 When I walked along in June and saw what had happened, my first thought was that they had dumped the excavations from the building works on the beach.  I realise now that wasn't the case,at least I hope not.

 In September it was even worse.Defino's sunbeds were almost floating and you had to paddle in the sea to get past them.

 I don't know what can be done to reverse the damage.The lovely horseshoe bay has been ruined.
Title: Re: Beach - a hypothesis
Post by: cambridge on October 19, 2015, 09:33:05 PM
If the weight of the structures at Delfino Blu and the Mango Bar extension were able to have an impact upon the beach, that impact would be even more dramatic, and obvious, around and on those structures. The displacement would also produce heave elsewhere, which again on this scale would be very difficult to miss.

Don’t ask me what has created the distortion to the beach, but my monies not on the downward pressure of buildings.
Title: Re: Beach - a hypothesis
Post by: Dupnica on November 13, 2015, 08:00:02 PM
 Just wondering Jimbo if you ever heard anything from the University of Athens.
Title: Re: Beach - a hypothesis
Post by: Jimbo on November 14, 2015, 01:44:05 PM
Not an iota.. or alpha, beta, gamma etc.
Title: Re: Beach - a hypothesis
Post by: Dupnica on November 15, 2015, 01:13:51 PM
 I guess that's the omega of that then.
Title: Re: Beach - a hypothesis
Post by: Jimbo on November 15, 2015, 06:13:34 PM
Ne
Title: Re: Beach - a hypothesis
Post by: Andy7 on December 06, 2015, 01:44:12 AM
I think as do some of the locals that the severe erosion of this section of the beach was due to the placement of many large stones in front of the Delphino Blue.

These stones distorted the water and tidal current during winter storms and 'back washed' the sand out to sea where it now sits in long ridges 30 meters out.

However this erosion is part of a larger scale shrinkage of the beach over the last few years which I think has been due to a succession of stormy winters in Corfu.

I have photos of the beach from my first visit in 2008 and it was massive, but when you check the weather records for Corfu between 2000 and 2008 you will find a long series of calm winters with few winter storms, however, winter 2009 was stormy and 2010 and 2011 even stormier as deep low pressure systems crossed Greece during the winter months. The recent winters 2012 to 2015 have seen further stormy winter spells although not as bad as those between 2009-2011.

We need a return of those calmer drier winters in Corfu to restore the beach and with high pressure now extended across the Eastern Mediterranean this winter could be the start of a beach revival.

Andy
Title: Re: Beach - a hypothesis
Post by: Jimbo on December 06, 2015, 03:27:02 PM
I agree with a lot of that, Andy. Whereas the beach use to be a shallow horseshoe shape it now has steep V shape in towards Mango. That steers the incoming tide in a concentrated way towards that point on the shore.

Maybe dumping a load of sand like an artificial dune across the affected spot would help. Down at the Waves end of the beach the seaweed helps to bind the sand at the edge, and it grew noticeably this year over the summer/autumn.
Title: Re: Beach - a hypothesis
Post by: buttyboy@live.co.uk on December 09, 2015, 06:16:45 PM
I was looking at the webcam today of the beach and it looked ok near Mango so why it comes right up in the summer who knows.
Title: Re: Beach - a hypothesis
Post by: Jimbo on December 10, 2015, 03:32:57 PM
It's more a case of storms rather than time of year. There were violent storms from the north this year. We could do with a WebCam on top of Havana Bar showing the beach area! That way I could capture an image once a day and make a video showing the beach state.
Title: Re: Beach - a hypothesis
Post by: buttyboy@live.co.uk on December 10, 2015, 05:44:14 PM
good idea Jimbo. Also san stefanos has become more popular over the years so all the people stuffing themselves with the good food and beer and then laying on the beach in that area has caused a weight issue  so the  sand sinks causing beach to come right in lol. Maybe the delfino blu will build one of those wooden pontoon areas there who knows. we still love it and will continue to go every year no matter what. I have a 6 week old daughter who will next year be taking her first steps in san stefanos and we cant wait for her to meet everyone. roll on the summer
Title: Re: Beach - a hypothesis
Post by: tonyco1 on December 27, 2015, 08:34:07 AM
I've looked this up and I think Jim & Andy are right here.
It's logical and I've heard of, in fact saw a similar thing on a beach in Goa.
Tides are fiercer there than Corfu, and usually only beach huts are erected during the "season", but a local hotel built a Restaurant out onto the beach.
The tides came right in over a year or two and a narrow hotspot occurred right up to the building.
Made me think reading this as the guys in the beach-hut next to it were saying the building caused the problem.


Title: Re: Beach - a hypothesis
Post by: Jimbo on December 30, 2015, 03:27:28 PM
Beachapedia.org has a great deal on this subject. To summarise the main points:

* Building near beaches causes erosion
* Sea walls or barriers to protect these buildings makes the situation better for the buildings but worse for the beach
* The best solution is to move the buildings !!!!!!!
* "Nourishing" the beach with identical sand may help, but it requires regular replenishment. And it's expensive

We may reasonably guess that the section past Mango and Havana will shortly be impassable except at very low tide. Agios Stefanos will then have accidentally destroyed its greatest asset apart from food. I wonder if this is being debated in the tavernas and kafenions in Avliotes?
Title: Re: Beach - a hypothesis
Post by: will7777 on January 04, 2016, 10:17:17 PM
Hi all
Just head that sanstef beach sounds like its on the move . ??? .uesed to see a horse shoe shape  and a gentle slope
Down to  blue water's ..hopping to be over with may wife and  kids ..hopefully it will be as safe as it always have bin
Title: Re: Beach - a hypothesis
Post by: Jimbo on January 05, 2016, 03:52:24 PM
It's very safe. So safe that you can lie on a bed outside Mango in the sea and order a beer!
Title: Re: Beach - a hypothesis
Post by: Dupnica on July 07, 2016, 07:08:13 PM
Bumped into Kostas(sunbeds) a couple of weeks ago as we walked along the beach. He 's not enjoying his retirement, misses all the people, and thinks he might  be back working next year.
I mentioned how wide the beach is this year beyond the Havana. He says it's all down to the direction of the wind during the Winter. If it blows from the South the beach will be wider in the Summer.If it blows from North it will be narrow.
So there you have it, all our theories about building on the coast blown out of the water so to speak!
Title: Re: Beach - a hypothesis
Post by: StevenM on July 07, 2016, 08:11:08 PM
Had the same conversation with Vagelis  who used to work in the Nafsika and now spends his time fishing and renting his villas. A few days back he said exactly the same thing, it's all down to the direction of the wind.
Title: Re: Beach - a hypothesis
Post by: Andy7 on July 09, 2016, 06:11:44 PM
Not sure about all the theories but I am sitting on the beach in front of the Havana now and I can't believe how wide it is this year, best I have seen it in 5-6 years. At a guess I estimate the beach is  40-50 meters wide in front of the Havana and further along the beach its big enough to accommodate 4 lines of sun beds.

It's great to see and a vast improvement on the last few years.

There is a lot of sea weed in front of Waves Taverna that will need clearing but all in all the beach is excellent and litter/rubbish free.

Andy