Tag Archives: Dornumersiel

A “Siel” – the valve in a dyke that lets freshwater out but no salt water in

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Ok now, after complaining about how I dislike mud and the “no water” (i.e. low water) times in the Wadden Sea yesterday, today I’ll tell you about some stuff I really love about the North Sea coast. For example, the pretty little villages full with shrimp trawlers everywhere!

Picture above is Neuharlingersiel, below is Dornumersiel.

And the pictures below are from my favourite “…siel” so far, Greetsiel. Even though I unfortunately didn’t take any pictures of the village itself! I was so fascinated with all the shrimp fishing vessels.

The boom trawlers with all the colorful nets and ropes and everything are just too pretty, even on an otherwise fairly miserable day!

But what I find fascinating in all the “…siel”s is how they bring together a nautical atmosphere (after all, most of these ships have been out on the open North Sea all night!) and a very inland-pretty-old-town vibe. And here is how they do that: with the “Siel”. The “Siel” is basically a valve that lets freshwater out into the sea, but which doesn’t let salt water come back in. The way that is done by doors that are opened if the pressure on the inside (i.e. the land side) is higher than on the outside, and that close if the pressure on the outside is higher than on the inside. Pretty smart, ey? That way the land gets drained during low water, but no salt water comes inland to mess up the agricultural land. But I find it fascinating how this one little door in a dyke can separate two completely different habitats that coexist peacefully just one step away from each other.

Above, you are looking from the inland on such a “Siel”, which is currently closed because the water is higher on the outside than on the inside.

Oh, and what I always love: Light houses!!!

Yep, so I definitely have to go back. Stay tuned! :-)

The wonders of a Wadden Sea. Or what someone addicted to #wavewatching thinks they are

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As someone living on the German Baltic Sea coast, I don’t spend a lot of time on the North Sea coast (except, actually, my week-long vacation after Easter with my godson and his family, and when my friend Frauke and I went to Sylt earlier this year, or when Frauke and I are going back to the North Sea next weekend. So maybe that’s actually not so little time on the North Sea coast compared to most other people?).

Anyway. I really like the North Sea, especially because I like the flat landscape where the highest points are dykes.

What I really dislike, though, is getting my feet muddy. But that’s pretty much the whole point of a North Sea vacation, according to my godson and his family.

On the other hand, though, having the opportunity to actively and directly influence water depth (or, as normal people would probably say, leaving footprints in the mud) makes for some pretty cool wave watching!

It’s a little hard to see, but if you look at the picture above, you see that the sun is coming from kinda behind my left shoulder, and the picture below is taken from a similar perspective (just telling you so you can interpret the footprints and resulting waves). So the left edges of the footprints are actually coming up and partly out of the water.

The wind is coming from the right, and you see the locally generated wind ripples and how they get defracted around the obstacles created by the foot prints!

Pretty cool, eh?

In the picture below, the wind is coming from the left and you see the muddy wakes of the fresh footprints! This I think is pretty awesome, especially because you at the same time see the refraction of waves around the obstacles.

What I also think is pretty cool are the little spaghetti piles of sand that the worms living in the mud leave behind.

And that, for each of the piles, there is a funnel somewhere close by, and a worm connecting the two inside the mud!

But then when the water is gone completely, it’s still pretty here, but also a liittle boring. Don’t you agree?

Ok, but it’s still pretty. But Wadden Sea and tides take the fun out of wave watching for quite substantial amounts of time every day, and I don’t approve of that ;-)

Influence of wind and water depth on a wave field (or: a beach vacation in Dornumersiel)

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I took the selfie above mainly to send to my mom from my vacation in Dornumersiel on the German North Sea coast. But then when looking through the hundreds of pictures I took that day, I realized that not only was my hair parted on the wrong side because it was so windy (ha!), the wave fields to my right and left looked actually quite different, without the reason for that being immediately obvious. So let me show you a picture facing the other way.

Above, you see this wave breaker like structure, protruding into the sea. The wind is coming from the right side, thus the waves are a lot larger on the right side of the breaker where they are getting more and more energy from the wind as they come towards us, than the waves on the left, the lee side of the breaker, where they don’t get any new energy input and are just refracted around the breaker.

Looking the other way, towards the shore, the difference becomes even more clear (picture below) isn’t this fascinating?

I really like watching how waves interact with structures. Below, for example, we see that the wave crests are coming towards the wave breaker at an angle, and that they are reflected and traveling away from it, too. This contributes to making this side look a lot more choppy than the other side!

On the other side, the waves look smooth. I was still standing on the breaker when taking the picture below, and you see where the sea surface is still sheltered from the wind and where the fetch is long enough so the surface roughness increases and ripples and capillary waves form.

Since we are in the Wadden Sea, the shore has a very shallow slope going into the North Sea, so waves look super interesting when they are in the shallow water. Below you see many many almost-breaking wave crests behind each other, coming towards us. The water depth is clearly a lot less than a wave length, the waves are interacting with the bottom and thus have really long and uniform troughs and steep, short crests. (btw, for those of you wondering how I could say anything about water depth in my #friendlywaves post on Saturday: This is how. This is an example of waves in very shallow water, and you clearly see their shape being different, don’t you?).

I love looking at the details of where they hit the beach! All the sparkle, all the little Mach cones around the pebbles where the water is running off, all the small capillary waves!

Below, someone accidentally walked into my picture, but that’s actually a good thing, because it gives you a scale, and if you look at the little wave rings that were created when she put her foot into the water and it splashing forward a little. The wave rings actually have comparable sizes to all the other small stuff going on on the sea surface!

And what’s also pretty impressive: How the crests get refracted by changing water depth. Below it almost looks like parabolic shapes coming in from the right, right? The side of the parabola that is further away is actually the wave crest that is coming in from the open sea, and the rest, i.e. the actual curved part, is partly diffraction around the breaker and then refraction because of changing water depths. So cool!

Since I spent quite some time there, here is a picture later that day with a lot less water. Tides and all that… ;-)

And then another day with a different wind direction and less sun.

I think it looks really cool to see the fairly wide area to the right of the breaker, in its lee, where the surface is really smooth!

So far, so good. Gotta go now! Do you find this as fascinating as I do?