In my last post, I introduced you to the idea of channels for draining the area behind the dikes for gaining farmland. The channels lead their water to bigger channels and where the water is led into the sea, they are called “Siel” (tidal outlet). Not only the outlet itself is called Siel, also the last and so biggest part of the channel system. You can often find towns at these outlets and big gates to prevent the water flooding the land during flood time. do you remember my post about the tidelands? These gates are constructed to close automatically when the flood comes. The rising water does it. And when the water level falls again, the gate is open from the inside by the pressure of the inside water.
Often you can find town where the Siels are. Sometimes the outer part of the Siel is used for a harbour like in Neuharlingersiel, where I took the image above. In the back you can see the harbour. Below the ground the water passes the tidal gate. The main part in this image is one of the upper flood-gates. This is only closed, when a serious storm flood is around the corner and the water level would rise higher than the harbour walls are. The gate is approximately 3m high.