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Borssumer Siel in Emden , waterfront with a view of the Ems

A sluice is a closable water passage in a dike . Closing is normally done by higher pressure when the water level is higher on the sea side, and opening by higher pressure from the inland side when the water level is low on the sea side. A sewer is therefore a valve for the passive drainage of the inland behind the dike, especially as part of the drainage system of marshland . The term is probably a word formation from Frisian that goes back to the verb to be, and therefore describes the point where water can flow out .

Construction methods

There are various ways of integrating the drainage path into the dike, the Kumpsiel, the Standersiel and covered stone sluice.

Kumpsiel (tree cave) and Ständersiel


In the Kumpsiel, a pipe is laid in the dyke, which consists mainly of sand or other earth material. Historically, this pipe consisted mostly of two hollowed-out tree trunk halves. The sea-side exit is protected by a flap that is pushed open by outflowing inland water and closed by incoming seawater. In some places there were many such kumpsiele, with which individual residents drained their lands directly behind the dike.

Stand shaft

Ständersiel gates from 1619 in Bensersiel

A stand bar has a large, mostly two-winged flood gate, the gate wings of which hang on hinges . These can be attached to heavy wooden posts built into the dike or to masonry. Stand columns were dimensioned in the past so that at low tide, when the gates were open, small ships could enter the canals behind the dike.

Vaulted pedicle

Gewölbesiel: Dreptersiel on the Unterweser , built in 1796, stones later filled in the dike, reassembled in 1998

Since all wooden parts of a chute were exposed to rotting and the attack of marine drilling mussels, one went over to building the solid parts of stone for large chimneys. Vaulted pillars were more resistant to storm surges than stone versions of stand pillars. Here an arched doorway was built through the dike. Large vaulted chests can also be used by smaller ships, e.g. B. coasters are driven through. In some places the (two to three times) are arranged in such a way that the sewer can also be used as a chamber lock . An example of both is the lock of the Hadelner Canal in Otterndorf .

Vaulted port as a lock: tidal side of the Otterndorf canal lock


  • Traces of a Kumpsiel from the 3rd century were found near Valkenburg (South Holland) .
  • A large part of a Kumpsiel from the 14th century was recovered from the remains of the dike near Stollhammer Ahndeich . This sluice find in Butjadingen in the Wesermarsch district is the oldest on the North Sea coast of Lower Saxony. The sewer must have been built before the Second Marcellus Flood of 1362 ("Grote Mandränke"). It then became unusable as a result of the flood.
It was at least fourteen feet long. The lake-side part consisted of a hollow oak trunk about 10.5 m in length, which rested on round cross-beams. The trunk had been divided lengthways to hollow it out. The halves were then put back together. Boards were nailed over the seam to connect. The mouth of the sluice had a clear width of about 80 cm at the lake-side end . The holder of the flap, which closed the sewer at high tide against overflowing water, was still preserved in the form of a pierced bar attached above the mouth. A find from Valkenburg near Leiden shows that this type of construction was used as early as the 3rd century.
  • In Seriem , Wittmund district , part of a stand column from the late 15th century was excavated. The 8.80 m long and 1.60 m wide structure belonged to an inlay dike that is no longer preserved 200 m from today's dike line and is therefore the only reliably datable component of a dike in today's Wadden Sea.


  • The news from Schlicker Siel "with bronze gates" south of today's Wilhelmshaven , part of the Golden Ring around Friesland , the first connected sea dike between the Weser and Ems, is legendary . According to local tradition, when the Schlicker Siel broke around 1218, the formation of the Jade Bay began.
  • In 1374, eight villages between Bremen (or its old town) and the Lesum agreed to build a new dike on the Lesum and to provide it with a sewer. The sewer should be ten feet wide , about three meters. So it became a stand, wide enough for a small boat to pass through.

Place names

Many place names along the German North Sea coast have the ending "-siel" based on the layout there. Today there are also inland sewage sites, as the coastline has shifted due to dikes in earlier centuries.

Corresponding places in the district of Friesland are about Crildumersiel , Ellensendammersiel , Horumersiel , Hooksiel , Mariensiel and on the Outer Weser Dreisielen , Fedderwardersiel , Golzwardersiel , Hollersiel , Kleinensiel , Neuenhuntorfersiel , Neuenlandersiel and Overwarfersiel . In East Friesland Altgarmssiel , Altharlingersiel , Bensersiel , Carolinensiel , Dornumersiel , Friederikensiel , Greetsiel , Harlesiel , Hilgenriedersiel , Neßmersiel , Neufunnixsiel , Neugarmssiel , Neuharlingersiel , Rüstersiel , Sophiensiel , Wapelersiel and Westeraccumersiel , and in North Friesland Katingsiel , Schlüttsiel and Bongsiel and Tammensiel and Ostersiel on the North Frisian island of Pellworm . Schülperneuensiel and Schülperaltensiel are districts of the community of Schülp in the district of Dithmarschen .

No places or districts were created near Großensiel (Brake), (Neue) Lunesiel , Blexer , Braker, Bütteler , Cappeler , Coldeborger , Dangaster , Drepte , Eckwarder , Friedeburger , Hamburg-Neuenfelde ( Vier Sielen Schleuse or Der Siel ), Hohenstiefer or Sankt Jooster , Spieka-Neufelder , Neues Strohauser , Ohmsteder , Petkumer , Steinhauser , Stollhammer , Ueterlander , Vareler , Waddenser en Wremer Siel and many smaller Sielen.

The Dutch ending "-zijl", West Frisian "-syl" also refers to places that are or were on a sewer, e.g. B. Delfzijl . As a technical term, however, the Siel is called spuisluis in Dutch (for example “outlet sluice ” - spuien means “let off”, spugen means “spit”), which can easily lead to imprecise terminology in German descriptions of Dutch coastal protection structures.


The rainwater that has collected in drainage ditches flows through the sluice channel and receiving water (also: deep ) to the sluice structure. A sewer structure usually consists of:

  1. the sewer building visible from the outside,
  2. the drive room and the helicopter chamber (inside the sewer building),
  3. the sewer chamber with its inlet and outlet structures (connecting "tunnel" between the receiving water and the lake).
Sielbauwerk in Hooksiel , (land side)

The sluice chamber is the actual passage of the water from the inland to the sea and leads under the dike. The gates of a sluice are open or closed depending on the water level. In this way, water can be dammed up from the inland or flow off freely.

At high tide , the gates of a sluice arranged on the lake side close automatically by the pressure of the water running up from the lake and open again when the internal pressure rises when the water level of the river or sea falls below the inland water level when the tide comes in. The gates are usually designed as stop gates , but there are also occasional mortise gates . The gates are used for dike safety.

As a further dike security, a lifting contactor made of metal or hardwood is usually arranged, which is connected to the contactor room via the contactor chamber and is operated.

Today there are pumping stations on many sluices ; When the water level in the receiving water is low, drainage is passive; when the water level is high, the water is pumped out of the dyke using machine power. However, in order to be able to cope with as large a part of the drainage as possible without using energy, there is a reservoir on the back of the dike in some places, in which water can accumulate during high tide to be drained off during low tide. Such a reservoir is particularly important in the event of storm surges lasting several days.

Legal regulation


In Germany, according to Art. 66 Introductory Act to the Civil Code, the state statutory provisions that are part of the dyke and sewer law remain unaffected by civil law . The legal basis of the Sielrecht is the respective state law.

The construction of the sewer structures and most of the other elements of the first line of the dike are financed by a joint fund of the federal government and coastal states. The operation and ownership of the sewers are regulated differently from state to state.


In the Netherlands , the Rijkswaterstaat is responsible for all flood protection facilities .


As Hamburgensie, Siel is the correct technical term for sewer systems in Hamburg .

See also


  • Johannes Ey in: Frank Both (editor): Archaeological monuments between Weser and Ems Isensee , Oldenburg State Association for History, Natural History and Local History / State Museum for Natural History and Prehistory, Oldenburg 2000, p. 177/9, ISBN 3-89598-752 -2 (= Oldenburg Research , Volume 13).
  • Kai Niederhöfer: Rungholt was also found elsewhere ... Archaeological traces of the lost town of Otzum. In: Archeology in Lower Saxony . Volume 11, Archaeological Commission for Lower Saxony, Isensee 2008, ISBN 978-3-89995-522-4 , pp. 80–83.
  • Kai Niederhöfer: Archaeological sites in the East Frisian Wadden Sea. Settlement history of a submerged landscape until 1570. Rahden / Wstf. 2016, pp. 225–227, ISBN 978-3-89646-938-0 (= contributions to archeology in Lower Saxony, volume 18).

Web links

Wiktionary: Siel  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. DWDS - Digital Dictionary of the German Language. Retrieved December 11, 2019 .
  2. ^ Heinrich Hoops: The History of the Bremen Blockland , 1927 (available in the reading room of the Bremen State Archives )
  3. Worth seeing Sieltor in Bensersiel
  4. ^ Oskar Tenge: Der Jeversche Deichband, 1889, Reprint 1999, ISBN 3-98o6956-0-3
  5. Bremisches Urkundenbuch III, No. 463 (p. 422/423): Confirmation of the agreement on the installation of the Waller Siels