Obvestilo

Klavže, mighty water barriers

Why were they used for?

Klavže served as crucial infrastructure for transporting timber to the Idrija mine, which constantly required substantial amounts of wood for various purposes such as burning cinnabar ore, constructing supports in tunnels and shafts, and constructing expansive mining structures. Until the early 20th century, the lack of suitable forest roads and transportation options meant that rafting on natural waterways remained the preferred method of delivering timber to the mine.

Photo: Klavže. Historical Archives Ljubljana. Unit in Idrija.

Why were they used for?

When were they built?

The klavže were initially constructed using wood and stone. The oldest wooden barriers were built in 1589 on the Zala stream, in 1595 on the Idrijca River, and in 1750 on the Belca stream. These wooden structures often suffered damage from floods and were subsequently replaced with masonry barriers on the Belca and Zala streams and on the Idrijca River during the reign of Empress Maria Theresa between 1767 and 1779. The masonry water barriers were constructed using limestone and dolomite blocks, held together with Pucolan mortar. Notably, the klavže on the Idrijca River, built in 1772, are the largest in terms of capacity and dimensions. The design and plans for these water barriers were created by the local surveyor and speleologist Jožef Mrak (1709-1786).

In the final year of the Illyrian provinces' existence under the rule of Emperor Napoleon I, specifically in 1813, the Kanomeljske klavže or Ovčjaške klavže were built on the Ovčjak stream, which is now referred to as Klavžarica.


Photo:  Klavže; Photo Library of the Idrija Manucipal Museum.

When were they built?

How did they float the timber?

When sufficient quantities of logs and metre wood were prepared and enough water had collected behind the barrier, floating was begun. After the gate was opened, the dammed water flowed through the two discharge channels in 20 to 30 minutes. The water floated the timber prepared beneath the water barrier. The forest workers along the length of the riverbed worked to ensure that the water carried away as much timber as possible. But many logs got caught in the rock walls and bushes. In a matter of hours, the water floated the timber over a distance of 20 km to Idrija, and the wood stacked under the Kanomlja klavže over a distance of 8 km to Spodnja Idrija.


Photo:  Klavže; Photo Library of the Idrija Manicipal Museum.

How did they float the timber?

How did the gate opening mechanism work?

An amazing scene. Opening of the giant wooden gate with a special opening mechanism. To ensure successful floating, the gates of both discharge channels had to be opened simultaneously. This was possible by means of an effective gate opening system devised by the designer of the klavže, Jožef Mrak, which operated continuously for 154 years. After releasing the opening mechanisms, the water pressure caused both gates to burst open and hit the channel wall with full force. The water then rushed through the discharge channel and floated the timber prepared in the riverbed below the barrier. In the entire period of its operation, the gate never gave way under the great pressure of the water.  The gate's opening and closing mechanisms prevented the outflow of accumulated water through the barrier. The discharge channels were closed by massive wooden gates, which opened and closed around a vertical axis by means of upper and lower hinges. On the opposite side of the hinges, the closed gate was secured with the so-called Big Man, which also rotated around a vertical axis. To prevent this from happening uncontrollably, it was held in place when stationary by the so-called Little Man. The Little Man could also rotate around a vertical axis, but this was prevented by a wedge or wooden piece that could move towards or away from the wall. To ensure that the wooden piece did not loosen under any circumstances, it was additionally protected with a stopper. The handle of the stopper extended upwards from the chamber through a special opening to the top (crown) of the klavže. Also passing through the same opening was the handle of the opener – a special pole used to trigger the opening of the gate from the top of the klavže. First the stopper was raised, then the opener was used to push the wooden piece to the wall. This released the Little Man, which turned and released the Big Man. Then the Big Man turned and released the gate, which opened instantly due to the enormous pressure of the accumulated water rushing through the discharge channels.


Illustration: Cveto Koder

How did the gate opening mechanism work?

What are "grablje"?

In Idrija, at the confluence of the Idrijca River and the Nikova stream, a grablje wooden rake was constructed in order to retain the floated timber. The grablje wooden rake at Lenštat in Idrija was 412.6 metres long. The basic structure of the grablje was comprised of oak piles with metal binding. 2,530 stakes with a diameter of 10 cm and a length of 5 metres were driven into the riverbed.

Photo: Grablje. Photo Library of the Idrija Municipal Museum.

What are "grablje"?

Who were "klavžarji"?

The klavže caretakers, called klavžarji, were responsible for opening, closing and repairing the gates and maintaining the facility. Their land served as a pledge for any damage arising from negligence. The klavže caretakers were usually the landowners of a nearby homestead. They were paid for their work by the Mine in the same way as miners and forest workers. Klavžarstvo – caretaking of the klavže was passed down from generation to generation. If the sons of a deceased klavžar refused the job, it was offered to someone else. Today the profession of klavžar no longer exists, but the names of homesteads have remained.


Photo: Klavžarji. Photo Library of the Idrija Municipal Museum.

Who were "klavžarji"?

Idrija Klavže in 3D

Watch the video and experience a virtual demonstration of  the Idrija Klavže

Idrija Klavže in 3D
Back to the top