Throughout  its  five  centuries,  the  mine  and  the  city  needed  vast  quantities  of  wood,  and  for  that  reason  forestry  was  from  time  immemorial  of  substantial  importance. The wood was used as pit wooden material, round timber, construction wood and fuel wood.

For that reason wooden water barriers were built as early as the 16th century. These constructions enabled sufficient water  accumulation,  independent   of  the  whims  of  nature. Usually  they  waited  fore  extensive  rainfall  and  the  rise  of  the  waters,  yet  the  unstable  territorial  streams  caused  constant  troubles. In  the  mid  16th  century    the  first  “GRABLJE”  (RAKES) – oblique  slanting  wooden  barriers  stretching  across  the  river,  where  the  drifting  wood   was  stopped – were  located  at  Lenštat  in  the  middle  of  Idrija,  in  direct  proximity   to  the  mine  and  overlooking  the  confluence  of  the  Idrijca  and  Nikova  rivers.

The river basin of the upper Idrijca river is rich with forests, which had been wisely managed in the past so that there was never a lack of timber. The forests, however, were located quite far away and were frequently fairly inaccessible, thus the natural waterways turned out to be the most appropriate means of transport. Drifting of wood started in the end of the 16th century and successfully lasted as long as 1926 when the catastrophic flooding severely damaged the wooden rakes in Idrija and in Spodnja Idrija. 

Around  the  year  1770,  new,  monumental  barriers  made  of  brick  and  stone  were  built,  to  which  in  Napoleon’s   days,  in  the  year  1812,  they  also  added  a  dam  at  Ovčjak  in  the  valley  of  the  Kanomljica  river. Master  Mrak   used  the  reputed  (whereby  clay  in  added  to  the  mortar),  a  veritable  ‘natural’  concrete  as  the  binding  material  of  the  monumental  structure  of  the  walls  and  vaulted  openings.  In  order  that  the  dam’s    barriers  could  effectively  withstand   the  water  pressure  and  extreme  water  conditions,  the  gigantic  doors  of  the  klavže  were  opened  by  means  of  an  ingeniously  designed  mechanism,  whereas  for  their  closure  they  used  a  pair  of  oxen.

Mrak’s  klavže  barriers  on  the  Idrijca  formed   an  almost    800-metre-long  lake,  wherein  210.000  m³  of  water  cold  be  accumulated.  By  means  of  this  barriers,  some  10.000  m3 of  wood  at  the  time  could  drift  all  the  way  to  Idrija,  which  lies  some  20  kilometres  downstream. Every  opening  of  klavže  was  reported  to  Idrija  by  fast  running messengers. The capacities of the other klavže were distinctly smaller.

The  drifting  of  wood  to  the  “rakes”  to  the  city  was  repeated  each  year,  mostly  in  autumn,  until  1926.   In  its  history  of  wood  drifting,  the  Idrijca    carried  on  its  waters  a  total  of  over  3,600.000  m3  of  fuel wood  and  approximately  300.000  m3  of  pit  wood  and  round  timber.At each klavže there was a klavžar, a man who was in charge of the construction and of the work around it. Usually the klavžar was the owner of the neighbouring farm. With their properties they were liable for any damage out of negligence. If the water swept klavže away because of the opened door during a storm, the money earned from selling klavžar’s farm would be used for building new ones. Being a klavžar was a well-paid job at the mine and the position was hereditary. If the sons of the deceased klavžar refused to continue their father’s position, it was offered to somebody else. Today there are no klavžars left, there are only the local names and klavže still there.

More information on the website: www.muzej-idrija-cerkno.si