The Tar canals
Koivukoski and Ämmakoski
Tervakanavat
Koivukosken kanava ja Ämmäkosken kanava
Located between the lakes Oulujärvi and Nuasjärvi.
Koivukoski canal, 1840 - 1847
Koivukoski canal does not exist anymore. The lock was located quite near the current Koivukoski hydroelectric power plant, which was built in 1940 - 1943.
Koivukoski hydroelectric power plant.
Tar an important export product
Tar was one of the most important export products from the 1500s to the 1800s. In the old days, Kainuu area produced the majority of tar in Finland. Tar was transported by using narrow wooden boats to the City of Oulu where it was stowed to sea-worthy ships and hauled to Europe.
Ämmäkoski in January 2010
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Locks for tar boats
In autumn 1838, it was decided to build locks to facilitate tar transport through the rapids of Kajaani. The length of an ordinary tar boat was about 46 feet and breadth 2226 inches; these measurements were used for defining the measures of the locks. It was not easy to design the locks due to differences between water levels: 18 feet in Ämmäkoski and 15 feet in Koivukoski. A simple structure was needed, thus locks with one chamber was built. Kristoffer Polhem had developed a suitable type in the 1710s at Trollhättan canal in Sweden.
Building locks
In Koivukoski, building of locks was commenced in 1840. Koivukoski lock was partly built on the south beach of the rapid, partly through the primary rock and partly above the ground level. The walls of the lock were made of wooden chests filled with stones and reinforced by wood lining.
Canal measures:
Length
| Fall height
| Number of lock chambers
| Max boat length
| Max boat breadth
| Max boat depth
|
125 m
| 4,45 m
| 1
| 14,25 m
| 2,38 m
| n. 1 m
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Ämmäkoski canal:
Building locks
In Ämmäkoski, building of locks was commenced in 1840. The lock chamber was built through the primary rock; the bottom and the walls were covered with wood lining. The difference between the thresholds was significant - almost 20 feet. The lower gate is 31 feet and the upper gate is about 15 feet high.
Canal measures:
Length
| Fall height
| Number of lock chambers
| Max boat length
| Max boat breadth
| Max boat depth
|
70,4 m
| 5,4 m
| 1
| 14,85 m
| 2,38 m
| n. 1 m
|
Kanavat suljetaan
Ämmäkosken ja Koivukosken kanavat suljettiin 1.1.1915, koska veneliikenne oli päättynyt. Kanavat olivat huonossa kunnossa. Koivukosken sulku purettiin, mutta Ämmäkosken sulku täytettiin hiekalla.
Abandoned canals
The canals of Ämmäkoski and Koivukoski were closed 1.1.1915 because boat traffic ended. The canals were in poor condition. The Koivukoski lock was torn down and the Ämmäkoski lock was filled with sand.
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The ruins of Kajaani castle.
| Ämmäkoski hydroelectric power plant located on the south side of Ämmäkoski rapid. Castle ruins in the front.
| Ämmäkoski lock chamber and a tar boat.
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© Photos Riitta Kankkunen
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A long and narrow tar boat with tar barrels.
| Ämmäkoski lock chamber and upper gate.
| Gate structure.
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© Photos Riitta Kankkunen
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Walls of the lock covered with wood lining.
| A view towards the lower gate.
| Lower gate. See the significant fall height.
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© Photos Riitta Kankkunen
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Lower gate and lower arch. The actual gate is behind the arch.
| Lower gate is visible through the arch made of stone.
| Canal towards the Lake Oulujärvi and the Gulf of Bothnia. The canal is about 3,28 ft deep and the bottom is easy to see.
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© Photos Riitta Kankkunen
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Excellent work was done in the old days.
| Channel towards the lake Oulujärvi.
| Lock keepers house.
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© Photos Riitta Kankkunen
Ämmäkoski canal today
Ämmäkoski lock chamber was re-opened in 1984. The wooden parts of the lock are new but the stone structures are original. Ämmäkoski is the only tar canal in the world and the only lock of this type in Finland. Ämmäkoski canal belongs to the Finnish Canal Museum. More information is available at: www.fma.fi/vapaa_aikaan/kanavat/index.php?page=kanavat
The canal is no longer used for tar transports. The Koivukoski hydroelectric power plant prevents sailing from the lake Nuasjärvi to the lake Oulujärvi. In summertime, tar boat shows are organised for tourists. More information about the locks and the City of Kajaani is available at: www.kajaani.fi.
Riitta Kankkunen
Sources: Turkka Myllykylä, Suomen kanavien historia, Helsinki: Otava; 1991. Riitta Kankkunens visits.
Do send comments or further information to Bosse Arnholm or Riitta Kankkuselle.
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