The damage to Lahnasenkoski is being repaired – the area is closed for the duration of the construction

There is an exceptionally abundant spring flood this spring, with a flow of about 30 m3/s, while a normal spring flood is 20 m3/s with and average flow  less than 10 m3/s. The new Lahnasenkoski well survived the first normal spring 2023. This spring’s exceptional spring flood and the strong flow caused by it moved the aggregates deposited below the former dam location and the water now flows along the narrow channel.

Good luck in an accident – the salmon fry are safe

There was observed salmon fry only at the top of the rapids, where spawning nests have also been found, so this event has not caused significant harm to salmon spawning.

In the pictures below, on the left, the situation on April 2, 2024, and on the right and in the top picture, the water in the lower part of the rapids flows in the bed eroded by the flood on April 15, 2024.

The bridge is fine, the boardwalk under water

The bridge crossing Lahnasenkoski was not damaged in the spring flood, so it is safe to walk on the bridge. The flood has raised the water level between Lahnasenkoski and Ritakoski on the path on the eastern riverside, which is not recommended until the water recedes. The best way to get to Lahnasenkoski rapids is from the west side.

The construction begins on Monday, April 22

The damage will be renovated by filling with big enough boulders, which even a strong current cannot carry away. The construction will be started quickly by the contractors who built the rapids. Because construction machinery traffic is past the campfire canopy, the canopy and the path to the bird tower have to be closed to hikers for safety reasons. You can go to the Lahnasenkoski bridge to follow the rapids and now also the progress of the construction site, but from the bridge you cannot go in the direction of the campfire canopy and the bird tower. The ban is valid until the restoration of the damage in the rapids is completed.

Follow dam removal and restoration of Lahnasenkoski rapids

This article contains pictures from the Hiitolanjoki Lahnasenkoski construction site. Follow the construction site here – moving around the construction site is strictly prohibited to ensure the safety of all parties! Walking on the scenic path is also prohibited.

The turbines of the Lahnasenkoski power plant, which started in 1911, stopped finally on July 31, 2022.

The construction site already started in July, before the end of the power plant’s operation, with the preparation of construction sites and the start of the work dam.

Preparations are being made to dismantle the turbines, the turbine chamber of the power plant must be allowed to dry. Photos by Hanna Ollikainen

Lahnasenkoski construction site, water runs through the silenced power plant and the dam can be dismantled. Photo Mikko Nikkinen 19 August 2022

The dam disappears from the landscape. Photos by Mikko Nikkinen 23 August 2022

How the restoration of Kangaskoski will proceed


Work in Kangaskoski began immediately at the beginning of August. The power plant’s Kaplan turbine turned to standstill after had been grinding electricity for almost 100 years.

When the water could no longer flow through the power plant, water rose in the canal and ran through the overflow hatches.

The water of the river  is flowing into the rapids

In order to prevent the water from rising too high above Kangaskoski dam, the hatches of the regulation dam were opened and the water was released into the natural rapids, ie the former river bed. Timing the start of the work at end of the summer when the flow is small, the work machines were able to move in the river bed. The spawning gravel for salmonids had been brought to the rapids in July before the dam demolishing project, when the riverbed was still dry.

The construction of the rapids was facilitated by a work dam.

Work was first started at the top of the future rapids by bringing rocks and quarries to the working dam. The machine was able to work on the work dam and shape the top of the rapids.

The rapids are shaped with stones.

Large rocks have been brought to the upper section of the rapids and the shoreline are designed.

A roller found at the bottom of the river.

At the bottom of the river was found such an old roller – what is it possible and what is its age?

The water starts to drain from the power plant channel.

When the upper part of the river is ready to maintain the level of the water surface above, the dam hatches were completely opened. As a result, water began to fall at the dam and the upper channel began to dry out.

Excavated rock and old structures were exposed from the canal.

Dry upper duct.
A new tributary of the rapids

A new tributary was excavated from the rapids, which also brings flow to the water basin below the power plant. In the excavation work was revealed a concrete slab, which is part ot the structures of the previously located paper mill was found on site. An opening to the creek was pierced through the concrete.

The power strainer appeared

Work on the upper duct began in in the beginning of September. The overflow openings and power plant duct will be blocked with concrete walls before the duct is filled. The power strainer can be seen now.

The water level begins to drop in the duct.

The dam will be finally opened, allowing the water level to fall above the dam and in the power plant channel.

The Kangaskoski dam was demolished in early September. To be able to work at the dam, a construction site was built cross the river, under which water was led through drum pipes. When the work at dam is done, all construction sites will be removed as well from at the upper part of the rapids and at the dam. The design of the Kangaskoski rapids will be finished in the river and at shorelines.

Actors of the Kangaskoski project

  • Developer: South Karelia Recreation Area Foundation
  • Builder consultant: Insinööritoimisto SuunnitteluKide Ltd
  • Main contractor: Oteran Ltd
  • Kosken suunnittelu: Maveplan Oy (ks. asemapiirros)
  • Expert in the design of the rapids: Markus Tapaninen, ELY Center for South-East Finland
  • Machine contractors: Heikki Vaittinen and Jani Nokelainen
  • Stones and gravel: Karjalan Betoni Oy
  • Maisemasuunnitelma: Maisema-arkkitehtitoimisto Näkymä (ks. maisemasuunnielma)

Financing of the Kangaskoski project

The restoration of Kangaskoski is an action of the RivTimes project co-financed by the Southeast Finland – Russia CBC program. The rest of the funding are grants and donations received for the restoration of Hiitolanjoki. The main donators for Kangaskoski are WWF, OP Simpele and Patagonia /Tides Foundation. The purchase of the power plants was financed with the grants from the Ministry of Agriculture and Forestry in Finland, South Karelian Foundation of the Savings Bank, Municipality of Rautjärvi and several private companies and persons.

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Images and the article Hanna Ollikainen, South Karelia Recreation Area Foundation