Case study:Restoration of Ingarskilanjoki River

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Location: 60° 4' 54", 24° 2' 58"
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Project overview

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Status Complete
Project web site
Themes Habitat and biodiversity
Country Finland
Main contact forename Harri
Main contact surname Aulaskari
Main contact user ID
Contact organisation Centre for Economic Development, Transport and the Environment for Uusimaa
Contact organisation web site
Partner organisations
This is a parent project
encompassing the following
Restored Knutsinvirta (photo: Harri Aulaskari)

Project summary

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The Ingarskilanjoki River is 50 km long and runs into the Gulf of Finland. The Ingarskilanjoki River is the only river in Finland where the population of extremely endangered migrating sea trout (Salmo trutta) is natural, not from stocking. Due to flooding of the fields the river was straightened and dredged in 1988. The river was restored in 2002-2007 to recreate habitats for trout and its reproduction for the whole river length. The goal of the restoration was to increase the morphological diversity of the river by e.g. creating more variation of depths and meanders and adding gravel for fish spawning. The goal was also to enable the trout to migrate between the river and sea. In addition buffer strips were created to the catchment to decrease the nutrient loading from arable areas and to decrease turbidity of the river water. The local land owners and river side inhabitants were interviewed in order to take into account their opinions due to restoration. To ensure the recovery of the natural sea trout population, the trout fishing was prohibited in the river after the restoration. Before the dredging of the river, natural trout were caught and raised for further farming. After the dredging, the trouts that were caught from the natural population were stocked back into the river. However, because of the clearing and lost habitats, the reproduction of the trout had been weakened. The key success factor was that the decision of the preservation was made by the local fishing society. This is most likely the reason for that the fishing restriction has been obeyed which again has been crucial for balancing the reproduction and population of the sea trout. Since strict fishing restrictions, restorations and additional fish stockings, the local trout population has grown. These results shows that the restoration as a whole was succeeded.

Monitoring surveys and results

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Lessons learnt

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Image gallery

Ingarskilanjoki River before restoration (photo: Harri Aulaskari)
Knutsinvirta after restoration (photo: Harri Aulaskari)

Catchment and subcatchment


River basin district
River basin Ingarskilanjoki River Basin


River name Ingarskilanjoki River
Area category 100 - 1000 km²
Area (km2) 160 km²
16,000 ha
Maximum altitude category
Maximum altitude (m)
Dominant geology Organic (i.e. Peat)
Ecoregion Fenno-Scandian Shield
Dominant land cover
Waterbody ID


Name Catchment of Ingarskilanjoki River
WFD water body codes
WFD (national) typology
WFD water body name
Pre-project morphology Straightened, Dredged
Reference morphology
Desired post project morphology
Heavily modified water body
National/international site designation
Local/regional site designations multiple designations across the site
Protected species present
Invasive species present
Species of interest
Dominant hydrology
Dominant substrate
River corridor land use Intensive agriculture (arable)
Average bankfull channel width category
Average bankfull channel width (m)
Average bankfull channel depth category
Average bankfull channel depth (m)
Mean discharge category
Mean annual discharge (m3/s)
Average channel gradient category
Average channel gradient
Average unit stream power (W/m2)

Project background

Reach length directly affected (m)
Project started 2002/01/01
Works started
Works completed 2007/01/01
Project completed
Total cost category
Total cost (k€)
Benefit to cost ratio
Funding sources

Cost for project phases

Phase cost category cost exact (k€) Lead organisation Contact forename Contact surname
Investigation and design
Stakeholder engagement and communication
Works and works supervision
Post-project management and maintenance

Reasons for river restoration

Mitigation of a pressure
Hydromorphology Structure & condition of riparian/ lake shore zones, Width & depth variation
Biology Invertebrates: Abundance, Fish: Disturbance-sensitive species
Physico-chemical Nutrient concentrations
Other reasons for the project


Structural measures
Bank/bed modifications Depth variation, Re-introducing stones, Introduction of gravel, Creation of fish passes
Floodplain / River corridor Buffer strips
Planform / Channel pattern
Non-structural measures
Management interventions
Social measures (incl. engagement)
Other Participation in design, Information provision


Hydromorphological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative

Biological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative
Fish: Abundance Improvement

Physico-chemical quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative

Any other monitoring, e.g. social, economic

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative

Monitoring documents

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Additional links and references

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Supplementary Information

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