Case study:Ritobäcken-environmentally preferable two-stage drainage channels

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Location: 60° 19' 5", 25° 12' 16"
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Project overview

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Status Complete
Project web site
Themes Flood risk management, Habitat and biodiversity, Land use management - agriculture, Water quality
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 Aalto University
Parent multi-site project
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Project summary

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Ritobäcken brook is a small tributary of River Sipoonjoki which is located near to Helsinki partly in a Sipoonkorpi National Park. Brook serves as a drainage channel for the surrounding agricultural fields which constitute 13% of the 10 km2 catchment area. The brook is also a reproduction area for the vulnerable sea run brown trout (Salmo trutta) of the Baltic Sea. Because of the significant bank and bed erosion in the upstream reaches and reduced conveyance in the downstream reaches fields were inundated during high flows. Brook was restored as the aim of maintaining and enhancing the habitat diversity of the brook for migratory fish while decreasing flooding of the fields. The two-stage cross-section was constructed on excavating a floodplain on one side of the channel and leaving the opposite side and bottom intact to prevent the digging of the stream bed. The flood terrace has so far been large enough to prevent flooding to the arable areas. Spawning brown trout have been monitored downstream in autumn 2010 and 2011, showing that no harm for fish was done by the excavation. The increase of trout habitat to the excavated section upstream can also be expected, with help of further restoration.

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Catchment and subcatchment

Catchment

River basin district Southern Finland
River basin Sipoonjoki River

Subcatchment

River name Ritobäcken brook
Area category 10 - 100 km²
Area (km2) 12 km²
1,200 ha
Maximum altitude category
Maximum altitude (m)
Dominant geology Organic (i.e. Peat)
Ecoregion Fenno-Scandian Shield
Dominant land cover Intensive agriculture
Waterbody ID



Other case studies in this subcatchment: Restorations of Ritobäcken brook


Site

Name Cathment of Brook Ritobäcken
WFD water body codes
WFD (national) typology
WFD water body name
Pre-project morphology Sinuous
Reference morphology Sinuous, two-stage cross-section, floodplain
Desired post project morphology
Heavily modified water body
National/international site designation EU - Special Area of Conservation
Local/regional site designations
Protected species present
Invasive species present
Species of interest
Dominant hydrology Ephemeral
Dominant substrate Clay
River corridor land use Intensive agriculture
Average bankfull channel width category Less than 2 m
Average bankfull channel width (m)
Average bankfull channel depth category 0.5 - 2 m
Average bankfull channel depth (m)
Mean discharge category
Mean annual discharge (m3/s)
Average channel gradient category
Average channel gradient 0.002
Average unit stream power (W/m2)


Project background

Reach length directly affected (m)
Project started 2009/01/01
Works started 2010/01/01
Works completed 2010/01/01
Project completed
Total cost category 10 - 50 k€
Total cost (k€) 15 k€
15,000 €
Benefit to cost ratio
Funding sources Ministry of Agriculture and Forestry, Academy of Finland, Maa ja vesitekniikan tuki ry

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
Monitoring Aalto University



Reasons for river restoration

Mitigation of a pressure Flood defence
Hydromorphology Continuity of sediment transport, Quantity & dynamics of flow, Structure & condition of riparian zones, Width & depth variation
Biology Fish: Abundance, Fish: Disturbance-sensitive species
Physico-chemical Nutrient concentrations
Other reasons for the project


Measures

Structural measures
Bank/bed modifications
Floodplain / River corridor Floodplain creation
Planform / Channel pattern
Other
Non-structural measures
Management interventions
Social measures (incl. engagement)
Other


Monitoring

Hydromorphological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative
Quantity & dynamics of flow Yes Improvement
Continuity for organisms Yes Improvement
Continuity of sediment transport Yes Improvement
Structure & condition of riparian zones Yes Improvement

Biological quality elements

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

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