Case study:Reopening of Mjølløst stream

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Location: 59° 9' 34.98" N, 10° 15' 39.20" E

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Project overview

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Status	Planned
Project web site
Themes	Habitat and biodiversity, Land use management - agriculture, Monitoring
Country	Norway
Main contact forename	Miguel A.
Main contact surname	Segarra Valls
Main contact user ID
Contact organisation	Tønsberg kommune
Contact organisation web site	http://www.tonsberg.kommune.no/
Partner organisations
Parent multi-site project
This is a parent project encompassing the following projects	No

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Project summary

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Mjølløst stream is part of a 17 km long stream system. Mjølløst stream has since the 1960s had a 270 meter long stream closure that prevents sea trout from accessing a 1.4 km stream stretch. The concrete pipe is getting closer to the end of its lifetime, and landowner and local and regional authorities are positive to remove it and restore the original stream. This project got funding from Norwegian Environment Agency (Miljødirektoratet) i 2020.

Monitoring surveys and results

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Results electrofishing October 2020 (before reopening of the stream):

Station 1 (downstreams closure): 141 trout / 100 m2. https://restorerivers.eu/wiki/index.php?title=File%3AMjollost_1_(downtreams)_october_2020.jpg Station 2 (upstreams closure): 1 trout / 100m2. Station 3 (200 m ustreams closuse): 57 trout / 100m2.

Fish from upstream stations is in principle stationary trout.

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Catchment and subcatchment Select a catchment/subcatchment Site Edit site Name WFD water body codes WFD (national) typology WFD water body name Pre-project morphology Reference morphology Desired post project morphology Heavily modified water body National/international site designation Local/regional site designations Protected species present Invasive species present Species of interest Dominant hydrology Dominant substrate River corridor land use 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 Edit project background Reach length directly affected (m) Project started Works started Works completed 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 Monitoring Reasons for river restoration Edit reasons for restoration Mitigation of a pressure Hydromorphology Biology Physico-chemical Other reasons for the project Measures Edit Measures Structural measures Bank/bed modifications Floodplain / River corridor Planform / Channel pattern Other Non-structural measures Management interventions Social measures (incl. engagement) Other Monitoring Hydromorphological quality elements Edit Hydromorphological quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Biological quality elements Edit biological quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Physico-chemical quality elements Edit 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 Edit Other responses Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Monitoring documents Upload monitoring documents Additional documents and videos Upload additional documents Additional links and references Edit links and references Link Description Supplementary Information Edit Supplementary Information