Case study:TEST Daylighting the Texas Valley stream

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Location: 59° 58' 44.67" N, 11° 14' 29.77" E

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Project overview

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Status	Complete
Project web site
Themes	Economic aspects, Flood risk management, Habitat and biodiversity, Hydromorphology, Monitoring, Social benefits, Spatial planning, Water quality, Urban
Country	Norway
Main contact forename	Kari
Main contact surname	Nordkvinne
Main contact user ID
Contact organisation	County Governor of Oslo og Viken
Contact organisation web site	http://https://www.statsforvalteren.no/en/oslo-og-viken/
Partner organisations	NIVA
Parent multi-site project
This is a parent project encompassing the following projects	No

2. Newly restored stretch of stream Texas Valley, one year after implementation of restoration measures, i.e. March 2017. Photo: Kari Nordkvinne/NIVA.

Project summary

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Daylighting of a previously culverted stream in a suburban area. The culvert was old and under dimensioned, thus it had to be either exchanged with a larger culvert, or removed. Based on a cost-benefit analysis, the latter was chosen, and the land owner decided on three main goals for the daylighting: 1) improve the water quality to good ecological status, 2) reduce bank erosion after removing the culvert, 3) increase the natural recreational area within this suburban zone.

The project was planned and prospected in 2015, the daylighting, flood protection and reconstruction of the riparian zone was conducted in 2016, and monitoring was conducted in 2017 and 2020.

Monitoring surveys and results

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Assessments of the ecological status based on nutrients, benthic algae, macroinvertebrates and fish were conducted twice, in 2017 and in 2020. The overall ecological status in 2017 and 2020 was bad due to lack of fish. This is due to a fish barrier (culvert) further down. However, macroinvertebrates increased from poor (2017) to good ecological status (2020), and benthic algae showed good status both years, thus these two organism groups had a good effect of the daylighting. Nutrients showed moderate status both years (Tot N and Tot P), which was the same as the upstream reference stretch.

Embankments were set in place to reduce the risk of bank erosion after daylighting, as this could lead to negative impacts on local buildings and infrastructure. 2 years of continuous monitoring of particle runoff in the daylighted stretch was compared to similar measurements at the upstream open section, and there were no differences in particle runoff from the two stretches.

To assess the recreational use of the area, the local bicycle club registered number of people using the new pathway and bench area every Saturday 10:00-14:00 from May-Oct 2017 and 2020. This showed an initial peak of users right after opening, then a slight decrease in 2017. However, the use was clearly higher in 2020, and the area was used by at least 9 people in the time registered every weekend in 2020.

Lessons learnt

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Opening the stream has had very good reviews from the local residents and on the ecological status for benthic algae and macroinvertebrates. The bank erosion measures seem to work well after installment, but were built in a period of heavy rain, causing surplus erosion that could have been avoided. If fish status is to be improved, then the downstream culvert also needs to reopen. The costs of these measures were similar to building a new culvert, but yearly maintenance costs have so far been lower, and the recreational benefits are positive. The local bicycle club also have some ownership of the area now, through their monitoring, which has resulted in their free involvement in keeping the area free of garbage.

Image gallery

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Catchment and subcatchment Select a catchment/subcatchment Site Edit site Name Texasbekken WFD water body codes 006-189-R WFD (national) typology REL2321 WFD water body name Texasbekken oppstrøms Texasdalen Pre-project morphology Closed culvert Reference morphology Naturally straight Desired post project morphology Naturally straight Heavily modified water body No National/international site designation Norway - Naturminne Local/regional site designations World Hertiage Site Protected species present No Invasive species present No Species of interest Dominant hydrology Artificially regulated Dominant substrate Clay River corridor land use Tall herb/rank vegetation 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) 150150 m <br />0.15 km <br />15,000 cm <br /> Project started 2015/02/02 Works started 2016/05/08 Works completed 2016/11/22 Project completed 2020/11/23 Total cost category 50 - 100 k€ Total cost (k€) Benefit to cost ratio Funding sources Norwegian Environment Agency (Miljødirektoratet), Lillestrøm Municpality 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