Case study:Upper Emscher

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Location: 51° 29' 43.59" N, 7° 32' 33.65" E
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Project overview

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Status Complete
Project web site
Themes Habitat and biodiversity, Hydromorphology
Country Germany
Main contact forename Mechthild
Main contact surname Semrau
Main contact user ID User:EGLV
Contact organisation Emschergenossenschaft
Contact organisation web site http://eglv.de
Partner organisations
Parent multi-site project

Emscher restoration

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encompassing the following
projects
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Project summary

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Part of the integrated river basin management for the Emscher Region (865 km2, 2.700 inhabitants/ km2) is the revitalization of the river Emscher and its tributaries. Due to industrialization the water bodies were systematically developed as open wastewater sewers in the beginning of the 20th century. Economic and technical alternatives such as closed sewer systems could not be implemented due to constant subsidence caused by coal mining.

Momentarily, the river system is being restructured in order to enable the Emscher to once again be a fully functioning, continuous water-based ecosystem with typical topology and vegetation. An ecological concept based on the assumption of a non-interrupted river as a connection from the source to the mouth has been developed.

Studies on the feasibility of restructuring the Emscher show, that due to coal mining, industrial impacts and population changes the “original” conditions can never be reached again. It will not be possible to return the Emscher to its original, meandering state. Therefore, the reference conditions are no direct goals for the river restoration, but they give orientation in the planning procedure.

The upper Emscher is a small river, in parts still a creek of a little more than 12 km in length. Its source is located in a small forest south of Dortmund. Flowing northwards the restored waterbody passes fields, shrubs and several towns/quarters of Dortmund as well as smaller industrial parks. Due to the many restrictions by buildings or infrastructure several box-culverts with natural substrates had to be built. The longest in Dortmund-Aplerbeck has a length of 120 m. Since there was hardly any space at all, the culvert and the sewage pipes were constructed more or less simultaneously, placing the culvert on top of the pipes.

Several flood water detention basins have been constructed along the watercourse. The biggest of which, the " Phoenix-See " (Phoenix-Lake), is mostly used as recreation area. Bicycle and pedestrian paths as well as a harbour for sailing boats have been placed in and around the Lake.

Because of the restrictions the Emscher is usually not meandering, but mostly in a more or less woven bed which has been sharply incised during the beginning of the 20th century. Except for the part parallel to the Phoenix-Lake and the many urban areas restricting the width and natural dynamics, natural succession can be allowed (sometimes only in the meadow, not on the slopes), thus creating different habitats of alder forest, Typha and Carex reeds, sedge, floodgrass and Potamogeton in the compensatory floodplain.

Monitoring surveys and results

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Lessons learnt

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Image gallery


Upper Emscher in Dortmund Schüren during construction
Upper Emscher with lots of restrictions on both sides
Typha-reeds as seen during normal water levels
16 m3 discharge, nearly flooding the detention basin
View towards the detention basin phoenix-lake
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Catchment and subcatchment

Catchment

River basin district Rhine
River basin Rhine

Subcatchment

River name Emscher
Area category
Area (km2) 865865 km² <br />86,500 ha <br />
Maximum altitude category
Maximum altitude (m)
Dominant geology quarternary, holocene
Ecoregion Central Plains
Dominant land cover Urban, Intensive agriculture (arable), Grassland, Broadleaf/mixed woodland (semi natural)
Waterbody ID DE_NRW_2772



Other case studies in this subcatchment: Flood detention basin (HRB) Ickern-Mengede


Site

Name Upper Emscher section
WFD water body codes DE_NRW_2772_64190
WFD (national) typology Type 18: small loess-loam dominated lowland river
WFD water body name Emscher
Pre-project morphology concrete lined bed and bank, Straightened, Over deepened
Reference morphology Actively meandering, groundwater dominated
Desired post project morphology Low gradient passively meandering, enabled contact between floodplain and water body
Heavily modified water body Yes
National/international site designation
Local/regional site designations
Protected species present Yes
Invasive species present Yes
Species of interest
Dominant hydrology Groundwater, quick run-off
Dominant substrate Clay, Silt, loam
River corridor land use urban, Improved/semi-improved grassland/pasture, Broadleaf/mixed woodland (semi natural), Intensive agriculture (arable)
Average bankfull channel width category 2 - 5 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
Average unit stream power (W/m2)


Project background

Reach length directly affected (m)
Project started 1993/01/01
Works started
Works completed 2013/12/31
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

Mitigation of a pressure
Hydromorphology Continuity for organisms, Continuity of sediment transport, Connection to groundwaters, Quantity & dynamics of flow, Width & depth variation, Structure & condition of riparian/lake shore zones
Biology Fish, Invertebrates, Macrophytes, Create a new natural habitat with continuity for benthos, fishes and other organisms
Physico-chemical
Other reasons for the project Landscape enhancement, Recreation


Measures

Structural measures
Bank/bed modifications Removal of concrete banks and bed, Opening the river about 2 km, Bed raising
Floodplain / River corridor Increase water retention area, Connection to wider floodplain, Wetland habitat
Planform / Channel pattern Removal of concrete bank protection, Adding sinuosity, Channel widening
Other
Non-structural measures
Management interventions
Social measures (incl. engagement) Information for the public, New bicycle path
Other


Monitoring

Hydromorphological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative
Channel pattern/planform No Yes Yes No No Awaiting results
Continuity for organisms No Yes Yes No No Awaiting results
Structure & condition of riparian/lake shore zones No Yes Yes No No Awaiting results
Substrate conditions No Yes Yes No No Awaiting results
Width & depth variation No Yes Yes No No Awaiting results

Biological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative
Fish No No Yes Yes No Awaiting results
Invertebrates Yes Yes Yes Yes No Awaiting results
Macrophytes No Yes Yes Yes No Awaiting results
Angiosperms No Yes Yes No No Awaiting results

Physico-chemical quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative
Temperature No Yes Yes Yes No Awaiting results
Nutrient concentrations No Yes Yes Yes No Awaiting results
Oxygen balance No Yes Yes Yes No Awaiting results
PH No Yes Yes Yes No Awaiting results
Salinity No Yes Yes Yes No Awaiting results

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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