Thur

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Thur


Factsheet: Thur

General
Country CH
River Name Thur
Site Name Thur
River Characterisation
    River typology
    Location (Lat Lon) 47.5918, 8.77114000000006
    Altitude mid-altitude: 200 - 800 m
    Catchment area large: > 1000 - 10000 km2
    Geology Calcareous
    National code/
    River type name
    Hydromorphological quality elements

    Biological quality elements
    Ecosystem Services
    EU Directives
    Pressures
    Measures
    Other
    Project size 1.6 km
    Approximate costs > 1 000 000 Euros
    Synergy Flood protection, ecology, recreation
    Status Realised
    Period of realization 2000 - 2003
    Evaluation Hydromorphological and ecological changes
    Implemented by Amt für Umwelt (Thurgau) and Amt für Abfall, Wasser, Energie und Luft (Zurich)



    Key features of the case study

    The recent rehabilitation of the river Thur has been one of the prominent restoration programmes in Switzerland. It is a clear example of restoration management in Switzerland, providing information concerning restoration effects, and stimulating current and future studies. Today, in Switzerland a strong political willingness exists to increase the space available for rivers, with the hope to improve their protecting role against floods and their ecological state at the same time.

    Site description

    The Thur is a 127 km long river flowing from the Swiss Alps in the north east of Switzerland. It is a tributary of the Rhine river which also originates in the Swiss Alps and ends in the North Sea. The Thur is the largest Swiss river without natural or artificial reservoirs along its course. Its discharge is similar to unregulated alpine rivers, the water level can therefore increase rapidly during rain events or snowmelt. For agricultural purposes and protection of residential areas, the Thur river was embanked (late 19th century) and its natural floodplain was drastically reduced.

    Before river engineering in 1890, the river braided, gravel bars were frequent, islands were present, natural alluvial forest accompanied the river. The complexity and heterogeneity of the habitats were maintained by the natural dynamics of the river itself. Its regulation created a monotonous channel surrounded by high levees and accompanied by embankments which fixed the river. New agricultural land was gained behind the levees for crop production, and between the levees and the embankments for grazing. At the same time, villages and cities were better protected from flood events during which discharge can raise to 1130 m3/sec (in 1999), far from the mean annual flow of 47 m3/sec. The stabilisation of the river bed also permitted to extract drinking water filtrated in the sediment. These human interventions had direct consequences on the hydromorphological conditions, the ecosystem functioning, and its biodiversity. Gravel bars disappeared, secondary channels terrestrialised, characteristic riverine species became rare, floodplain related species disappeared and the complexity of the system was largely reduced (see photos below).

    Degraded section with bank fixation and levees (orange arrows) and narrow floodplains (P. Reichter, A. Paillex)

    Measures selection

    Parts of the Thur river were restored, as for example in 2002 on a 2 km stretch close to the villages of Niederneunforn and Altikon (i.e. stretch selected as the restored site for the Reform project). The river was widened on one or both sides of the main river channel. Along the course of the river, embankments were removed to provide a larger space to the river. Additional wood structure were added to enhance the ability of the river to meander. Both are expected to increase diversity of instream habitats and corresponding biota. A higher interaction between the river and the old-disconnected floodplain is expected to happen. To date, hydromorphological and biological indicators both suggest an increase in river quality and conditions after restoration. Fish species like the Chondrostoma nasus and bird species like the Actitis hypoleucos found habitats within the new landscape [1]. Socio-economic studies will complement ecological approaches, to assess the benefits or restoration costs for local citizens. Moreover, long-term ecological studies will permit to study in details the success or failure of restoration. The Thur restoration is a clear example of restoration management in Switzerland, providing information concerning restoration effects, and stimulating current and future studies.

    Unrestored site, view upstream, autumn 2013
    Restored site, view downstream, autumn 2013

    Socio-economic aspects

    Socio-economic studies will complement ecological approaches, to assess the benefits or restoration costs for local citizens.

    Contact person within the organization

    Prof. Mario Schirmer, Eawag, Überlandstrasse 133, CH 8600 Dübendorf, Switzerland

    Extra background information

    Link to project website:

    http://www.cces.ethz.ch/projects/nature/Record

    http://www.rhone-thur.eawag.ch/

    References

    European Centre for River Restoration (ECRR). 2008. ECRR Addressing practitioners


    Related Measures

    Related Pressures