Difference between revisions of "Thur"

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=Thur =  
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=Thur=
  
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<googlemap version="0.9" lat="47.592778" lon="8.590278" zoom="15" scale="yes" overview="yes" controls="large"> </googlemap>  
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<googlemap version="0.9" lat="47.592" lon="8.76514" zoom="13" width="100%" height="400" scale="yes" overview="yes" toc="no" controls="large">
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(A) 47.592, 8.76514
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</googlemap>
  
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{{forecasterTemplate
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<Forecasterlink type="getProjectInfoBox" code="262" />
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|site_name=Thur
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|river_name=Thur
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|river_type_name=large slow-flowing river over sand/clay
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|country=CH
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|altitude=high: > 800 m
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|catchmentarea=large: > 1000 - 10000 km2
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|geology=Calcareous
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|latitude=47.592778
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|longitude=8.590278
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|natcode=XXX
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|pressures=Morphological alterations<br>  Channelisation/Cross section alteration<br>
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|measures=Working with physical form and function of river and floodplains<br>  River bed raising or lowering<br>Structural modifications<br>  Construction of new structures<br>  Modify/replace existing structures<br>Changes in system operation<br>  Appropriate vegetation management plan<br>
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|size=1
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|size_unit=km2
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|costs= 0
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|costs_unit= EUR
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|synergy=Flood control
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|status_name= Realised
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|period= 1999
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|evaluation=Yes
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|organization=
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}}
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<div class="visualClear"></div>
 
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'''Attention:'''The information presented below has been reproduced from the ECRR brochure<ref>ECRR brochure (click [http://www.ecrr.org/pdf/ecrrbrochure.pdf here] for online source)</ref>.
 
  
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<br>
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==Key features of the case study==
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The Thur river is one of the main rivers in the Cantons St. Gallen, Thurgau and Zürich in Switzerland. It has a lenght of 127 km and a catchment area of 1,750 km<sup>2</sup> with about 456 creeks and brooks. The highest point is the summit of Säntis at 2,551 masl. The 100 years flow is estimated at 1,350 m<sup>3</sup>/s, the lowest runoff is 2,24 m<sup>3</sup>/s, and the average flow is 47 m<sup>3</sup>/s. The Thur  is a wild river with no lake or dam or big floodplain for retention.
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The first flood control works were constructed in the second half of the 19th century. Today, the ancient dikes and other measures applied in the late 19th century no longer adequately cope with modern discharge conditions, mainly due to insufficient heights, inappropriate construction materials, and poor maintenance. The river bed has been filled with sediment deposits, limiting discharge capacity and increasing flood peaks, while the increased human occupation of the valley in some places limits the extent of the floodplain and interferes with surface roughness (trees) in others.
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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.
  
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After the catastrophic flooding due to the breaking of the dikes in 1978, urgent response measures included the repairing and heightening of the dikes and the removal of
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==Site description==
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surface layer sediments from the confined stream bed. The increased attention paid to ecological aspects in later years resulted in a removal of the old stonewall parallel
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to the stream bed, while groynes were build in combination with obliquely placed blocks and willow trees.
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[[Image:Thur_river_before_after_photos.png|400px|thumb|left|Widening of the Thur river, Switzerland]]
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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.
  
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The resulting variety of river works provide both protection while allowing the river a greater freedom to spread and move. Over a length of 1,500 m and a width of 500 m
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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 m<sup>3</sup>/sec (in 1999), far from the mean annual flow of 47 m<sup>3</sup>/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).
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the Thur river now can redevelop its natural course, in which erosion and sediment deposition processes freely alternate. Scours and rapids as well as wandering gravel
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beds have once again become a part of the river. This new design of the river was successfully tested by the flood of 1999 (Q 1,000m<sup>3</sup>/s), in which only a few blocks were moved downstream, and no extensive repairing appeared necessary.  
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The river restoration works also proved a great success for the ecological state of the Thur river. Fish species like the ''Chondrostoma nasus'' and bird species like the ''Actitis hypoleucos'' found new habitats within the new river landscape.  
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[[File:Thur_Degraded.jpg|thumbnail|none|Degraded section with bank fixation and levees (orange arrows) and narrow floodplains (P. Reichert, A. Paillex)]]
  
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The experiences with the river restoration project of the Thur river provide important perceptions for further projects on other rivers. More space for rivers gives opportunities to restore natural wild flora and fauna. Besides, the character of the river changes from a dull canal to a diversified river environment, offering opportunities for tourism and recreation. The Thur river restoration project shows that flood control by means of nature friendly technical river works not necessarily oppose nature conservation interests.
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==Measures selection==
  
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'''References:'''
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To date, important efforts are made to restore a natural morphology within the river. The aims are to increase natural protection against floods, and to increase natural processes and habitat diversity. Parts of the Thur river were restored, as for example in 2002 on a 1.5 km stretch close to the villages of Niederneunforn and Altikon (i.e. stretch selected as the restored site for the Reform project, Figure 2). 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 braid. The dynamic processes were expected to be return, with natural patterns of erosion and deposition, better connection between the main river channel and the floodplain, and recreation of secondary channels. Overall, an increase of instream and terrestrial habitats diversity was expected, leading to an increase in biotic richness and diversity, both in the river and on the banks.
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<references />
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[[File:Thur_Restored.jpg|thumbnail|none|Restored gravel bar (left), stagnant water body (right), and overview of the restored section (bottom)(A. Paillex, H. Mottaz)]]
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==Hydromorphological and ecological response==
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To date, hydromorphological and biological indicators both suggest an increase in river quality and conditions after restoration. As a result from river restoration, we can observe that gravel bars were recreated, secondary channels appeared, and zones of erosion and deposition now co-exist at the scale of the restored reach. Less visible, but measurable with appropriate methods, are the biological improvements in the restored reach compared to regulated stretches. The richness in benthic invertebrates, fish, ground beetles, aquatic vegetation and floodplain vegetation has increased in the restored section (see table below). According to a valuation of richness and of threatened and invasive species, the improvement was important for fish and ground beetles, intermediate for floodplain vegetation, and less significant for benthic invertebrates and aquatic plants. A positive effect is that threatened species (e.g. the fish Chondrostomas nasus) took advantage of this restoration project, while a negative side effect is the occurrence of an invasive aquatic plant in the restored site (i.e. Elodea nuttallii). A combined valuation of biological and morphological conditions indicates an overall positive effect of restoration on the ecological state of the river.
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{| class="wikitable"
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|-
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! Indicators !! Degraded !! Restored
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|-
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| Macroinvertebrates || 39 || 47
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|-
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| Fish || 7 || 10
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|-
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| Ground beetles || 3 || 13
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|-
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| Aquatic vegetation || 3 || 9
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|-
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| Riparian vegetation || 20 || 29
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|-
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|}
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==Socio-economic aspects==
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A positive effect of this enhanced naturalness is an increased number of people visiting the river, especially on sunny days. This is supported by an easier access to the river and more opportunities for recreational activities.
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==Outlook==
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However, there is still a lot to do to sustain this improvement for the long term. Today, we may have to prevent invasive species from colonising the recovered habitats, and improve the water quality to increase the biological success. Finally, it is important to recall that this restored part is only 1.5 km long while the majority of the remaining 130 km of the river are still totally embanked.
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==Contact person within the organization==
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Prof. Mario Schirmer or Dr. Amael Paillex, E-mail: Mario.Schirmer or Amael.Paillex[at]eawag.ch, Eawag, Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, CH 8600 Dübendorf, Switzerland
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==Extra background information==
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Link to project website:
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http://www.cces.ethz.ch/projects/nature/Record
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<br />
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http://www.rivermanagement.ch/en/welcome.php
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<br />
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http://www.rhone-thur.eawag.ch/
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==References==
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Eawag, WSL, ETHZ, EPFL, 2005: Integrales Gewässermanagement - Erkenntnisse aus dem Rhone-Thur Projekt http://www.rivermanagement.ch
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Schirmer, M., Luster, J., Linde, N., Perona, P., Mitchell, E. A. D., Barry, D. A., Hollender, J., Cirpka, O. A., Schneider, P., Vogt, T., Radny, D., and Durisch-Kaiser, E. 2014 Morphological, hydrological, biogeochemical and ecological changes and challenges in river restoration – the Thur River case study, Hydrol. Earth Syst. Sci., 18, 2449-2462, http://www.hydrol-earth-syst-sci.net/18/2449/2014/hess-18-2449-2014.html
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European Centre for River Restoration (ECRR). 2008. ECRR Addressing practitioners.
  
  
 
[[Category:Case_studies]]
 
[[Category:Case_studies]]
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== Related Measures ==
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<Forecasterlink type="getMeasuresForProject" code="262" />
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== Related Pressures ==
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<Forecasterlink type="getPressuresForProject" code="262" />
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[[Category:Quantity and dynamics of water flow]] [[Category:Connection to groundwater bodies]] [[Category:River continuity]] [[Category:River depth and width variation]] [[Category:Structure and substrate of the river bed]] [[Category:Structure of the riparian zone]] [[Category:Structure of the floodplain]] [[Category:Phytoplankton]] [[Category:Macrophytes and phytobenthos]] [[Category:Benthic invertebrates]] [[Category:Fish]]

Latest revision as of 13:59, 15 December 2015

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. Reichert, A. Paillex)

    Measures selection

    To date, important efforts are made to restore a natural morphology within the river. The aims are to increase natural protection against floods, and to increase natural processes and habitat diversity. Parts of the Thur river were restored, as for example in 2002 on a 1.5 km stretch close to the villages of Niederneunforn and Altikon (i.e. stretch selected as the restored site for the Reform project, Figure 2). 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 braid. The dynamic processes were expected to be return, with natural patterns of erosion and deposition, better connection between the main river channel and the floodplain, and recreation of secondary channels. Overall, an increase of instream and terrestrial habitats diversity was expected, leading to an increase in biotic richness and diversity, both in the river and on the banks.

    Restored gravel bar (left), stagnant water body (right), and overview of the restored section (bottom)(A. Paillex, H. Mottaz)

    Hydromorphological and ecological response

    To date, hydromorphological and biological indicators both suggest an increase in river quality and conditions after restoration. As a result from river restoration, we can observe that gravel bars were recreated, secondary channels appeared, and zones of erosion and deposition now co-exist at the scale of the restored reach. Less visible, but measurable with appropriate methods, are the biological improvements in the restored reach compared to regulated stretches. The richness in benthic invertebrates, fish, ground beetles, aquatic vegetation and floodplain vegetation has increased in the restored section (see table below). According to a valuation of richness and of threatened and invasive species, the improvement was important for fish and ground beetles, intermediate for floodplain vegetation, and less significant for benthic invertebrates and aquatic plants. A positive effect is that threatened species (e.g. the fish Chondrostomas nasus) took advantage of this restoration project, while a negative side effect is the occurrence of an invasive aquatic plant in the restored site (i.e. Elodea nuttallii). A combined valuation of biological and morphological conditions indicates an overall positive effect of restoration on the ecological state of the river.

    Indicators Degraded Restored
    Macroinvertebrates 39 47
    Fish 7 10
    Ground beetles 3 13
    Aquatic vegetation 3 9
    Riparian vegetation 20 29

    Socio-economic aspects

    A positive effect of this enhanced naturalness is an increased number of people visiting the river, especially on sunny days. This is supported by an easier access to the river and more opportunities for recreational activities.

    Outlook

    However, there is still a lot to do to sustain this improvement for the long term. Today, we may have to prevent invasive species from colonising the recovered habitats, and improve the water quality to increase the biological success. Finally, it is important to recall that this restored part is only 1.5 km long while the majority of the remaining 130 km of the river are still totally embanked.

    Contact person within the organization

    Prof. Mario Schirmer or Dr. Amael Paillex, E-mail: Mario.Schirmer or Amael.Paillex[at]eawag.ch, Eawag, Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, CH 8600 Dübendorf, Switzerland

    Extra background information

    Link to project website:

    http://www.cces.ethz.ch/projects/nature/Record
    http://www.rivermanagement.ch/en/welcome.php
    http://www.rhone-thur.eawag.ch/

    References

    Eawag, WSL, ETHZ, EPFL, 2005: Integrales Gewässermanagement - Erkenntnisse aus dem Rhone-Thur Projekt http://www.rivermanagement.ch

    Schirmer, M., Luster, J., Linde, N., Perona, P., Mitchell, E. A. D., Barry, D. A., Hollender, J., Cirpka, O. A., Schneider, P., Vogt, T., Radny, D., and Durisch-Kaiser, E. 2014 Morphological, hydrological, biogeochemical and ecological changes and challenges in river restoration – the Thur River case study, Hydrol. Earth Syst. Sci., 18, 2449-2462, http://www.hydrol-earth-syst-sci.net/18/2449/2014/hess-18-2449-2014.html

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

    Related Measures

    Related Pressures

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