Difference between revisions of "Remove bank fixation"

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(General description)
(Expected effect of measure on (including literature citations):)
 
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=Remove bank fixation=
 
=Remove bank fixation=
 
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Category 07. Riparian zone improvement
  
 
==General description ==
 
==General description ==
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In this fact-sheet, the removal of bank fixation and creation of habitats at the river bank (e.g. gravel bars) is described, which does not necessarily include other large scale measures to restore a natural planform or channel dynamics.  
 
In this fact-sheet, the removal of bank fixation and creation of habitats at the river bank (e.g. gravel bars) is described, which does not necessarily include other large scale measures to restore a natural planform or channel dynamics.  
 
Bank fixation is removed and shallow gravel banks are created using heavy machinery. In some cases, the toe of the bank is still fixed to prevent complete bank erosion and channel widening to ensure navigability (Figure 1).
 
Bank fixation is removed and shallow gravel banks are created using heavy machinery. In some cases, the toe of the bank is still fixed to prevent complete bank erosion and channel widening to ensure navigability (Figure 1).
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[[Image:BankRemoval.jpg|600px|thumb|centre|Figure 1: Removal of bank fixation with toe protection (modified after http://www.donau.bmvit.gv.at/projekt/massnahmen/uferrueckbau/).]]
  
 
==Applicability ==
 
==Applicability ==
  
The applicability depends mostly on the socio-economic functions jeopardised by removing bank protection. It is mostly possible in rural, but hardly in urbanised areas. E.g. in the Netherlands buying buffer zones (15 m along small streams; 75 m along large rivers) from farmers is combined with this measure. When bank erode it does not affect agriculture.
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This kind of bank removal can especially be applied and will be very efficient in impounded large gravel bed rivers like the upper Danube, where gravel bars are drowned and shallow low-velocity habitats are virtually absent. In these impounded rivers, spawning and nursery habitats like shallow near-bank gravel bars, side channels, and backwaters are often the bottleneck for stream-type specific fish species. River banks have been heavily fixed and the potential for river restoration is limited due to uses like navigation, hydropower or flood protection and mitigation measures are restricted to the river banks..
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Similar or complementary measures to enhance river bank habitat are to modify hydraulic structures like groynes (see fact sheet “Remove or modify in-channel hydraulic structures (e.g. groynes, deflectors)”) and the placement of large wood (e.g. rootwads).
  
 
==Expected effect of measure on (including literature citations): ==
 
==Expected effect of measure on (including literature citations): ==
*HYMO (general and specified per HYMO element)
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There are some empirical studies published as grey literature but no information on this measure in open scientific literature (see below). Therefore, the assessment of the effect of this measure is mainly based on expert judgement.
  
Bank removal may contribute to enlarge river depth and width variation and diversify the structure of the riparian zone as well as the structure and substrate of the river bed.
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'''Hydromorphology (general and specified per HYMO element)'''
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*physico-chemical parameters
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This measure has little to no effect on the physical-chemical parameters.
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* Increase of shallow gravel bar habitat, low-velocity zones and backwaters, i.e. spawning and nursery habitats for fish (Zauner et al. 2001).
  
*Biota (general and specified per Biological quality elements
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* Increase of fine sediment deposition in backwater areas downstream from near-bank gravel bars (Zauner et al. 2001).
  
The change in substrate on the bank from artificial to natural has significant effects on all biota. Vegetation - both aquatic and riparian - will develop, while benthic invertebrate and fish species composition will in due course adapt the new habitat conditions (from hard and bare to more soft and vegetated substrate). Eventhough this development is towards a more natural ecological state, indices may suggest otherwise because the artificial hard substrate used to protect bank are quite often populated by rheophilic and lithophilic communities.
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'''Physico-chemical parameters'''
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* No information available.
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'''Biota (general and specified per biological quality elements)'''
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{| class="wikitable" border="1" style="text-align:center"
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|-
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! BQE !! Macroinvertebrates !! Fish !! Macrophytes !! Phytoplankton
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|-
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| Effect || high || high || high || no effect
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|}
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''Macroinvertebrates:''
 
   
 
   
==Temporal and spatial response  ==
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* Increase in diversity and limnophilic species (Zauner et al. 2001).
  
The spatial response will mostly be restricted to the strecth where bank were removed. Erosion processes that are again possible will change sediment loads downstream. The magnitude of the process determines whether it is of any significant influence.
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''Fish:''
  
The temporal response (years to decades) depends on the magnitude of dynamic forces (e.g. stream power; flood events) and the erodibility of the banks until a dynamic equilibrium is reached.
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* Increase in abundance and dominance of rheophilic fish species, for example common nase, barbel, and dace in the Danube river (Zauner et al. 2001, Zauner 2003).
  
The change in biotic communities depends on the change in habitat conditions and the colonisation potential in the catchment.
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* Increase in abundance of juvenile fish (Zauner et al. 2001, Zauner 2003).
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''Macrophytes:''
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* Most probably significant increase in number and abundance of macrophytes due to the increase in shallow low-velocity zones, which are virtually absent in impounded large, degraded rivers (e.g. waterways like the Danube river).
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''Phytoplankton:''
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* Probably no effect on phytoplankton.
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==Temporal and spatial response  ==
  
 
==Pressures that can be addressed by this measure ==
 
==Pressures that can be addressed by this measure ==
 
<Forecasterlink type="getPressuresForMeasures" code="M53" />
 
<Forecasterlink type="getPressuresForMeasures" code="M53" />
 
==Cost-efficiency ==
 
==Cost-efficiency ==
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Medium cost-efficiency: Medium to high cost for removal of riprap and creation of gravel bars, high ecological effect in highly degraded and impounded rivers since the main bottlenecks are addressed by the measure.
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==Case studies where this measure has been applied ==
 
==Case studies where this measure has been applied ==
 
<Forecasterlink type="getProjectsForMeasures" code="M53" />
 
<Forecasterlink type="getProjectsForMeasures" code="M53" />
 
==Useful references ==
 
==Useful references ==
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Zauner, G., Pinka, P. & Moog, O. (2001) Pilotstudie oberes Donautal - Gewässerökologische Evaluierung neugeschaffener Schotterstrukturen im Stauwurzelbereich des Kraftwerks Aschach. Bundesministerium für Verkehr, Innovation und Technologie, Wien, 132 pages.
  
Surian, N,  L Ziliani, F Comiti, MA Lenzi 2 & L Mao (2009) Channel adjustments and alteration of sediment fluxes in gravel-bed rivers of North-Eastern Italy: potentials and limitations for channel recovery. River Research & Applications 25: 551-567
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Zauner, G. (2003) Fischökologische Evaluierung der Biotopprojekte Ybbser-Scheibe und Diedersdorfer Haufen - Studie im Auftrag der Wasserstraßendirektion. Ezb - TB Zauner, Engelhartszell, Austria, unpublished report, 70 pages.
  
 
==Other relevant information ==
 
==Other relevant information ==
  
 
[[Category:Measures]][[Category:07. Riparian zone improvement]]
 
[[Category:Measures]][[Category:07. Riparian zone improvement]]

Latest revision as of 13:09, 7 January 2019

Remove bank fixation

Category 07. Riparian zone improvement

General description

In many rivers, habitat quality at the river banks is poor due to bank fixation (e.g. using riprap). Removal of bank fixation is a prerequisite for many other measures like re-meandering or widening as well as initiating later channel migration and dynamics.

In this fact-sheet, the removal of bank fixation and creation of habitats at the river bank (e.g. gravel bars) is described, which does not necessarily include other large scale measures to restore a natural planform or channel dynamics. Bank fixation is removed and shallow gravel banks are created using heavy machinery. In some cases, the toe of the bank is still fixed to prevent complete bank erosion and channel widening to ensure navigability (Figure 1).

Figure 1: Removal of bank fixation with toe protection (modified after http://www.donau.bmvit.gv.at/projekt/massnahmen/uferrueckbau/).

Applicability

This kind of bank removal can especially be applied and will be very efficient in impounded large gravel bed rivers like the upper Danube, where gravel bars are drowned and shallow low-velocity habitats are virtually absent. In these impounded rivers, spawning and nursery habitats like shallow near-bank gravel bars, side channels, and backwaters are often the bottleneck for stream-type specific fish species. River banks have been heavily fixed and the potential for river restoration is limited due to uses like navigation, hydropower or flood protection and mitigation measures are restricted to the river banks..

Similar or complementary measures to enhance river bank habitat are to modify hydraulic structures like groynes (see fact sheet “Remove or modify in-channel hydraulic structures (e.g. groynes, deflectors)”) and the placement of large wood (e.g. rootwads).

Expected effect of measure on (including literature citations):

There are some empirical studies published as grey literature but no information on this measure in open scientific literature (see below). Therefore, the assessment of the effect of this measure is mainly based on expert judgement.

Hydromorphology (general and specified per HYMO element)

  • Increase of shallow gravel bar habitat, low-velocity zones and backwaters, i.e. spawning and nursery habitats for fish (Zauner et al. 2001).
  • Increase of fine sediment deposition in backwater areas downstream from near-bank gravel bars (Zauner et al. 2001).

Physico-chemical parameters

  • No information available.

Biota (general and specified per biological quality elements)

BQE Macroinvertebrates Fish Macrophytes Phytoplankton
Effect high high high no effect

Macroinvertebrates:

  • Increase in diversity and limnophilic species (Zauner et al. 2001).

Fish:

  • Increase in abundance and dominance of rheophilic fish species, for example common nase, barbel, and dace in the Danube river (Zauner et al. 2001, Zauner 2003).
  • Increase in abundance of juvenile fish (Zauner et al. 2001, Zauner 2003).

Macrophytes:

  • Most probably significant increase in number and abundance of macrophytes due to the increase in shallow low-velocity zones, which are virtually absent in impounded large, degraded rivers (e.g. waterways like the Danube river).

Phytoplankton:

  • Probably no effect on phytoplankton.

Temporal and spatial response

Pressures that can be addressed by this measure

Cost-efficiency

Medium cost-efficiency: Medium to high cost for removal of riprap and creation of gravel bars, high ecological effect in highly degraded and impounded rivers since the main bottlenecks are addressed by the measure.

Case studies where this measure has been applied

Useful references

Zauner, G., Pinka, P. & Moog, O. (2001) Pilotstudie oberes Donautal - Gewässerökologische Evaluierung neugeschaffener Schotterstrukturen im Stauwurzelbereich des Kraftwerks Aschach. Bundesministerium für Verkehr, Innovation und Technologie, Wien, 132 pages.

Zauner, G. (2003) Fischökologische Evaluierung der Biotopprojekte Ybbser-Scheibe und Diedersdorfer Haufen - Studie im Auftrag der Wasserstraßendirektion. Ezb - TB Zauner, Engelhartszell, Austria, unpublished report, 70 pages.

Other relevant information