Case study:Lek Bij Everdingen

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Project overview

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Status Complete
Project web site
Themes Habitat and biodiversity, Monitoring, Water quality
Country Netherlands
Main contact forename M
Main contact surname Greijdanus-Klass
Main contact user ID
Contact organisation Rijkswaterstaat Waterdienst
Contact organisation web site http://www.rijkswaterstaat.nl/over ons/adressen en diensten/landelijkediensten/waterdienst/
Partner organisations
Parent multi-site project
This is a parent project
encompassing the following
projects
No
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Project summary

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The Lek river is one of the major Rhine tributaries in the Netherlands. The river is channelised and groynes are present to keep the river suitable for navigation purposes. Also, banks are fixated to avoid sediment input into the main channel. The specific site of this project is situated near the town of Everdingen. The area is characterized by continual passing of ships and barges. This causes disturbance of the water flow which in turn is thought to disturb the biota in the groyne areas.

To avert the disturbance in the water flow caused by passing ships a number of groynes were shielded off by artificial structures placed in front of the groynes. These structures were made of two rows of wooden poles with branches in between them. The reasoning behind this measure was that the coils in the water would be stopped by these poles and a more suitable habitat, primarily for macrophytes, would be established in the groyne fields. The presence of macrophytes would in turn increase habitat availability for fish and benthic invertebrates. Benthic invertebrates were thought to also be able to benefit from the newly available substratum of the wooden poles. In some of the groyne fields the bank fixation was (partially) removed so that more knowledge of the effect of the shielding could be retrieved from monitoring efforts.

The goal of the project was to stimulate the development of shore and waterplant vegetation. This may also positively affect the other WFD BQEs, namely benthic invertebrates and fish. No definitive values were determined for the success or failure of the project or the respective BQEs at the start of the project. The BQEs were all monitored and evaluated by experts in their respective fields.

Monitoring surveys and results

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The project makes use of a selective placement method. It is assumed that groyne fields are identical, as such selective placement of shields makes it possible to test the effectiveness of the method. Shielded and unshielded groynes are monitored for the different BQEs. Monitoring and related studies were carried out by the Rijkswaterstaat Waterdienst Oost and by AquaTerra-KuiperBurger. All monitoring data is property of Rijkswaterstaat Netherlands.

Benthic Invertebrates Benthic invertebrates were monitored in 2006 and 2008. The conclusions from the monitoring is that there are no significant differences between the groyne fields that are shielded by the rows of poles and those that are not. This leads to the conclusion that the measure does not have the desired effect on benthic invertebrates.

Nematodes In contrast to the rest of the benthic groups the nematodes show clear differences between shielded and unshielded fields. The groyne fields that were shielded had a higher occurrence and taxa diversity than the unshielded fields. Also, between 2006 and 2008 an overall increase in nematodes was found in the shielded fields. The conclusion is easily drawn that nematodes are positively affected by the measure.

Macrophytes and phytobenthos Macrophytes were monitored in both shielded and unshielded fields. Another hypothesis was tested by making enclosures of wire frames. This was done to eliminate possible grazing by water-birds. Results show strong signs of grazing in non-enclosed parts of the groyne fields. Macrophyte development has been limited, even in the enclosures. No clear difference in macrophyte occurence was found between shielded and unshielded areas. The conclusion is that the artificial structures do not promote the occurrence of macrophytes so far. It should be noted that more time may be needed for the desired effect to present itself.

Fish The difference in fish composition and occurrence between the groyne fields (both shielded and unshielded) is quite large. This has led to difficulties in determining statistically significant effects. The general image is that some specific fish species are benefiting from the shields and are showing increase in presence of brood. The expectation is that with time the vegetation will develop further and with that the fish population will benefit as well.

Hydromorphological response was not monitored.

costs Benthic invertebrates: 66 500.- Euro Nematodes: 23 300.- Euro Fish: 88 700.- Euro Vegetation: 49 300.- Euro Chemical: 9 500.- Euro

Lessons learnt

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Catchment and subcatchment

Catchment

River basin district Rhine
River basin Lek

Subcatchment

River name Lek
Area category more than 10000 km²
Area (km2)
Maximum altitude category 100 - 200 m
Maximum altitude (m)
Dominant geology Calcareous
Ecoregion Central Plains
Dominant land cover Grassland, Urban
Waterbody ID



Site

Name Lek Everdingen
WFD water body codes
WFD (national) typology R7
WFD water body name
Pre-project morphology Single channel, Straight
Reference morphology
Desired post project morphology
Heavily modified water body true
National/international site designation
Local/regional site designations
Protected species present
Invasive species present
Species of interest
Dominant hydrology Tidal, Estuary
Dominant substrate Gravel, Silt
River corridor land use Urban, Extensive agriculture
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

Reach length directly affected (m) 700 m
0.7 km
70,000 cm
Project started
Works started 2005/01/01
Works completed 2006/01/01
Project completed
Total cost category 100 - 500 k€
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 Rijkswaterstaat Waterdienst
Stakeholder engagement and communication Rijkswaterstaat Waterdienst
Works and works supervision
Post-project management and maintenance Rijkswaterstaat Waterdienst
Monitoring 100 - 500 k€ Rijkswaterstaat Waterdienst



Reasons for river restoration

Mitigation of a pressure Navigation, Channelising of the river
Hydromorphology Quantity & dynamics of flow, Flow velocities, Continuity for organisms
Biology Invertebrates, Macrophytes, Fish: Abundance
Physico-chemical
Other reasons for the project


Measures

Structural measures
Bank/bed modifications Introduction of coil rolls to protect groynes
Floodplain / River corridor
Planform / Channel pattern
Other
Non-structural measures
Management interventions
Social measures (incl. engagement)
Other


Monitoring

Hydromorphological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative

Biological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative
Invertebrates Yes Yes Yes Inconclusive
Macrophytes Yes Yes Yes Inconclusive
Fish: Abundance Yes Yes Yes Inconclusive

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

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative


Monitoring documents



Additional documents and videos


Additional links and references

Link Description
http://wiki.reformrivers.eu/images/d/dc/LekEverdingen chem.pdf Datarapport 2008 bodemchemie Lekoevers bij Everdingen/Steenwaard

Supplementary Information

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