Case study:Lek Bij Everdingen

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Location: 51° 58' 4.80" N, 5° 10' 26.40" E

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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

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Catchment and subcatchment Select a catchment/subcatchment Edit the catchment and subcatchment details (affects all case studies in this 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 Edit site Name Lek Everdingen WFD water body codes WFD (national) typology R7; intertidal WFD water body name Pre-project morphology Single channel, Straight Reference morphology Desired post project morphology Heavily modified water body Yes National/international site designation Local/regional site designations Protected species present No Invasive species present No 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 Edit project background Reach length directly affected (m) 700 m0.7 km <br />70,000 cm <br /> 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 Edit reasons for 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 Edit 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 Edit Hydromorphological quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Biological quality elements Edit 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 Edit 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 Edit Other responses Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Monitoring documents Upload monitoring documents Additional documents and videos Upload additional documents Additional links and references Edit links and references Link Description http://wiki.reformrivers.eu/images/d/dc/LekEverdingen chem.pdf Datarapport 2008 bodemchemie Lekoevers bij Everdingen/Steenwaard Supplementary Information Edit Supplementary Information