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Aaijen - Removal of Bank Fixation

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Key features of the case study

Near the town of Aijen the bank fixation along a bank of the river Meuse was removed over a stretch of 400 meters. The goal of this measure was to allow natural river dynamics and bank formation to take place and through this stimulate nature development. The banks were monitored and erosion was apparent. However, the characteristic steep bank sides were not formed due to the relatively low height of the river bank. Also, erosion was impeded by remnant hard debris in the banks. The macrophytes show no response to the measure, the benthic invertebrates show a positive response to the measure.

Site description

The river Meuse is intensively used as a shipping route. As such the river is periodically deepened to make it possible for ships to sail through. This deepening leads to a decrease in natural hydromorphological dynamics in the river. To restore dynamics the bank fixation has been removed in a number of locations along the river Meuse. This is done in a project by the name of Nature-friendly Banks Meuse (Natuur(vriende)lijke Oevers Maas; NVO). One of these areas is the riverbank near the village of Aaijen. This is a stretch of 400m of river bank which was fixated with hard material. In the sixties and seventies the bank area was fortified with rock filling. Later on the banks were fortified with broken stone material. The adjacent area consists of rough pastures and has seen intensive agricultural use over the past few decades.

Measures selection

To counteract the loss of dynamics in the river Meuse the bank fixation was removed along the 400 meter stretch of the riverbank near Aaijen. This measure was taken as the reintroduction of erosion processes is thought to contribute to the occurrence of flora and fauna that is interesting from a nature perspective. Also, the actual work of removing the fixation is quick to carry out. After removal of the fixation natural processes are left to shape the riverbank.

Success criteria

Five common goals have been established for all the NVO projects.

1. Registering ecological and morphological changes in the banks.
2. Registering social affects of the measure; are other functions of the river damaged, is flood protection guarenteed?
3. Determining if the measure contributes to the quality demands of the WFD.
4. Determining if the measure contributes to the local policy goals; is the change caused by the measure conform the guiding image?
5. Determining what manner of nature friendly bank management is most effective.

No specific goals were set for this project.

Ecological response

Macrophytes and phytobenthos

No macrophytes were found at this site. Locally Phragmites australis and Phalaris arundinacea was encountered along the banks. This is similar to the situation prior to the removal of bank fixation. Macrophytes are not (yet) affected by the measure.

Benthic Invertebrates

A number of benthic invertebrate species and groups were found, 23 in total. This is an increase compared to the 19 species found before implementation of the measure. Also the number of invertebrates found at the site per species increased due to the measure.

Fish

The site was not monitored for fish. It can be expected however that the site is comparable in fish composition and abundance as the site of Bergen which is located just upstream. No pre-project data on fish was gathered, thus it is impossible to determine the effect of the measure on the fish population.

Other biota

Dry bank flora

No rare plant species were found. This is likely caused by the high level of eutrophication in the soil due to past agricultural use.

Insects

Nine species of insects were found at the site. Three of these insect species are labeled as rare species. Before the measure a total of 14 species were found, none of these species were labeled as rare however.

Birds

The terrain is used intensively by the geese during their molting period. No rare bird species were found. The lack of rare bird species is identical to the situation prior to project implementation.

Hydromorphological response

Hydrological regime

Unaffected

River continuity

Unaffected

Morphological conditions

The measure has led to an increase in erosion of the banks. This erosion in turn leads to an increase of sediment availability to the river, though this is relatively minor. The erosion of the banks initially moved quite rapidly with a speed of up to 3 meters per year. However, due to the old stone depositions in the banks from the sixties and seventies the erosion speed has since slowed down locally. This is dependant upon the local presence or absence of the rock fillings in the bank. Due to the limited height of the bank no characteristic steep banks are formed.

Monitoring before and after implementation of the project

Monitoring was carried out just prior to the project implementation in early 2006, this was done to establish a baseline situation for comparison. Bird monitoring were carried out by SOVON in 2002 for a different inventarisation. Post-project monitoring has been conducted in the years 2006, 2007, 2008 and 2009. All monitoring is carried out by or under supervision of Rijkswaterstaat. This includes the monitoring of benthic invertebrates, macrophytes, dry bank flora, insects and birds. The physical and chemical state of the site is also monitored.

Socio-economic aspects

Ecosystem goods and services

Not affected.

Conflicts and synergies

This project was carried out in such a way that the navigation on the river Meuse should not be affected by it. Even so, an increase in erosion of the banks will in time lead to channel bed sedimentation and thus potentially conflict with the function of the Meuse as a shipping route.

Project costs

Monitoring

The total monitoring costs of the entire NVO project 141.000 euro/year

Individual project implementation cost

On average the removal of bank fixation in the entire NVO project costs 75.000 euro/km. This depends greatly on the type of bank fixation that is removed and the state of the fixation though.

Contact person within the organization

F.C.M. Kerkum, Rijkswaterstaat Waterdienst, e-mail

Extra background information

• Monitoring plan for the current and future bank fixation removal projects in the Netherlands _{(language: dutch)}
• Monitoring and evaluation report of the entire Nature Friendly Banks project (Natuur(vriende)lijke Oevers; NVO) _{(language: dutch)}

References

• Kerkum F.C.M., J. van Schie, R. Hoenjet, A. Knotters, B. Peters, I. Spierts; 2009. Monitoring en evaluatie van Natuur(vriendelijke)oevers Maas, deelrapportage 1 & monitoringsplan. Rijkswaterstaat, Waterdienst. _{(language: dutch)}
• Peters, B., 2006. Proefproject Vrij Eroderende Oevers langs de Maas, locaties Bergen, Aijen en De Waerd. Monitoring 0-situatie 2006. Studie in opdracht van de Maaswerken. Bureau Drift, Berg en Dal. _{(language: dutch)}
• Peters, B.; 2007. Proefproject Vrij Eroderende Oevers langs de Maas, locaties Bergen, Aijen en De Waerd. Deel 2. monitoring 2007, situatie na 1 jaar Studie in opdracht van Rijkswaterstaat Maaswerken. Bureau Drift, Berg en Dal. _{(language: dutch)}

Related Measures

• Remove bank fixation

Related Pressures

• Channelisation / cross section alteration
• Alteration of riparian vegetation
• Alteration of instream habitat
• Embankments, levees or dikes