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Bergen - Removal of Bank Fixation

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Key features of the case study

Near the town of Bergen (NL) bank fixation was removed from the riverbanks of the river Meuse over a stretch of 1 kilometer. The project was monitored for both morphological effects as for biological response to this removal of bank fixation. The erosion of the banks and the formation of more natural geomorphological river bank structures seems to be well underway. The biotic response of the macrophytes and the benthic invertebrates to the measure is positive, though they vary greatly from in both species composition and diversity from a natural system. Fish were only monitored after the project was carried out. As such the effect of the measure on fish is unclear.

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 (Natuurvriendelijke Oevers Maas; NVO)One of these areas is the riverbank just southwest of the village of Bergen. This is a stretch of one kilometer of river bank which was fixated with broken stone material. The adjacent area consists of old agricultural land which had not been managed for 4 years between 2003 and 2008. In 2008 part of the area was sown with a standard mixture of grass.

Measures selection

To counteract the loss of dynamics in the river Meuse the bank fixation was removed along the one kilometer stretch of the riverbank near Bergen. 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. The forest and shrub vegetation on the river bank was removed as well.

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

A total of three species of macrophytes have been found in the area after the project was carried out. Prior to the project macrophytes were absent at the site. The measure has a positive effect on the macrophyte occurrence.

Benthic Invertebrates

A number of benthic invertebrate species and groups were found, 32 in total. Prior to the measure only 13 benthic invertebrates were found at the site. Though this is a clear increase in invertebrate abundance due to the measure it should be noted that the site still scores as inadequate for the WFD ecological status.

Fish

No fish were monitored prior to the project implementation. As such it is hard to determine if the measure has had a positive effect on fish. Five species of fish were caught in springtime, of which one was a rheophilic fish. In fall 8 species of fish were caught, two of these were rheophilic. The abundance of fish was significantly higher in fall then in spring. Also, brood was only found during fall.

Other biota

Dry bank flora

Two rare plant species were found. The overall vegetation has changed slightly, likely due to natural succession. The rare species also occurred in the area prior to the measure being implemented. Their abundance has increased however, leading to a positive effect of the measure on the dry bank flora.

Insects

Nine species of insects were found at the site. Three of these insect species are labeled as rare species. Compared to the 14 species encountered prior to the project implementation this is a clear decrease in species diversity. The rare species have remained the same. It seems that the measure has a negative effect on insect diversity.

Birds

A number of rare bird territories have been discovered in the area. They remain limited still, but compared to the situation prior to the measure, where no rare birds were found, a positive effect can be discerned.

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 6 meters per year. It is expected that the bank erosion will eventually slow down and become more stable. Characteristics steep banks have formed in the area.

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 2004. It should be noted that no data on fish is available from before implementation of the project. Post-project monitoring has been conducted in the years 2006, 2007, 2008 and 2009. All monitoring is carried out by Rijkswaterstaat. This includes the monitoring of benthic invertebrates, macrophytes, fish, 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 shipping traffic 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, frans.kerkum@rws.nl

Extra background information

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. Media:Kerkum_2009.pdf

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.Media:Peters_2006.pdf

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.Media:Peters_2007.pdf

Related Measures

• Remove bank fixation

Related Pressures

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