Beneden-Leeuwen - Side channel

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Beneden-Leeuwen - Side channel

Factsheet: Beneden-Leeuwen - Side channel

Country NL
River Name Waal
Site Name Beneden-Leeuwen - Side channel
River Characterisation
    River typology
    Location (Lat Lon) 51.8885706852741, 5.52809715270996
    Altitude lowland: < 200 m
    Catchment area very large: > 10000 km2
    Geology Siliceous
    National code/
    River type name
    Hydromorphological quality elements

    Biological quality elements
    Ecosystem Services
    EU Directives
    Project size 18 ha
    Approximate costs
    Synergy Ecology & Flood protection
    Status Realised
    Period of realization 1994 - 1997
    Evaluation Hydromorphological and ecological changes
    Implemented by Rijkswaterstaat

    Key features of the case study

    The Beneden-Leeuwen project illustrates how flood defence through the strengthening of dikes with clay from the site can be combined with nature development. A large variety of habitats was created in this project by connecting old side arms, clay and sand pits. The effects of the morphology are apparent, though there are signs that the dynamics are relatively low in the side channel (no sedimentation, no specific benthic invertebrate species). The project has a clear positive effect on fish, mostly by providing nurturing habitats. Benthic invertebrates seem to be less affected, and macrophytes are scarce. The later is likely caused by the relatively steep banks of the side channel which is less suited for macrophytes.

    Site description

    Beneden-Leeuwen is a site situated along the river Waal, a tributary of the Rhine in the Netherlands. It is characterized by a number of old sand and clay excavation pits and a cut of meander which was part of the Waal river prior to canalization. The floodplain was largely cut off from the main channel due to dikes situated on the banks of the river. The banks are fortified and groynes are in place in the channel. This has led to a decrease in hydromorphological processes and a subsequent decrease in ecological value of the area.

    Measures selection

    In an attempt to restore the ecological potential of the area as well as fortifying the dikes a deep sand and a clay excavation pit were connected. During high water this clay pit was connected to a former river bend. In years to follow a number of clay pits were dug and three secondary branches were connected, leading to a side channel. This side channel was connected to the main river, creating a side channel which flows with the river during 95% of the time. During low water levels the flow in the channel is reduced by a sill between the sand pit and the channel. The clay that was dug up from the clay pits was used to fortify dikes in the area. These dikes were not yet up to the set national standard. This measure made it possible to both fortify the dikes and at the same time facilitate ecological development of the area.

    Success criteria

    The project served as a pilot to monitor and analyse the effects. Scientific research was done on the channel to identify if the channel indeed served to (re)create habitat and biotopes that had disappeared due to channelization and artificial alterations of the Rhine and its tributaries in the Netherlands. The primary success criteria in this research were an increase in characteristic wading birds, fish and macro invertebrates.

    Ecological response

    Macrophytes and phytobenthos

    Macrophyte-zonation due to slow rising slopes is absent in this side channel due the steep banks of the side channel. This creates a relatively uniform macrophyte community with relatively low diversity and abundance of species. No rare species were found.

    Benthic Invertebrates

    Benthic invertebrates showed a comparable total number and abundance of taxa throughout the monitoring period. Some rheophilic taxa were found, but permanent settlement of rare species proved problematic. The flowing parts of the channel showed an increase in rheophilic taxa, but held no unique species. The occurrence of the rheophilic species seems to be largely related to the available substrate, which is more abundant at higher water levels. Also, a lot of exotic species were found in the area. Due to the large number of habitat (oxbow lake, sand/clay pits, flowing channel) a good number of benthic invertebrates were able to settle in the area. The absence of certain species of benthic invertebrates indicates that there is a shortage of dynamics in the channel. Species composition is largely similar to that of the groynefields of the main channel, indicating a limited effect of the side channel on bentic invertebrates.


    Age-1+ eurytopic fish species were dominant in abundance throughout the side channel. Rheophilic fish were rare and occurred only in the flowing parts of the side channel, and only in relatively low abundance. The total fish abundance was highest in the clay pits. The site shows a strong occurrence of eurytopic fish species, which seems to increase throughout the years. The Age-0 fish showed increases in abundance of both eurytopic and rheophilic species. This indicates that the channel is a suitable nursery habitat.

    Other biota

    Dry land Flora

    The dry land flora flourishes due to the large variety of habitats. Due to management (grazing) and the dynamics of flooding there is a diversity in succession in the area which gives a great diversity of plant species from different succession stages.

    Wading birds

    The number of wading birds is relatively low for both the clay pits as the flowing channel. Though some species visit, their presence is not very proclaimed. This is likely caused by the steep banks which are not an ideal habitat for most wading birds.

    Hydromorphological response

    Hydromorphological monitoring showed an improvement towards a natural situation with greater floodplain inundation and a flowing side channel. The lateral connectivity was improved by the measure. Also, the natural processes of erosion and sedimentation can take place in the channel, though no sedimentation has been observed. The slopes of the banks are rather steep which hampers the development of certain characteristics of the side channel. Large parts of the site are stagnant during shorter or longer parts of the year.

    Monitoring before and after implementation of the project

    The following project monitoring has been carried out.

    Sample year(s)
    Different types of collected monitoring data with years in which they were collected. Years listed in italic indicated pre-project monitoring data.
    Species composition aquatic macroinvertebrates 1994






    Adult Odonates species composition and reproduction activity 1994



    Species composition fish 1994


    Age-0 fish composition 1997


    Age-1+ fish composition 1997


    Submerged macrophytes and bank vegetation 1993


    Macrophyte association 1995
    Wading birds during autumnal migration 1994


    Dry land flora 2008

    Data was collected by RIZA, Klink ecological advisory and FREE. It should be noted that nearly all monitoring was carried out as the first stages of the project were already underway.

    Socio-economic aspects

    Ecosystem goods and services

    Clay and sand mining.

    Conflicts and synergies

    The clay which was mined from the clay pits was used for strengthening the dikes of the site which were not up to safety standards. The main channel has not been negatively affected by the side channel.

    Project costs

    Exact costs unknown.

    Contact person within the organization

    Extra background information


    Related Measures

    Related Pressures