Résumé
Summary
In the 1950s–60s, the Alzette floodplain was straightened for intensive agriculture, reducing water retention and ecological value. At Dumontshaff (Schifflange), the project set out to restore river-floodplain functioning (frequent overbanking, wetland habitat recovery) and to shift meadows to extensive management (late mowing, no fertiliser or biocides). After feasibility and land reallocation, works returned the river to its natural thalweg, widened and raised the bed, reactivated a secondary arm, and enabled floodplain and wetland restoration.
The main works on the Dumontshaff–Lameschmillen reach were completed in 2005 within a ~1.4 km section of the Alzette (plus ~600 m of the Kiemelbaach), with thalweg relocation and bed re-profiling; a dedicated project page reports a cost of ~€920k (excl. VAT). The wetland was formally designated as a National Nature Reserve in May 2023. Management now relies on year-round extensive grazing by Galloway cattle and water buffalo over >40 ha, and a nature trail (~4.4 km, 24 stations, observation tower) supports public access. Ecological outcomes include the return of Greater Spearwort (Ranunculus lingua) in 2009 and regular breeding of White Stork in the restored valley. Nearby, further renaturation on the Kiemelbaach was undertaken in 2020, while broader Alzette restoration continues upstream in separate projects.
Photo gallery
Vue d'ensemble
Year of issue
2025
Project
NWRM
Implementation status
Completed
Contact
Alexandra Rossi, ACTeon
Location of the project
North of Schifflange, along the Alzette floodplain between Chemin de Bergem and Lameschmillen, near the A4 and Rue Denis Netgen; trailhead at Chemin de Bergem (L-4149).
Country
Luxembourg
NUTS2 Code
Luxembourg
Sponge measures implemented in the case study
Re-meandering
Meadows and pastures
Objectives
Restore frequent floodplain connectivity and wetland habitats; shift channel to thalweg, widen bed, reactivate side arm; manage meadows extensively; increase storage & slow peaks (e.g., +20,000 m³; −30 cm at Am Brill), lengthen river corridor (+140 m).
Involved partners
| Authority type | Authority name | Authority role | Comments | Authority responsibility |
|---|---|---|---|---|
| National water authority | Sutainable development and infrastructure ministry | Initiation of the measure | Project management and financing | Responsible |
| Other | Agriculture, vineyard and rural development ministry | Initiation of the measure | Project management and financing | Responsible |
| Farmers | Famers (Friedrich from Bertange, Friedrich from Aspelt and Witry from Bergem) | Implementation | They developed extensive agriculture and extensive grazing | — |
| Other | Shifflange, Bettembourg, Mondercange and Roeser municipal administrations | Implementation | Project partner. They owned a part of plantations. | Responsible |
| Architects / Engineers | Micha Bunusevac design office | Determination of design details of the measure | — | Supporting |
| Other | Acacia hotel, An der Schmedd restaurant, De Pefferkar restaurant | Other | They propose meals including meat produced in the area of the project. | — |
| NGO | Proactif association | Other | This association helps people remote from the labour market. They have breeding activities. | Supporting |
Site Information
Climate Zone
Cool temperate moist
Precipitation
853.00 mm
Temperature (°C)
9.00 °C
Elevation range
292 m
Vegetation class
Wetland herbaceous communities dominate: reedbeds (Phragmites roselières), tall-sedge meadows (magnocariçaies/cariçaies), wet Calthion meadows, eutrophic still waters and floodplain channels; with patches of alluvial/riparian woodland. The Natura 2000 habitat set includes 3150 (eutrophic lakes), 3260 (running waters with Ranunculion fluitantis), 6430 (tall-herb fringes) among others.
WFD Ecological status
Bad
WFD Chemical status
Failing to achieve good
Water quality status
Elevated nutrients and oxygen stress near Schifflange WWTP: ortho-P ~0.20 mg/L vs 0.07 good-status threshold; low O₂ saturation episodes; plus occasional accidental pollution events (2024).
Design and Implementation
Project scale
Meso
Project scale specifications
It addresses a river reach and floodplain (Alzette + Kiemelbaach) across multiple communes, shifting planform, reactivating side arms and managing ~100+ ha of floodplain grasslands: beyond a single micro-site but not a whole basin.
Project area
40
Project area specifications
The area of the project is approximately 40 ha. The biodiversity is affected by the project in the area itself. Concerning the flood risk, it is reduced downstream, about 2 km away from the area.
Area subject to Land use change or Management/Practice change (ha)
10.00 ha
Design capacity
The project was designed to restore a natural wetland area. The dimensions were based on the original area. This information comes from old micording wetlands, swamps and bogs.litary maps re
Principles
The project was designed to restore the natural functions of the river and of its flood plain. Works were designed on this principle. Another important target was the management of the area after the project. This involved extensive agriculture and extensive grazing. The overall land planning led to enrich the landscape and its aesthetic value.
Favourable preconditions
Land was owned by farmers. The possibility to proceed to land exchange was a good opportunity; otherwise farming activities would have been a big constraint.
Financing
Total cost information
No information available
Costs investment information
No information available
Costs capital
920000.00 €
Costs operation maintenance information
No information available
Policy and Governance
Policy description
In the 50s and the 60s, the alluvial plain of the Alzette river was deeply modified. The river was channelized, the valley bottom was drained and dried, intensive agriculture had been developed. As a consequence, this land planning increased flood risk downstream and had a significant impact on biodiversity and landscape.
Land ownership
Mixed: c.61% private, 17% Commune(s) (Schifflange/Mondercange/Bettembourg), 17% State, 0.4% inter-municipal syndicates, 4% natur&ëmwelt – Fondation Hëllef fir d’Natur.
Policy targets
Runoff control
Peak-flow reduction
Erosion Control
Improved Biodiversity
Target remarks
Even if the flood risk mitigation was not the main project of the project, it had a real impact on it. Indeed, due to the large area concerned by the project, the impact on water retention and flood mitigation was relay important. Although, as it was not the main objective, the impact downstream was not assessed.
Policy pressure
| Directive | Relevant pressure |
|---|---|
| WFD identified pressure | Physical alteration of channel/bed/riparian area/shore of water body for agriculture |
| Floods Directive identified pressure | Other pressure contributing to flooding /flood risk |
Policy impact
| Directive | Relevant impact |
|---|---|
| Floods Directive identified pressure | Protected areas |
| Floods Directive identified pressure | Landscape |
| Floods Directive identified pressure | Rural Land Use |
| WFD identified pressure | Altered habitats due to morphological changes |
Requirement directive
| Requirement directive | Specification |
|---|---|
| Other EU | Habitat directive 92/43/EEC |
| WFD-achieving objectives for Protected areas | A bird protection area was implemented |
| WFD-mitigation of significant pressure | Restoration of the water course itself |
Policy challenges requirements
The project targets are in line with the Luxembourg legislation. Thus, the law published the 19th January 2004 about nature protection provides conservation and restoration of ecological values.
Part of a wider plan
Non
Public consultation
Non
Has contractual arrangements
Non
Impacts and Monitoring
Monitoring System
Monitoring parameters
A biological monitoring is realized. Animal and plant species are observed and counted.
Socio-economic Impacts
Direct benefits information
The main benefit is due to biodiversity improvement.
Ancillary benefits information
The wetland rehabilitation led to reduce flood risks downstream. The wetland also has a water purification function.
Biophysical impacts: Hydrology
Information on retained water
Flood storage & attenuation: at the adjacent Am Brill reach, ~20,000 m³ added storage and ~30 cm reduction in high-water level; Dumontshaff reach: floodplain reconnection & reactivated secondary channel (qualitative gain).
Information on runoff reduction
Wetland functions of the area were restored. The flood plain is filled by rain falls and then restitutes water. As a consequence, the project led to a reduction in runoff. However, this effect has not been quantified.
Information on peak flow reduction
The rainwater storage in the wetland shifts the peak flow and reduces it thanks to the overall vegetation and natural pounds. However, this effect has not been quantified.
Information on reducing flood risks quantity
Due to the peak flow shift and reduction, the project contributes to reduce flood risks. As it was an environmental project, this was not assessed.
Information on peak delay effects
The rainwater storage in the wetland shifts the peak flow and reduces it thanks to the overall vegetation and natural pounds.
Biophysical impacts: Biodiversity
Improved biodiversity
Oui
Information on improved biodiversity
The extensive grazing and the restoration of the river and of wetlands were beneficial for water quality and for the development of biodiversity (insects, birds, bats, etc.).
Biophysical impacts: Water & Soil Quality
Information on water quality overall
Wetlands have self purifying capacities. In contrast to channeled rivers, wetlands and pounds increase oxygen exchange. This oxygen allows the development of activities of micro-organisms which degrade organic matter. Wetlands are also a place of sedimentation.
Information on soil quality overall improvements
N/A
Biophysical impacts: Others
Ecosystem impact climate regulation
Increased permanent biomass
Lessons Learned
Key lessons
The Alzette restoration led to the development of extensive agriculture. The river restoration has many benefits for biological diversity and landscape beauty. It can be economically rewarding by changing the type of land-use and socio-economic settings. Although the main objective was to improve the ecological state of the area, the project has big impact on flood prevention and flood mitigation. The hydraulic effects (flood protection) and public awar ness rising are essential to increase public acceptance for such projects. Its success lead to further renaturation for the river, for example in the city Steinsel (Alzette and its tributary river Pétrusse) in 2023.
Transferability
Approach is transferable to straightened lowland rivers with available floodplain space. Critical enablers: land tenure/multi-owner agreements, room for lateral migration, and nutrient-source control upstream. National guidance stresses integrating hydraulic, habitat and water-quality goals and designing for frequent floods, not just rare extremes