General
National Id
Luxembourg_2
Site name
Ernz Blanche renaturation at Larochette
Summary
The Ernz Blanche (Luxembourg) river restoration project aimed at erasing the effect of the river chanelling, which caused the river uniformisation and floods downstream. The project consisted in a remeandering, increase of the base level of the river and widening of the riverbed.
NUTS Code
Luxembourg
RBD code
LU RB_000
Transboundary
0
Data provider
Alexandra Rossi, ACTeon
Source(s)
NWRM(s) implemented in the case study
Longitude
6.2194
Latitude
49.7837
Site information
Climate zone
cool temperate moist
Mean rainfall
853
Mean rainfall unit
mm/year
Average temperature
9,2
Type
Case Study Info
Light or indepth?
Light
Average slope range
2-5%
Performance
Performance impact estimation method
Edge of Field/Plot
Performance impact estimation information
A hydrological study was realised in order to measure the impact of the NWRM.
Design & implementations
Application scale
River
Installation date
2002
Performance timescale
> 20 years
Area (ha)
6596000
Size
10
Size unit
km
Design capacity description
NWRM aimed at reducing the maximum peak flow.
Basis of design
The NWRM was designed to reduce the peak flow for a 10-years storm (from 18.8 m3/s to 15 m3/s).
Constraints
No main constraint identified.
Favourable preconditions
Land next to the river is owned by the Grand Duchy of Luxembourg.
Peak flow rate
18,7999992370605
Contractural arrangements
0
Design contractual arrangement
| Arrangement type | Responsibility | Role | Comments | Name |
|---|
Design consultation activity
| Activity stage | Key issues | Name | Comments |
|---|
Design land use change
| Land use change type |
|---|
Design authority
| Authority type | Role | Responsibility | Name | Comments | |
|---|---|---|---|---|---|
Lessons, risks, implications...
Key lessons
The natural water retention measure was more cost effective than a classical measure. The possibility of building a rainwater retention reservoir was considered but costs amounted to about 10M€. The cost of the wetland restoration project was about 2,9M€.
Success factor(s)
| Success factor type | Success factor role | Comments | |
|---|---|---|---|
|
Other
|
The land next to the river was owned by the Grand Duchy of Luxembourg. In consequence, no land acquisition was necessary (which can need a lot of time). |
Financing
| Financing type | Comments | |
|---|---|---|
|
National funds
|
Driver
| Driver type | Driver role | Comments |
|---|
Financing share
| Financing share type | Share | Comments |
|---|
Policy, general governance and design targets
Policy description
Larochette is a village located along the Ernz Blanche River. It is regularly flooded, leading to damages on houses and community facilities. Classical flood protection measures (dikes, river banks, etc.) exacerbate the flood risk down stream.
The overall flood risk is due to urbanisation and the river canalisation upstream from Larochette, as well as river realignments.
The overall flood risk is due to urbanisation and the river canalisation upstream from Larochette, as well as river realignments.
Policy target
| Target purpose | |
|---|---|
|
Peak-flow reduction
|
|
|
Increase Water Storage
|
|
|
Improved Biodiversity
|
Policy pressure
| Pressure directive | Relevant pressure |
|---|
Policy area
| Policy area type | Policy area focus | Name | Comments |
|---|
Policy impact
| Impact directive | Relevant impact |
|---|
Policy wider plan
| Wider plan type | Wider plan focus | Name | Comments |
|---|
Policy requirement directive
| Requirement directive | Specification |
|---|
Socio-economic
Direct benefits information
The benefits could in theory be assessed based on the costs of avoided damages due to floods in Larochette. This assessment has not been done.
Costs investment
2940000
Costs investment information
The investment costs cover all the earthworks and structures.
Costs operation maintenance
The maintenance costs were not assessed in the feasability document. However, we can assume that they are low and that there are no extra maintenance costs compared to a usual river management.
Costs total
2940000
Ecosystem improved biodiversity
1
Information on Ecosystem improved biodiversity
Wetland restoration is beneficial for the aquatic biotope.
Ecosystem impact climate regulation
No specific impact
Biophysical impacts
Information on increased water storage
The NWRM increased the volume of water retained up to 110 000m3.
Peak flow rate reduction
15
Peak flow rate reduction unit
m3/sec
Water quality overall improvements
Positive impact-WQ improvement
Information on Water quality overall improvements
The wetland restoration leads to the improvement of self-purifying properties. This leads to improved overall water quality. Though, no assessment has been realized.
Soil quality overall soil improvements
N/A info
