Restoration of the Ernz Blanche river, Luxemburg

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):

Restauration des prairies humides le long de l'Ernz Blanche entre Altinster et Larochette

Interview with Micha Bunusevac

NWRM(s) implemented in the case study:

Re-meandering

Wetland restoration and management

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.

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

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):

Type	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:

Type	Comments
National funds

Barrier:

Driver:

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

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.

Policy pressure:

Policy requirement directive:

Policy impact:

Policy wider plan:

Policy area:

Policy target:

Target purpose
Peak-flow reduction
Increase Water Storage
Improved Biodiversity

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:

Design consultation activity:

Design land use change:

Design authority:

Authority type	Role	Responsibility	Name	Comments
Other	Initiation of the measure		Environment Ministery	National environment authority

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Last updated: 28 Dec 2014 | Top

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Restoration of the Ernz Blanche river, Luxemburg

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