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. Light or indepth? Light 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 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 Other Initiation of the measure Environment Ministery National environment authority 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 Financing Financing type Comments National funds Barrier Barrier type Barrier role Comments 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. 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 Full Context Pathway(aka Context) Default view Area(aka Level or Site) ALL