General
National Id
France_14
Summary
The major bed of the Save River includes a vast complex of wet meadows directly upstream of the municipality of Isle Jourdain (Gers), located partly in a floodplain area. A water abstraction well is located downstream of this complex for the supply of drinking water to the municipality. In order to reduce the risk of diffuse pollution from catchment, restore wetland habitats and contribute to downstream flood prevention, a 13 hectare parcel, riparian of the Save, was bought by the local community (CCGT) and leased to a farmer with a special contract. The field was converted to permanent natural grassland, and detention basins were dug to increase the storage capacity of the floodplain and development of wet plants community. The technique used for sowing the meadow is the "hay flower", hay from adjacent wetlands harvested late to include a wide seed bank, and makes it possible to obtain a floral procession adapted to the conditions of the meadow. This project has enhanced the natural grassland complex in the major bed of the Save. The project must still be completed by the conversion of another adjacent parcel, still cultivated.
Light or indepth?
In-depth
The in-depth description of the case study
Location description
The parcel is located in the major bed of the Save River, upstream of Isle-Jourdain. It is located in a floodplain area, 500m upstream of a drinking water catchment area in the Save supplying a population of 10,000 inhabitants. The particularity of the site is that it is located between a vast wetland complex with floodplain natural grasslands alternating with wood and crops, and a growing activity zone (artisanal zone).
NUTS Code
Midi-Pyrénées
RBD code
FRD-Le Rhône et les cours d'eau côtiers méditerranéens
Transboundary
0
Source(s)
NWRM(s) implemented in the case study
Longitude
1.057169
Latitude
43.596914
Monitoring maintenance
Monitoring parameters
Flood monitoring
the ADASEA du Gers monitors flood episodes by establishing a register of floods and recording area submersed, noting the duration of the flood, submersion extension and nature of the submerged areas with the associated water levels.
Floral monitoring.
Floral monitoring is carried out each year by the national botanical conservatory of Midi-Pyrénées to watch the meadow's evolution.
the ADASEA du Gers monitors flood episodes by establishing a register of floods and recording area submersed, noting the duration of the flood, submersion extension and nature of the submerged areas with the associated water levels.
Floral monitoring.
Floral monitoring is carried out each year by the national botanical conservatory of Midi-Pyrénées to watch the meadow's evolution.
Performance
Biophysical impact assessement method
Flood monitoring
Floral monitoring
Floral monitoring
Design & implementations
Project scale
Small
Installation date
2013
Area (ha)
13 ha
Favourable preconditions
The wet grasslands in the surrounding provide a reservoir for recolonization of wetland fauna and flora when new wetland is created. The conversion to hay meadow allowed the restoration of semi-open wet habitats, in direct proximity to functional habitats of this type, with a direct interest in the associated biodiversity. In addition, the change in land use made it possible to reduce polluting pressures (no use of inputs), thus helping to protect the catchment downstream from diffuse pollution. Finally, the excavation of detention basins made it possible to increase the volume of water stored in the floodplain.
Design contractual arrangement
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Design consultation activity
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Design land use change
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Design authority
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Lessons, risks, implications...
Key lessons
Looking back, ADASEA regrets that piezometers have not been installed to quantify the hydrological effects of the measurement.
Success factor(s)
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Financing
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Driver
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Availability of subsidies
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secondary driver
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The water agency and FEDER subsidies allowed mobilise all actors necessary for the project.
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Past flooding events
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main driver
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A wetland already recognised in the surrounding, an abstraction well sensitive to diffuse pollution, and the risk associated with the downstream urban area sensitive to flooding (floodable)
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Financing share
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Policy, general governance and design targets
Policy description
The field was initially cultivated with a rotation of cereals in conventional agriculture, involving in particular the use of pesticides.
The area is flooded regularly, and is totally submerged every 5 years on average.
Objectives of the NWRM:
Protect the downstream drinking water abstraction well.
Increase the storage capacity of a flood expansion area.
Promote the typical biodiversity of wet grasslands.
Preserve the quality of the living environment and landscape.
The area is flooded regularly, and is totally submerged every 5 years on average.
Objectives of the NWRM:
Protect the downstream drinking water abstraction well.
Increase the storage capacity of a flood expansion area.
Promote the typical biodiversity of wet grasslands.
Preserve the quality of the living environment and landscape.
Policy target
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Policy pressure
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Policy area
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Policy impact
| Impact directive | Relevant impact |
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Policy wider plan
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Policy requirement directive
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Socio-economic
Information on Ecosystem improved biodiversity
In the absence of flooding in the 2 years after establishment of the meadow, it is mostly mesophilic grassland which developed. Even in detention ponds that were somewhat flooded in winter, there was no vegetation associated with wetlands.
Monitoring shows the evolution of plant communities towards natural grassland species. Ryegrass dominated regrowth in 2014, before declining sharply the following year to make way for natural grassland species. As at Spring 2018, the floristic composition is thus close to a natural meadow.
The flora that has developed is mesophilic, even in the detention ponds. This may be due to relatively dry years after planting, particularly 2016 and 2017.
Monitoring shows the evolution of plant communities towards natural grassland species. Ryegrass dominated regrowth in 2014, before declining sharply the following year to make way for natural grassland species. As at Spring 2018, the floristic composition is thus close to a natural meadow.
The flora that has developed is mesophilic, even in the detention ponds. This may be due to relatively dry years after planting, particularly 2016 and 2017.
Photo gallery
The main opportunities were the involvement of farmers who were "donors" of the hay that was used to seed the prairie. The CCGT was a driving force behind the project, notably through its environmental officer. The presence of a drinking water catchment area and an urban floodplain downstream of the meadow favoured the project's emergence. The funding provided by the Water Agency also facilitated the project, in particular by allowing the involvement of all stakeholders beyond the renewal of individuals and elected officials.