Revision as of 08:53, 15 April 2010

Low reach of River Cinca

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Key features of the case study

The objective of the project is to restore the stream morphology and floodplain conditions in the right bank of the river Cinca, in the lower reach, between Velilla de Cinca and Fraga. There is a major actuation that consists of remove a levee that only protects crops.

Site description

The river Cinca is one of the largest rivers in the Ebro Basin that drains part of the North of Aragon, in Spain. The river has a lot of impacts in both riverbanks: crops, urban areas, reforested areas, levees, communication infrastructures...

There is a huge presence of sediments inside the stream that usually formed bars, more or less colonized by natural vegetation. The flow regime is regulated by upstream dams like "Mediano" o "El Grado" (436hm³ and 399hm³).

The presence of crops and cultivated areas has contributed to build defenses and to profit the fertile soils to plant black poplars.

View of the levee that only defends crops

Measures selection

There are two groups of measures: Morphological and about riparian vegetation.

MORPHOLOGICAL The main measure consists of increase the Fluvial Mobility Space through the remove of the levee that is closer to the river. There is other levee that protects the 500-year flood, but it will be preserved. This actuation will increase the lateral connectivity between the stream and the riparian vegetation.

RIPARIAN VEGETATION Here are included 2 different tasks:
a)Natural riparian vegetation recovery through the cut down of black poplars plantation. There are going to plant native species: Salix, Corylus avellana, Fraxinus, Populus, Ulmus.
b)Reforest areas without vegetation.

Success criteria

Ecological response

Riparian vegetation

To reestablish the vegetation, there are some actuations like selective prunes in trees to make the correct ecosystem development better; or cut down black poplars plantations in different phases.
Of course, there also have new plantations of native species: Salix purpurea, Salix alba, Corylus avellana, Fraxinus angustifolia, Populus nigra, Populus alba, Ulmus minor.

Hydromorphological response

Hydrological regime

Unaffected

Morphological conditions

The location of Fraga, a city with a population about 14.000, downstream the study area and the urban development in the right bank of this city are some of the reasons to actuate in this work, in order to protect the city from floods.
The remove of the levee is going to increase the Fluvial Mobility Space upstream Fraga. This measure will reduce the water level in Fraga because floods use the new space to flow and loose energy.

Monitoring before and after implementation of the project

During the execution phase, there will be different researches: Water Quality; Fishes and other communities; Sediments analysis.
During the actuation phase, there will be an environmental and technical control.
Before the finalization of the project, there will be another time, the researches in Water Quality; Fishes and other communities; Sediments analysis.

Socio-economic aspects

Contact person within the organization

Extra background information

References

http://oph.chebro.es/DOCUMENTACION/Restauracion/Restauracion.htm

Related Measures

• Link flood reduction with ecological restoration
• Widen water courses
• Allow/increase lateral channel migration or river mobility
• Set back embankments, levees or dikes
• Develop riparian forest
• Remove hard engineering structures that impede lateral connectivity
• Revegetate riparian zones

Related Pressures

• Alteration of riparian vegetation
• Embankments, levees or dikes