Difference between revisions of "Narew river restoration project"
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==Hydromorphological response== | ==Hydromorphological response== | ||
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| + | '''Brief description of observed effects of the measures over different hydromorphological elements:''' | ||
| + | * Hydrological regime – in the north part of the area flow pattern and extent and duration of floods are resembles the situation that was prior the hydrotechnical works, when the south part of the area functions satisfactory in the cold part of the year. In summer and autumn, the volume of water diverted into old arms is not sufficient to secure continuum of river, too much water is lost by evapotranspiration and connection of old arms and main channel is broken. | ||
| + | * River continuity – in general is restored in this stretch, but there are some problems in the south part of the site in the warm part of the year (see Hydrological regime). | ||
| + | * Morphological conditions – they improved significantly, even in the main river channel, and the hydromorphological indices (of RHS method) are higher than in many rivers in the region. | ||
==Monitoring before and after implementation of the project== | ==Monitoring before and after implementation of the project== | ||
Revision as of 11:35, 27 May 2014
Narew river restoration project
Key features of the case study
The Narew river restoration project concentrates on the area of the buffer zone of Narew National Park (NPN). NPN was created in 1996. Narew valley between Suraż village and Żółtki village (area of the NPN and its buffer zone) was fully natural area until implementation of hydrotechnical works that were carried out in the Narew valley from 1960 until 1980. Prior the regulation, the Narew river was of anastomosing character along entire length of this stretch. The main aim of the restoration project was protection of environment in Marshy Valley of the Narew (Natura 2000 site code PLB200001) with a special consideration of hydrological conditions and integrated program of economic development. The work proceeded in stages and focuses on restoring an anastomosing system of Narew river downstream of the NPN in its buffer zone.
Site description
Particular conditions of the site: size, river type, type of pressures, ecological status, etc.
Narew river is located in North-east Poland. Narew is a large lowland river with catchment area exceeding 28 000km2 (up to gauge station in Zambski Kościelne) and length reaching almost 500km. It is the fifth biggest river in Poland. The restored part of the river is located in the upper part of the catchment, between Rzędziany-Pańki levee and the road bridge in Żółtki village in podlaskie voivodeship. In this stretch the Narew river is classified as type 24 Small and medium size river in the area influenced by peat forming process, according to the national river typology. The area of the restored site is 13.4 km2. On this area, the following habitat and vegetation transformations, resulted from river valley reclamation works, were observed:
- drying out and disappearance of old river beds
- changes in the species composition and disappearance of mesotrophic rushes Caricetum elatae, strictly connected with long-term flooded fens
- increase of the number and size of the area of expansive plants species as Calystegia sepinum, Phalaris arundinacea, Urtica dioica, Phragmites australis
- expansion of the invasive species Echinocystis lobata
- increase size of the area of extremely poor in species aggregation of Phragmites australis and Urtica dioica
- decrease of mesotrophic grasslands areas
- increase of the area of Salix L. and marshy deciduous forests.
Measures selection
Motivation/argumentation behind the selection of the measures implemented:
In the restoration process several different types of measures were implemented in attempt to achieve planned targets and to stop and if possible reverse process of the site degradation. These measures included direct ones implemented in the river to change its physical features (e.g. cleaning old river beds) and indirect ones (e.g. buying out a land in the riparian area) that shall increase chance for successful implementation of the entire restoration. In the first group the most important measures were: - reconstruction of old rivers bed by removing an excess of sediment and vegetation overgrowing these beds and by reconnecting them to the main river bed to make side arms of the Narew river open for the water flow; - building weir structures (underwater thresholds) to increase water level and to divert part of water flow from the main channel into side arms. Additionally, the Rzędziany – Pańki embankment was repaired and reconstructed by replacing small pipe culverts with bridges of suitable throughput to open it for large water flow directed into old river beds; and two dams were built at the end of the side arms to increase water storage capacity and time in the floodplain area. From the indirect measures the most important ones were related to restoring and promoting an extensive agriculture land use in the riparian area. They included: - buying out some parcels in this area, - removing bushy vegetation from this area, and – building small wooden bridges to make the area accessible for farmers for hay making.
Success criteria
Brief description of the parameters used to assess the success of the project:
- water quality improvement (hydrochemical measurements)
- increasing number of breeding birds
- increasing flood frequency and duration in riparian zones and floodplains
- increasing groundwater level
- slowing down or inhibiting process of marsh formation
- invertebrate fauna in river corridor
- increasing number of amphibians
- river corridors functioning
Ecological response
Brief description of observed effects of the measures over different types of organisms:
- Phytoplankton
No data found
- Macrophytes and phytobenthos
Macrophytes were found in 21 places on the restored area. Plant communities, which exist on a Nature 2000 sites 3150-2, consist of plants species from Lemnetea and Potametea classes. No data found for Phytobenthos
- Benthic Invertebrates
Measurements made after restoration showed large number of taxa of benthic invertebrates. This proves a good quality of habitat which is favorable for biodiversity of invertebrates. A well-developed bank zone with seasonally developing vegetation create a good place to larval and an adult creatures development of many species of invertebrates.
- Fish
20 species of fish were found. Species were classified to 7 classes: vulnerable (VU)- Lota lota, Chondrostoma nasus, near threatened (NT)- Misgurnus fosilis, Rodeus sericeus, dependent on conservation (CD)- Anguilla anguilla, other 14 species classified as the last concern (LC) species- Esox lucius, Alburnus alburnus, Abramis bjoerkna, Abramis brama, Leuciscus idus, Rutilus rutilus, Perca fluviatilis, Leuciscus cephalus, Aspius aspius, Scardinius erythrophthalmus, Tinca tinca, Gobio gobio, Cobitis taenia, Carasius carasius, critically endangered (CE) and endangered (EN) species were not found. The diversity of fish species is higher than before restoration. 8 more species were found.
- Other biota
Hydromorphological response
Brief description of observed effects of the measures over different hydromorphological elements:
- Hydrological regime – in the north part of the area flow pattern and extent and duration of floods are resembles the situation that was prior the hydrotechnical works, when the south part of the area functions satisfactory in the cold part of the year. In summer and autumn, the volume of water diverted into old arms is not sufficient to secure continuum of river, too much water is lost by evapotranspiration and connection of old arms and main channel is broken.
- River continuity – in general is restored in this stretch, but there are some problems in the south part of the site in the warm part of the year (see Hydrological regime).
- Morphological conditions – they improved significantly, even in the main river channel, and the hydromorphological indices (of RHS method) are higher than in many rivers in the region.
Monitoring before and after implementation of the project
Socio-economic aspects
Contact person within the organization
Extra background information
References
Related Measures
- Improve/Create water storage
- Increase minimum flows
- Improve water retention
- Water diversion and transfer
- Reduce erosion
- Improve continuity of sediment transport
- Increase flood frequency and duration in riparian zones or floodplains
- Manage aquatic vegetation
- Establish environmental flows / naturalise flow regimes
- Remove barrier
- Widen water courses
- Allow/increase lateral channel migration or river mobility
- Modify aquatic vegetation maintenance
- Initiate natural channel dynamics to promote natural regeneration
- Remove sediments
- Remove or modify in-channel hydraulic structures
- Develop riparian forest
- Adjust land use to develop riparian vegetation
- Adjust land use to reduce nutrient, sediment input or shore erosion
- Remove hard engineering structures that impede lateral connectivity
