Case study:Lower Aurino river: Gatzaue riverbed widening

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Location: 46° 50' 55", 11° 57' 21"
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Project overview

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Status Complete
Project web site
Themes Flood risk management, Habitat and biodiversity, Hydromorphology, Social benefits, Spatial planning
Country Italy
Main contact forename Caterina
Main contact surname Ghiraldo
Main contact user ID
Contact organisation Provincia Autonoma di Bolzano
Contact organisation web site
Partner organisations
This is a parent project
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Project summary

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The Aurino river is a typical Alpine watercourse (basin Area 630 km2, average discharge in summer 30-50 m3/s) affected in the past by gravel extraction, construction of bank defences along part of its course and a major reduction of sediment load from upstream, due to weirs and other protection measures in most tributaries. This determined channel incision, reduction of riverbed width, alteration of morphological structures and dynamics and as a consequence reduced connection with the floodplain, lowering of the groundwater level and loss of riparian habitats (especially hygrophilic riparian forests of Alnus incana). A major effect was also a reduced flood retention capacity, and its recovery by reverting the incision process was one of the main drivers, together with biodiversity increase, to implement a catchment scale restoration scheme. This has been carried out, step by step, for more than a decade and further measures are foreseen. The three interventions in Gatzaue in 2005, 2009 and 2011 included removing a total of 50000 m3 of gravel from the formerly disconnected floodplain, widening the riverbed by approximately 35 m and, in order to stop incision, the construction of a ramp in 2005 and, in 2009 and 2011, the reintroduction in the same stretch of part of the gravel excavated from the river banks. A monitoring activity was implemented to study the geomorphological and biological effects of the project.

Works include: Creation of new lateral habitat for fishes,amphibians and birds (alcedo atthis).

Monitoring surveys and results

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Lessons learnt

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Image gallery


Aerial view before works
Aerial view after works
The riverbed after the works
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Catchment and subcatchment



Site

Name Gatzaue
WFD water body codes 03SS3N
WFD (national) typology
WFD water body name D_c Torrente Aurino
Pre-project morphology Single channel
Reference morphology Braided
Desired post project morphology
Heavily modified water body No
National/international site designation
Local/regional site designations
Protected species present Yes
Invasive species present No
Species of interest
Dominant hydrology Artificially regulated
Dominant substrate Gravel
River corridor land use Grassland
Average bankfull channel width category 10 - 50 m
Average bankfull channel width (m)
Average bankfull channel depth category 0.5 - 2 m
Average bankfull channel depth (m)
Mean discharge category 10 - 100 m³/s
Mean annual discharge (m3/s)
Average channel gradient category
Average channel gradient
Average unit stream power (W/m2)


Project background

Reach length directly affected (m) 1000
1,000 m
1 km
100,000 cm
Project started 2003
Works started
Works completed 2011/01/04
Project completed
Total cost category 100 - 500 k€
Total cost (k€) 195
195 k€
195,000 €
Benefit to cost ratio
Funding sources Provincia Autonoma di Bolzano

Cost for project phases

Phase cost category cost exact (k€) Lead organisation Contact forename Contact surname
Investigation and design
Stakeholder engagement and communication
Works and works supervision
Post-project management and maintenance
Monitoring



Reasons for river restoration

Mitigation of a pressure Biodiversity increase, flood risk control, morphology restoration
Hydromorphology Width & depth variation, Connection to groundwaters and floodplain
Biology Fish, Invertebrates
Physico-chemical
Other reasons for the project Increase social activities


Measures

Structural measures
Bank/bed modifications creation of new branches
Floodplain / River corridor Floodplain reconnection
Planform / Channel pattern Creation of new channel, Channel widening
Other Fish habitat restoration
Non-structural measures
Management interventions
Social measures (incl. engagement) Citizen participation in the restoration project
Other


Monitoring

Hydromorphological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative
Channel pattern/planform No Yes Yes No Yes Improvement
Connection to groundwaters Yes Yes No Yes No Improvement
Structure & condition of riparian/lake shore zones No Yes No No No Improvement

Biological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative
Invertebrates No Yes No Yes Yes No change

Physico-chemical quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative

Any other monitoring, e.g. social, economic

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative
Riparian vegetation No Yes Yes No No No change


Monitoring documents




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Supplementary Information

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