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Assessment of hydraulic interventions on the Arno river drainage channel

The Arno floodway is the most important strategic work for mitigating flood risk in the Arno valley and the city of Pisa. The EIA Study has been associated with the Appropriate Environmental Assessment Study, due to the interaction of the projects with natural sites of the Natura 2000 Network.

Project: Environmental impact assessment of hydraulic interventions on the Arno river drainage channel.

Location: Pisa - Livorno, Italy

Client: Province of Pisa – Soil Defense Service.

Cost of total Works: 8,879,300.00 €

Services: Environmental Impact Assessment and Environmental Appropriate Assessment.

Period: 10/2012 – 01/2013

The floodway is 28.3 km long, and it was originally designed for a total capacity of 1,400 m3/s.
Currently, the capacity of the floodway is strongly reduced due to silting, subsidence of the banks and partial obstruction of the floodway mouth. All these aspects put at risk the safety of the local population and the city of Pisa.
The project includes: restoration of the banks and the floodway mouth, protection of the floodway mouth by means of two piers, dredging of the floodway to restore the original bottom elevation, restoration and enhancement of the shoreline. The project includes also a treatment plant for the dredged sediments, aimed to their reuse along the banks.
The EIA study analyzes in detail the project (construction and operation phases) in order to highlight the main interactions between the works and the context. The interferences between the project and the requirements and constraints contained in the territorial planning programs have been analyzed, focusing on the ones related to shoreline management and hydrological risk.
An accurate description of the current state of the environment has been performed, based on bibliographic data, results of the investigations carried out to support the design activities (e.g.: geological, hydrological, water quality and sediment quality surveys) and several data collected from local environmental Authorities.
Particular attention has been paid to the natural value of the project area, which is located along a national park and European protected areas (Natura 2000 Network) and which is an important site for migrant species (Bird international protected area).
An effective checklist of the impacts has been drafted in order to identify impacts in the short and long term as well as at various spatial scales. A degree of significance has been associated to each impact. The key environmental aspects under study were:

  • Sediments quality in relation to dredging and treatment activities;
  • Modeling simulation of the hydrodynamic and hydrological condition, with particular attention to the effects on the coastline (shoreline extension and coastal circulation) and to turbidity and salinity levels (marine water quality);
  • Landscaping of the new structures;
  • Modeling of the propagation of noise emissions and air pollutants during the construction phase;
  • Noise annoyance on bird community during construction and operation phases; and
  • Annoyance of the marine fauna, with particular attention to the marine mammals, as the sea area in front of the floodway mouth is part of the Pelagos Sanctuary for Mediterranean Marine Mammals.