Pollution abatement in water draining into the lagoon from the hinterland is the responsibility of the Veneto Region which has established a framework programme of measures to reduce pollution in the drainage basin. Many of these are now in an advanced design phase, others are already underway.
Projects to “arrest and reverse deterioration in the lagoon basin”, in other words, measures to improve the quality of water and sediment in the lagoon, are on the other hand the competence of the State and implemented by the Venice Water Authority through the Consorzio Venezia Nuova. These interventions are closely coordinated with measures programmed by the Veneto Region for the drainage basin to reduce the loads arriving in the lagoon and with strategies established by the Region in the Outline Plan 2000.

Erosion of the lagoon can partly be attributed to natural dynamics and partly to man’s intervention both in the past (with deviation of the rivers away from the lagoon) and during this century (with dredging of large shipping channels and construction of jetties at the lagoon inlets).
Erosion, together with the increase in water depth caused by subsidence and eustasy, has triggered the current tendency of the lagoon to turn into a bay. The main and most evident manifestations of this are the gradual deterioration of the smaller islands, the progressive disappearance of mudflats and salt marshes, the constant increase in water depth and the silting up of the channels.

This is a term used in Special Law no. 798/84 which lists among the objectives falling within the competence of the State: “arrest and reversal of the process of deterioration in the lagoon basin”. It is used to describe all interventions aimed at improving water and sediment quality in the lagoon implemented by the Venice Water Authority through the Consorzio Venezia Nuova.

Because wave and current motion, high waters, the rise in sea level and the drop in land level have progressively led to the disappearance of mud flats and salt marshes which slowly erode and crumble, slipping into the channels and silting them up.
Reconstruction of mudflats and salt marshes using sediment obtained during lagoon channel dredging is therefore part of efficient maintenance of the lagoon ecosystem, making use of environmental restoration techniques and involving the development of new or revived technologies.
These measures are designed and implemented according to a strategy aiming not to restore the “shape” of the lagoon and give it back its former appearance, but rather to restore the hydrodynamic and environmental function of each constituent element such as mud flats and salt marshes, namely to stimulate flushing, moderate wave motion and limit sediment dispersion in the lagoon and loss to sea. Particular attention is also paid to the natural history and environmental aspects of the measures which restore a primary habitat, irreplaceable for flora and fauna.

This has always been done and, since 1993, a specific protocol distinguishes the types of dredged material and regulates use according to its chemical and physical characteristics. The document identifies the various categories of mud, classified on the basis of the relevant pollutant concentrations.