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Venice 2014

Remedies: 'Diffuse'

Salt Marshes

Natural Saltmarshes, Lagoon, Venice

Beyond the more restricted ‘local’ measures, a broader secondary ‘diffuse’ action as been undertaken in the entirety of the lagoon. Mitigating the tides and rehabilitating the habitats can implement stronger defenses against flooding and environmental degradation. The lagoon faces issues of erosion, high waters, and wave motion, which for years have been transforming the shallow marshy wetlands of the lagoon into a deeper marine habitat. ‘Diffuse’ methods offer two lines of defense.[12] The first is to reduce the height and impact of high tides by restoring the lagoon’s morphology. The second line of defense is to return the lagoon to its former physical and biological state of a shallow marshy area. These measures are accomplished by the rehabilitation of the natural saltmarshes, the additional of man-made saltmarshes, and controlling the release of pollutants into the water system.

 

Growth Stages of Man-made Saltmarshes

Man-made Saltmarshes, Lagoon, Venice

The rate at which saltmarshes and mudflats are disappearing stems from a number of factors including: reclamation, erosion, pollution, and natural and human-induced subsidence. The process of restoring the natural saltmarshes is complex and depends on the energy of the waves and their ability to dampen the marshes, the amount and flow of sediment in the system, and the biological mix of species. The effects of erosion on the sides of the saltmarshes are causing a greater loss of vegetation then can be replenished by the marshes. Experimental techniques are being tested to see whether wooden piles, gabions (wire cages filled with rocks or another heavy material) and artificial sandbars and beaches can slow the erosion process. 

[12] Fletcher, Caroline and Jane Da Mosto. The Science of Saving Venice. Turin: Umberto Allemandi & Co., 2004. p. 52.