The Lagoon of Venice: natural environmental trend and man-induced modification / La Lagune de Venise: l'évolution naturelle et les modifications humaines

Abstract

This paper describes factors which have modified the original equilibrium of the Venetian Lagoon ecosystem. Human intervention started in 1400 AD. During the last two centuries man's activity upset the hydraulic and physical-biological balance of the lagoon by digging canals, modifying port entrances, filling-in marsh areas and more recently withdrawing groundwater resources. This last occurrence has induced a serious land subsidence all over the territory which, coupled with the natural subsidence and a eustatic rising of sea level, has reduced the average height of the city above mean sea level by about 20%. This loss in elevation, equal to 22 cm, is the most responsible factor of the more and more frequent “acque alte” (flooding).