In the last century, vast areas of the lagoons and surrounding marshes were drained to obtain new agricultural, industrial and urban land. To prevent stagnation, filling was undertaken, adding material to raise the ground, or by draining the low-lying land with ditches, pumps or flap gates in embanked areas. The first system is normally adopted in areas to be built on, while the second is used for agriculture. The reclaimed land is served by water pumps if the land is permanently below sea level and in this case it is “mechanically drained”, while if the land is at least temporarily higher than the water level, embankments are used together with flap gates that open and close by pressure difference. It was the brilliant mind of Leonardo that devised this system, enabling the “intermittent” natural drainage that is locally visible along the Brancolo. Finally, if the land is permanently higher than the “filling” water, only “natural” drainage is effected.