La mappa del Valle (1801) come strumento d’indagine dell’evoluzione idrografica nella pianura veneta centro-meridionale

The “Mappa del Padovano, del Polesine di Rovigo, del Dogado, della parte meridionale del Vicentino, del Trevigiano e della parte settentrionale del Ferrarese” of Giovanni Valle (1801) describes an area that, from early history, was the scene of deep interactions between man and environment. This map provides a “diachronic picture” of this land in a single document, especially for hydrography. As reported in the cartouche: «…si contrassegnarono lungo ai Littorali, ai Porti e ai Fiumi le lor denominazioni antiche e moderne. L’Epoca che furon eseguiti i Canali artefatti, i rettifili de Fiumi, i nuovi alvei de medesimi originati da una rotta, e nel Dogado la situazione delle città demolite e dell’Isole sommerse». As the author continues, the map depicts «…grandiose e stupende operazioni eseguite sopra i Fiumi e sul Mare come Sostegni idraulici, Rettifili de Fiumi e Canali, artefatti si utili agli usi sociali, al Commercio, alla Navigazione e a preservare la Città di Venezia dagl’interramenti de Fiumi…». In this paper the map is described as a precursor of modern eomorphological maps and also as a possible tool for the construction of cognitive frameworks in the plans for exploitation and territorial development of the central-southern Venetian plain. As reported, many of the water-related elements represented by the map and described in this paper, are suitable to be natural and cultural heritages. The abandoned meander of Pettorazza Grimani and the artificial cutting of Adigetto Canal, that are well represented by the Valle map, are described this way. The Volta Pettorazza artificial meander cut-off is a main example of the cut-offs made along the lower course of the Adige River by the Venice Republic in the eighteenth century. This palaeohydrographic element is of great interest not only geomorphological and geo-historical but also educational. The artificial cutting of Adigetto Canal (1760), included in the broader agenda of river management of the Serenissima Republic, is related to the formation of the Lezze little Lake (Gorgo), already subject of valorization attempt. In this case, a map such as that of Valle (1801), that represents a “diachronic picture” of the territory, could be used to explain, even to a non-specialist public, the “man-water” dynamics of the Venetian government.