The Lame del Sesia Park features a typically fluvial environment with swamps ("lame"), meanders, stretches of water, woods, gravel and sandy banks. Throughout its entire length (7.5 km), from the river Sesia, its morphological appearance is in stark contrast to the surrounding landscape which features the monoculture of rice. The Sesia, having a seasonal nature, with wide differences between its lean period and its full one, varies from season to season based on the presence or otherwise of water in its bed. Hence the changing features of the environments that distinguish the protected area. The alluvial deposits, consisting of pebbles and gravel interspersed with sand, are located in areas since abandoned by the river, in positions barely noticeable with respect to the current watercourse's bed. Colonised by thermo-xerophile vegetation, they form the clearings of the woods and are called “gerbidi”. These are then progressively invaded by shrubs and trees. The same process happens with the swamps ("lame"), which undergo a slow process of landfill by first become wetlands and then becoming woodlands.