Description
The section of valley in question is striking for its distinctly U-shaped cross-section, with overhanging rock faces on both sides. This is the typical morphology of valleys of glacial origin, resulting from the digging action exerted by glaciers during the Quaternary period, which ended about 15,000 years ago. The entire biotope area lies on alluvial deposits consisting of gravel, sand and fine silts. These materials, transported and subsequently deposited here by the Brenta River over the millennia, have filled the bottom of the wide U-shaped valley.
One of the main reasons for its naturalistic interest is its particular water system: the protected area in fact includes some important springs at the bottom of the valley that are in direct communication with the karst complex of the Bigonda and Calgeron caves (one of the largest in Italy), caves that open up on the right side of the valley, not far from the biotope.
The underground network of the caves collects water from rainfall on the plateau above; this water re-emerges through alluvial deposits, giving rise to the aforementioned springs.
The rapidity of the outflow allowed by the underground network is evidenced by the fact that the springs at the bottom of the valley can come into action as early as 24 hours after rainfall on the plateau. Late spring is the period of maximum flow, coinciding with the melting of snow on the mountains.
In the past, these resurgence phenomena determined the perennial stagnation of water over the entire biotope area. The drainage works undertaken since 1950, with the digging of drainage canals and the channelling of streams, together with the lowering of the water table due to the extraction of gravel in the Brenta River, have led to the almost total drying up of the area, bringing it to its current situation.
The Reserve is environmentally diverse, comprising patches of riparian woodland, meadows, cultivated land, the river and riverbed, as well as minor watercourses.
The riparian forest, consisting of black alder (Alnus glutinosa), white alder (Alnus incana) and white willow (Salix alba) is the most characteristic vegetation component of the Biotope and perhaps the most valuable.
In the dense vegetation, numerous bird and mammal species find refuge, feeding and breeding opportunities.
The Brenta River, for the stretch included in the nature reserve, presents interesting natural conditions. The right bank for a good stretch is devoid of artificial banks, and the action of depositing has allowed the formation of a wide gravel bed, frequented by various species of riparian birds, including the rare little ringed plover (Charadrius dubius) and little piro piro (Actitis hypoleucos); The majestic grey heron (Ardea cinerea), the dipper (Cinclus cinclus) and the splendid kingfisher (Alcedo atthis) also frequent the waterway assiduously.
