Articolo disponibile anche in: Italian
There is a brief portion of the river Pesa, located at Ponterotto in the direction of Cerbaia (near the town of San Casciano), that is particularly unusual. We can even say it is fascinating.
Here, in fact, the water leaves its natural bed and enters a sort of canyon with mini rapids and small caverns where various species of ﬁsh are found. Technically it is a phenomenon of regressive erosion of the riverbed of the Pesa, a completely natural aspect that has been visible and recognized for some time.
The uniqueness of the location is due to its variety of geologic layers, where conglomerates of gravel and pebbles alternate with underlying claylike soil, ﬁner and more compact.
It bears testimony that a body of water is a living, dynamic organism, that digs from one part and deposits from another with equilibrium .
Here it is useless and possibly dangerous to intervene with drainage, excavations and rigid systems. It is something unique which is better admired in periods of low tide, a phenomenon that only nature can reserve.