2.1.4. River Bed Quarrying

One of the most effective causes of reduction in sediment river input to the coast is riverbed extraction of aggregates [57]. This activity was conducted on an occasional basis and with modest means up to the last century and has become a real "industry" in recent decades, driven by the demand for construction materials for building and communication routes [58]. From river beds, each year materials have been removed with volumes far greater than the bed load of the rivers themselves, so much so that their level has been lowered by several meters, which has triggered serious problems of instability in banks and bridges. For example, ten times for the Po River [59], Italy; forty times according to for the Vembanad Lake catchments, India [60]. This operation was also favored by the fight against floods, as widening and deepening of river beds leads to an increase in the hydraulic variables. The fallout area of these interventions, the coastal strip, is too far, physically and politically, from populations affected by the floods and the fight against extractions has not yet been won everywhere. Damage caused by this activity is such that, even where mining has been banned for more than twenty years (e.g., Cecina River, Tuscany), the morphology of the rivers has not yet assumed the natural configuration and deep holes are still evident in their longitudinal and transverse profiles; actually, approximately 4 × <sup>10</sup><sup>6</sup> <sup>m</sup><sup>3</sup> of aggregates was extracted on the 40 km terminal river course from the 1960s to early 1970s [61].
