On the morphological impacts of gravel mining: the case of the Orco river

Gravel mining may induce deep changes in river morphology including bank instabilities, downstream as well upstream bed incision. In the present work, morphological changes due to a large sediment mining in the Orco river (a tributary of the Po river, located in the Piemonte Region) are documented and modeled. The river mining occurred in 2003–2004, a volume of about 130,000 m3 of sediment was extracted over a surface of about 70,000 m2 at about 25 km upstream the confluence with the Po river. The mining and the response of the river to this intervention is well-documented through an experimental methodology developed by the CNR-IRPI and based on four distinct LIDAR surveys realized in the years 2003, 2004, 2006 and 2007. The observed morphological changes that occurred immediately after the gravel extraction in the time period 2004–2006 were then reproduced using the hydro-morphological 1D model BASEMENT developed by the ETH (www.basement.ethz.ch). Results indicate the model is able to capture not only the depositional and erosional areas, but it also provides a good estimate of the volume of sediment mobilized.