Scouring in the Po river Basin at the Upper Plain (Italy)

The Po River basin, the largest in Italy (about 70,000 km2), highlights channel network adjustment at the populated alluvial plain of the upper basin (35,000 km2) related to the geological uplift and hydrological changes. Changes in the upper network result by channel straightening and deepening. Shorter channel length allows faster flood propagation as in 1994 and 2000 floods, the major floods since 1940s in the Po River basin, when peak flow values attained 13,000 m3s-1 at 325 km from the source. Sediment supply is decreasing along the channels and pre-Holocene bedrock is exposed at the channel bottoms that is subject to the surface scratching due to bed-load sediment transfer from the coarse alluvial river banks. Fluvial processes enhance erosion at the river system and scouring at the channel bottom. Scouring effects include water loss from the surface water bed. Hydraulic instability induces bridge hazard.