Linking flow-stream variability to grain size distribution of suspended sediment from a satellite-based analysis

Several coastal regions on Earth have been increasingly affected by intense, often catastrophic, flash floods that deliver significant amounts of sediment along shorelines. One of the critical questions related to the impact of these impulsive runoffs is "are flash floods more efficient in delivering non-cohesive sandy sediment along the coasts?" Here we relate flow stages (i.e., from erratic to persistent) to the grain-size distribution of the suspended load, by performing a synergic analysis of in-situ river discharge and satellite-retrieved grain-size distribution, from 2002 to 2014, covering the 2012 Tiber River (Italy) exceptional flood event. Our analysis shows the capability of remote sensing in characterizing suspended sediment in terms of grain-size distribution and reveals that erratic stages favour delivering smaller grain-size sediment with respect to the persistent stages. This conclusion is supported by numerical simulations and is consistent with previous studies on suspended sediment rating curves.