ABSTRACT
Cohesive sediments play an important role in the riverine and estuarine environments, since they reduce the capacity of predicting both sediment transport and bed morphology. Particles like flocs are typical of such muddy environments. They are generated by the combination of multiple materials like clay minerals, colloidal metals and biopolymers. The floc dynamics is more complex than that of non-cohesive sediments and probably much more interesting, especially in view of their primary role in the transport/deposition of contaminants, due to the ionic charges on the clay surfaces. All these processes span wide ranges of temporal/spatial scales. The EsCoSed Project, a collaborative NICOP Project between the Università Politecnica delle Marche (Italy), the Naval Research Laboratory (MS, USA) and the Office of Naval Research (USA), aims at undertaking a field-scale experiment in a controlled environment, minimizing the scale effects of laboratory experiments, and at monitoring the physical, chemical and geotechnical properties of both suspended and deposited flocs. In the first phase of the project, both hydrodynamics and bed morphology have been investigated in the most downstream part of Misa River (Senigallia, Italy). Surface flows, flow rates, soil characteristics and river bed elevations were collected in both river, estuary and sea. The preliminary analysis of riverine data reveals that there is a strong interaction between tidal motions, waves/currents coming from the sea with river flow and discharge. This suggests that there is a complex interaction of estuarine hydrodynamics in the most downstream portion of the river, which leads to the generation of areas where sediments will readily be deposited during flocculation (salinity around 0–5 psu) and of deposition regions (salinity larger than 10 psu), i.e. in the final 500 m of the river.
