Hydrological and dynamical characteristics of the River Louros plume, western Greece

Most sediments delivered to the oceans are associated with sediment-laden river outflows. Consequently, oceanographic and sedimentation processes in the receiving basins are influenced by the presence and dispersion of the river plumes. The physical characteristics (temperature, salinity, density, and suspended sediment) and velocity regime of the plume of the River Louros are examined here, in association with deposition of the suspended material. During high freshwater discharges (approx. 50 m3/s), the plume has a thickness of 2 m near to the river mouth; it spreads then as a thin layer (< 0.5 m) of fresher water, extending southwards over distances of several kilometres. Velocities along its main axis reduce rapidly in the shallow waters (< 2 m) of the river mouth area due to bottom friction. Further offshore, river outflow spreads as a buoyant plume, decelerating due to the upwards entrainment of the ambient water. Hence, coarser suspended sediment are deposited near the river mouth, whilst finer-grained material is dispersed seaward. The later is deposited either as individual particles according to their size, or by the action of biophysicochemical processes (i.e., flocculation, pelletization).