Observations of Turbidity Maximum Zones in a Microtidal Environment

Abstract:

Estuaries with relatively large tidal excursions (e.g., meso- or macro-tidal environments) are typically characterized by Turbidity Maxima Zones (TMZ), where large amounts of suspended sediment concentration exist. Conversely, TMZ are rarely observed in microtidal environments, where the tidal excursion is reduced, and the related forcing action is thought to have a smaller impact compared to either river current or wave action, especially during storms. However, it has been seen that tides commonly propagate upriver in microtidal environments up to relevant distances (order of kilometers), thus the existence of TMZ cannot be excluded.

To better understand this mechanism, we here analyze the data collected during a wintertime (Jan 2014) field campaign in the microtidal environment of the Misa River estuary (Marche Region, Central Italy). The TMZ formation has been investigated across a range of quiescent and storm dynamical conditions, with a series of main purposes, i.e. (1) identification of both the conditions under which TMZs generate and its main contributors; (2) the TMZ characterization, both spatially and temporally; (3) the role of stormy conditions in the TMZ generation, also comparing with the typical cases of meso-/macro-tidal estuaries.

Additional analyses have been carried out using water and sediment samples collected during the campaign in the final 700m of the river and 500m offshore. The contribution of the estuarine hydrodynamics during quiescent and stormy conditions is here used to better understand such data in view of an overall interpretation of both sediment transport and floc dynamics in the investigated environment.