Sediment storage at tidal inlets in northern Adriatic lagoons: Ebb-tidal delta morphodynamics, conservation and sand use strategies

Abstract

Several morphological and sedimentological investigations were carried out along barrier islands in the northern Adriatic (Italy) in order to evaluate the sand reservoir potential associated with ebb-tidal deltas. The classical exponential A– P (cross-sectional area vs. spring tidal prism) relationship was used to draw a synthesis of the hydrodynamic equilibrium conditions and demonstrates that both natural and artificially fixed inlets exhibit the same morphological adaptations to tidal conditions. A new semi-automatic geostatistical GIS procedure was developed to process bathymetrical data. With this, a first estimate of ebb-delta volumes, was obtained. Sand storage potential at natural and almost natural inlets varied considerably, as a function of the tidal prism, from ca. 0.27 × 10 6 to ca. 11 × 10 6 m 3. The same procedure, applied to the large jettied inlet of Lido, produced 10% of the expected volume that was calculated with the tidal prism. The immaturity status of the ebb delta was confirmed by the application of a simplified version of the Tidal Inlet Reservoir Model, which takes into account the time delay of sand bypassing inside the inlet system. This study also presents the use of GIS as a tool for cataloguing sediment stored in ebb deltas with the potential application of using this material for nourishment plans aimed at restoring neighbouring beaches which are subject to erosion.