Relationships between torrent check dam systems and shoreline dynamics in semi-arid Mediterranean area: A sub-regional focus in Calabria, Italy

The work reports the results of investigations on the historical evolution of the shoreline in relation to the presence of check dam systems along streams of the Mediterranean environment. To this end, a survey methodology specifically developed in a previous work, which provided initial indications worthy of more extensive evaluation, was integrated and applied to the watershed-coast system of eight Calabrian streams, six falling on the Ionian side and two on the Tyrrhenian side of the Aspromonte Massif, as the sides present significantly different climatic and geomorphological characteristics. The streams under investigation, with watershed areas ranging from 39.2 to 160.3 km2, have been affected by relevant restoration programmes with transverse control works carried out over four periods from 1954 to today. Overall, about 690 check dams were examined, distributed over the “mountain”, “intermediate” and “valley” reaches that were normalised for comparison purposes. Based on the intensity of intervention with check dams, five watersheds are included in the “medium-high” category and three in the “low” category. The volumes of sediment corresponding to shoreline movements (retreats or, less frequently, advances) and those retained upstream of the check dams, generally silted a few years after construction, were estimated and analysed. The overall results obtained highlight a relationship between the retirement tendency of the shoreline (with observed retreats up to 170 m and affected long shores up to 5 km) and the construction of transverse control works, suggesting that particular attention should be paid to the insertion of transverse works, as well as to their typology, in the valley reaches, in one effort to combine the requirements concerning with the hydrogeological safety and the stability of the shoreline asset, limiting the need of remediation measures for coastal protection, as it actually happens along the widespread urbanized strips.