Innovative sand groin beach nourishment with environmental, defense and recreational purposes

The paper presents a 3D experimental investigation (in scale 1 to 50) carried out to reproduce the short-term evolution of a beach nourishment with different disposals of the same volume (15’000 m3). In the first configuration, two 50 m long sandy groins, representing two localized nourishments, were built over the initial profile. In the second configuration, starting from the same initial profile, a distributed nourishment was built, giving an advancement of the shoreline of the order of 17 m, along a 300 m long stretch of beach. The aims of this note are: 1) to investigate the short-term planform and profile evolution for the two cases, under the wave forcing of typical Adriatic sea (Italy) storms, 2) to compare the experimental results for both configurations with a 2DH numerical model (X-Beach). The simulated storm is a schematization of a real storm registered on 01/12/2008 at the “CNR Platform – Acqua Alta” located in the Northern Adriatic Sea. The response to the storm, subdivided into three sea states, is described in terms of seabed evolution, leveled with an automatic laser profiler. The presence of large eddies both up-drift and down-drift the sandy groins, combined with a large cross-shore transport from the seaward zone to the onshore zone, creates a complex scenario that is difficult to reproduce except using a 2DH numerical model. The groin shaped nourishment, necessary to mitigate the erosion, evolves into a dune-lagoon system very attractive both for environmental purposes and for recreational activities.