ONE-LINE CONTOUR MODELS FOR EQUILIBRIUM DESIGN: THE SHORELINE RESPONSE BEHIND DIFFRACTIVE STRUCTURES

Beach erosion is one of the main critical issues affecting coastal areas; its mitigation and prevention are significant challenges for the engineering community. The “headland control” approach indeed represents an interesting solution, since using diffractive structures might induce shoreline responses characterized by a static equilibrium condition (Hsu and Silvester, 1990).

In this work, we have examined the capability of two different one-line models in reproducing such a behavior. In particular, we have compared the well-established one-line model GENESIS (Hanson 1989) with the new one ShorelineS, which has been recently developed by IHE Delft and Deltares (Roelvink et al. 2018). The models differ in various aspects, such as the diffraction modelling and the numerical approach adopted (i.e., ShoreliseS is a flexible vector-based model, while GENESIS exploits a fixed grid). Therefore, the present study aims to assess whether the novelties introduced in ShorelineS make it a more robust and reliable model for predicting shoreline changes behind diffractive structures.

Specifically, we have modelled the static equilibrium profiles behind isolated detached breakwaters and the so-called headland bay beaches and compared numerical outcomes with literature benchmarks. Although GENESIS has provided consistent results, it exhibits some drawbacks that might influence the accuracy of predictions. On the other hand, ShorelineS has proved to be a promising tool able to remarkably predict shoreline equilibrium beaches ruled by diffractive structures.

References

Hanson, Hans (1989). “GENESIS: a generalized shoreline change numerical model”. In: Journal of Coastal research, pp. 1–27.

Hsu, John RC and Richard Silvester (1990). “Accretion behind single offshore breakwater”. In: Journal of waterway, port, coastal, and ocean engineering 116.3, pp. 362–380.

Roelvink, D, B Huisman, and A Elghandour (2018). “Efficient modelling of com plex coastal evolution at monthly to century time scales”. In: Proceedings of the Sixth International Conference on Estuaries and Coasts (ICEC-2018), Caen, France, pp. 20–23.