Protective role of a gravel-beach nourishment on built-up area during an extra tropical storm (Fiona, September 2022)

Faced with climate change and the increasing pressure exerted by marine dynamics on the coastline (notably coastal erosion and marine submersion), adapting impacted territories has become a major challenge. Several solutions exist to protect coastal communities. In Quebec, numerous beach nourishments have been completed or are currently underway. This type of solution is increasingly being implemented (Hinkel et al., 2013). However, follow-up studies are necessary to better quantify their impact on the coast, particularly through multidisciplinary approaches (socio-economic, ecological, geomorphological, etc.).

In September 2022, an extratropical storm (Fiona) significantly affected Quebec's coastline. A heritage site of importance (Havre-Aubert, Îles-de-la-Madeleine) experienced significant marine submersion. A beach nourishment had been carried out shortly before this event. In-situ measurements were taken a few days before and after the storm, allowing for the creation of an exceptional dataset on the storm and its impacts on the site.

This dataset was used to perform various numerical simulations with the open-source morphodynamic model XBeach (Roelvink et al., 2009). This model allows for different computation modes: phase-averaged or phase-resolved, as well as a specific mode for gravel beaches (XBeach-G, McCall et al., 2014). All these configurations were used to simulate this storm event with and without the beach nourishment. The results of these simulations are compared and discussed.

Our results show that the nourishment played a protective role by significantly reducing marine submersion and damage to infrastructure. Under the impact of the storm, the nourishment rapidly adjusted towards a Dean-type equilibrium profile. A reprofiling of the nourishment was observed without significant sediment loss offshore.

 

Hinkel, J., Nicholls, R. J., Tol, R. S., Wang, Z. B., Hamilton, J. M., Boot, G., ... & Klein, R. J. (2013). A global analysis of erosion of sandy beaches and sea-level rise: An application of DIVA. Global and Planetary change, 111, 150-158.

McCall, R. T., Masselink, G., Poate, T. G., Roelvink, J. A., Almeida, L. P., Davidson, M., & Russell, P. E. (2014). Modelling storm hydrodynamics on gravel beaches with XBeach-G. Coastal Engineering, 91, 231-250.

Roelvink, D., Reniers, A., Van Dongeren, A. P., De Vries, J. V. T., McCall, R., & Lescinski, J. (2009). Modelling storm impacts on beaches, dunes and barrier islands. Coastal engineering, 56(11-12), 1133-1152.