Post-overtopping impact on urbanized seafront exposed to extreme storm waves

Context
In the last decades, the intensive urbanization of coastal zones has increasingly exposed seafront buildings
to direct ocean wave action. This situation has led to significant damages during repeated storm events
and has raised awareness among coastal authorities about the risks associated with severe storms. To
address these new challenges, in a worsening context of rising sea level, it is essential to develop robust
methods for accurately quantifying wave impacts during extreme storms and for assessing the efficiency of
coastal defenses, both in the current situation and in the future.

Objectives
In this context, the main objective of the PhD is to further improve and extend methods for the
determination of forces exerted on seafront infrastructures by waves overtopping a protective seawall.
More specifically, the project will focus on shallow to very shallow foreshore in sandy beaches backed by a
seawall. The chosen study site is characterized by a meso-tidal range, limited storm surges and
occasionally extreme wave conditions. Furthermore, the seawall top is occupied by many coastal facilities
that can be exposed to overtopping waves, both in the current situation or in the future due to climate
change effect. Consequently, the Phd project will seek to characterize the overtopping flow and the
subsequent mechanical impact on coastal facilities by carrying on field measurements. This characterization
will be used to assess the efficiency of the current protection system for different storm conditions. In
addition, a numerical modelling method will be developed to assess the evolution of the overtopping
processes and their effect in the future climate. This method will rely on recent phase-resolving modelling
approaches to compute nearshore wave transformation, wave runup and overtopping.

Methodology
- Field measurements : develop and deploy a Wave Impact Pressure (WIP) measurement station
(Imbertie et al. 2022) and complementary devices to measure hydrodynamics parameters prior to
overtopping impacts
- Numerical modelling : develop approaches to compute wave impact forces based on phase
resolving hydrodynamics computation as proposed by Imbertie (2024) or Gruwez et al. (2020)
- Climate scenarios : define different local scenario combining global climate projections and local
wave conditions. Simulate storm impacts and assess sea defense efficiency for the different
scenario.

References
Imbertie, E. (2024). Characterization of the impact of storm wave overtopping on a vertical structure at the
top of an upper-beach dike based on field measurements and phase-resolving depth-integrated numerical
modeling - https://theses.fr/2024PAUU3099

Imbertie, E., Morichon, D., Larroque, B., Delpey, M., Hernanz, B., & Lavayssiere, C. (2022). Autonomous
measuring system of overtopping wave impact pressure in real field conditions. XVIIèmes Journées
Nationales Génie Côtier – Génie Civil. https://doi.org/10.5150/jngcgc.2022.047

Gruwez, V., Altomare, C., Suzuki, T., Streicher, M., Cappietti, L., Kortenhaus, A., & Troch, P. (2020). An inter-
model comparison for wave interactions with sea dikes on shallow foreshores. Journal of Marine Science
and Engineering, 8(12), 985.

The proposed PhD project will be carried out within the framework of the KOSTARISK laboratory. KOSTARISK
is a joint cross-border research laboratory dedicated to observation and modelling to support coastal risk
management. It brings together 3 partner organizations: the SIAME laboratory of the University of Pau et
Pays de l'Adour (UPPA), the Spanish technology center AZTI, and the monitoring and forecasting center
Rivages Pro Tech (RPT) of the SUEZ group. The laboratory brings together researchers from the three
organizations in order to implement scientific and technological cooperation in the fields of numerical
modelling, physical measurement systems and advanced data analysis, for the development of tools to
support the management and mitigation of coastal risks. The KOSTARISK team is composed of 5 teacher-
researchers and 11 partner researchers (6 for RPT and 5 for AZTI).

About the employer institution
The PhD enrollment will be at University of Pau (UPPA) and attached to the laboratory SIAME, located in
Anglet (France). UPPA is the third largest university in southwestern France with around 12 000 students.
The laboratory SIAME develops research in several fields including a team dedicated to wave and wave-
structure interaction studies. Inside this team, Dr. Denis Morichon research activity focuses on the study of
nearshore wave dynamics and wave-structure interactions, combining field observation and numerical
modelling techniques.

About the PhD partner institutions
RPT is SUEZ's monitoring and forecasting center for the management of water environments. Located in
Bidart and Pessac (France), RPT develops and operates operational oceanography solutions to support local
authorities in coastal management. The services offered by RPT are divided into two main activities: (i)
Water quality & health and (ii) Waves & coastal hazards. The PhD fellow will be conducted in connection
with the Waves & Coastal Hazard department.

The candidate must hold a master's degree (or equivalent) in physical oceanography or fluid mechanics. In-depth knowledge of wave dynamics and/or coastal processes would be appreciated. Good physical condition for fieldwork and good communication skills would be an advantage.