Preprints
https://doi.org/10.5194/essd-2023-459
https://doi.org/10.5194/essd-2023-459
11 Jan 2024
 | 11 Jan 2024
Status: a revised version of this preprint was accepted for the journal ESSD and is expected to appear here in due course.

Insights from topo-bathymetric and oceanographic dataset for coastal flooding studies: The French Flooding Prevention Action Program of Saint-Malo

Léo Seyfried, Laurie Biscara, Héloïse Michaud, Fabien Leckler, Audrey Pasquet, and Marc Pezerat

Abstract. The Action Program for Flood Prevention of Saint-Malo, France, requires the assessment of coastal flooding risks and the development of a local flooding warning system. The first prerequisite is a knowledge of the topography and bathymetry of the bay of Saint-Malo; the acquisition of new multibeam bathymetric data was performed in 2018 and 2019 to densify existing topo-bathymetric datasets and produce two high resolution (20 m and 5 m) topo-bathymetric digital terrain models. Second, the hydrodynamics associated with coastal flooding were investigated through a dense and extensive oceanographic field experiment conducted during winter 2018–2019, using a network of 22 moorings with 37 sensors : the network included 2 directional buoys, 2 pressure tide gauges, 18 wave pressure gauges, 4 single-point current meters, 7 current profilers and 4 acoustic wave-current profilers from mid-depth (25 m) up to the upper beach and the dike system. The oceanographic dataset thus provides an extended overview of hydrodynamics and wave processes in Saint-Malo bay, from coastal up to over-flooding and over-topping areas. It helps to identify the physical drivers of the coastal flooding, and provides a quantification of their respective contributions. In particular, the wave processes at the foot of the protection structures can be observed: in this macrotidal environment, during high spring tides, short and infragravity waves propagate up to the protection structures, while the wave set-up remains negligible, and overtopping by sea packs can occur. The combination of high-resolution topo-bathymetric and oceanographic datasets allows the construction, calibration and validation of a wave and hydrodynamic coupled model that is used to investigate more deeply flooding processes, and might be integrated in a future local warning system by Saint-Malo intercommunality.

The topo-bathymetric and oceanographic datasets are available freely at doi: https://doi.org/10.17183/MNT_COTIER_GNB_PAPI_SM_20m_WGS84, https://doi.org/10.17183/MNT_COTIER_PORT_SM_PAPI_SM_5m_WGS84 and https://doi.org/10.17183/CAMPAGNE_OCEANO_STMALO (SHOM, 2020a, b, 2021).

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Léo Seyfried, Laurie Biscara, Héloïse Michaud, Fabien Leckler, Audrey Pasquet, and Marc Pezerat

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on essd-2023-459', Anonymous Referee #1, 31 Jan 2024
    • AC1: 'Reply on RC1', heloise michaud, 14 Feb 2024
    • AC2: 'Reply on RC1', heloise michaud, 28 Feb 2024
  • RC2: 'Comment on essd-2023-459', Anonymous Referee #2, 31 Jan 2024
    • AC3: 'Reply on RC2', heloise michaud, 28 Feb 2024

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on essd-2023-459', Anonymous Referee #1, 31 Jan 2024
    • AC1: 'Reply on RC1', heloise michaud, 14 Feb 2024
    • AC2: 'Reply on RC1', heloise michaud, 28 Feb 2024
  • RC2: 'Comment on essd-2023-459', Anonymous Referee #2, 31 Jan 2024
    • AC3: 'Reply on RC2', heloise michaud, 28 Feb 2024
Léo Seyfried, Laurie Biscara, Héloïse Michaud, Fabien Leckler, Audrey Pasquet, and Marc Pezerat

Data sets

Coastal topo-bathymetric DEM of a part of the Norman-Breton gulf Shom https://doi.org/10.17183/MNT_COTIER_GNB_PAPI_SM_20m_WGS84

Coastal topo-bathymetric DEM of the harbor of Saint-Malo and its surroundings Shom https://doi.org/10.17183/MNT_COTIER_PORT_SM_PAPI_SM_5m_WGS84

Sea Campaign for the French Flooding Prevention Action Program of Saint-Malo Shom https://doi.org/10.17183/CAMPAGNE_OCEANO_STMALO

Léo Seyfried, Laurie Biscara, Héloïse Michaud, Fabien Leckler, Audrey Pasquet, and Marc Pezerat

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Short summary
In Saint-Malo, France, an initiative to enhance marine submersion prevention began in 2018. Shom conducted an extensive sea campaign, mapping the bay's topography and exploring coastal processes. High-resolution data improve knowledge of the interactions between waves, tide and surge, and determine processes responsible for submersion. Beyond science, these findings contribute crucially to a local warning system, providing a tangible solution to protect the community from coastal threats.
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