Computer Methods in Applied Mechanics and Engineering

Coastal areas epitomize the notion of ‘at-risk’ territory in the context of climate change and sea level rise (SLR). Knowledge of the water level changes at the coast resulting from the mean sea level variability, tide, atmospheric surge and wave setup is critical for coastal flooding assessment. This study investigates how coastal water level can be altered by interactions between SLR, tides, storm surges, waves and flooding. The main mechanisms of interaction are identified, mainly by analyzing the shallow water equations. Based on a literature review, the orders of magnitude of these interactions are estimated in different environments. The investigated interactions exhibit a strong spatiotemporal variability. Depending on the type of environments (e.g., morphology, hydrometeorological context), they can reach several tens of centimeters (positive or negative). As a consequence, probabilistic projections of future coastal water levels and flooding should identify whether interaction processes are of leading order, and, where appropriate, projections should account for these interactions through modeling or statistical methods.

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Interactions Between Mean Sea Level, Tide, Surge, Waves and Flooding: Mechanisms and Contributions to Sea Level Variations at the Coast

Introduction to RISC-KIT: Resilience-increasing strategies for coasts

The knowledge of extreme coastal water levels is useful for coastal flooding studies or the design of coastal defences. While deriving such extremes with standard analyses using tide gauge measurements, one often needs to deal with limited effective duration of observation which can result in large statistical uncertainties. This is even truer when one faces outliers, those particularly extreme values distant from the others. In a recent work (Bulteau et al., 2014), we investigated how historical informationof past events reported in archives can reduce statistical uncertainties and relativize such outlying observations. Weadapted to the specific case of coastal water levels a Bayesian Markov Chain Monte Carlo method initially developed in the hydrology field (Reis and Stedinger, 2005). We applied this method to the site of La Rochelle (France), where the storm Xynthia in 2010 generated a water level considered so far as an outlier. Based on 30 years of tide gauge measurements and 8 historical events, the results showed a significant decrease in statistical uncertainties on return levels when historical information is used. Also, Xynthia's water level no longer appeared as an outlier and we could have reasonably predicted the annual exceedance probability of that level beforehand (predictive probability for 2010 based on data till end of 2009 of the same order of magnitude as the standard estimative probability using data till end of 2010). Such results illustrate the usefulness of historical information in extreme value analyses of coastal water levels, as well as the relevance of the proposed method to integrate heterogeneous data in such analyses. Classical extreme value analysis on La Rochelle tide gauge measurements. The outlying observation circled in red (Xynthia's observed water level) leads to large uncertainties on extreme return levels estimates.

https://hal-brgm.archives-ouvertes.fr/hal-01363905/document

How historical information can improve estimation and prediction of extreme coastal water levels

Effectiveness assessment of risk reduction measures at coastal areas using a decision support system: Findings from Emma storm.

Managed realignment to mitigate storm-induced flooding: A case study in La Faute-sur-mer, France

In this paper, we investigate the water renewal of a highly populated marina, located in the south-west of France, and subjected to a macro-tidal regime. With the use of a 3D-numerical model (TELEMAC-3D), three water transport timescales were studied and compared to provide a fully detailed description of the physical processes occurring in the marina. Integrated Flushing times (IFT) were computed through a Eulerian way while a Lagrangian method allowed to estimate Residence Times (RT) and Exposure Times (ET). From these timescales, the return-flow (the fraction of water that re-enters the marina at flood after leaving the domain at ebb) was quantified via the Return-flow Factor (RFF) and the Return Coefficient (RC) parameters. The intrinsic information contained in these parameters is thoroughly analysed, and their relevance is discussed. A wide range of weather-marine conditions was tested to provide the most exhaustive information about the processes occurring in the marina. The results highlight the significant influence of the tide and the wind as well as the smaller influence of the Floating Structures (FS) on the renewal. Besides, this study provides the first investigation of the water exchange processes of La Rochelle marina. It offers some content that interest researchers and environmental managers in the monitoring of pollutants as well as biological/ecological applications.

https://www.mdpi.com/2073-4441/11/10/2050/pdf

Characterisation of the Water Renewal in a Macro-Tidal Marina Using Several Transport Timescales

Dynamics and management of siltation in a macro-tidal marina: The case of La rochelle marina, France

Harbor siltation is a problem that will exist as long as harbors exist and it is intrinsically linked to their primary function: providing shelter for anchorage and operative conditions for...

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Jean-Rémy Huguet

Papers

Managed realignment to mitigate storm-induced flooding: A case study in La Faute-sur-mer, France

Characterisation of the Water Renewal in a Macro-Tidal Marina Using Several Transport Timescales

Dynamics and management of siltation in a macro-tidal marina: The case of La rochelle marina, France

Influence of Floating Structures on Tide- and Wind-Driven Hydrodynamics of a Highly Populated Marina

Hydrodynamic and siltation management in a highly populated marina (La Rochelle, south-west France)