Climate-driven Impacts in Ports on a Tectonically Active Coast Under Mid- and End-of-century RCP 8.5 Scenario

Economic costs due to operational downtime and wave overtopping under the RCP 8.5 scenario are evaluated at 7 Chilean ports located on a tectonically active-coast. Wave statistics for a historical period (1985-2004), mid-century (2026-2045) and end-of-century projections (2081-2100) are computed with a Pacific-wide model, forced by wind fields from six General Circulation Models. Offshore waves are then downscaled to each port, where downtime is computed by comparing wave heights with vessel berthing criteria. The difference in downtime between the historical and projected periods is attributed to climate change. While changes in offshore wave climate will be moderate and spatially smooth in the region, some ports will reduce and others increase downtime for mid-century projections due to local effects. By the end-of-century, however, all ports will experience downtime reduction. Additionally, by mid-century, overtopping will increase in northern ports as a combination of extreme waves and sea-level rise (SLR), while in southern ports it will be slightly reduced due to milder waves. By the end-of century, overtopping will increase in the whole region, mainly driven by SLR. Overtopping rates, however, are significantly altered by coseismic uplift/subsidence which may occur during the design-life of coastal works. Adaptation measures are finally proposed.

On the Likelihood of Encountering Design Conditions During Heavy Transport - A Case Study of 56 Replicate Voyages From Korea to the Suez Canal

A critical element in heavy transport design is the identification of design wave conditions. Since most transports are one-of-a-kind, statistically meaningful comparisons of observed vs. design conditions are nonexistent. The present paper examines the experience from a recent oil and gas giga-project, encompassing 56 replicate voyages from Korea to the Suez Canal. In doing so, this paper provides an anchor point for assessing the real-world likelihood of exceeding design wave conditions during heavy transport. Voyage maximum wave conditions from the 56 replicate voyages are found to closely follow a Weibull distribution, allowing for the ready evaluation of observed 1-in-N voyage extremes. These observed wave conditions are compared with corresponding design values on both a year-round and seasonal (3-month) basis. Three important observations are drawn from these comparisons. First, operating limits established by heavy transport contractors to avoid waves above a predetermined threshold do not eliminate the need to design for higher wave conditions. Over the 56 replicate voyages studied, observed wave conditions slightly exceeded the contractor's self-imposed operating limit (i.e., by approximately 10% or less) on five separate voyages; on a sixth voyage, this same operating limit was exceeded by approximately 40%. Second, simplified tools for evaluating design wave conditions using Global Wave Statistics do not consistently estimate the 1-in-10 voyage extreme. While the simplified approach is shown to be conservative for the route studied, the associated design margin varies considerably throughout the year. Third, SafeTrans voyage simulations are observed to well-predict the 1-in-10 voyage extreme for the route studied.

Statistics of Simulated Storm Waves over Bathymetry

This paper shows simulations of high waves over different bathymetries to collect statistical information, particularly kurtosis and crest exceedance, that quantifies the occurrence of exceptionally extreme waves. This knowledge is especially pertinent for the design and operation of marine structures, safe ship trafficking, and mooring strategies for ships near the coast. Taking advantage of the flexibility to perform numerical simulations with HAWASSI software, with the aim of investigating the physical and statistical properties for these cases, this paper investigates the change in wave statistics related to changes in depth, breaking and differences between long- and short-crested waves. Three different types of bathymetry are considered: run-up to the coast with slope 1/20, waves over a shoal, and deep open-water waves. Simulations show good agreement in the examined cases compared with the available experimental data and simulations. Then predictive simulations for cases with a higher significant wave height illustrate the changes that may occur during storm events.

Comprehensive Wind and Wave Statistics and Extreme Values for Design and Analysis of Marine Structures in the Adriatic Sea

Wind and waves present the main causes of environmental loading on seagoing ships and offshore structures. Thus, its detailed understanding can improve the design and maintenance of these structures. Wind and wave statistical models are developed based on the WorldWaves database for the Adriatic Sea: for the entire Adriatic Sea as a whole, divided into three regions and for 39 uniformly spaced locations across the offshore Adriatic. Model parameters are fitted and presented for each case, following the conditional modelling approach, i.e., the marginal distribution of significant wave height and conditional distribution of peak period and wind speed. Extreme significant wave heights were evaluated for 20-, 50- and 100-year return periods. The presented data provide a consistent and comprehensive description of metocean (wind and wave) climate in the Adriatic Sea that can serve as input for almost all kind of analyses of ships and offshore structures.

Anomalous wave statistics following sudden depth transitions: application of an alternative Boussinesq-type formulation

Recent studies of water waves propagating over sloping seabeds have shown that sudden transitions from deeper to shallower depths can produce significant increases in the skewness and kurtosis of the free surface elevation and hence in the probability of rogue wave occurrence. Gramstad et al. (Phys. Fluids 25 (12): 122103, 2013) have shown that the key physics underlying these increases can be captured by a weakly dispersive and weakly nonlinear Boussinesq-type model. In the present paper, a numerical model based on an alternative Boussinesq-type formulation is used to repeat these earlier simulations. Although qualitative agreement is achieved, the present model is found to be unable to reproduce accurately the findings of the earlier study. Model parameter tests are then used to demonstrate that the present Boussinesq-type formulation is not well-suited to modelling the propagation of waves over sudden depth transitions. The present study nonetheless provides useful insight into the complexity encountered when modelling this type of problem and outlines a number of promising avenues for further research.

Extreme wave statistics of random waves propagating over a 3D varying bathymetry

<p>Non-uniform bathymetry may modify the wave statistics for both surface elevation and velocity field.<br>Laboratory evidence reported by Trulsen et al. (2012) shows that for a relatively long unidirectional<br>waves propagating over a sloping bottom, from deep to shallower water, there can be a local maximum<br>of kurtosis and skewness in surface elevation near the edge of the shallower side of the slope. Recent<br>laboratory experiments of long-crested irregular waves propagating over a shoal by Trulsen et al. (2020)<br>reported that the kurtosis of horizontal velocity field have different behaviour from the kurtosis of surface<br>elevation where the local maximum of kurtosis in surface elevation and horizontal velocity occur at<br>different location.<br>In present work, we utilize numerical simulation to study the evolution of skewness and kurtosis for<br>irregular waves propagating over a three-dimensional varying bathymetry. Numerical simulations are<br>based on High Order Spectral Method (HOSM) for variable depth as described in Gouin et al. (2017)<br>for wave evolution and Variational Boussinesq model (VBM) as described in Lawrence et al. (2021) for<br>velocity field calculation.</p><p> </p><p>References</p><p>GOUIN, M., DUCROZET, G. & FERRANT, P. 2017 Propagation of 3D nonlinear waves over an elliptical<br>mound with a High-Order Spectral method. Eur. J. Mech. B Fluids 63, 9–24.<br>LAWRENCE, C., GRAMSTAD, O. & TRULSEN, K. 2021 Variational Boussinesq model for kinematics<br>calculation of surface gravity waves over bathymetry. Wave Motion 100, 102665.<br>TRULSEN, K., RAUSTØL, A., JORDE, S. & RYE, L. 2020 Extreme wave statistics of long-crested<br>irregular waves over a shoal. J. Fluid Mech. 882, R2.<br>TRULSEN, K., ZENG, H. & GRAMSTAD, O. 2012 Laboratory evidence of freak waves provoked by<br>non-uniform bathymetry. Phys. Fluids 24, 097101.</p>

Various experimental wave statistics emerging from a single energy spectrum

<p>As it strongly impacts the design of offshore structures, the accurate control of experimental wave fields is of great interest for the ocean engineering community. A significant majority of sea keeping tests are based on the stochastic approach. Long duration runs of irregular design sea states are generated at model scale in numerical or experimental wavetanks. The run duration is carefully chosen to observe the emergence of extreme events. The quality of the wavefield at the domain area of interest is assessed thanks to i) the wave energy spectrum and ii) the crest height distribution. The accurate reproduction of those two quantities stands a difficult process. Numerous complex phenomena such as wave breaking or Benjamin Feir (modulational) instabilities strongly impact the wave field. The shapes of i) the wave spectrum and ii) the tail of crest height distributions significantly evolve along the tank depending i) the wave steepness, ii) the spectral width, iii) the water depth and iv) the directional spreading (for directional sea states) [1, 2, 3].</p><p>The vast majority of the work in this area has focused on reproducing realistic wave energy spectra at the location of interest, assuming the indirect control of wave statistics. The present study intends to question such a characterization of a sea state. We address the problem within the framework of long crested irregular deep water waves generated in an experimental wave tank. In this respect, using the Ecole Centrale de Nantes (ECN) towing tank (140m*5m*3m), a narrow banded sea state has been generated at several locations of a long domain. The shape of the spectrum is accurately controlled thanks to a procedure based on wavemaker motion iterative correction [4]. For such nonlinear wave conditions the statistics along the wave propagation in the tank are known to be enhanced by significant spatial dynamics [1, 3]. As a result, configurations characterized by strictly identical wave spectra lead to the emergence of strongly different crest distributions. The data yielded by the study provide convincing evidence that the characterization of the wave field using the sole energy spectrum is insufficient. Particular attention must be given to the spatial dynamics of the wave field in order to control the wave statistics.</p><p>[1] Janssen, P. A. (2003). Nonlinear four-wave interactions and freak waves. <em>Journal of Physical Oceanography</em>, <em>33</em>(4), 863-884.</p><p>[2] Shemer, L., Sergeeva, A., & Liberzon, D. (2010). Effect of the initial spectrum on the spatial evolution of statistics of unidirectional nonlinear random waves. <em>Journal of Geophysical Research: Oceans</em>, <em>115</em>(C12).</p><p>[3] Onorato, M., Cavaleri, L., Fouques, S., Gramstad, O., Janssen, P. A., Monbaliu, J., ... & Trulsen, K. (2009). Statistical properties of mechanically generated surface gravity waves: a laboratory experiment in a three-dimensional wave basin.</p><p>[4] Canard, M., Ducrozet, G., & Bouscasse, B. (2020, August). Generation of 3-hr Long-Crested Waves of Extreme Sea States With HOS-NWT Solver. In <em>International Conference on Offshore Mechanics and Arctic Engineering</em> (Vol. 84386, p. V06BT06A064). American Society of Mechanical Engineers.</p><p> </p>