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  1. null (Ed.)
    During tropical cyclones, processes including dune erosion, overwash, inundation, and storm-surge ebb can rapidly reshape barrier islands, thereby increasing coastal hazards and flood exposure inland. Relatively few measurements are available to evaluate the physical processes shaping coastal systems close to shore during these extreme events as it is inherently challenging to obtain reliable field data due to energetic waves and rapid bed level changes which can damage or shift instrumentation. However, such observations are critical toward improving and validating model forecasts of coastal storm hazards. To address these data and knowledge gaps, this study links hydrodynamic and meteorological observations with numerical modeling to 1) perform data-model inter-comparisons of relevant storm processes, namely infragravity (IG) waves, storm surge, and meteotsunamis; and 2) better understand the relative importance of each of these processes during hurricane impact.Recorded Presentation from the vICCE (YouTube Link): 
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  2. Abstract

    Coherent waves are pairs of waves having identical frequency and waveform with constant phase difference leading to a stationary wave interference in the wavefield of phase‐resolving wave models. The resulting stationary interference due to the presence of coherent water waves results in the longshore variation of the wave height in longshore uniform topography. Consequently, this variation affects the radiation stress throughout the domain and leads to the longshore variation in mean water level, mean current field, shear wave amplitude, wave setup, and wave runup. Here, we have developed a new method of wave energy spectrum discretization for the phase‐resolving wave models like FUNWAVE‐TVD, which either eliminates the coherent waves at the offshore boundary condition or limits them to a controlled number. Then, effects of the coherent waves on some nearshore wave processes are probed using both a flat bottom case as well as a longshore uniform sloping beach. The results shed light on the effects of wave coherence on the nearshore wave processes and demonstrate the usefulness of the newly developed wavemaker as a tool for the scientific community to further assess the hydrodynamics in nearshore environments.

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  3. Abstract

    This paper documents development of a multiple‐Graphics Processing Unit (GPU) version of FUNWAVE‐Total Variation Diminishing (TVD), an open‐source model for solving the fully nonlinear Boussinesq wave equations using a high‐order TVD solver. The numerical schemes of FUNWAVE‐TVD, including Cartesian and spherical coordinates, are rewritten using CUDA Fortran, with inter‐GPU communication facilitated by the Message Passing Interface. Since FUNWAVE‐TVD involves the discretization of high‐order dispersive derivatives, the on‐chip shared memory is utilized to reduce global memory access. To further optimize performance, the batched tridiagonal solver is scheduled simultaneously in multiple‐GPU streams, which can reduce the GPU execution time by 20–30%. The GPU version is validated through a benchmark test for wave runup on a complex shoreline geometry, as well as a basin‐scale tsunami simulation of the 2011 Tohoku‐oki event. Efficiency evaluation shows that, in comparison with the CPU version running at a 36‐core HPC node, speedup ratios of 4–7 and above 10 can be observed for single‐ and double‐GPU runs, respectively. The performance metrics of multiple‐GPU implementation needs to be further evaluated when appropriate.

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  4. Abstract

    Quantifying and forecasting the impact of boat traffic on the health of coastal ecosystems must account for the multiscale nature of the process: from minutes (individual wakes), to days (tidal phase), weeks, and longer (tide modulation, seasonal traffic). Direct numerical simulations covering all these scales are difficult, not in the least because specifying the vessel type and navigation characteristics for every wake is practically impossible. To overcome this problem, we propose a statistical‐mechanics description of the wake field that focuses on classes of wakes, defined by a set of characteristic parameters, and their joint probability density in the characteristic‐parameter space. Here, we demonstrate the first steps of the approach using existing numerical tools and parametrizations. Because vessel type and navigation characteristics are not available, an investigation of wake parameter space is not possible at this time. Instead, we use the leading‐order Froude‐number parametrization defined by a linear model to classify the wake population observed during the field experiment. Numerical tests applying the FUNWAVE‐TVD model across all wake‐classes identified show excellent skills for weakly dispersive wakes. The model is challenged by the short waves generated by small, slow boats. However, simulations suggest that the problem is confined to the deeper water domain and linear evolution. Nonlinear wake shoaling, essential for modeling wake‐induced sediment transport and wake impact on the environment, is described well.

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  5. Abstract

    The Baiyun slide complex contains geological evidence for some of the largest landslide ever discovered in the continental slopes of the South China Sea. High‐resolution seismic data suggest that a variety of landslides with varied scales have occurred repeatedly in this area. The largest landslide reconstructed from bathymetric and seismic data has an estimated spatial coverage of ~5,500 km2and a conservative volume of ~1,035 km3. Here, using geomorphological and geotechnical data, we construct a series of probable landslide scenarios and assess their tsunamigenic capacity. By treating the slides as deformable mudflows, we simulate the dynamics of landslide movements. The simulated landslide motions match the geophysical observations interpreted in previous studies. Particularly, we are able to reproduce the spatial distribution of observed runout, including the distance, shape, and deposit thickness, for the most credible slide scenario. We investigate tsunami impacts generated by different slide scenarios and highlight the importance of initial water depth, sliding direction, and nearshore bathymetry. The worst‐case scenario is capable of producing basin‐wide tsunami, with maximum wave amplitudes reaching ~5 m near Hong Kong and Macau, 1–3 m in western Philippines, and at least 1 m along central Vietnam, southeast Hainan, and southern Taiwan. The most noticeable phenomenon we observed is that the southern Chinese coast is the hardest‐hit region in all the simulated scenarios regardless of the diverse slide features. We conclude that the persistence of high tsunami impact is caused by the unique bathymetric feature of the wide continental shelf in front of southern China.

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