This paper introduces a new dynamically adaptive high-resolution tsunami (DART) model. The model solves the two dimensional (2D) nonlinear shallow water equations on a dynamically adaptive structured grid system. The system performs local mesh refinement by simply specifying different subdivision levels of cells on the background uniform coarse grid covering the computational domain. The 2D shallow water equations are solved using a well-balanced finite volume Godunov-type scheme, implemented with a non-negative (in terms of water depth) reconstruction technique for wetting and drying. The performance of the model was validated by simulating tsunami overflow over idealized topographies, laboratory tsunami runup in Okushiri Island, and actual tsunami propagation and inundation in Kamaishi Bay.
Numerical solutions of stationary progressive water waves are obtained through a new method using nonlinear wave equations, where advection equations are satisfied for physical quantities, i.e., surface/interface displacements, velocity, or velocity potential. In the calculation process, the Newton-Raphson method is applied to find convergence solutions. In the present study, the nonlinear wave equations based on a variational principle are adopted as the fundamental equations. Stationary solutions of traveling surface/internal solitary waves are obtained to be compared with the corresponding theoretical solutions, as well as numerical solutions of Euler equations, such that the accuracy of solutions through the wave equations is verified also for large amplitude internal solitary waves with large wave celerity and flatter wave profiles.
This paper presents a new characteristic finite element formulation, named SLG (semi-Lagrange Galerkin) method, on unstructured triangle / tetrahedral meshes to solve two- or three-dimensional advection equations / hyperbolic flow problems. In the present method, the calculation procedure is divided into two phases which are advection and non-advection phases. The advection phase is computed by the semi-Lagrange procedure using a 10 or 20 degrees of freedom triangular / tetrahedral element which consists of complete cubic polynomials given by function values and first order derivatives on each vertex and a function value on barycenter of triangle surface. The non-advection phase is calculated by the Galerkin finite element procedure using the 3 DOF triangular or 4 DOF tetrahedral linear elements.
Particle methods have been widely used in coastal engineering. However, in most cases, implicit LES by omitting sub-particle-scale (SPS) viscosity, in which existence of pressure fluctuation might play some role as a pseudo viscosity, has been conducted. But as the accurate particle methods for attenuation of pressure fluctuation have been developed, explicit description of SPS turbulence has been highlighted. In this study, the SPS turbulent model is introduced into the accurate particle method, namely CMPS-SBV-HS-HL-ECS method. A benchmark test to examine the performance of the model is conducted in a free jet condition. Then, a simulation of wave breaking is implemented by the proposed model to examine its validity by comparison with previous experiment and conventional MPS-method.
Nonlinear four-wave interactions have significant influences on the statistical properties for deep-water extreme waves. However, the characteristics of freak waves generated in deep-water shoaling to shallow water regions are still not clearly understood. In this study, the numerical simulations using the Boussinesq model are conducted to investigate the aftereffects of the third-order nonlinear interactions from deep to shallow water regions related to freak wave occurrences. It is possible to understand the characteristics of freak wave occurrences in shallow water regions using the Boussinesq model, if appropriate higher-order nonlinear correction is considered analytically.
In this paper, one free-surface single-phase flow “CADMAS-SURF/3D” and two multiphase flow models “DOLPHIN-3D and OpenFOAM”, which are based on Eulerian description, were compared with the previous two laboratory experiments on collision problems between bore and a structure. The validity of the models was confirmed by the comparison between the numerical and experimental results in terms of water surface elevation and pressure acting on the structure. As a result, the three models used in this study were found to have good accuracy although the difference of the models has an influence on the numerical results. The comparison examination of numerical models is said to provide the useful information contributing to the further development of computational fluid dynamics.
This study applies the newly developed high precise MPS method to simulate the tsunami impact pressure. This high precise MPS method has overcome the pressure-related problems involved in the existing MPS method. Numerical simulation results of the tsunami impact pressure acting on the up right section of a seawall show a good agreement with experimental data. This new method is applied to simulate the shoaling effect of a solitary wave on a plane slope to evaluate the impact pressure of breaking waves,thus this study clarifies the relationship between pressure and wave-height. And this method shows how the tsunami impact pressure acts on a seawall, which is hard to observe in real hydraulic experiments.
In order to investigate interaction between upper and inside flow of a porous medium, the microscopic structure of upper and inside flow of the porous medium placed in oscillatory flow was measured by the Particle Tracking Velocimetry (PTV) with the refractive index matching method. The strong shear flow was observed in the vicinity of the porous medium and the depth of shear flow varied with the phase of the oscillatory flow. The depth of non-dimensional shear flow was almost constant and independent with the Reynolds number. Besides, the phase difference of oscillatory flow between upper and inside flow of the porous medium was observed.
The internal and external fluid flows induced by oscillatory flow over a porous medium were measured by the Particle Tracking Velocimetry (PTV) with matching the refraction index method using two high-speed cameras. The characteristics of spatial variance of velocity components were shown in detail with the time phase variance. Further, the properties of the turbulent quantities such as turbulent kinematic energy and the Reynolds' stress were presented and the relationship among the turbulence properties, the Reynolds' number, and the KC number was discussed.
This paper measured bubble-mediated oxygen transfers by using fluorescence image measurement, and modeled the relationship between bubble size and oxygen transfer velocity. The measured gas transfer coefficients increase with bubble size and there is a significant deviation from the theoretical one. This result indicates an effect of turbulent diffusion. The constructed model has been applied to aerated flow under circular jet to validate our model. Modeling of bubble-mediated gas transfer is important to understand air-sea gas exchange in the surf zone.
This paper presents vorticity instabilities occurring during wave breaking process, which interprets formations of the initial three-dimensional vortex structure, scarifying and fingering surface via surface-vorticity interactions, and the sea-spray fragmenting from the finger jets. Three-dimensional linear instability analyses are performed for identifying these instability modes to describe a series of local surface deformations featuring the splashing process in this study.
Recent observational studies have rediscovered that littoral currents are inevitable for interaction between surfzone and inner shelf (e.g., Lentz et al., 2008). A synoptic, detailed numerical experiment is conducted to pursue this problem with a multi-nested coupling system consisting of ROMS-WEC (Uchiyama et al., 2010), SWAN and WRF at horizontal resolutions down to 20 m. Both the Eulerian and Lagrangian analysis clearly demonstrate that wave-driven three-dimensional currents significantly enhance lateral and vertical mixing and dispersion. Lagrangian particle tracking and two-particle analysis exhibit that rip and undertow induce vertical secondary flow that plunges those particles downwards beyond the pycnocline, leading to markedly increased initial dilution and thus much faster relative dispersion tendency.
A hybrid model switched from the Boussinesq model to the nonlinear shallow water model by omitting the diffusion terms after wave breaking is proposed. The present model can reproduce the deformation of wave profile in surf zone with good accuracy due to the distribution of turbulence energy in time and spatial domain, which is calculated with the wave breaking model. Both the spatial distribution of undertow considering the mass flux of surface roller in addition to the depth-integrated velocity and the vertical distribution given by the turbulence energy with the turbulence scale assumed as 10% settled water depth are estimated with good accuracy. Furthermore the reproduction by this model indicates that the undertow around the breakwater on a sloping beach is not negligible comparing with the wave-induced currents.
This paper presents fundamental features of flow structures and shear distributions in run-up waves on uniform slopes on the basis of experimental image experiments. It was found that there were high velocity gradients near the bottom and surface boundaries within the thin run-up water layer, resulting in multiple shear layers. The local flow structure in the run-up waves depends on the local surface gradient and shear distributions. Typical features of the boundary layer flows during run-up process are also discussed in this paper.
Experiments on swash zone range by short waves, long waves and their combined waves respectively are conducted both on a steep and on a gentle slope. Long waves which form standing waves at the shoreline provide swash oscillation, and short waves which break and are partially reflected give both wave set-up and the small oscillation. Max run-up and max run-down height of the combined waves are evaluated by linear sum of those heights by component waves. In addition, the heights as well as the median of swash zone range of regular waves are expressed by functions of surf similarity parameter.
The influence of wave-driven seepage flow on swash sediment transport with the grain size changes is investigated experimentally and numerically. The movement of fluorescent sand on saturated-unsaturated slope is measured in bore wave experiments. In the case of fine sand grains,the seepage flow leads to the activation of sediment transport in the direction of runup and backwash under the saturated condition. This effect becomes weaker with the grain size increases. A numerical approach for the tractive force under the influence of seepage is presented,that is quantified through a permeable Shields parameter. The results of prediction are in good qualitative agreement with those of experiments.
Laboratory experiments were conducted to measure the joint distribution of surface elevation and slopes for nonlinear random waves. The slopes of random waves were measured by a small and precise accelerometer as well as the surface elevation. The correlation coefficients between the surface elevation and slopes were very small for nonlinear waves with the JONSWAP spectrum and Bretschneider-Mitsuyasu sprectrum. The skewness and kurtosis took different values from a Gaussian distribution. A method for estimating the joint distribution of surface elevation and slopes were developed by using the principle of maximum entropy. The estimated distributions were compared with the measured distributons, together with the Gram-Charlier series and two variate Gaussian distributions. The present method found to produce a similar distribution of the measured one.
In recent years, extreme waves larger than the design wave have repeatedly been observed along the coasts of The Sea of Japan. The present paper discusses concepts of ‘accidental waves’ based on observed and simulated wave data. The discussion has derived the following concepts of the accidental waves: (1) Their long return periods more than 200 years. (2) The large ratio of Hmax / H1/3 such as 2.0 in the offshore area. (3) Classification of accidental waves into two types of wind waves and swell. The stability of the breakwater against the accidental waves has been checked by confirming if the safety factor is more than 1.0 or not.
In the present study, we aimed to understand characteristics and utilization of 2 databases, the DB with long period of time which has poor spatial resolution (global DB) and the DB with short period of time which has high spatial resolution (local DB). As a result, (1) there is a good correlation between wave height of local DB and observed wave height of NOWPHAS. (2) We found that global DB is useable for wave statistics with long period. (3) Through the application of distribution function obtained by extreme value statistics making use of global DB with period of time sufficiently long, it is possible to obtain the suitability result of distribution function obtained by using local DB with short period of time.
100-year return storm surge height η100 and return wave height H100 at Ise Bay which have not been discussed together previously are compared. Both η100 and H100 are estimated by hindcastings for 107 storms in the past 56 years from 1950 to 2005 using the same computational grid and the same wind conditions. Spatial distribution shows storm surge height is large at coastal areas especially at the inner part of the bay and wave height is large at offshore areas. Alongshore distribution illustrates η100 along the coast is larger than that of H100 near Nagoya and Atsumi Bay. η100 near Nagoya is about 3.2m which is nearly 1.5 times H100. Spread parameter of storm surge η50/η10 is larger than that of wave height H50/H10 and η50/η10 is large at the coast near Nagoya and Atsumi Bay.
Based on shallow water wave hindcastings for a 65-year period of historical typhoons and a 100,000-year period of simulated typhoons, extremes of wave heights in the East China Sea are discussed. Main findings are 1)variation of the 100-year return wave height in the sea is less than ±5% for a 10-year extension of the data period, in cases where the maximum of the wave heights is around 16 m; 2)the location-dependent largest wave height generated by the historical typhoons ranges from 60 to 80 % of the probable maximum(pmx) wave height estimated for simulated typhoons; and 3)the 100-year return wave height in local areas around Kabashima close to the Goto Islands changes from 15 m at offshore points to 10 m at onshore points, which is more than 2 m greater than the previous estimate.
This paper presents the measurement- and hindcast-based return values of wind speeds and wave heights at the measurement stations in Tokyo Bay, Ise Bay and Seto Inland Sea. Main findings are as follows. 1)Annual maximum data samples of not only the measured storm surge heights but also the hindcast wind speeds and wave heights indicate the occurrence of their largest values at earlier years in the data period and the resulting non-stationary decreasing trends. 2)The return values of wind speeds and wave heights estimated using both the hindcast and measured data samples are in overall agreement. 3)A year period of the data samples should be taken as long as possible for a proper estimation of the return values. 4)Rough estimates for the 100-year return wind speeds and wave heights are 40 - 45 m/s and 4 - 5 m respectively.
Legendary extremes are recently excessively expected in the public eye to be ultilized for examining the design of coastal defence. Uncertainty accompanied with such legendary extremes has been not enough clear in the statistical literature, thus it has been disregarded in some applications so as to consider the legendary extremes to be having the same quality as the modern measurements have. Unfortunately, if the length of legendary term is unknown, the incremental amout is insignificant in the degree of experience, and it is remarkable that the durability toward the future becomes retreated because the peak shifts farther to the remote past, which will interpret the statistical properties of legendary extremes.
This study deals with the statistics of wave climates (hourly H1/3, for example) which are simulated applying the spectrum modeling method (Kimura and Ota. 2012). Especially, their micro statistical properties such as monthly numbers of days of H1/3 >< H* and the run of H1/3 >< H* are compared with the observed data (NOWPHAS), where H* is the threshold wave heights. The statistical properties of the simulated data show good agreements with the observed data. The present model is applied to two examples in the last. One is the definition of the starting date of a year which minimizes a number of high wave days during the construction works. Another is a long-term presumption of non-stationary wave climate during the in service period of the structure due to the global warming, for example.
We investigated the impact of nonlinear energy transfer (Snl) on wave fields by performing hindcast experiments and analyzing field data. This study highlights the impact of source terms on spectral shape under a realistic model setting. Analysis of spectral shape indicated that the Snl played a major role in maintaining the equilibrium range; it reacted to changes in the net external sources to cancel out the total source term. These results also show that the magnitude of high-frequency dissipation controls the spectral tail exponent and that the balanced net external source is responsible for the reproduction of the f4 power law behavior in the equilibrium range.
The strong winter storm crossed from the west to east of the Sea of Japan developing rapidly in early April, 2012. The minimum pressure of the winter storm reached 964 hPa at 21:00 on 3rd April. The storm generated wind waves more than 10 m in the significant wave height and gave severe damages to coastal structures. This study analyzed observed wave records at 12 stations along the Sea of Japan. A series of numerical analysis was performed to understand the characteristics of extreme wave sea condition. The maximum wave heights were estimated based on the spectral wave model and nonlinear short wave statistical theory. The estimated maximum wave heights by the nonlinear theory show better agreement with the observed peaks of maximum wave height than that by the linear theory.
The characteristics of nonlinear energy transfer of gravity wave spectra have been investigated through theoretical, experimental and numerical approaches so far. However, most of them were for deep water waves, and very few were for finite water waves. In this paper, we numerically investigated the characteristics of nonlinear energy transfer in finite water depths by the FD-RIAM method (Hashimoto, et.al 1996, Komatsu, et.al, 2001) having high accuracy and stability. The amplification factor of nonlinear energy transfer and frequency downshift were investigated as functions of some parameters, such as relative water depth and energy concentration parameters in frequency and direction, etc. The drawback of the amplification factors used in DIA were also discussed with comparing the results computed by FD-RIAM.
For the purpose of clarifying the appropriate values of the sea surface drag coefficient in high wind speed, the ADWAM was modified to estimate the sea surface drag coefficients as its control variables of the model. In this study, we apply the method to the actual wave observation data to investigate the sea surface drag coefficient. As a result, we confirm that the sea surface drag coefficient was automatically corrected to appropriate values (similar to Mitsuyasu & Honda's equation in wind speed less than 30m/s) from arbitrary initial values with the method. It was also confirmed that the possibility of the estimation of the sea surface drag coefficient under stormy conditions on the basis of the wave data remotely observed from storms.
Characteristics of significant and maximum waves under strong wind of typhoons are analyzed numerically by applying the wave model SWAN and the maximum-wave estimation proposed by Mori et al. The traveling speed of typhoons is changed in the numerical simulations and its influence to the significant and the maximum waves is investigated. The largest wave height occurs when the typhoon's traveling speed is a little smaller than the group velocity of the corresponding significant waves. The directional and frequency concentrations in the wave spectrum are also inclease with the speed,and it causes of the largest maximum-waves.
This study aims to develop an image-based monitoring system for observations of surf zone hydrodynamics especially focusing on evolution and propagations of long wave components. Laboratory experiment was first performed to link between measured surface water fluctuations inside the surf zone and shoreline changes captured by images. Long wave components extracted from observed shoreline changes agree well with those based on measured surface water fluctuations in terms of their alongshore distributions of phases and amplitudes. The same image-based technique was applied to the field, the Seisho coast when the typhoon 1112 approached the site. It was found through the analysis that extracted longwave components were consistent with offshore wave data and showed characteristics of edge waves.
This study investigates the relationship between the tsunami source geometry and its local amplifications due to resonance. Linear long wave equations were first applied for computations of the 2011 Tohoku earthquake tsunami and the Nankai earthquake tsunami, respectively, and focusing sites were selected where dominant amplification was observed at a certain frequency. The model was also applied for computations of tsunami generated from the unit sources at various locations. Power spectra and phase of the computed surface water fluctuations at the focusing sites were plotted at locations of unit source. Influence of the tsunami source geometry was finally discussed based on the obtained spatial distributions of power spectra and phase.
Secondary undulations locally called “Abiki” are frequently observed in Urauch Bay at Koshiki Islands. To take countermeasures against the secondary undulations,it is important to understand amplifying characteristics of Urauch Bay under various conditions. In this study,responses of Urauch Bay to several factors affecting amplification of secondary undulations were evaluated by numerical analyses. As the result,it is clarified that amplification factor depends on not only a period of incident waves but also amplitude or a composite effect of those. In addition,change of depth due to a tide and tidal current near straits at the mouth of Urauch Bay have affects on amplification factor of Urauch Bay.
This study describes the deformation and resonance of solitary waves in coastal areas and along a river. When tsunamis propagate into shallow water regions, they may deform into a train of solitary waves due to the nonlinear shallow water deformation. Also, the change in the river width is expected to cause resonance of solitary waves along the oblique riverbank. This study thus aims to investigate the deformation of solitary waves in a shallow water region around a coast and the resonance due to the oblique boundary in a river. As a result, it is found that solitary waves can be reproduced by using the 3rd order theoretical solutions even when they progress over a mild uniform slope. Also, the amplification of amplitude of solitary waves is revealed to be larger than the Mile's solutions when they approach to an oblique boundary.
Wave deformation with fission of solitons and wave breaking of the dispersive tsunami was observed in the 2011 off the Pacific coast of Tohoku earthquake tsunami hitting Kuji Port. Estimation of impacts of such a deformed tsunami is necessary for estimation of damage induced by tsunamis, especially the maximum considered tsunami. A wave breaking model is incorporated in the mathematical model of STOC that is a hybrid model of a hydrostatic model (STOC-ML) and non-hydrostatic model (STOC-IC) for calculation of tsunami propagation and inundation. It is confirmed that the improved STOC-IC with the wave breaking model can estimate the tsunami with fission of solitons and wave breaking in comparison with physical model tests in a wave flume and the observed tsunami in Kuji Port.
The 2011 Tohoku earthquake tsunami hit wide stretch of the Pacific coast of Japan and measured tsunami inundation heights showed significant variations within the same bay. Ryori Bay, located in Iwate prefecture, is one of such bays. The authors reported the presence of the short period wave developed complex fluid motion in the Ryori Bay. This study aims to investigate the physical mechanisms of such complex tsunami behaviors based on numerical simulation. The results showed the locally tsunami concentrating and the short period wave were derived from multiple wave reflection and wave dispersion in a specific shallow area respectively. Furthermore, the superposition of short period wave was suggested to have significant impacts on local amplification of tsunami and thus damage on coastal structures.
Three-dimensional evolution of local fluid flow and surface shape under partial water column collapse, which models overflow due to local failure of a vertical wall, is characterized in computational experiments using three-dimensional large eddy simulation. Free-surface responses highly depends on the collapse level and ambient water layer depth via mechanical interactions between the surface and vortices. The fluid stresses due to the overflow are parameterized by a simple hydraulic model proposed in this study.
A tsunami source inversion analysis has been carried out to estimate static crustal deformation associated with the 2011 off the Pacific Coast of Tohoku Earthquake. We use the Mansinha and Smylie's(1971) analytical solution for the displacements of inclined faults to estimate the slip distribution so that the crustal deformation at each observation site coincides with the displacements calculated from 40 and/or 60 subfaults of 20×20 km2. The maximum slip displacement reaches to 50m at the location about 50km away from the epicenter. Tsunami waveformes are calculated with the fault model assuming a constant rise time of 20s on each subfault and a rapture velocity of 2 km/s. The tsunami waveforms are similar to those of Fujii and Satake simulation which is tsunami waveform inversion with pressure and GPS wave gauge data.
Tsunami induced by the 2011 Tohoku Earthquake reached coastal areas of Tokai area, where is far more than 500km from the epicenter. Toward a future disaster prevention plan against tsunami hazard, it is significant to consider the impact of the tsunami on Tokai area. This paper investigated tsunami characteristics in Tokai coastal area from the observed tsunami data and the numerical results with a 2-D depth-integrated tsunami flow model. Through the observed data, the tsunamis reaching Tokai coastal area were found to have maximum heights in the range of 0.4 m to 1.8 m. The numerical results revealed that tsunami heights were amplified by the local coastal topography in some regions. It was also confirmed that strong flow with about 2 m/s occurred due to tsunami backwash in Gokasho bay where fishery damages were caused.
The main purpose of this study is to develop a H2D-Q3D coupled model, which consists of a quasi-three-dimensional ocean current model CCM (Q3D model) and a horizontal two-dimensional inundation model using a CIP method (H2D model), in order to analyze storm surge-induced inundation with efficiency and low computational load. The validity of the coupled model was verified by comparing with the existing numerical results and the experimental ones. As a result, the coupled model was confirmed to be consistent with the existing numerical scheme. Furthermore, the numerical results were found to be in good agreement with the experimental ones, which indicated that the coupled model was capable of analyzing inundation with high accuracy.
The 2011 Tohoku Tsunami caused serious damage along the Japanese coastal areas. The tsunami invaded along the rivers resulting in significant damages and loss of lives. River bank was conventionally designed without considering tsunami effects; hence once it breached, the damage increased significantly. Careful investigations on the river-related tsunami effects will therefore provide us with invaluable lessons to learn for reduction of tsunami disasters. Because a quality video footage that captured the tsunami attack is available, we have conducted a field survey in and around Kido River basin (Naraha, Fukushima) to find the flood traces left by the tsunami. We also carried out numerical simulation to study the behavior of the tsunami and indicated the potential danger by the tsunami flooding from the river.
While most of post-tsunami studies focus on tsunami inundation heights, this study mainly focuses on inundating tsunami flow, which may have more direct impact on damages of the inundated area. Based on tilted poles and trees in the inundated area, this study collected data of tsunami flow directions at Rikuzen-takata, Ootsuchi, and Naraha. Obtained data totaled more than 850. Numerical tsunami inundation model was then applied to each of these sites to link simulated time-varying flow patterns with observed flow directions, which may represent the direction at which the largest force acted at each location. Proposed methodology is useful to deepen our understandings on the dynamics of the inundation tsunami flow.
To improve the reliability of numerical simulations, hydraulic experiments and numerical simulations of 3-D and plane 2-D models in the case of the Hamaoka Nuclear Power Station site were carried out. The hydraulic experiments were conducted using a 28 m long and 11 m wide plane test tank. The scale of models was 1/150. As the results of the hydraulic experiments, tsunami flowed into the site in the state of jet flow. When the high velocity flow dashed against the front of a structure, the water level went up higher than the maximum water head. As the results of the numerical simulations, the 3-D and plane 2-D models reproduced the hydraulic experiments reasonably well. However, in case that the high velocity flow dashed against the front of a structure, the 3-D model showed more accurate results of water level wave pattern.
Video images taken in the 2011 Tohoku Earthquake qualitatively showed that the Teizan canal has a potential for the reduction effect of tsunami disaster. The main purpose of this study is to examine the tsunami mitigation effect of the Teizan canal numerically with the numerical wave flume “CADMAS-SURF”. The numerical results revealed that the present Teizan canal has some effects on tsunami disaster reduction, such the time delay of tsunami run-up and the decrease of inundation depth. The prevention and mitigation functions of the canal for tsunami disaster were confirmed to go up by increasing the height of the dike and the width of the canal. Furthermore, the tsunami mitigation effect of the canal was found to be more efficient for small-scale tsunami than large-scale tsunami.
Comparative study on tsunami height between the numerical simulation of the 2011 Tohoku Earthquake Tsunami and carefully examined tsunami height records obtained by the field survey are carried out. Geometric average and geometric deviation of ratios of observed values to calculated values are considered as reference indexes to evaluate the statistical uncertainty of the tsunami simulation. Principal results obtained from this study are as follows. Geometrical averages (K) decrease against the increasing distances from shore line, while geometric deviations (κ) increase with the distances. The geometric deviations (κ) decrease against the increasing tsunami heights. However, there are some differences in the four different fault models. The geometric deviations (κ) increase against the decreasing grid size of finite difference analysis.
It has been considered that Mikawa Port located in the eastern inner part of Mikawa Bay is safe for the storm surges in the case of a typhoon passing the south of Mikawa Bay because wind-drift effects are not excited on them. However, a storm tide 2.8 m, which exceeds the largest storm tide 2.6 m ever recorded in Mikawa Port and design values for the storm tide 2.75 m, were predicted by a potential vorticity bogussing scheme of a tropical cyclone and an atmosphere-ocean-wave coupled model. Simulated results using the scheme and model showed that the principal cause of the storm tide 2.8 m is not the wind-drift effect but a water oscillation in Mikawa Bay.
A massive earthquake of magnitude of 9.0 occurred on 11 March 2011, off the Pacific coast of northeast Japan, causing devastating damage. The tsunami resulting from the earthquake traveled to Tokyo Bay, 350 km from the epicenter, causing damage along the shore. Two cities in Chiba recorded a particularly high tsunami height compared to other cities. This study investigates the mechanism that caused these tsunamis using numerical hindcasting simulations and spectrum analysis of the data recorded in Tokyo Bay. It was found that the wave height in Katsunan Port was caused by multi wave refractions of the tsunami and seiches occurring in the port.
Three events of storm surge which yielded different tidal departures in the head of Mikawa Bay are compared and discussed from the viewpoint of response to the wind forcing. The mechanism of sudden sea level rise is investigated based on the data of wind, sea level and velocity obtained in the period of three different Typhoons which passed near the bay. The magnitude of preceding east wind which gives rise to the sea level in Ise Bay and quick change in wind direction from east to west are key factors to the development of large tidal departure in the head of Mikawa Bay. The propagation of surge waves as a free long wave is confirmed through the velocity profile data and also tested using a 2D simple numerical model.
The tsunami generated by the 2011 off the Pacific coast of Tohoku earthquake inundated coastal flat areas, moved auto vehicles, boats and ships and destroyed part of a breakwater in Hachinohe Port. In this paper, propagation and inundation calculations of the tsunami are implemented from an estimated tsunami source. Consideration of the breakwater damage in the calculations provides a good result of the tsunami in the port in comparison with the waveform observed at a tide station in the port, the measured inundation border and heights of tsunami watermarks. Based on the time of breakwater destructions in the calculation, failure mechanisms of the breakwater damage are estimated. Further, movement of a ship in the port is calculated and compared with a result of video footage analysis.
In this study, the PV-based typhoon bogussing scheme is so suitably modified to initialize typhoon internal structure and its environment for a coupled atmosphere-ocean-wave model that well-matured typhoons likely make landfall along the Osaka Bay area with the worst impact. For the typhoon initialization, the environmental PV field is divided into average PV field relating to typhoon intensity and anomalous PV field relating to typhoon movement. Substituting the average PV field of Typhoon 5915 and the anomalous PV field of Typhoon 0918, it is estimated that the maximum potential storm surge induced by a fully developed and closely approaching typhoon become about 3.3 m at the Port of Osaka, which is greater than 3.1m, the highest storm surge during the entire history.
In the paper, the sensitivity of real-time storm surge forecast models to the input parameters is described based on the artificial neural network in order to predict the storm surge at Sakai Minato in the Sanin coast. In addition, the forecast time spans of 01, 02, 03, 04, 05, 12 and 24 hours are investigated. The study reveals that the real-time forecast model for the 24 forecast successfully predicted the observation at Sakai Minato. The performance of the real time forecast model for the 24h forecast was best when using the data set consisting of the storm surge, the sea level pressure, the depression rate of the sea level pressure and the typhoon position.