Finite Volume Coastal Ocean Model Research Articles

The Role of Topographically Induced Form Drag on the Channel Flows Through the East/Japan Sea

AbstractThe dynamics responsible for the East/Japan Sea throughflow are examined using the Finite Volume Coastal Ocean Model. Existing ocean data assimilation models (Δx ~10 km) present overestimates of the volume transport through the Tsugaru Strait, and the outflow partitioning between the Tsugaru and Soya/La Perouse Straits also differs depending on the models. We find that this overestimate occurs when the form drag that is induced by detailed bottom topographic features in the Tsugaru Strait is not adequately resolved. A range of experiments with different horizontal resolutions in the Korea/Tsushima, Tsugaru, and Soya/La Perouse Straits were conducted to examine how detailed bottom topographic features in these three straits may affect the throughflow. We find that the volume transport is highly sensitive to the spatial resolution at the Tsugaru Strait but not at the Korea/Tsushima and Soya/La Perouse Straits. The high‐resolution experiment showed a decreased outflow through the Tsugaru Strait and a reduction in the model bias. The outflow through the Soya/La Perouse Strait increased, while the inflow through the Korea/Tsushima Strait remained relatively unchanged. Additional experiments with modified topography further indicated that the abrupt change of the topography located at the upstream side of the Tsugaru Strait plays an important role in the outflow partitioning of the East/Japan Sea throughflow.

A numerical study on the effect of tidal flat’s slope on tidal dynamics in the Xiangshan Bay, China

The Xiangshan Bay is a semi-enclosed and narrow bay, which is characterized by large scale tidal flats and has been historically utilized through coastal construction and aquaculture engineering. The hydrodynamic model using the Finite Volume Coastal Ocean Model (FVCOM) was constructed to examine the changes of tidal dynamics due to the variation of tidal flat slopes. According to the model results, a decreased slope of a tidal flat would amplify the M2 tidal amplitude and delay the M2 tidal phase in the inner harbor, due to an increased tidal prism, and vice versa. The amplitude of the main shallow-water tide M4 would be amplified/dampened in the entire bay due to the changed bottom friction, if the tidal flat’s slope were reduced/increased at the Tie inlet. The phase was advanced. The change of a tidal flat’s slope at the Tie inlet had greater impacts on tidal amplitude, phase and duration asymmetry, than that at the Xihu inlet. The impact of changes of the tidal flat slope at the Xihu inlet was small and was constrained locally. Changes in the tidal flats’ slopes at the Tie and Xihu inlets changed the tidal duration asymmetry, residual current and tidal energy via modulating tides. The ebb dominance decreased when the tidal flat’s slope at the Tie inlet was changed. Decreased/increased ebb dominance occurred when the tidal flat’s slope was reduced/increased at the Xihu inlet. The residual current and tidal energy density was amplified/dampened and more/less tidal energy was dissipated, with reduced/increased slope at both of the inlets. The findings in this study are instructive to coastal engineering and estuarine management.

Impact of tides and winds on estuarine circulation in the Pearl River Estuary

The Finite-Volume Coastal Ocean Model (FVCOM) is used to simulate the dynamics of the circulation in the Pearl River Estuary (PRE), validated against the in-situ measurements of a cruise survey. The model simulation agrees well with observed sea level at local tide gauge stations and reproduces observed characteristics of the currents. A simplified model run without wind forcing reveals that there is a significant spring-neap variation in the along-estuary circulation. Additional sensitivity runs that include up-estuary and/or down-estuary winds are also implemented. These results reveal that the cross-estuary adjustment of stratification and mixing induced by along-estuary winds is stronger than the along-estuary wind straining effect; these yields enhanced stratification and weakened mixing under the up-estuary wind. During spring tide, the response of the along-estuary circulation to the along-estuary wind forcing is weak, while during neap tide, the up-estuary and down-estuary winds may induce substantial variations in the along-estuary circulation. The analysis on the momentum budget and turbulent stress reveals the different dynamic response of the estuarine circulation in the PRE to different wind forcing conditions, identifying a significant modification to estuarine circulation by the wind-tide interaction.

Effects of Wave–Current Interactions on Suspended-Sediment Dynamics during Strong Wave Events in Jiaozhou Bay, Qingdao, China

AbstractWave–current interactions are crucial to suspended-sediment dynamics, but the roles of the associated physical mechanisms, the depth-dependent wave radiation stress, Stokes drift velocity, vertical transfer of wave-generated pressure transfer to the mean momentum equation (form drag), wave dissipation as a source term in the turbulence kinetic energy equation, and mean current advection and refraction of wave energy, have not yet been fully understood. Therefore, in this study, a computationally fast wave model developed by Mellor et al., a Finite Volume Coastal Ocean Model (FVCOM) hydrodynamics model, and the sediment model developed by the University of New South Wales are two-way coupled to study the effect of each wave–current interaction mechanism on suspended-sediment dynamics near shore during strong wave events in a tidally dominated and semiclosed bay, Jiaozhou Bay, as a case study. Comparison of Geostationary Ocean Color Imager data and model results demonstrates that the inclusion of just the combined wave–current bottom stress in the model, as done in most previous studies, is clearly far from adequate to model accurately the suspended-sediment dynamics. The effect of each mechanism in the wave–current coupled processes is also investigated separately through numerical simulations. It is found that, even though the combined wave–current bottom stress has the largest effect, the combined effect of the other wave–current interactions, mean current advection and refraction of wave energy, wave radiation stress, and form drag (from largest to smallest effect), are comparable. These mechanisms can cause significant variation in the current velocities, vertical mixing, and even the bottom stress, and should obviously be paid more attention when modeling suspended-sediment dynamics during strong wave events.

Fine-resolution Numerical Simulations to Estimate Storm Surge Height and Inundation Vulnerability Considering Future Climate Change Scenario

Yoon, J.J., 2018. Fine-resolution Numerical Simulations to Estimate Storm Surge Height and Inundation Vulnerability Considering Future Climate Change Scenario. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 916–920. Coconut Creek (Florida), ISSN 0749-0208.Typhoons are significant natural disasters in Korea, causing considerable damage to property. Climate change worsens the situation. The most severe loss of life and property in Korea was caused by Typhoon Maemi in September 2003. When storm surges coincide with high tides, they cause even greater damage. Therefore, it is desirable to accurately forecast storm surges, to enable detailed evacuation planning, including hazard mapping. To estimate the maximum probable inundation area while planning a hazard map, it is necessary to consider future climate change scenarios. The simulation of the largest storm surge inundation was successfully carried out with the Typhoon Maemi scenario using the Finite-Volume Coastal Ocean Model (FVCOM). According to the recent IPCC AR5 report, the rate of sea level rise (SLR) could accelerate to 1.4–2.0 m by the end of the 21st century. This estimate should be considered when designing coastal structures in order to prevent coastal disasters. We applied the results of SLR to coastal inundation simulations. We considered the effects of additional future SLR on the traditional storm surge inundation simulation of Typhoon Maemi. Virtual scenarios with additional SLR were simulated to evaluate the maximum probable surge height, and inundation depth and area for each climate change scenario along the southern coast of Korea. The increase in inundation heights and areas at the regional scale was found to be approximately 67–70% and 414–527%, respectively. This study provides a method to determine the maximum probable inundation area due to surge wave propagation.

Nearshore Flow Patterns in a Complex, Tidally Driven System in Summer: Part I. Model Validation and Circulation

AbstractCirculation models are often validated with respect to temporal rather than spatial variability, yet spatial variability is often very important for many questions subsequently addressed with the models. We validated a high‐resolution nearshore circulation model using both temporal and spatial data sets and used the model to investigate small‐scale nearshore flow patterns along the complex eastern Maine coast. The Finite Volume Coastal Ocean Model (FVCOM) was run from April to September 2014. In the temporal comparison, the model captured variation in sea level (model skill of 0.98) and the seasonal warming trend (model skill of 0.94). Temperature fluctuations were largely due to horizontal temperature divergence, implying the sensitivity to the forcing at the open boundary. To evaluate spatial variation in performance, we calculated model skill for current profile transects, which ranged from 0.99 to 0.60 in the east/west direction and 0.99 to 0.62 in the north/south direction. The combination of temporal and spatial validation improved confidence in the model's ability to recreate realistic flow patterns. Residual currents across the entrance to the bays showed flows that move out of the bays via the upper western side and into the bays in the lower water column before surfacing on the eastern side. As the coastal current passed by headlands and islands, eddies formed in the wake of several of them. Residual flows varied among months and location along the shelf. This model is a valuable first step in understanding how particulates move through such a complex and variable nearshore region.

Finite volume coastal ocean model for water-level fluctuation due to climate change in Aguelmam Sidi Ali Lake (Middle Atlas, Morocco)

Climate changes are the main motivation for alteration of ecosystems; in fact the effects of these changes on biodiversity and ecosystems are considered as the most challenging cases in present century. Therefore, since the lakes are the most important services and functions of ecosystems, the effect of climate change on water level fluctuations of Aguelmam Sidi Ali Lake (Morocco) was analyzed as a natural ecosystem in this essay. The regular observations from the lake have found that a very sensitive withdrawal of their water level during the dry years. Therefore, a hydrodynamic model has been used to simulate the condition of Aguelmam Sidi Ali Lake, with observed field data (model has been set up to run annually for a total 35 year data,i.e., precipitation, evaporation, runoff discharges and water-level which are available for the last 35 years) being used for model calibration and validation. Additionally, the model validation process showed that the model results fit the observed data fairly well (R2 = 0.70−0.74, root mean square error [RMSE] = 1.63−1.71 m). On the other hand, different hydrological conditions regarding lake input and output data were tested and water depth was calculated using bathymetry to predict water-level fluctuations in the future. The results predict that the water-level will decrease continuously (In 2044, the water level will reach to 6.20 m). The water level decrease due to the climate change in both scenarios (dry and very dry) is dramatic and a profound adverse impact on the environmental balance is predicted in the region. Additionally, the lake will be dried up in about 20 years if very dry conditions continue in the region. This reveals the importance of this type of approach for obtaining a first-order estimate of water-level variations in Sidi Ali Lake, affected by climate change.

Numerical investigation of pollution transport and environmental improvement measures in a tidal bay based on a Lagrangian particle-tracking model

In view of the severity of oceanic pollution, based on the finite volume coastal ocean model (FVCOM), a Lagrangian particle-tracking model was used to numerically investigate the coastal pollution transport and water exchange capability in Tangdao Bay, in China. The severe pollution in the bay was numerically simulated by releasing and tracking particles inside it. The simulation results demonstrate that the water exchange capability in the bay is very low. Once the bay has suffered pollution, a long period will be required before the environment can purify itself. In order to eliminate or at least reduce the pollution level, environmental improvement measures have been proposed to enhance the seawater exchange capability and speed up the water purification inside the bay. The study findings presented in this paper are believed to be instructive and useful for future environmental policy makers and it is also anticipated that the numerical model in this paper can serve as an effective technological tool to study many emerging coastal environment problems.

Impact of Phase III Project of Maji Mountain Port on sediment siltation in adjacent sea area

Based on a 3-D Finite Volume Coastal Ocean Model (FVCOM), tidal dynamics has been studied in the sea area around the Phase III Project of Maji Mountain Port (MMP). Furthermore, taking typhoon “Canhong” as an example, a storm surge and sediment model has also been established to study the impact of the Phase III Project on current flows and siltation during extreme weather. Tidal currents before and after the project have been compared. Model results show that the changes of tidal current mainly occur in the engineering areas with a magnitude change of 0.3–0.4 m/s during maximum flood and ebb tides. The flow condition for the port has been improved as the flow direction is changed to parallel to the wharf after the completion of the project. There is little siltation in the adjacent area, which will not affect the safety of ship navigation. Besides, the sudden siltation during typhoon period is relatively weak. The back silting in two days is less than 5 cm indicating no sudden siltation occurs.

Monitoring E. coli in a changing beachscape

Increased emphasis on protection of recreational water quality has led to extensive use of fecal indicator bacteria monitoring of coastal swimming waters in recent years, allowing for long-term, widespread retrospective studies. These studies are especially important for tracking environmental changes and perturbations in regional waters. We show that E. coli concentrations (EC) have decreased in Lake Michigan over the last 15years, coincident with the rapid invasion of Eurasian quagga mussels (Dreissenidae). While median water clarity in Lake Michigan increased by 32% from 2000 to 2014, median EC decreased by 34.9%. Of the 45 Lake Michigan beaches studied, 42 (93.3%) showed a relative decrease (76% significantly, p<0.05), in mean log E. coli between pre- and post-2007. As a result, Lake Michigan beach advisory frequency decreased by 40.0% (p<0.001) from 19.9% in 2000–2007 to 11.9% in 2008–2014. Finite Volume Coastal Ocean Model simulations at Ogden Dunes beach confirm that EC would decrease in response to the observed changes in water clarity (predicted=4.3%, actual=2.3%). In contrast, mean EC in western Lake Erie showed the opposite trend, with 17 of 19 (89.5%) beaches increasing in mean EC after 2007 (p<0.001). We explore plausible explanatory influences on lakewide EC and conclude that bacterial photoinactivation due to increased water clarity is an important contributing factor explaining the general decrease of E. coli densities in Lake Michigan. The trends and explanatory factors reported here may have important public health, management and ecological implications.

Cold Front Driven Flows Through Multiple Inlets of Lake Pontchartrain Estuary

AbstractWith in situ observations using acoustic Doppler current profilers (ADCPs) and numerical experiments using the Finite Volume Coastal Ocean Model (FVCOM), this study investigates atmospheric cold front induced exchange of water between Lake Pontchartrain Estuary and coastal ocean through multiple inlets. Results show that the subtidal hydrodynamic response is highly correlated with meteorological parameters. Northerly and westerly winds tend to push water out of Lake Pontchartrain, while south and east winds tend to produce currents flowing into it. For most cases, the subtidal water level is inversely correlated with the east wind, with the correlation coefficient being ∼0.8. The most important finding of this work is that, contrary to intuition, the cold front induced remote wind effect has the greatest contribution to the overall water level variation, while the local wind stress determines the surface slope inside the estuary. It is found that wind driven flow is roughly quasi steady state: the surface slope in the north‐south direction is determined by the north‐south wind stress, explaining ∼83% of the variability but less so in the east‐west direction (∼43%). In other words, the north‐south local wind stress determines the water level gradient in that direction in the estuary while the overall water level change is pretty much controlled by the open boundary which is the “remote wind effect,” a regional response that can be illustrated only by a numerical model for a much larger area encompassing the estuary.

Sensitivity Analysis of Hurricane Arthur (2014) Storm Surge Forecasts to WRF Physics Parameterizations and Model Configurations

Abstract Through a case study of Hurricane Arthur (2014), the Weather Research and Forecasting (WRF) Model and the Finite Volume Coastal Ocean Model (FVCOM) are used to investigate the sensitivity of storm surge forecasts to physics parameterizations and configurations of the initial and boundary conditions in WRF. The turbulence closure scheme in the planetary boundary layer affects the prediction of the storm intensity: the local closure scheme produces lower equivalent potential temperature than the nonlocal closure schemes, leading to significant reductions in the maximum surface wind speed and surge heights. On the other hand, higher-class cloud microphysics schemes overpredict the wind speed, resulting in large overpredictions of storm surge at some coastal locations. Without cumulus parameterization in the outermost domain, both the wind speed and storm surge are grossly underpredicted as a result of large precipitation decreases in the storm center. None of the choices for the WRF physics parameterization schemes significantly affect the prediction of Arthur’s track. Sea surface temperature affects the latent heat release from the ocean surface and thus storm intensity and storm surge predictions. The large-scale atmospheric circulation models provide the initial and boundary conditions for WRF, and influence both the track and intensity predictions, thereby changing the spatial distribution of storm surge along the coastline. These sensitivity analyses underline the need to use an ensemble modeling approach to improve the storm surge forecasts.

Stratification and salt-wedge in the Seomjin river estuary under the idealized tidal influence

Advection, straining, and vertical mixing play primary roles in the process of estuarine stratification. Estuaries can be classified as salt-wedge, partially-mixed or well-mixed depending on the vertical density structure determined by the balancing of advection, mixing and straining. In particular, straining plays a major role in the stratification of the estuarine water body along the estuarine channel. Also, the behavior of a salt wedge with a halocline shape in a stratified channel can be controlled by the competition between straining and mixing induced by buoyancy from the riverine source and tidal forcing. The present study uses Finite Volume Coastal Ocean Model (FVCOM) to show that straining and vertical mixing play major roles in controlling along-channel flow and stratification structures in the Seomjin river estuary (SRE) under idealized conditions. The Potential Energy Anomaly (PEA) dynamic equation quantifies the governing processes thereby enabling the determination of the stratification type. By comparing terms in the equation, we examined how the relative strengths of straining and mixing alter the stratification types in the SRE due to changes in river discharge and the depth resulting from dredging activities. SRE under idealized tidal forcing tends to be partially-mixed based on an analysis of the balance between terms and the vertical structure of salinity, and the morphological and hydrological change in SRE results in the shift of stratification type. While the depth affects the mixing, the freshwater discharge mainly controls the straining, and the balance between mixing and straining determines the final state of the stratification in an estuarine channel. As a result, the development and location of a salt wedge along the channel in a partially mixed and highly stratified condition is also determined by the ratio of straining to mixing. Finally, our findings confirm that the contributions of mixing and straining can be assessed by using the conventional non-dimensional parameters with respect to salt-wedge behavior.

CyberConnector: a service-oriented system for automatically tailoring multisource Earth observation data to feed Earth science models

Feeding multisource Earth observation (EO) data into Earth science models (ESM) remains a daunting challenge. This paper presents a service-oriented approach as an alternative solution. It uses geospatial web services to process the EO data and geoprocessing workflow for automation. Different from existing approaches, it takes advantage of virtual data products (VDP) to release modelers from intensive data processing. It can directly connect ESMs to public EO sources via Cyberinfrastructure. A prototype called CyberConnector is implemented. CyberConnector supports intuitive building of VDP, automatic execution of workflows and effortless retrieval of model-ready input files. We used it to stream multiple datasets to several ESMs including finite-volume coastal ocean model (FVCOM) and cloud-resolving model (CRM). The results show that CyberConnector can truly benefit modelers on time saving and effort minimizing.

A GPU accelerated finite volume coastal ocean model

With the unstructured grid, the Finite Volume Coastal Ocean Model (FVCOM) is converted from its original FORTRAN code to a Compute Unified Device Architecture (CUDA) C code, and optimized on the Graphic Processor Unit (GPU). The proposed GPU-FVCOM is tested against analytical solutions for two standard cases in a rectangular basin, a tide induced flow and a wind induced circulation. It is then applied to the Ningbo's coastal water area to simulate the tidal motion and analyze the flow field and the vertical tide velocity structure. The simulation results agree with the measured data quite well. The accelerated performance of the proposed 3-D model reaches 30 times of that of a single thread program, and the GPU-FVCOM implemented on a Tesla k20 device is faster than on a workstation with 20 CPU cores, which shows that the GPU-FVCOM is efficient for solving large scale sea area and high resolution engineering problems.

Impacts of wind-field correction on the numerical simulation of storm-surge inundation during typhoon “Rammasun”

Accurate wind forcing is an important prerequisite of storm-surge and inundation simulations. However, traditional methods of wind-field improvement, such as an increase in resolution and the assimilation of observations, are difficult to provide because of either computational limitations or the lack of observations, which detracts from the ability to make quick assessments. Therefore, a method for correcting the wind field is developed for low-resolution wind fields, depending on the underlying surface. We investigate the ability of the correction method to simulate storm surge and inundation using the Finite-Volume Coastal Ocean Model (FVCOM), with the Typhoon “Rammasun” as an example. The total elevations, astronomic tides and surges are validated against routine observations, while inundation areas and submerged depths before and after the wind-field correction are compared with the results of field surveys. Corrected wind fields in the harbor and inundated regions significantly increase the simulated water elevations, inundation areas and submerged depths, with the submerged depths being more consistent with observations. Our local wind-field correction method for different underlying surfaces is a simple and effective tool for providing more accurate wind forcing for storm-surge and inundation simulations.

The impacts of land reclamation on suspended-sediment dynamics in Jiaozhou Bay, Qingdao, China

A three-dimensional, high-resolution tidal model coupled with the UNSW sediment model (UNSW-Sed) based on Finite Volume Coastal Ocean Model (FVCOM) was set up to study the suspended-sediment dynamics and its change in Jiaozhou Bay (JZB) due to land reclamation over the period 1935 to 2008. During the past decades, a large amount of tidal flats were lost due to land reclamation. Other than modulating the tides, the tidal flats are a primary source for sediment resuspensions, leading to turbidity maxima nearshore. The tidal dynamics are dominant in controlling the suspended-sediment dynamics in JZB and have experienced significant changes with the loss of tidal flats due to the land reclamation. The sediment model coupled with the tide model was used to investigate the changes in suspended-sediment dynamics due to the land reclamation from 1935 to 2008, including suspended-sediment concentrations (SSC) and the horizontal suspended-sediment fluxes. This model can predict the general patterns of the spatial and temporal variation of SSC. The model was applied to investigate how the net transport of suspended sediments between JZB and its adjacent sea areas changed with land reclamation: in 1935 the net movement of suspended sediments was from JZB to the adjacent sea (erosion for JZB), primarily caused by horizontal advection associated with a horizontal gradient in the SSC; This seaward transport (erosion for JZB) had gradually declined from 1935 to 2008. If land reclamation on a large scale is continued in future, the net transport between JZB and the adjacent sea would turn landward and JZB would switch from erosion to siltation due to the impact of land reclamation on the horizontal advection of suspended sediments. We also evaluate the primary physical mechanisms including advection of suspended sediments, settling lag and tidal asymmetry, which control the suspended-sediment dynamics with the process of land reclamation.

Effects of cluster land reclamation projects on storm surge in Jiaojiang Estuary, China

Variations in coastline geometry caused by coastal engineering affect tides, storm surges, and storm tides. Three cluster land reclamation projects have been planned for construction in the Jiaojiang Estuary during the period from 2011 to 2023. They will cause significant changes in coastline geometry. In this study, a surge-tide coupled model was established based on a three-dimensional finite-volume coastal ocean model (FVCOM). A series of numerical experiments were carried out to investigate the effects of variations in coastline geometry on tides, storm surges, and storm tides. This model was calibrated using data observed at the Haimen and Ruian gauge stations and then used to reproduce the tides, storm surges, and storm tides in the Jiaojiang Estuary caused by Typhoon Winnie in 1997. Results show that the high tide level, peak storm surge, and high storm tide level at the Haimen Gauge Station increased along with the completion of reclamation projects, and the maximum increments caused by the third project were 0.13 m, 0.50 m, and 0.43 m, respectively. The envelopes with maximum storm tide levels of 7.0 m and 8.0 m inside the river mouth appeared to move seaward, with the latter shifting 1.8 km, 3.3 km, and 4.4 km due to the first project, second project, and third project, respectively. The results achieved in this study contribute to reducing the effects of, and preventing storm disasters after the land reclamation in the Jiaojiang Estuary.

Tidal propagation and dissipation in the Taiwan Strait

Previous research on tides and tidal dynamics in the Taiwan Strait (TS) is reviewed in this paper. Tidal dynamics, which is the basic and dominant hydrodynamics in this area, attracts much interest in the last 30 years and till now its physical mechanism is still in debate. In this study, the major research methods and findings of previous works on barotropic tides in the TS are summarized.Based on Finite Volume Coastal Ocean Model (FVCOM), the main tidal constituents (M2, S2, K1, O1) are well simulated with the mean root-mean-square (RMS) errors of 4.7, 2.0, 1.3 and 0.7cm between the observed and simulated tidal constants, respectively. It has been proved that semi-diurnal tidal movement is mainly determined by the waves from the East China Sea (ECS), while waves from the ECS and the Luzon Strait (LS) play comparable roles in diurnal tidal movement in the TS by linear superposition and the interaction of these two waves is the main cause for the progressive diurnal tidal waves in the TS. Furthermore, energy analysis revealed that the M2 tidal wave system in the TS and its adjacent area south to the shoal is an standing wave system and the anti-node appears in the central TS while the wave node locates in the shoal area, which can be contributed to the interaction of the incident waves from the ECS and the topography step south to Taiwan island, while the shoal also has an impact on the whole semi-diurnal tidal wave system in the TS. This standing wave system is consistent with the little energy dissipation in the central TS and much energy dissipation in the southern TS, where the shallow water effect also contributes to the local dissipation to some extent.

Numerical Simulations of Storm-Surge Inundation Along Innermost Coast of Ariake Sea Based on Past Violent Typhoons

The Ariake Sea has Japan’s largest tidal range – up to six meters. Given previous Ariake Sea disasters caused by storm surges and high waves, it is considered highly likely that the bay’s innermost coast will be damaged by typhoon-triggered storm surges. Concern with increased storm-surge-related disasters is associated with rising sea levels and increasing typhoon intensity due to global warming. As increasingly more potentially disastrous typhoons cross the area, preventing coastal disasters has become increasingly important. The first step toward doing so is damage prediction, which requires numerical simulation. Our study considers the tracks of typhoons considerably influencing the Ariake Sea. To examine storm-surge risk related to both inundation area and process, we calculated storm surges inundating the Sea’s innermost coastal area using an improved ocean-flow finite-volume coastal ocean model. Results showed that enhanced storm surges were to be anticipated and that inundation areas could be extensive where typhoons followed a route from west to northeast across the Sea. We also found that even under current climatic conditions, typhoons able to cause significant storm-surge and inundation disasters could adversely affect the Bay’s innermost coastal area. Our analysis of this area and process indicated that the inundation extent around the bay’s innermost coast varies with the typhoon, confirming the importance of determining typhoon routes triggering the potentially greatest inundation damage.