Large Storm Surge Research Articles

SUITABLE BOUNDARY LOCATION IDENTIFCATION FOR RAINFALL-RUNOFF AND SURGE MODEL COUPLING TO EVALUATE COMPOUND FLOOD HAZARDS IN COASTAL REGIONS

Flooding in many coastal regions is exacerbated due to complex interactions of multiple flood drivers such as rainfall-runoff and coastal surge which can occur simultaneously or sequentially during storm events, leading to compound flooding hazards. The Texas Gulf Coasts (USA) are especially vulnerable from compound flooding due to frequent occurrence of tropical storms which bring strong winds to drive storm surge and heavy rainfall to generate inland flooding. Large scale studies {Coastal Texas Restoration and Protection Study (CTX, 2021), Texas General Land Office’s Texas River Basin Study, Base Level Engineering Study} are being conducted by state and federal agencies for flood hazard assessment and for development of mitigation and abatement strategies for reducing this risk and increasing community resilience. Traditionally, large scale storm surge models do not account for runoff contributions to water levels in the interior of their domain. Riverine models for their part use either normal depth or mean high water levels to assign downstream boundary conditions within tidally influenced area, thus ignoring effects of storm surge. In this Planning Assistance to States (PAS) study, located in the Lower Clear Creek and Dickinson Bayou watersheds (Texas, USA), we have evaluated rainfall-runoff and storm surge interactions to determine suitable locations to use as model boundary conditions for exchanging data between rainfall-runoff and surge models under compound flooding conditions.

Recovery of salt marsh vegetation after ice-rafting

Sediment transport on salt marsh platforms is usually brought about through storm events and high tides. At high latitudes, ice-rafting is a secondary mechanism for sediment transport, redistributing sediment from tidal flats, channels, and ponds to marshland. In January 2018, winter storm Grayson hit the North Atlantic coast, producing a large storm surge and a significant decrease in temperature. The Great Marsh in Plum Island Sound, Massachusetts, USA, experienced an unprecedented sediment deposition due to ice-rafting, burying marsh vegetation. Plant vegetation recovery was investigated in 17 sediment patches, dominated by Spartina patens, Distichlis spicata, Juncus gerardi, and S. alterniflora. The analysis was carried out considering the number of stems and stem height for each vegetation species. D. spicata firstly occupied bare patches, while S. patens, once smothered by sediment, regrew slowly. The number of stems of S. patens inside the sediment patches recovered, on average, after 2 growing seasons. The number of J. gerardi stems was not significantly affected by ice-rafted sediment deposition. S. alterniflora dynamics were different depending on physical and edaphic conditions. At some locations, S. alterniflora did not recover after sediment deposition. The deposition of the sediment layer had a positive effect on vegetation vigor, increasing stem height and maintaining high stem density. The results suggest a beneficial effect of sediment deposition not only for marsh accretion, but also for marsh vegetation growth, both of which are fundamental for marsh restoration.

Future changes in extreme storm surge based on a maximum potential storm surge model for East Asia

ABSTRACT We analyzed tropical cyclones (TC) based on the theory of Maximum Potential Intensity (MPI) and Maximum Potential Surge (MPS) for a long-term assessment of extreme TC intensity and storm surge heights. We investigated future changes in the MPI fields and MPS for different global warming levels based on 150-year continuous scenario projections (HighResMIP) and large ensemble climate projections (d4PDF/d2PDF). Focusing on the Western North Pacific Ocean (WNP), we analyzed future changes in the MPI and found that it reached a maximum in the latitudinal range of 30–40°N in September. We also analyzed future changes in the MPS in major bays of East Asia and along the Pacific coast of Japan. Future changes in the MPS were projected, and it was confirmed that changes in the MPS are larger in bays where large storm surge events have occurred in the past.

Ensemble forecast for storm tide and resurgence from Tropical Cyclone Isaias

Ensemble-based probabilistic forecasting of storm surge is increasingly being used to provide metrics for emergency management decisions such as the near-worst case scenario. The Stevens Flood Advisory System is an ensemble prediction system used to forecast total water levels over a broad coastal region and street-scale flood levels for several New York Harbor (NYH) critical infrastructure sites. As a part of our continuous assessment of this system’s performance, we evaluate its prediction of storm tide and resurgence during Tropical Cyclone Isaias (2020), which tracked northward along the Pennsylvania/New Jersey border and caused the largest storm surge in NYH since Hurricane Sandy. Isaias specific track and speed generated an unusual flood event consisting of a storm surge, a blowout, then a significant resurgence that caused minor flooding. The analysis shows that the super-ensemble spread provided an equal or better estimate of uncertainties than sub-ensembles based only on any single meteorological forcing system. Because of ensemble averaging, the central forecast under-predicted peak water levels and the resurgence peak though these were predicted by some of the ensemble members. The impacts of errors in forecast storm arrival time and resolution-related biases in coarse global atmospheric models on the predictions are noted. A limited comparison for this single storm with the National Hurricane Center’s forecast show SFAS providing better accuracy and spread. Advantages and challenges of SFAS and other similar mid-latitude flood forecast systems are identified along with recommendations for analysis and improvement.

Mere Nuisance or Growing Threat? The Physical and Economic Impact of High Tide Flooding on US Road Networks

High tide flooding (HTF) already affects traffic in many US coastal areas, but the issue will worsen significantly in the future. While studies show that large storm surge events threaten to be ever more costly, less damaging, but more frequent HTF events remain understudied and potentially carry a comparable economic impact. This study advances our understanding of the risks and impacts of HTF on vulnerable traffic corridors using hourly tide gauge water levels, sea-level rise projections, and link-level spatial analysis. It is the first study to estimate HTF economic impacts for varying levels of intervention, including reasonably anticipated driver-initiated rerouting and ancillary protection of adjacent property. The 2020 annual national-level costs of $1.3 to $1.5 billion will increase to $28 to $37 billion in 2050 and $220 to $260 billion in 2100 for medium to high greenhouse gas (GHG) emissions scenarios, respectively. Total costs over the century are $1.0 to $1.3 trillion (discounted 3%). Additional cost-effective protection by building sea walls or raising road surfaces could significantly reduce 2100 costs to $61 to $78 billion, but there remain many barriers to adopting least-cost adaptation decisions, and these gains may only be realized with careful planning and information sharing.

Effects of nonlinear terms and topography in a storm surge model along the southeastern coast of China: a case study of Typhoon Chan-hom

Based on Finite Volume Coastal Ocean Model (FVCOM), this study constructed a numerical model covering the Bohai Sea, Yellow Sea, and East China Sea. National Centers for Environmental Prediction’s Climate Forecast System Reanalysis (NCEP-CFSR) data were used to drive the model to simulate a large storm surge generated by Typhoon Chan-hom. The model was validated by multiple in situ observations of water levels taken at tidal gauge stations. The effects of the nonlinear terms and topography on the modeling of storm surges were then studied. First, the tide–surge interaction during the storm surge process was analyzed. The results show that the tide–surge interaction can suppress the storm surge at the climax of the astronomical tide and benefit the growth of the storm surge at the ebb of the astronomical tide. The tidal constituents M2, S2 and K1 were added to analyze the influences of the amplitudes and periods of tides on the nonlinear reaction. The results indicate that the nonlinear effect will be enhanced by an increased tidal height; additionally, the nonlinear interaction of semidiurnal tides is more significant than that of diurnal tides. The semidiurnal fluctuation that appears near the peak-value time is also attributed to the tide–surge interaction. Moreover, the tide–surge interaction can be influenced by the water depth and position of the area of interest. According to the numerical results, topography has a certain impact on the storm surge: The peak value of the storm surge will decrease with increasing slope. The existence of the Ryukyu Islands reduces the area influenced by the storm surge on the southeast coast of China but expands the high-value storm surge area.

Social lives of tsunami walls in Japan: Concrete culture, social innovation and coastal communities

This paper is the beginning of a reflection on the ways in which the Great East Japan Disaster (2011) might have changed people’s perception of seawalls and hard coastal defence in Japan. A highly developed society that is prone to frequent large tsunamis and storm surges, Japan’s spending on physical coastal defence has few equals around the world. The development of sea defence became a priority during the 1960-70s when coastal engineers and related agencies developed national standards. One of the chief strategies has been the edification of seawalls and other hard structures, which today surround more than 40% of Japan’s coastlines. This technological advancement might have created a general sentiment of security and trust in the ability of these coastal structures to protect coastal communities, their infrastructures and their nuclear plants. On March 11 2011, however, this general sense of safety was hardly shaken by a M9 earthquake and its ensuing tsunami taking away the lives of over 15,000 individuals and causing a material loss of over 210 billion dollars. If experts had anticipated such a large earthquake, the height of the tsunami waves and the extent of the damaged suffered along the coast of northeast Japan surpassed even the most pessimistic predictions. Reflecting on the impact of this tragedy, this paper is a first attempt to appreciate whether Japanese people’s perception of and approaches to seawalls and other coastal defences might have changed as a result. The first part of this paper provides a brief analytical overview of the culture of sea defence and its socio-economic significance in Japanese society. The second part examines more specifically the ways in which seawalls might have influenced people’s behaviour during the events of the Great East Japan Earthquake, including their creating a false-sense of security. Finally, the third part focuses on relatively innovative approaches to coastal defence in post-disaster Japan, with a particular focus on a national project known as the Great Forest Wall. Rather than its engineering efficacy, the interest in this project lies in the ways in which the project might inform us of changing people relationships and ideas with coastal defence.

AN EXPERIMENTAL STUDY ON WAVE RUNUP ON QUAY TOP AND ITS REPRODUCTION BY USING A BOUSSINESQ-TYPE WAVE MODEL

Ports and coastal industrial and commercial regions in Osaka bay were inundated with water due to storm wave overtopping during Typhoon Jebi passing through on September 4, 2018. Although the large storm surge was observed at the end of the bay, the sea level rarely rises over seawalls which prevent sea water from intruding onto residential areas, fortunately. Therefore, in this study, the characteristics of wave runup over the gap between berthing depth and quay top in high, normal and middle tide condition are investigated with vertical 2D model experiments. Moreover, numerical simulations are conducted by using a Boussinesq-type wave model, which can be also applied to wave overtopping and inundation in horizontal 2D computational region, to reproduce the results of model experiments.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/HCiUoj68xyY

Mid-Winter Breakout of Landfast Sea Ice and Major Storm Leads to Significant Ice Push Event Along Chukchi Sea Coastline

During the winter of 2016, anomalous sea ice conditions and a powerful storm culminated in a destructive erosion event along the Chukchi Sea coastline of Cape Espenberg, Alaska. This event is commonly referred to as an "ice push" or "ivu,” the Inupiat word for an ice ridging event. In this paper we report the process and impact of this event by combining traditional ecological knowledge, news accounts, meteorological data, remote sensing, and ground surveys. The mid-winter detachment of shorefast ice was caused by a low-pressure system and wind-driven swell that destabilized shorefast ice, while northerly winds developed an open-water lead offshore to the eventual impact area. These conditions preceded the impact of an extratropical cyclone on December 31, 2016, when powerful southerly winds and the second largest storm surge in Kotzebue Sound since at least 2003 led to the compressional failure of the ice cover under uni-axial loading perpendicular to the southern coastline of the Cape, resulting in the ice push event. Ice-pushed debris were shoved up to 6.2 m above mean high water, with ~3.5 km of coastline experiencing net erosion. The largest accumulation of ice-pushed debris had a volume of 1,000 m3, and rose 3+ m above the surrounding ground surface even after roughly 6 months of melting. On low-lying areas, driftwood and other debris were deposited 130 m landward by the surge 5.0 m above mean high water, indicating the potential threat of such events to property, infrastructure and, in this case, archeological sites and associated cultural resources. The anomalous environmental and sea ice conditions that preceded the ivu, seem to suggest that such events may occur more frequently in a warmer Arctic.

Nonlinear tide-surge-wave interaction at a shallow coast with large scale sequential harbor constructions

The southwestern part of Bohai Bay in northeastern China is a shallow-water coast with a long fetch for water to pile up to produce large storm surge under strong wind action during the extreme weather condition. In addition, the coastline along the bay has experienced significant environmental impacts from large scale harbor constructions in the past two decades. Consequently, there is a pressing need to better understand the effects of two local large scale sequential harbor constructions on storm surge and coastal vulnerability in the bay area. The extreme cold front weather on 10-13th October 2003 caused a 1.31 billion Yuan damage. A two-way coupled tide-surge-wave Delft3D model is used to investigate the impact of the harbor constructions from 2003 to 2016 on the interaction of tide, storm surge and wave during a storm like that. The wind field by the newly-released global reanalysis wind product ERA5 of European Centre for Medium-Range Weather Forecasts (ECMWF) has been improved by assimilation with field observations at a higher resolution than previous version and is used to drive the tide, surge and wave modelling framework. The model results indicate that the storm surge in the study area is dominated by the wind-induced surge before and after the constructions whereas the maximum contribution from wave-induced surge (wave setup) is increased from 5%-15% to 8%–20% by the harbor constructions between 2003 and 2016. It is found that semi-diurnal modulation of storm surge is generated by nonlinear tide-surge interaction, which is mainly attributed to local tidal acceleration in the offshore zone and bottom stress in the nearshore zone respectively. The harbor constructions affect the coastal storm surge mainly through nonlinear tide-surge-wave interaction. In addition, the quarter-diurnal variation of storm surge induced by the harbor constructions is due to the influences of the harbor constructions on the local quarter-diurnal tidal constituents and their modulation of wave momentum transfer to coastal circulation.

IMPACT ASSESSMENT OF CLIMATE CHANGE ON COASTAL HAZARDS DUE TO WINTER CYCLONE AROUND JAPAN USING LARGE ENSEMBLE DATABASE

IPCC AR5 reported that the extreme events like tropical cyclone, heavy rainfall and so on will be strengthen. The winter cyclone is one of the cause of coastal hazard. The winter cyclone is defined as the extratropical depression with rapid development. It causes high wave and storm surge from winter to spring, and Japan sometimes have casualties and economical loss. Some researches reported that the number of winter cyclone tend to increase. Because its tendency seems to go on, future change estimation of winter cyclone activity is important for disaster reduction. Understanding of winter cyclone is developing. For example, Yoshida and Asuma showed that the winter cyclones are classified by their track and the development of winter cyclone is related to lateral heat flux. On the other hand, almost of all researches of impact assessment on coastal hazard focus on the tropical cyclone. Mori et al. showed the maximum potential storm surge in Japan using maximum potential intensity of tropical cyclone and GCM outputs, and large storm surge will increase. Shimura et al. showed that extreme wave caused by the tropical cyclone will develop at offshore region of east from Japan. This research aims to reveal stochastic future change of winter cyclone using the database for policy decision making for future climate change (after here, d4PDF) which is huge ensemble dataset of present- and futureclimate. Then, the risk of coastal hazard will be evaluate.

Developing signals to trigger adaptation to sea-level rise

Dynamic adaptive policy pathways (DAPP) is emerging as a ‘fit-for-purpose’ method for climate-change adaptation planning to address widening future uncertainty and long planning timeframes. A key component of DAPP is to monitor indicators of change such as flooding and storm events, which can trigger timely adaptive actions (change pathway/behavior) ahead of thresholds. Signals and triggers are needed to support DAPP—the signal provides early warning of the emergence of the trigger (decision-point), and the trigger initiates the process to change pathway before a harmful adaptation-threshold is reached. We demonstrate a new approach to designing signals and triggers using the case of increased flooding as sea level continues to rise. The flooding frequency is framed in terms of probable timing of several events reaching a specific height threshold within a set monitoring period. This framing is well suited to adaptive planning for different hazards, because it allows the period over which threshold exceedances are monitored to be specified, and thus allows action before adaptation-thresholds are reached, while accounting for the potential range of timing and providing a probability of premature warning, or of triggering adaptation too late. For our New Zealand sea level case study, we expect early signals to be observed in 10 year monitoring periods beginning 2021. Some urgency is therefore required to begin the assessment, planning and community engagement required to develop adaptive plans and associated signals and triggers for monitoring. Worldwide, greater urgency is required at tide-dominated sites than those adapted to large storm-surges. Triggers can be designed with confidence that a change in behavior pathway (e.g. relocating communities) will be triggered before an adaptation-threshold occurs. However, it is difficult to avoid the potential for premature adaptation. Therefore, political, social, economic, or cultural signals are also needed to complement the signals and triggers based on coastal-hazard considerations alone.

On the interaction between a hurricane, the Gulf Stream and coastal sea level

Tropical storms and hurricanes in the western North Atlantic Ocean can impact the US East Coast in several ways. Direct effects include storm surges, winds, waves, and precipitation and indirect effects include changes in ocean dynamics that consequently impact the coast. Hurricane Matthew [October, 2016] was chosen as a case study to demonstrate the interaction between an offshore storm, the Gulf Stream (GS) and coastal sea level. A regional numerical ocean model was used, to conduct sensitivity experiments with different surface forcing, using wind and heat flux data from an operational hurricane-ocean coupled forecast system. An additional experiment used the observed Florida Current (FC) transport during the hurricane as an inflow boundary condition. The experiments show that the hurricane caused a disruption in the GS flow that resulted in large spatial variations in temperatures with cooling of up to ~ 4 °C by surface heat loss, but the interaction of the winds with the GS flow also caused some local warming near fronts and eddies (relative to simulations without a hurricane). A considerable weakening of the FC transport (~ 30%) has been observed during the hurricane (a reduction of ~ 10 Sv in 3 days; 1Sv = 106 m3 s−1), so the impact of the FC was explored by the model. Unlike the abrupt and large wind-driven storm surge (up to 2 m water level change within 12 h in the South Atlantic Bight), the impact of the weakening GS on sea level is smaller but lasted for several days after the hurricane dissipated, as seen in both the model and altimeter data. These results can explain observations that show minor tidal flooding along long stretches of coasts for several days following passages of hurricanes. Further analysis showed the short-term impact of the hurricane winds on kinetic energy versus the long-term impact of the hurricane-induced mixing on potential energy, whereas several days are needed to reestablish the stratification and rebuild the strength of the GS to its pre-hurricane conditions. Understanding the interaction between storms, the Gulf Stream and coastal sea level can help to improve prediction of sea level rise and coastal flooding.

Saltwater Intrusion of Coastal Soils

Saltwater Intrusion of Coastal Soils

The Increased Risk of Flooding in Hampton Roads: On the Roles of Sea Level Rise, Storm Surges, Hurricanes, and the Gulf Stream

AbstractThe impact of sea level rise on increased tidal flooding and storm surges in the Hampton Roads region is demonstrated, using ~90 years of water level measurements in Norfolk, Virginia. Impacts from offshore storms and variations in the Gulf Stream (GS) are discussed as well, in view of recent studies that show that weakening in the flow of the GS (daily, interannually, or decadal) is often related to elevated water levels along the U.S. East Coast. Two types of impacts from hurricanes on flooding in Hampton Roads are demonstrated here. One type is when a hurricane like Isabel (2003) makes a landfall and passes near the Chesapeake Bay, causing a large but short-term (hours to a day) storm surge. The second type is when Atlantic hurricanes like Joaquin (2015) or Matthew (2016) stay offshore for a relatively long time, disrupting the flow of the GS and leading to a longer period (several days or more) of higher water levels and tidal flooding. Analysis of the statistics of tropical storms and hurricanes since the 1970s shows that, since the 1990s, there is an increase in the number of days when intense hurricanes (Categories 3‐5) are found in the subtropical western North Atlantic. The observed Florida Current transport since the 1980s often shows less transport and elevated water levels when tropical storms and hurricanes pass near the GS. Better understanding of the remote influence of the GS and offshore storms will improve future prediction of flooding and help mitigation and adaptation efforts.

Mid- to late-Holocene marine inundations inferred from coastal deposits facing the Nankai Trough in Nankoku, Kochi Prefecture, southern Japan

This study investigates the Holocene sedimentary history of a small coastal lowland in Nankoku, Kochi Prefecture, on the coast of southern Japan facing the Nankai Trough. The sedimentary fill of the lowland area consists mainly of marine-brackish clay overlain by beds of freshwater clay and peat. We found four laterally extensive sand sheets, one directly underlying the freshwater deposits and the other three interbedded with them. Radiocarbon dates show that these sand sheets were deposited between 5970 and 2440 cal. BP. Although the sand sheets contained few marine-brackish diatoms, they were concentrated in the seaward part of the study site, suggesting that they were deposited by marine inundations. These sand sheets were formed as a result of tsunamis or unusually large storm surges. The apparent frequency of marine inundations during 5970–2440 cal. BP was much lower than that of megathrust earthquakes along the Nankai Trough recorded during the last 1300 years. Event deposits were absent between 2440 and 960 cal. BP, a gap that we attribute to the development of beach ridges. The new marine inundation records reported here will aid efforts to reconstruct the timing and recurrence intervals of megathrust earthquakes in the western Nankai Trough.

Synoptic Characteristics of Surge-Producing Extratropical Cyclones along the Northeast Coast of the United States

AbstractExtratropical cyclones (ETCs) are responsible for most of the large storm-surge events in the northeastern United States. This study uses the ECMWF atmospheric reanalysis of the twentieth century (ERA-20C) and NOAA tide gauge data to examine the local, regional, and large-scale atmospheric circulation accompanying the 100 largest ETC-driven surge events at three locations along the northeastern coast of the United States: Sewells Point (Norfolk), Virginia; the Battery (New York City), New York; and Boston, Massachusetts. Results from a k-means cluster analysis indicate that the largest surges are generated when slowly propagating ETCs encounter a strong anticyclone, which produces a tighter pressure gradient and longer duration of onshore winds. The strength of the anticyclone is evident in the middle and upper troposphere where there are positive 500-hPa geopotential height anomalies overlying the surface anticyclone for the majority of clusters and nearly all of the five biggest surge events. Multiple clusters feature a slower-than-average storm and a strong anticyclone, indicating that various circulation scenarios can produce a large storm surge. This favorable environment for large surge events is influenced by well-known modes of climate variability including El Niño, the Arctic Oscillation (AO), the North Atlantic Oscillation (NAO), and the Pacific–North American (PNA) pattern. ETCs are more likely to produce a large surge during El Niño conditions, which have been shown to enhance the East Coast storm track. At Boston and the Battery, maximum surge occurs preferentially during the positive phase of PNA and the negative phases of AO/NAO.

Radiocarbon dating of coastal boulders from Kouzushima and Miyake islands off Tokyo Metropolitan Area, Japan: Implications for coastal hazard risk

Over the last two decades, two giant tsunamis generated by earthquakes of approximately Mw 9 (the 2004 Sumatra–Andaman and 2011 Tohoku earthquakes), and a large storm surge associated with the 2013 Super Typhoon Haiyan, have caused catastrophic damage to infrastructure, property, and industry in many areas of the western Pacific. If we are to improve coastal hazard assessment for the Pacific coast of the southwestern Japanese mainland, a reconstruction of the history of tsunamis and storm surges during the late Holocene is required.This study surveyed coastal boulders to determine whether such events have previously affected the islands of Niijima, Shikinejima, Kouzushima, and Miyakejima that lie offshore from the Tokyo Metropolitan Area. Coastal boulders on Kouzushima and Miyakejima were found with marine organisms attached. Radiocarbon dating of these organisms indicates that the boulders were emplaced during the periods AD 1694–Modern and Modern, respectively. The boulder on Kouzushima (13.3 ton at 1.4 m ground elevation) was transported by historical tsunamis or severe storm surges, whereas the boulder on Miyakejima (33.4 ton at 7.1 m ground elevation) was probably transported by a storm surge associated with Typhoon 7920 in 1979. An emerged marine sessile assemblage on Miyakejima (2.31–3.06 m above mean sea-level (amsl)) was dated to ca. 3900–3500 years BP. This high relative sea-level can be explained by a mid-Holocene highstand and uplift associated with volcanic activity.

Evaluation of surface wind fields for prediction of directional ocean wave spectra during Hurricane Sandy

Hurricane Sandy was the largest storm on historical record in the Atlantic Ocean basin with extensive coastal damage caused by large waves and high storm surge. In this study, three different spatially-varying surface wind and atmospheric pressure fields that are used for forecasting or hindcasting hurricane waves on the continental shelf are investigated. These wind fields include two 2D parametric wind models (Holland model, H80; Generalized Asymmetric Holland Model, GAHM), and a 3D atmospheric model with data assimilation (WeatherFlow Regional Atmospheric Modelling System, WRAMS). These wind fields are used to drive wave hindcasts using coupled Delft3D-SWAN hydrodynamic and ocean wave models on a regional grid, and the bulk wave statistics and the directional wave spectra are compared to observations at offshore wave buoys to investigate the impact of differences between the complex wind fields on predictions of the sea surface evolution.The spatial and temporal distribution of bulk wave parameters are different for each wind field. The WRAMS wind field produces wave model predictions in the best agreement with significant wave height observations, followed by the GAHM and H80 wind fields, with mean correlation coefficients of 0.91, 0.82 and 0.75, respectively averaged over 9 sites. The directional wave spectra for Hurricane Sandy was bi-modal predominantly in the two left quadrants of the hurricane, in agreement with buoy observations. The results indicate that a regional atmospheric wind model that has the best description of the wind field is the most appropriate forcing for hindcasting hurricane waves when detailed observations are available. However a parametric vortex model that incorporates wind at multiple isotachs results in very good agreement with wave observations when used in the wave model, and is a useful too for forecasting hurricane sea surface conditions. The results of this study are relevant for other tropical cyclones that undergo extratropical transition or are influenced by other atmospheric disturbances at mid-latitudes, resulting in storms with large spatial size and high asymmetry.

Modeling of waves overtopping and flooding in the coastal reach by a non-hydrostatic model

This paper describes a model package that simulates wave transformation, overtopping and flooding in coastal reaches. The present model is extended from the non-linear shallow water equations by means of including the non-hydrostatic pressure terms in the momentum equations. The transformed vertical coordinate, i.e. the σcoordinate, is adopted to fit the free surface and the uneven bottom. When a wave is ready to break, the non-hydrostatic model is locally switched to hydrostatic model by suppressing the dispersive effects. The breaking wave front is handled as a shock, and the shock wave can be simulated by non-linear shallow water equations with conservative numerical strategy. The treatments of the wave breaking and the shoreline motion are validated by experiments. One extensive application of the model to predict flooding induced by large waves or storm surge is presented to verify the efficiency of the present model in modeling of wave transformation and flooding over complex geometry in coastal reaches.