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The actions of wind and atmospheric pressure associated with tropical cyclones (e.g. typhoons) are considered the primary factors behind the generation of storm surges, though the fields used in meteorological models can sometimes deviate from observations. To improve these, the direct modification method (DMM) has been previously proposed, though this only modifies the wind field of a typhoon, and further development is necessary for applying it to storm surge hindcasts. The present work describes the development of a semi-empirical gradient wind balance-based method (GWB-M) for modifying both the wind and pressure fields in meteorological models, based on the dynamic relationship between the wind and pressure in typhoons (i.e. gradient wind balance). The applicability of GWB-M was assessed through a storm surge hindcast based on Typhoon Faxai in 2019, which generated powerful waves and a storm surge at Tokyo Bay. GWB-M improved the time series of 10 m wind speed and sea level pressure, with their spatial distributions being more realistic than those in DMM and blending parametric typhoon models (BM), which cannot take into account the influence of the complex topography around Tokyo Bay. Further, the maximum sea level anomalies after the typhoon made landfall were also captured by GWB-M with a higher accuracy than DMM. [ABSTRACT FROM AUTHOR]

Haiyan in 2013 was one of the most powerful typhoons to have affected the Philippines, devastating in its path a wide portion of Leyte, and causing extensive damage to structures in Tacloban City. To understand the likely impacts that would be exerted by a storm surge on a structure deemed important, the authors used a coupled model that hindcasted the flooding that took place during Haiyan. This coupled model included the use of the Weather Research and Forecasting (WRF) Model (with Bogussing scheme) to simulate the atmospheric conditions during the passage of Haiyan, the Finite Volume Coastal Ocean Model (FVCOM) to simulate the storm surge and obtain the boundary conditions for the wind and flood (hydrostatic, hydrodynamic, and breaking wave), and the Structural Analysis and Designing Program (STAAD.Pro) to calculate the corresponding axial, shear, and bending moment envelopes based on the storm surge simulation. A 4-floor public school building in Tacloban was modeled and the effects that the storm surge would have on a corner column were analyzed. Based on the results, the axial, shear, and moment at the corner column significantly increased when considering flood loads, indicating the importance of including such loads in the design of essential structures. [ABSTRACT FROM AUTHOR]

The object of the present study is to numerically evaluate the characteristics of future potential typhoons and storm surges around Tokyo Bay under a RCP8.5 scenario usinga simple one-way model system composed of ARW-WRF and FVCO. In order to evaluate the effect of the expected future increase in sea surface temperature (SST), air temperature (AT) and relative humidity (RH) four types of cases were considered in the 2041–2060 and 2081–2100 horizons. The results show how higher SST will likely lead to more intense typhoons and storm surges, though higher AT in troposphere and tropopause will somehow moderate this effect. In addition, a simple method to estimate the most influential wind direction that can generate surge elevations in Yokohama, Tokyo and Funabashi was examined by using the results of a numerical simulation. Finally, a simple methodology to calculate the required design height of sea walls and dykes in Tokyo Bay was developed, which shows how current design levels will be insufficient to maintain the present acceptable risk levels in the area. [ABSTRACT FROM AUTHOR]

On the 22nd of December 2018 the shorelines of Sunda Strait, Indonesia, were hit by tsunami waves generated by the flank collapse of the Anak Krakatau volcano. The authors conducted a field survey of the affected areas in both Sumatra and Java islands to collect information on tsunami inundation and run-up heights, damage patterns at each coastal community, and the evacuation behaviour and tsunami awareness of the affected people. The survey results showed that in Sumatra island inundation heights of more than 4 m were measured along the coastline that was situated to the north-north-east of Anak Krakatau, while less than 4 m were measured along the north-western direction. Inundation heights of over 10 m were measured at Cipenyu Beach (Pandeglang Regency) in Java island (south-south-eastern direction from Anak Krakatau). A questionnaire survey conducted by the authors revealed residents' perception of danger and evacuation patterns during the event. The results indicate the importance of having an operational tsunami warning system in Sunda Strait and the establishment of an appropriate evacuation plan so that residents can start evacuation immediately and reach a safe place without facing severe congestion along evacuation routes. [ABSTRACT FROM AUTHOR]

The present work evaluates potential future typhoon and storm surges around the islands of Samar and Leyte in the Philippines taking into account monthly mean sea surface temperatures, atmospheric air temperature, and relative humidity (hereafter, SST, AAT, and RH) from MIROC5 according to four scenarios proposed by IPCC AR5. Super-typhoon Haiyan (2013), which caused catastrophic damage to coastal areas in the Philippines due to its high winds and storm surge, was used as the case study storm given that it was one of the tropical cyclones recorded in modern history. In this study, the Advanced Research Weather Research and Forecasting Model (ARW-WRF) is used to estimate the characteristics of both the present-day Haiyan and a typhoon with a similar return period under the climate condition of the year 2100. The unstructured, Finite Volume Community Ocean Model (FVCOM) was used to estimate both the present and potential future storm surges. The research has two main focuses. First, both the historical event and its storm surge are simulated and contrasted with field measurements of the storm surge height in order to prove the accuracy of the model. Second, the future typhoon and storm surge are estimated using the monthly mean value differences in SST, AAT, and RH from MIROC5 between 2011-2020 and 2091-2100 for the different scenarios. The characteristics of the simulated typhoon route and storm surge heights agree well with those of the best track data and field measurements. The numerical results of the future typhoon show that, if climate change is considered to only increase SST, its intensity and storm surge will be larger than under the present climate. The minimum sea-level pressure (hereafter, MSLP) of the future typhoon under scenario RCP 8.5 would be about 21 hPa lower and the storm surge 2.7 m higher than in the present climate. However, if SST, AAT, and RH are also taken into account, then the increase in typhoon intensity will not be as marked as if only SST is considered, with the MSLP under RCP 8.5 decreasing only by 13 hPa and the storm surge increasing by 0.7 m. The results of the present research thus suggest that while increases in SST can contribute to the intensification of future typhoons, increases in AAT and RH will somehow moderate this effect. Nevertheless, all scenarios considered point out to stronger typhoons and higher storm surges, clearly highlighting the perils posed by future climate change. [ABSTRACT FROM AUTHOR]

Category 5 Typhoon Haiyan was one of the strongest typhoons to hit the Philippines in modern times, and introduced the term 'storm surge' to the vocabulary of many local residents, who had not heard about such phenomena prior to this event. The storm surge manifested itself on the 8th November 2013 as Haiyan made landfall, devastating large areas in the islands of Leyte and Samar. To attempt to gain an understanding of the level of awareness that local residents had about storm surges the authors conducted structured questionnaires () and focus group interviews with local residents, and discussed the results obtained with key informants (government officers and disaster risk managers). One of the key problems identified during the interviews was how people were not able to clearly understand the concept of a storm surge, with many respondents emphasizing how it would have been better for authorities to describe it as a 'tsunami'. A discussion is also made on the recent evolution in world-wide coastal disaster awareness, comparing it to recent developments in storm surge awareness in the Philippines and other countries in the area, such as Vietnam and Japan. The authors conclude that, in terms of its influence on world-wide disaster awareness, typhoon Haiyan constitutes an event of similar importance to major recent high-impact tsunami events such as the 2004 Indian Ocean and 2011 Tohoku events. As a result, the authors will outline a number of lessons learnt from Haiyan, such as the necessity for creating multi-layer safety strategies and improving how information about storm surges is transmitted to local residents. [ABSTRACT FROM AUTHOR]

Typhoon Haiyan (Yolanda) struck the islands of Leyte and Samar, the central part of the Philippines, on 8 November 2013, bringing large-scale devastation to coastal areas due to the high winds and large storm surge and waves associated with it. In order to obtain the distribution of storm surge heights and damage covering the wide stretch of affected coastline, the authors carried out a series of field surveys in the aftermath of the typhoon (in December 2013, May 2014, and October 2014). In the present paper, the authors detailed the results of these field surveys and summarized the characteristics of the storm surge and main causes of the damage, especially focusing on the Leyte Gulf coast, which is surrounded by the eastern coast of Leyte and the southern coast of Samar. Finally, the wide range of types of storm surge disasters were also discussed by comparing Typhoon Haiyan with other recent major events. [ABSTRACT FROM AUTHOR]

Sea level rise and an increase in typhoon intensity are two of the expected consequences from future climate change. In the present work, a methodology to change the intensity of tropical cyclones in Japan was developed, which can be used to assess the inundation risk to different areas of the country. As a result, the probability of a storm with an equivalent return period in the year 2100 to that of the worst storm in the 20th century overcoming sea defences around Tokyo Bay could be calculated. The risk of higher storm surges, coupled with different sea-level-rise scenarios, highlights how the dykes around Tokyo or Kawasaki could fail unless adaptation measures against climate change are attempted. The cost of adapting to both of these effects by building higher coastal dykes and raising port areas outside them was quantified. Finally, an estimation of the cost of allowing the areas behind the defences to be flooded was also made, clearly showing that the cost of adaptation measures is clearly lower than the cost of inaction. [ABSTRACT FROM AUTHOR]

Storm surges are one of the most important risks to coastal communities around the Bay of Bengal, and it is feared that the threat they pose will increase with climate change in the future. To understand the threats that these events pose, a summary of the field surveys performed in Yangon River Basin after cyclone Nargis in Myanmar in 2008 is presented. Though due to government restrictions survey activities were limited to the area near Yangon city, it was found out that the tide due to the storm surge was probably between 3 and 4 m high and travelled around 50 km upstream of the river mouth of Yangon River. Cyclone Nargis could be accurately reproduced using a numerical model that integrated weather, wave, coastal ocean models, and tide prediction system. The application of such an integrated model is relatively new for storm surge simulation and has never been used for the Bay of Bengal storms. The model was then used to also simulate future cyclones over the Bay of Bengal considering a future climate change scenario. [ABSTRACT FROM AUTHOR]

Typhoon Jebi struck Japan on the 4 September 2018, damaging and inundating many coastal areas along Osaka Bay due to the high winds, a storm surge, and wind driven waves. In order to understand the various damage mechanisms, the authors conducted a field survey two days after the typhoon made landfall, measuring inundation heights and depths at several locations in Hyogo Prefecture. The survey results showed that 0.18–1.27 m inundation depths were caused by Typhoon Jebi. As parts of the survey, local residents were interviewed about the flooding, and a questionnaire survey regarding awareness of typhoons and storm surges, and their response to the typhoon was distributed. The authors also mapped the location of some of the containers that were displaced by the storm surge, aiming to provide information to validate future simulation models of container displacement. Finally, some interesting characteristics of the storm surge are summarized, such as possible overtopping at what had initially been thought to be a low risk area (Suzukaze town), and lessons learnt in terms of disaster risk management are discussed. [ABSTRACT FROM AUTHOR]

The present paper examines the impact of floodwater caused by the storm surge brought about by Typhoon Haiyan in 2013, focusing on downtown Tacloban in Leyte Island, the Philippines. A reliable numerical model for predicting such flooding was developed by calibrating the results of field investigations, including footage from a video clip taken during the storm surge. The simulation reveals that flow velocities along the streets in downtown Tacloban reached up to 7 m/s due to flow contraction along the high-density blocks of houses, and how water levels reached their peak in just 10 min. According to the depth–velocity product criteria, often used for evaluating the vulnerability of people and buildings to floodwaters, only 8% of the length of streets in downtown Tacloban were within the safe limits that allow pedestrian evacuation. Based on these findings, the present research concludes that pedestrian evacuation in the middle of a storm surge generated by a strong typhoon is a high - risk behavior . Thus, clearly and objectively, evacuation during this time should not be encouraged, even when seawater intrudes the houses of local residents. In this respect, it would appear imperative that prior to the arrival of the typhoon all residents should evacuate areas at risk of being flooded. Though the flood height was significant in the downtown area, the damage to these houses was limited. If it was not possible for some reason to evacuate prior to the arrival of the typhoon, those in solid houses should first consider vertical evacuation and the possibility that they could survive in their place, rather than courageously evacuating in an unpredictable water flow. [ABSTRACT FROM AUTHOR]