Climate-induced storminess forces major increases in future storm surge hazard in the South China Sea region

It is vital to robustly estimate the risks posed by extreme sea levels, especially in tropical regions where cyclones can generate large storm surges and observations are too limited in time and space to deliver reliable analyses. To address this limitation for the South China Sea region, we force a hydrodynamic model with a new synthetic database representing 10,000 years of past/present and future tropical cyclone activity, to investigate climate change impacts on extreme sea levels forced by storm surges (± tides). We show that, as stronger and more numerous tropical cyclones likely pass through this region over the next 30 years, both the spatial extent and severity of storm surge hazard increases. While extreme storm surge events in this location become generally a more frequent occurrence in the future, larger storm surges around Vietnam and China coastlines are projected to regionally amplify this hazard. This threatens low-lying, densely-populated areas such as the Red and Mekong River deltas, while sections of the Cambodian and Thai coastline face previously unseen storm surge hazards. These future hazards strongly signal that coastal flood management and adaptation in these areas should be reviewed for their resilience against future extreme sea levels.

Impact of Human Intervention and Sea Level Rise on Water-Logging Scenarios inside Polders-24 And 25 of Bangladesh

Coastal region of Bangladesh possesses a fragile ecosystem and is exposed to hazards like cyclones, floods, storm surges, and water-logging. A detail understanding on the impact of water-logging due to various natural, man-made and climate change scenarios is still lacking. Considering this research gap, the present research is aimed to study impacts of these scenarios inside polders-24 and 25 which are situated on the western part of the coastal region. In this Study as natural scenario, sedimentation in the Hari River; as man-made scenario, new polders in the south-central region and as SLR scenario, an extreme sea level rise of 1.48m are considered. Long-term satellite images are analyzed, and numerical model is applied in the study area. The result shows that water-logging is more acute inside polder-25 compared to polder-24. Sedimentation in Hari River aggravates the water-logging condition. Dredging in Hari River does improve the situation. Journal of Engineering Science 12(3), 2021, 73-83

Accurate Storm Surge Prediction with a Parametric Cyclone and Neural Network Hybrid Model

Storm surges are one of the most devastating coastal disasters. Numerous efforts have continuously been made to achieve better prediction of storm surge variation. In this paper, we propose a parametric cyclone and neural network hybrid model for accurate, long lead-time storm surge prediction. The model was applied to the northeastern coastal region of Taiwan, i.e., Longdong station. A total of 14 historical typhoon events were used for model training and validation, and the results and questions associated with this hybrid approach carefully discussed. Overall, the proposed method reduced the complexity of network structure while retaining the important typhoon indicators. In particular, local pressure and winds estimated from the storm parameters through physically-based parametric cyclone models allow for inferring the possible future influence of a typhoon, unlike the simple collection and direct usage of observation data from local stations in earlier works. Meanwhile, the error-tolerance capability of the neural network alleviated some discrepancy in the model inputs and enabled good surge prediction. Further, the proposed method showed better and faster convergence thanks to the retention of storm information and the reduced dimensions of the search space. The hybrid model presented excellent performance or maintained reasonable capability for short lead-time and long lead-time storm surge prediction. Compared with the pure neural network model under the same network dimensions, the present model demonstrated great improvement in accuracy as the prediction lead time increased to 8 h, e.g., 33–40% (13–21%) and 32–37% (18–29%) RMSE and CE, respectively, in the training/validation phase.

A statistics and physics-based tropical cyclone full track model for catastrophe risk modeling

Catastrophe (CAT) risk modeling of perils such as typhoon and earthquake has become a prevailing practice in the insurance and reinsurance industry. The event generation model is the key component of the CAT modeling. In this paper, a physics-based tropical cyclone (TC) full track model is introduced to model typhoons events in the western North Pacific basin. At the same time, a comprehensive test of the model is presented from the perspective of CAT risk modeling for insurance and reinsurance applications. The full track model includes the genesis, track, intensity, and landing models. Driven by the global environmental circulations, the model employs the advection and beta drift theory in atmospheric dynamics to model the track of typhoons. The proposed model is novel in the way of modeling the genesis of TCs with three-dimension kernel distributions in space and time. This enables the simulation of seasonal characteristics of TCs. By generating 10,000-year TC events, we comprehensively test the model from the standpoint of CAT insurance and reinsurance applications. The typhoon hazard model and the generated events can serve as the inputs for assessing the typhoon risk and insured loss caused by winds, rains, floods, and storm surges.

Numerical simulation of storm surge associated with severe cyclonic storms in the Bay of Bengal during 2008-11

tc Hkh m".kdfVca/kh; pØokr vkrk gS rc Hkkjr vkSj blds fudVorhZ {ks=ksa esa rwQkuh leqnzh rjaxksa dh vkinkvksa ds dkj.k tku vkSj eky dh Hkkjh gkfu] rVh; <k¡pksa dh {kfr vkSj —f"k dks gkfu igq¡prh gSA uoEcj 1970 esa caxykns’k ¼igys iwohZ ikfdLrku½ esa vk, ,d vR;ar iapaM pØokr dh otg ls yxHkx 3]00]000 yksxksa dh tkus xbZaA uoEcj 1977 esa vkU/kz esa vk, pØokr us Hkkjr ds iwohZ rV dks rgl ugl dj fn;k ftlesa yxHkx 10]000 yksxksa dh tkus xbZaA vDrwcj 1999 esa Hkkjr ds mM+hlk ds rV ij ,d izpaM pØokrh rwQku vk;k ftlls ml {ks= esa laifRr dh vR;kf/kd gkfu gksus ds vfrfjDr 15]000 ls Hkh vf/kd yksxksa dh tkus xbZaA gky gh esa ebZ 2008 esa vk, pØokr uxhZl ls E;kaekj esa yxHk.k 1]40]000 yksxksa dh tkusa xbZa vkSj laifRr dk vR;f/kd ek=k esa uqdlku gqvkA ;s fo’o dh lcls cM+h ekuoh; vkink;sa eq[;r% m".kdfVca/kh; pØokrksa ls lac) gaS o leqnzh rwQkuh rjaxksa ls izR;{k:i ls tqMh gSA vr% ml {ks= esa laf{kIr iwokZuqeku vkSj leqnzh rwQkuh rjaxksa dh iwoZ psrkouh nsus dk izko/kku ml {ks= ds fgr esa gksrk gSA bl 'kks/k i= dk eq[; mÌs’; caxky dh [kkM+h vkSj vjc lkxj esa mBus okyh leqnzh rwQkuh rjaxksa dk iwokZuqeku djus ds fy, gky gh esa fodflr fd, x, ekWMyksa dks izdk’k esa ykuk gSA bl 'kks/k&i= esa o"kZ 2008 ls 2011 ds nkSjku caxky dh [kkM+h esa cus izpaM pØokrksa ls tqM+h leqnzh rjaxksa dk iwokZuqeku [email protected] djus esa fun’kZ ds fu"iknu dk Hkh mYys[k fd;k x;k gSA Storm surge disasters cause heavy loss of life and property, damage to the coastal structures and the losses of agriculture in India and its neighborhood whenever a tropical cyclone approaches. About 3,00,000 lives were lost in one of the most severe cyclone that hit Bangladesh (then East Pakistan) in November 1970. The Andhra Cyclone devastated the eastern coast of India, killing about 10,000 persons in November 1977. Orissa coast of India was struck by a severe cyclonic storm in October 1999, killing more than 15000 people besides enormous loss to the property in the region. More recently the Nargis cyclone of May 2008 killed about 1,40,000 people in Myanmar as well as caused enormous property damage. These and most of the world's greatest human disasters associated with the tropical cyclones have been directly attributed to storm surges. Thus, provision of precise prediction and warning of storm surges is of great interest in the region. The main objective of the present paper is to highlight the recent developments in storm surge prediction model for the Bay of Bengal and the Arabian Sea. Paper also describes the performance of the model in forecasting/simulating the surges associated with severe cyclones formed in the Bay of Bengal during 2008 to 2011.

Preparedness of recovery to the vulnerability of climate change in the coastal areas in Bangladesh

Purpose of the Study: This research aims to identify the susceptibility of Bangladesh's coastal areas to natural disasters related to climate change and raise vigilance in the region. Methodology: We have conducted a survey of farmers in eight coastal Unions to identify the impact of climate change and the ability to implement coping mechanisms and their family size and income level. Face-to-face interviews, in-depth case studies, and focus group discussions were carried out in the survey. We further summarized the effect and recent consequences of cyclones, the major disaster in the country that are followed by flooding. Main Findings: The finding of the study reveals that the shelters are insufficient to accommodate the dense population and will be a crowded space under the influence of COVID-19, further raising the vulnerability of those affected by a disaster. The coping mechanisms implemented were the storage of rainwater and groundwater and empowering women to produce dairy products and sustain the household income. The experts’ opinion to counteract the climate change was adaptation and mitigation. Since building resilience requires a fair budget and global support, we focused on adaption, considering three adaptive approaches: accommodation, protection, and retreat. Among those, considering the densely populated nature of Bangladesh, improving accommodation and protection were the feasible solution to be proposed. In conclusion, people's livelihood activities could be diversified by providing need-based training and motivations. Research Implications: One-fourth of the total population lives in the coastal areas in Bangladesh, which frequently faces tropical cyclones, storm surges, coastal erosion, and sea-level rise that cost enormous loss to the crops, livestock, forestry, and human selves. The biodiversity of the Sundarban, one of the most vulnerable ecosystems, is also at risk of those natural disasters. The novelty of the study: Climate change is posing major threats to Bangladesh's coast. This study's findings will help individuals recover from the effects of climate change and prepare for the future.

A DISPERSIVE LONG-WAVE MODEL FOR PREDICTING COASTAL FLOODING DUE TO STORM SURGES AND SURFACE WAVES IN MANILA BAY

Manila Bay is a shallow coastal water encompassing the urban areas of Metro Manila and variouscities of sub-urban provinces in the Philippines. It is a relatively shallow semi-enclosed basinwith an average depth of 20 m whose coastal areas are crowded with residential, industrial,agricultural, and aquaculture production. Its shallow depths imply that the effect of wind stress onsea level becomes appreciable in driving storm surges even during enhanced Southwest Monsoonand the passage of moderate storms.Using a dispersive long-wave model coupled with the significant wave model of the CoastalEngineering Research Center (CERC), the occurrence of potentially devastating storm surgeflooding around Manila Bay was numerically simulated. A unique characteristic of the new modelis the inclusion of the dispersive terms in the associated momentum balance equations. Deepwater gravity waves are always dispersive and inclusion of the dispersive terms is expected toprovide more accurate modelling results.The predictive capability of the model was verified using observations during the passage ofseveral storms including Typhoon Milenyo (2006) and Typhoon Pedring (2011). The occurrenceof the anomalously high storm surge of about 2.5 metres during the passage of Typhoon Pedringfar north of the area was correctly simulated. Numerical integration of the dispersive long-wavemodel with the addition of higher order terms in the momentum balance appears to give accuratepredictions of the coastal flooding due to storm surges and waves.The hydrodynamic set-down which occurs in many coastal areas during strong typhoons can besimulated well by the model. A new empirical model for the hydrodynamic force exerted by thecombined action of storm surges, waves, and extreme currents is also presented. Initial calculationsof hydrodydynamic forces generated by an actual typhoon crossing Manila Bay are discussed.

Assessment of building damages and adaptation options under extreme flood scenarios in Shanghai

Plenty of various measures have been taken to mitigate flood losses in Shanghai over thousands of years, including the construction of sea dikes and floodwalls. However, the combined effects of intensified rainstorms, sea-level rise, land subsidence, and rapid urbanization are exacerbating extreme flood risks and potential flood losses in the fast-developing coastal city. In light of these changes, this article presents an assessment of possible exposure and damage losses of buildings in Shanghai (including residential, commercial, workplace, and industrial buildings). Based on extreme flood scenarios caused by storm surges, precipitation, and fluvial floods, current flood-defence standards will soon be overtaken. Further analyses show that the inundation area could reach 9 %, 16 %, 24 %, and 49 % of Shanghai (excluding the area of islands) under the 1/200, 1/500, 1/1000, and 1/5000-year flooding scenarios, respectively. This study finds, in terms of the total building damage, the 1/5000-year flood scenario damage is more than ten times the 1/200-year flood scenario. Accordingly, the average annual loss (AAL) of residential, commercial, office, and industrial buildings are 13.9, 2.3, 5.3, and 3.9 million USD. Specifically, among the 15 (non-island) districts in Shanghai, Pudong has the highest exposure and AAL at all the four flood scenarios, while the inner city (including seven districts) is also subject to extreme AAL of up to 40 % of its total building values. This study further addresses the possibilities of these extreme flood scenarios, and adaptation options such as: strategic urban planning, advanced building protections, and systematic flood management. Conclusions of the study provide information for scenario-based decision making and cost-benefit analysis for extreme flood risk management in Shanghai and is applicable to other similar coastal megacities.