Simulation of water levels and extent of coastal inundation due to a cyclonic storm along the east coast of India

The devastation due to storm surge flooding caused by extreme wind waves generated by the cyclones is a severe apprehension along the coastal regions of India. In order to coexist with nature’s destructive forces in any vulnerable coastal areas, numerical ocean models are considered today as an essential tool to predict the sea level rise and associated inland extent of flooding that could be generated by a cyclonic storm crossing any coastal stretch. For this purpose, the advanced 2D depth-integrated (ADCIRC-2DDI) circulation model based on finite-element formulation is configured for the simulation of surges and water levels along the east coast of India. The model is integrated using wind stress forcing, representative of 1989, 1996, and 2000 cyclones, which crossed different parts of the east coast of India. Using the long-term inventory of cyclone database, synthesized tracks are deduced for vulnerable coastal districts of Tamil Nadu. Return periods are also computed for the intensity and frequency of cyclones for each coastal district. Considering the importance of Kalpakkam region, extreme water levels are computed based on a 50-year return period data, for the generation of storm surges, induced water levels, and extent of inland inundation. Based on experimental evidence, it is advocated that this region could be inundated/affected by a storm with a threshold pressure drop of 66 hpa. Also it is noticed that the horizontal extent of inland inundation ranges between 1 and 1.5 km associated with the peak surge. Another severe cyclonic storm in Tamil Nadu (November 2000 cyclone), which made landfall approximately 20 km south of Cuddalore, has been chosen to simulate surges and water levels. Two severe cyclonic storms that hit Andhra coast during 1989 and 1996, which made landfall near Kavali and Kakinada, respectively, are also considered and computed run-up heights and associated water levels. The simulations exhibit a good agreement with available observations from the different sources on storm surges and associated inundation caused by these respective storms. It is believed that this study would help the coastal authorities to develop a short- and long-term disaster management, mitigation plan, and emergency response in the event of storm surge flooding.     

The impact of extra-tropical transitioning on storm surge and waves in catastrophe risk modelling: application to the Japanese coastline

Catastrophe risk models are used to assess and manage the economic and societal impacts of natural perils such as tropical cyclones. Large ensembles of event simulations are required to generate useful model output. For example, to estimate the risk due to wind-driven storm surge and waves in tropical cyclone risk models, computationally efficient parametric representations of the wind forcing are required to enable the generation of large ensembles. This paper presents new results on the impact of including explicit representations of extra-tropical transitioning in parametric wind models used to force storm surge and wave simulations in a catastrophe risk modelling context. Extra-tropical transitioning is particularly important in modelling risk on the Japanese coastline, as roughly 40 % of typhoons hitting the Japanese mainland are transitioning before landfall. Using both a historical and idealized track set, we compare maximum storm surge and wave footprints along the Japanese coastline for models that include, and do not include, explicit representations of extra-tropical transitioning. We find that the inclusion of extra-tropical transitioning leads to lower storm surge (10–20 %) and waves (5–15 %) on the southern Japanese coast, with significantly higher storm surge and waves along the northern coast (25–50 %). The results of this paper demonstrate that useful risk assessment of coastal flood risk in Japan must consider the extra-tropical transitioning process.     

Vulnerability from storm surges and cyclone wind fields on the coast of Andhra Pradesh,India

The results presented here are from a study conducted for the government of the state of Andhra Pradesh (GOAP) in India, as part of a World Bank project on cyclone mitigation. A set of detailed maps were prepared depicting the Physical Vulnerability (PV), specifically storm surge inundation zones are shown for frequent occurrence, 50-year return period, likely scenario for global warming and extreme global warming. Similarly vulnerable areas from strong wind field from tropical cyclones (TCS) are also presented for the same four parameters. Vulnerability zones are presented from a social point of view also based upon certain socio-economic parameters that were included in determining the overall vulnerability of each Mandal in a coastal district (a Mandal represents a group of villages and towns) include: population, senior citizens, women, children under different age groups, type of housing, income level, cyclone shelters, hospitals and medical centres, schools and caste based population. The study is about scenarios that could happen if global warming and the predicted intensification of TCS actually occur as predicted by some numerical models.     

Cyclones and storm surges in Bangladesh: Some mitigative measures

Bangladesh, with its repeated cycle of floods, cyclones, and storm surges, has proved to be one of the most disaster-prone areas of the world. During the years from 1797 to 1991, Bangladesh has been hit by 60 severe cyclones (mostly accompanied by storm surges). This paper gives a brief account of these disasters with particular reference to the wind speed, surge height, loss of life, and damage to crops and properties, etc.In order to protect the coastal areas of Bangladesh from cyclonic storm surges and floods, a major system of embankments was constructed during the 1960s and 1970s, but this is now in need of rehabilitation. The Cyclone Protection Project, which was approved by the World Bank in 1989, would rehabilitate some of the existing embankments, build new embankments, and construct roads. Locally available materials, indigenous technology, and cheap surplus manpower should be used in this project. A variety of fruit trees should be planted along the dikes and roads.To the south-western part of Bangladesh bordering the Bay of Bengal, lies the world's largest single mangrove tract, known as the Sunderban, which covers a total area of 571 500 ha. This mangrove forest is of extreme importance since it provides efficient protection to life and property against cyclones and storm surges. But due to deforestation, the width of the mangrove belt is being rapidly diminished. The author therefore lays emphasis on coastal afforestation.Absolute security against cyclone hazard is probably out of the question, but an effective cyclone warning response can definitely reduce loss of life and damage to property. The author discusses the current conditions for cyclone forecasting and warning in Bangladesh, and then puts forward some proposals for improving the Cyclone Preparedness Programme.     

Classification of cyclone hazard prone districts of India

Hazards associated with tropical cyclones are long-duration rotatory high-velocity winds, very heavy rain and storm tide. India has a coastline of about 7,516?km of which 5,400?km is along the mainland. The entire coast is affected by cyclones with varying frequency and intensity. The India Meteorological Department (IMD) is the nodal government agency that provides weather services related to cyclones in India. However, IMD has not identified cyclone-prone districts following any specific definition though the districts for which cyclone warnings are issued have been identified. On the other hand, for the purpose of better cyclone disaster management in the country, it is necessary to define cyclone proneness and identify cyclone-prone coastal districts. It is also necessary to decide degree of hazard proneness of a district by considering cyclone parameters so that mitigation measures are prioritised. In this context, an attempt has been made to prepare a list of cyclone hazard prone districts by adopting hazard criteria. Out of 96 districts under consideration, 12, 45, 31 and 08 districts are in very high, high, moderate and low categories of proneness, respectively. In general, the coastal districts of West Bengal, Orissa, Andhra Pradesh and Tamil Nadu are more prone and are in the high to very high category. The cyclone hazard proneness factor is very high for the districts of Nellore, East Godawari, and Krishna in Andhra Pradesh; Yanam in Puducherry; Balasore, Bhadrak, Kendrapara and Jagatsinghpur in Orissa; and South and North 24 Parganas, Medinipur and Kolkata in West Bengal. The results give a realistic picture of degree of cyclone hazard proneness of districts, as they represent the frequency and intensity of land falling cyclones along with all other hazards like rainfall, wind and storm surge. The categorisation of districts with degree of proneness also tallies with observed pictures. Therefore, this classification of coastal districts based on hazard may be considered for all the required purposes including coastal zone management and planning. However, the vulnerability of the place has not been taken into consideration. Therefore, composite cyclone risk of a district, which is the product of hazard and vulnerability, needs to be assessed separately through detailed study.     

Developments in storm tide modelling and risk assessment in the Australian region

An overview is provided of some of the significant storm tide modelling and risk assessment studies undertaken over the past few years within Australia and the nearby oceanic regions for government and industry. Emphasis is placed on the need for integrated planning and forecasting approaches for storm tide risk assessment. The importance of the meteorological forcing and the appropriate modelling of each of the storm tide components, namely, astronomical tide, storm surge, breaking wave setup and coastal inundation is discussed. The critical role of tropical cyclone “best track” datasets for risk assessment studies and the potential impacts on design criteria and risk assessment studies is highlighted, together with the challenge of developing credible enhanced-greenhouse climate change scenarios. It is concluded that storm tide modelling needs to be undertaken in a holistic framework that considers the relative uncertainties in each of the various elements—atmospheric, hydrodynamic and data, as well as addressing operational forecasting, design and planning needs.     

The Tropical Cyclone Risk in Cairns

Because of its location close to a region of tropical cyclone formation, the city ofCairns is regularly affected by tropical cyclones. Most cyclones occur in the monthsJanuary–March, although some have affected Cairns in December and April. There is a strong year-to-year variation in tropical cyclone numbers in the Cairns region, with twice as many impacts occurring during La Niña conditions than during El Niño. Several case studies are presented of cyclone impacts on Cairns. Rapidly developing cyclones are a particularly difficult forecast problem, as they can strike the city with less than 24 hours warning. Serious inundation from storm surge often occurs some time after landfall at Cairns.     

Classifying inundation limits in SE coast of India: application of GIS

A study on the possible inundation limit in SE coast of India was carried out using various physical, geological and satellite imageries. The coastal inundation hazard map was prepared for this particular region as it was affected by many cyclones, flooding, storm surge and tsunami waves during the last six decades. The results were generated using various satellite data (IRS-P6 LISS3; LANDSAT ETM; LANDSAT-5 ETM; LANDSAT MSS) and digital elevation models (ASTER GLOBAL DEM), and a coastal vulnerability index was generated for the entire coastal stretch of Nagapattinam region in SE coast of India. The coastal area which will be submerged totally due to a 1–5 m rise in water level due to any major natural disaster (tsunami or cyclone) indicates that 56–320 km² will be submerged in this particular region. The results suggest that nearly 7 towns and 69 villages with 667,477 people will be affected and indicate that proper planning needs to be done for future development.     

Extremity analysis of storm surge for fixing safe design water level

Phenomenal storm surge levels associated with cyclones are common in East Coast of India. The coastal regions of Andhra Pradesh are in rapid stride of myriad marine infrastructural developments. The safe elevations of coastal structures need a long-term assessment of storm surge conditions. Hence, past 50 years (1949–1998), tropical cyclones hit the Bay are obtained from Fleet Naval Meteorological & Oceanographic Center, USA, and analyzed to assess the storm surge experienced around Kakinada and along south Andhra Pradesh coast. In this paper, authors implemented Rankin Hydromet Vortex model and Bretschneider’s wind stress formulation to hindcast the surge levels. It is seen from the hindcast data that the November, 1977 cyclone has generated highest surge of the order of 1.98 m. Extreme value analysis is carried out using Weibull distribution for long-term prediction. The results reveal that the surge for 1 in 100-year return period is 2.0 m. Further the highest surge in 50 years generated by the severe cyclone (1977) is numerically simulated using hydrodynamic model of Mike-21. The simulation results show that the Krishnapatnam, Nizampatnam and south of Kakinada have experienced a surge of 1.0, 1.5 and 0.75 m, respectively.     

Tropical cyclone risk perceptions in Darwin,Australia: a comparison of different residential groups

Different individuals and groups perceive risk differently. This can significantly affect risk management and mitigation practices and requirements. This paper presents findings from a study of tropical cyclone risk perceptions in the city of Darwin in the Northern Territory of Australia. Primary in-depth interview data and other secondary data are analysed, focussing in particular on wind damage, storm surge and life safety risk perceptions of residents since Cyclone Tracy, which impacted in 1974, and perceptions of future climate change as it relates to tropical cyclone risk. The analysis reveals that a number of perceptions prevail. In particular, the study reveals a wide difference of perceptions between short-term residents (Group 1) and long-term and expert residents (Group 2) in relation to wind damage, storm surge and life safety risk. It also reveals a large division between laypersons (Group 3) and expert residents’ (Group 4) perceptions of climate change risk as it relates to tropical cyclone risk. The author recommends that flexible, multiple and integrative management and mitigation approaches are required to deal with such different perceptions and divisions in the resident population.     

Storm Surge Hazard in Canada

Storm surges occur frequently in Canada mainlydue to extra-tropical cyclones (ETC'S) also referred to as winter storms. The hurricanes from the Gulf of Mexico can affect eastern Canada including Lakes Ontario and Erie regions, after they get modified and acquire some extra-tropical characteristics. Storm surges have occurred both on the Atlantic and Pacific coasts, in the Gulf of St.Lawrence, St.Lawrence Estuary, Bay of Fundy, Hudson Bay, James Bay, Northwest Passage, Beaufort Sea, the Great Lakes and other large lakes such as Lake Winnipeg.Squall lines which are embedded in the largerscale synoptic systems like the ETC'S could also generate storm surges (referred to as edge waves) in Lakes Huron, Erie and Ontario (edge waves are most prominent in Lake Michigan, but Canada has no territory touching this lake). The effect of climate change on storm surges in the Canadian water bodies could be two-fold. First, there may be some possible intensification of the weather systems and the associated wind fields resulting in bigger surges. Second, and probably even more relevant, is an east-west and north-south shift in the tracks of the weather systems, which could expose certain new areas to storm surge activity.A high priority for proper assessment of storm surge hazard is the production of maps showing inundation zones for storm surges that might occur in populated coastal areas. Such maps can be used to improve public awareness of tsunamis and for planning purposes (i.e., to reduce or avoid the risk).     

Impact of cyclonic wind field on interaction of surge–wave computations using finite-element and finite-difference models

Both finite-element and finite-difference numerical models are applied to simulate storm surges and associated currents generated by tropical cyclones that struck the coast of Andhra Pradesh, located on the east coast of India. During a cyclone, the total water level at any location on the coast is made up of the storm surge, surge–wind wave interaction and the tide. The advanced circulation two-dimensional depth-integrated (ADCIRC-2DDI) model based on finite-element formulation and the two-dimensional finite-difference model of storm surges developed at IIT Delhi, hereafter referred as IITD storm surge model, are used. These models are driven by astronomical tides at the open ocean boundary and cyclonic asymmetric winds over the surface of the computational domain. Comparison of model simulated sea-surface elevations with coarse and finer spatial resolutions suggests that the grid resolution near the coast is very crucial for accurate determination of the surges in addition to the local bathymetry. The model underpredicts surges, and the peak surge location shifts more to the right of the landfall as the spatial resolution of the model becomes coarser. The numerical experiments also demonstrate that the ADCIRC model is robust over the IITD storm surge model for surge computations as the coastline is better represented in the former.     

Evaluation of coastal inundation hazard for present and future climates

Coastal inundation from hurricane storm surges causes catastrophic damage to lives and property, as evidenced by recent hurricanes including Katrina and Wilma in 2005 and Ike in 2008. Changes in hurricane activity and sea level due to a warming climate, together with growing coastal population, are expected to increase the potential for loss of property and lives. Current inundation hazard maps: Base Flood Elevation maps and Maximum of Maximums are computationally expensive to create in order to fully represent the hurricane climatology, and do not account for climate change. This paper evaluates the coastal inundation hazard in Southwest Florida for present and future climates, using a high resolution storm surge modeling system, CH3D-SSMS, and an optimal storm ensemble with multivariate interpolation, while accounting for climate change. Storm surges associated with the optimal storms are simulated with CH3D-SSMS and the results are used to obtain the response to any storm via interpolation, allowing accurate representation of the hurricane climatology and efficient generation of hazard maps. Incorporating the impact of anticipated climate change on hurricane and sea level, the inundation maps for future climate scenarios are made and affected people and property estimated. The future climate scenarios produce little change to coastal inundation, due likely to the reduction in hurricane frequency, except when extreme sea level rise is included. Calculated coastal inundation due to sea level rise without using a coastal surge model is also determined and shown to significantly overestimate the inundation due to neglect of land dissipation.     

渤海湾西部风暴潮漫滩数值模拟

基于ROMS海洋模式,结合近年的地质实测资料,建立了渤海湾西部地区风暴潮漫滩的数值模型。对模型进行验证后,对渤海湾西部区域重现期为50a、100a、200a及500a的风暴潮漫滩进行了数值模拟,分析了不同重现期风暴潮漫滩发展的动态过程及最大漫滩淹水范围。结果表明,数值模型基本能反映风暴潮的增水趋势,能够模拟风暴潮漫滩发生发展的动态过程。随着风暴潮强度的增加,渤海湾西部地区淹水范围具有从东海岸向西部内陆区域扩展的趋势。通过曲线拟合发现,风暴潮最大漫滩面积比值与高水位之间基本呈线性关系。     

Community-based disaster risk and vulnerability models of a coastal municipality in Bangladesh

Bangladesh is one of the most natural hazard-prone countries in the world with the greatest negative consequences being associated with cyclones, devastating floods, riverbank erosion, drought, earthquake, and arsenic contamination, etc. One way or other, these natural hazards engulfed every corner of Bangladesh. The main aim of this research paper is to carry out a multi-hazards risk and vulnerability assessment for the coastal Matlab municipality in Bangladesh and to recommend possible mitigation measures. To this aim, hazards are prioritized by integrating SMUG and FEMA models, and a participation process is implemented so as to involve community both in the risk assessment and in the identification of adaptation strategies. The Matlab municipality is highly vulnerable to several natural hazards such as cyclones, floods, and riverbank erosion. The SMUG is a qualitative assessment, while FEMA is a quantitative assessment of hazards. The FEMA model suggests a threshold of highest 100 points. All hazards that total more than 100 points may receive higher priority in emergency preparedness and mitigation measures. The FEMA model, because it judges each hazard individually in a numerical manner, may provide more satisfying results than the SMUG system. The spatial distributions of hazard, risk, social institutions, land use, and other resources indicate that the flood disaster is the top environmental problem of Matlab municipality. Hazard-specific probable mitigation measures are recommended with the discussion of local community. Finally, this study tries to provide insights into the way field research combining scientific assessments tools such as SMUG and FEMA could feed evidence-based decision-making processes for mitigation in vulnerable communities.     

Impact of Sea-level Rise and Storm Surges on a Coastal Community

A technique to evaluate the risk of storm tides (the combination of a storm surge and tide) under present and enhanced greenhouse conditions has been applied to Cairns on the north-eastern Australian coast. The technique combines a statistical model for cyclone occurrence with a state-of-the-art storm surge inundation model and involves the random generation of a large number of storm tide simulations. The set of simulations constitutes a synthetic record of extreme sea-level events that can be analysed to produce storm tide return periods. The use of a dynamic storm surge model with overland flooding capability means that the spatial extent of flooding is also implicitly modelled. The technique has the advantage that it can readily be modified to include projected changes to cyclone behaviour due to the enhanced greenhouse effect. Sea-level heights in the current climate for return periods of 50, 100, 500 and 1000 years have been determined to be 2.0 m, 2.3 m, 3.0 m and 3.4 m respectively. In an enhanced greenhouse climate (around 2050), projected increases in cyclone intensity and mean sea-level see these heights increase to 2.4 m, 2.8 m, 3.8 m and 4.2 m respectively. The average area inundated by events with a return period greater than 100 years is found to more than double under enhanced greenhouse conditions.     

Dynamic analysis of emergency inter-organizational communication network under public health emergency: a case study of COVID-19 in Hubei Province of China

Storm surge induced by hurricane is a major threat to the Gulf Coasts of the United States. A numerical modeling study was conducted to simulate the storm surge during Hurricane Michael, a category 5 hurricane that landed on the Florida Panhandle in 2018. A high-resolution model mesh was used in the ADCIRC hydrodynamic model to simulate storm surge and tides during the hurricane. Two parametric wind models, Holland 1980 model and Holland 2010 model, have been evaluated for their effects on the accuracy of storm surge modeling by comparing simulated and observed maximum water levels along the coast. The wind model parameters are determined by observed hurricane wind and pressure data. Results indicate that both Holland 1980 and Holland 2010 wind models produce reasonable accuracy in predicting maximum water level in Mexico Beach, with errors between 1 and 3.7%. Comparing to the observed peak water level of 4.74 m in Mexico Beach, Holland 1980 wind model with radius of 64-knot wind speed for parameter estimation results in the lowest error of 1%. For a given wind model, the wind profiles are also affected by the wind data used for parameter estimation. Away from hurricane eye wall, using radius of 64-knot wind speed for parameter estimation generally produces weaker wind than those using radius of 34-knot wind speed for parameter estimation. Comparing model simulated storm tides with 17 water marks observed along the coast, Holland 2010 wind model using radius of 34-knot wind speed for parameter estimation leads to the minimum mean absolute error. The results will provide a good reference for researchers to improve storm surge modeling. The validated model can be used to support coastal hazard mitigation planning.