Wave Hazard Research Articles

Automated Sensing of Wave Inundation across a Rocky Shore Platform Using a Low-Cost Camera System

Rocky coastlines are frequently used for recreation, however, they are often highly exposed and hazardous environments resulting in high risk to visitors. Traditional approaches to managing human safety in coastal settings (such as the surf lifesaving clubs that have proven effective on beaches) are not necessarily transferable to rock platforms due to their often remote and fragmented distribution and the different recreational uses. As such, a different approach is required. To address this, we present a low-cost camera system to assess the wave hazard on a high-visitation rocky shore platform: the Figure Eight Pools Rock Platform, New South Wales, Australia. The camera system is shown to be highly effective and allows identification of both the distance and frequency of wave inundation on the platform using a novel pixel analysis technique. Nearshore wave height is shown to be the primary factor driving inundation frequencies along the cross-platform transect investigated with some influence from wave period. The remotely sensed camera data are used to develop a preliminary overwash hazard rating system, and analysis of the first month of data collected suggests that the platform is highly hazardous to visitors. Future work will expand this hazard rating system, developing a predictive tool that estimates the overwash hazard level based on forecast wave and tide conditions to improve visitor safety at the site.

Extreme Wave-Induced Oscillation in Paradip Port Under the Resonance Conditions

A mathematical model is constructed to analyze the long wave-induced oscillation in Paradip Port, Odisha, India under the resonance conditions to avert any extreme wave hazards. Boundary element method (BEM) with corner contribution is utilized to solve the Helmholtz equation under the partial reflection boundary conditions. Furthermore, convergence analysis is also performed for the boundary element scheme with uniform and non-uniform discretization of the boundary. The numerical scheme is also validated with analytic approximation and existing studies based on harbor resonance. Then, the amplification factor is estimated at six key record stations in the Paradip Port with multidirectional incident waves and resonance modes are also estimated at the boundary of the port. Ocean surface wave field is predicted in the interior of Paradip Port for the different directional incident wave at various resonance modes. Moreover, the safe locations in the port have been identified for loading and unloading of moored ship with different resonance modes and directional incident waves.

Humid heat waves at different warming levels

The co-occurrence of consecutive hot and humid days during a heat wave can strongly affect human health. Here, we quantify humid heat wave hazard in the recent past and at different levels of global warming. We find that the magnitude and apparent temperature peak of heat waves, such as the ones observed in Chicago in 1995 and China in 2003, have been strongly amplified by humidity. Climate model projections suggest that the percentage of area where heat wave magnitude and peak are amplified by humidity increases with increasing warming levels. Considering the effect of humidity at 1.5° and 2° global warming, highly populated regions, such as the Eastern US and China, could experience heat waves with magnitude greater than the one in Russia in 2010 (the most severe of the present era). The apparent temperature peak during such humid-heat waves can be greater than 55 °C. According to the US Weather Service, at this temperature humans are very likely to suffer from heat strokes. Humid-heat waves with these conditions were never exceeded in the present climate, but are expected to occur every other year at 4° global warming. This calls for respective adaptation measures in some key regions of the world along with international climate change mitigation efforts.

Public crowdsensing of heat waves by social media data

Abstract. Investigating on society-related heat wave hazards is a global issue concerning the people health. In the last two decades, Europe experienced several severe heat wave episodes with catastrophic effects in term of human mortality (2003, 2010 and 2015). Recent climate investigations confirm that this threat will represent a key issue for the resiliency of urban communities in next decades. Several important mitigation actions (Heat-Health Action Plans) against heat hazards have been already implemented in some WHO (World Health Organization) European region member states to encourage preparedness and response to extreme heat events. Nowadays, social media (SM) offer new opportunities to indirectly measure the impact of heat waves on society. Using the crowdsensing concept, a micro-blogging platform like Twitter may be used as a distributed network of mobile sensors that react to external events by exchanging messages (tweets). This work presents a preliminary analysis of tweets related to heat waves that occurred in Italy in summer 2015. Using TwitterVigilance dashboard, developed by the University of Florence, a sample of tweets related to heat conditions was retrieved, stored and analyzed for main features. Significant associations between the daily increase in tweets and extreme temperatures were presented. The daily volume of Twitter users and messages revealed to be a valuable indicator of heat wave impact at the local level, in urban areas. Furthermore, with the help of Generalized Additive Model (GAM), the volume of tweets in certain locations has been used to estimate thresholds of local discomfort conditions. These city-specific thresholds are the result of dissimilar climatic conditions and risk cultures.

Urban heat wave hazard and risk assessment

Abstract Heat waves are one of the largest causes of environmentally-related deaths globally. The intensification of the effects of heat waves by the urban heat island during extended periods of extreme heat, combined with urban demographics, are key elements leading to these disasters and are likely to become more numerous as a result of climate change. Climatological weather station data, moderate resolution thermal imagery from Earth-orbiting satellites, and demographic information for selected cities were use in this research to develop a heat wave risk product as a potential warning tool for public health decision makers and the general public.

Reservoir-induced landslides and risk control in Three Gorges Project on Yangtze River, China

The Three Gorges region in China was basically a geohazard-prone area prior to construction of the Three Gorges Reservoir (TGR). After construction of the TGR, the water level was raised from 70 m to 175 m above sea level (ASL), and annual reservoir regulation has caused a 30-m water level difference after impoundment of the TGR since September 2008. This paper first presents the spatiotemporal distribution of landslides in six periods of 175 m ASL trial impoundments from 2008 to 2014. The results show that the number of landslides sharply decreased from 273 at the initial stage to less than ten at the second stage of impoundment. Based on this, the reservoir-induced landslides in the TGR region can be roughly classified into five failure patterns, i.e. accumulation landslide, dip-slope landslide, reversed bedding landslide, rockfall, and karst breccia landslide. The accumulation landslides and dip-slope landslides account for more than 90%. Taking the Shuping accumulation landslide (a sliding mass volume of 20.7 × 106 m3) in Zigui County and the Outang dip-slope landslide (a sliding mass volume of about 90 × 106 m3) in Fengjie County as two typical cases, the mechanisms of reactivation of the two landslides are analyzed. The monitoring data and factor of safety (FOS) calculation show that the accumulation landslide is dominated by water level variation in the reservoir as most part of the mass body is under 175 m ASL, and the dip-slope landslide is controlled by the coupling effect of reservoir water level variation and precipitation as an extensive recharge area of rainfall from the rear and the front mass is below 175 m ASL. The characteristics of landslide-induced impulsive wave hazards after and before reservoir impoundment are studied, and the probability of occurrence of a landslide-induced impulsive wave hazard has increased in the reservoir region. Simulation results of the Ganjingzi landslide in Wushan County indicate the strong relationship between landslide-induced surge and water variation with high potential risk to shipping and residential areas. Regarding reservoir regulation in TGR when using a single index, i.e. 1-d water level variation, water resources are not well utilized, and there is also potential risk of disasters since 2008. In addition, various indices such as 1-d, 5-d, and 10-d water level variations are proposed for reservoir regulation. Finally, taking reservoir-induced landslides in June 2015 for example, the feasibility of the optimizing indices of water level variations is verified.

Effect of fiber geometry on the electromagnetic shielding performance of mortar

The increased awareness of electromagnetic wave hazards has prompted studies on electromagnetic shielding using conductive materials in the construction industry. Previous studies have explored the effects of the types of conductive materials and their mix proportions on the electromagnetic shielding performance; however, there has been insufficient research on the effect of the geometry of the conductive materials on the electromagnetic shielding performance. Therefore, in this study, the dependence of the electromagnetic shielding performance on the cross-sectional geometry, diameter and length of fibers was investigated. The results showed that the electromagnetic shielding performance improved when the fiber length increased or the diameter decreased, but the effect of the cross-sectional geometry of the fibers was smaller than the effect of the fiber spacing factor.

Impact assessment of coastal hazards due to future changes of tropical cyclones in the North Pacific Ocean

Abstract Tropical cyclones generate severe hazards in the middle latitudes. A brief review and applications of dynamical and statistical downscaling of tropical cyclone (TC) are described targeting extreme storm surge and storm wave hazard assessment. First, a review of the current understanding of the changes in the characteristics of TCs in the past and in the future is shown. Then, a review and ongoing research about impact assessment of tropical cyclones both dynamical downscaling and statistical model are described for Typhoon Vera in 1959 and Typhoon Haiyan in 2013. Finally, several examples of impact assessment of storm surge and extreme wave changes are presented. Changes in both TC intensity and track are linked to future changes in extreme storm surge and wave climate in middle latitude.

Areal Extent of Erosion and Accretion in and around the Gahirmatha Coast, NW of Bay of Bengal by Remote Sensing and GIS Analysis of Multi-Temporal Satellite Imagery

The shoreline morphology change due to erosion and deposition is a major concern for coastal zone management. In the present study, a highly dynamic coast of Gahirmatha on Bay of Bengal in northeast India is experiencing active erosion, which is mainly wave and tide erosion related hazard threat ending human habitation and sustainability of the coast. In our study, high resolution satellite imagery of time series provided detailed sequence of coastal morphology and their changes in all respects. Comparison study of relative shoreline positions on time series satellite data spanning three decades from 1973 to 2004 covering for the years of 1973, 1983, 1987, 1990, 1998, 2000 and 2004, provided regional changes with accelerated erosion and accretion. The result of the studies have revealed that the areas of severe erosion found along the coast are confined to the promontories of the present day mouths itself of the Baitrani at Dhamra and Brahmani at Maipura inlets. In this background, it is significant to understand the magnitude of factors that are responsible for prograding or retrograding of coast. The present study is an attempt in this direction.

Abstract 19263: Vasodilator Use and Wave Intensity Patterns in Hypertension

Background: Blood pressure is the result of interactions between the heart and the arteries. Although the effects of vasoactive blood pressure-lowering drugs on arteries has been widely investigated, their in vivo effects on ventricular-arterial interactions are not well understood. Hypothesis: We aimed to assess the relationship between antihypertensive drug use and ventricular arterial interactions assessed via wave intensity analysis (WIA), which quantifies the energy contained in waves generated by the heart and/or reflected from the periphery (figure). Methods: We studied 152 subjects with treated hypertension. We measured central pressure using carotid arterial tonometry. Ascending aortic flow was quantified with through-plane phase-contrast MRI. We performed WIA and assessed the relationship between specific classes of blood pressure lowering drug use and WIA patterns. Results: In models that adjusted for age, gender, body size, race, presence of diabetes and glomerular filtration rate, angiotensin receptor blocker (ARB) use was associated with a greater likelihood of a mid-systolic expansion (i.e., suction) wave (Hazard Ratio=31.1; P=0.005), whereas beta-blocker use was associated with a lower likelihood of such wave (HR=0.16; P=0.02). ARB use was also independently associated with a lower energy in the late systolic forward suction wave (Beta=-0.18; standardized beta=-0.24; P=0.007). This association persisted after adjustment for the forward compression wave (beta=-0.13; standardized beta=-0.16; P=0.008). No associations between WIA patterns and calcium channel blocker use, diuretic use, ACE inhibitor use or long-anting nitrate use were found. Conclusions: Wave intensity analysis is a useful tool to assess the effects of vasodilators on ventricular-arterial interactions. ARB use is selectively associated with systolic suction waves (from blood inertia), which may in turn unload the heart in mid and late systole.

COMPARATIVE RISK ASSESSMENT AT ISLA DEL CARMEN AND CANCUN, MEXICO

Tropical cyclones and Cold-Fronts lead to storm surge and wave hazards annually in the coastal zones of the Gulf of Mexico and Caribbean Sea. Anthropogenic intervention over a wide extension of these coasts has affected their natural equilibrium and resilience to these extreme natural phenomena. An integrated risk analysis is presented here, which aims to prevent or reduce serious beach erosion damage and inundation of settlements next to these beaches. Two important coastal lagoon barriers in Mexico were selected to develop the risk assessment methodology: Isla del Carmen, on the Gulf of Mexico; and Cancun, on the Caribbean coast. While both are important for socio-economic and ecological reasons, the contrast between the high-poverty zones in Isla del Carmen and the luxurious tourist development of Cancun facilitates the integration of a common vulnerability approach, which can be applicable to any other location affected by similar hazards. This paper proposes a methodology to evaluate the socioeconomic risk of inundation; integrating the SPRC concept and the spatial variability of the risk, focusing on the parameters related to the resilience of the receptors and intangible indirect losses.

Heat wave hazard modelling: Qatar case study

Heat waves are considered to be the major cause of environmental and weather-related fatalities. Heat waves also have a severe impact on people with chronic cardiac and respiratory diseases, such as asthma. With climate change and global warming processes taking place, general global climatic models predict that heat wave events will increase in frequency, duration, and intensity. Therefore, heat wave modelling has attracted considerable attention from scientists and decision-makers alike. Yet it remains challenging, complex, and an imperative problem. This complexity is introduced mainly by land surface and atmospheric spatial variability, such as land use and air pollution concentration. This study addresses this spatial complexity by using remotely sensed thermal data in the form of Land Surface Temperature (LST) images, along with meteorological data to model heat waves in Qatar. Multi-criteria/multi-parameters/multi-layer analysis is carried out using Geographic Information System (GIS) by combining many complex parameters that influence or determine heat waves in the region. Gumble statistical frequency analysis is carried out on time series data to predict heat wave events. Results from the model show that a high portion of the population's vulnerable age groups are likely to be severely affected by future heat wave events in Qatar- based on a five year return period. The analysis revealed that at least 87% of children aged 4 or under would be exposed to a very high intensity level of heat wave events, while more than 86% of elderly people, over 65 years of age, would be exposed to the same intensity level of hazard. The study proves that thermal satellite imaging improves heat wave hazard modelling, as it addresses the complex spatial variability of land surface. The developed model is applicable at a local, as well as regional, scale, making an original contribution to heat wave modelling.

Spectral Density Analysis for Wave Characteristics in Pohang New Harbor

The Pohang New Harbor (PNH), located at the Yongil bay in the northeastern part of Pohang city, South Korea, has experienced extreme wave hazards of about 3.0–5.0 m in elevation due to the seasonal swell from the far ocean. In this paper, both analytical and numerical studies are performed to investigate the wave-induced oscillations in an arbitrary shaped harbor with corner point consideration. By taking the consideration of the actual topography and bathymetry data, the boundary of PNH is constructed. Our theoretical model is based on the assumptions of inviscid, irrotational fluid, infinitesimal wave amplitude, and finally, the Helmholtz equation and its Weber’s solution. The numerical simulations are conducted to analyze the spectral density of the standing waves in PNH at eight respective synthetic record points. The simulation results are validated with real-time measurement data, which is obtained by wave heights and tide gauges at the specified record points within and outside the PNH. To improve the harbor’s design, a tactic such as building the breakwater at the entrance of the harbor is implemented and then spectral density is estimated in the modified geometry of the PNH. The consequential effects are proposed at the same time, suggesting the feasibility of the improvement measures.

Wave field analysis in a harbor with irregular geometry through boundary integral of Helmholtz equation with corner contributions

A mathematical model has been designed to analyze the wave characteristics in a harbor, averting any possible situation of occasional extreme wave hazards due to the seasonal weather conditions. Helmholtz equation has been considered with appropriate boundary conditions on the basis of small amplitude hypothesis. Further, a solution of the Helmholtz equation is given by Green’s identity formula and then it is utilized to predict the ocean surface wave fields due to refraction and diffraction of various directional incident waves in the context of the shallow water waves. The corner angle coefficient is firstly determined at each corner segment on the boundary of the harbor and then corner contribution on the boundary is imposed by multiplying the corner angle coefficient to the boundary wave field. Further, the Chebyshev point discretization is implemented on the boundary of harbor to improve the numerical accuracy at the sharp corners. This numerical model is validated through the quantitative comparison with existing studies in literature. Further the logarithmic convergence rate is achieved for the proposed numerical scheme as well. We have implemented this numerical model practically on the Pohang New Harbor (PNH), Pohang, South Korea to compute the resonance modes for various directional incident waves. Furthermore, the wave elevation is obtained in the whole interior domain of the harbor at various modes of resonance with specific incident waves. In conclusion, this numerical scheme is a competent tool to foster the prediction of the ocean surface wave field on the boundary and interior of the harbors with complex geometries.

Rocky coast hazards and public safety: Moving beyond the beach in coastal risk management

The coast is an environment enjoyed by people around the world, yet it is also hazardous, accounting for innumerable fatalities each year. The management of day-to-day hazards is an ongoing challenge for managers because the risk of a person drowning is the result of a combination of the number of people on the shore, their vulnerability, and the wave processes occurring at any one time. As it is nearly impossible to reduce the magnitude of waves or the number of people visiting the shore, managers often rely on strategies to reduce visitor vulnerability such as the provision of lifeguards. Education is also seen as key to reducing people's vulnerability by increasing awareness of the hazards. For beaches, morphodynamic models are used to provide a hazard rating for such landforms and this has been very successful in reducing drownings on sandy coasts. However, on adjacent rocky coasts there has been an increase in fatalities, particularly amongst rock fishers. Fatalities occur particularly on the edge of rocky ledges, termed shore platforms, found at the foot of cliffs when people are washed into the sea by waves. Rocky coasts are currently not incorporated in the existing shoreline risk assessments and their exclusion is a major gap in coastal management especially because, unlike beach users, people recreating on the rocky coast are often unprepared for entering the water and swimming. This paper explores the underlying principles of the beach safety models and develops a hazard framework for rock coasts which is tested on microtidal shore platforms of Australia and New Zealand. The height and slope of shore platforms as well as their depth immediately offshore are identified as the key elements in determining how much wave energy can impact the platform and therefore be hazardous to people. The rocky coast hazard framework provides a simple and effective tool for the assessment of wave hazard exposure through combining platform elevation with the depth immediately offshore of the platform edge. This new framework provides managers with a rapid assessment tool for quantifying rocky coast hazards.

Heat wave hazard classification and risk assessment using artificial intelligence fuzzy logic

The average summer temperatures as well as the frequency and intensity of hot days and heat waves are expected to increase due to climate change. Motivated by this consequence, we propose a methodology to evaluate the monthly heat wave hazard and risk and its spatial distribution within large cities. A simple urban climate model with assimilated satellite-derived land surface temperature images was used to generate a historic database of urban air temperature fields. Heat wave hazard was then estimated from the analysis of these hourly air temperatures distributed at a 1-km grid over Athens, Greece, by identifying the areas that are more likely to suffer higher temperatures in the case of a heat wave event. Innovation lies in the artificial intelligence fuzzy logic model that was used to classify the heat waves from mild to extreme by taking into consideration their duration, intensity and time of occurrence. The monthly hazard was subsequently estimated as the cumulative effect from the individual heat waves that occurred at each grid cell during a month. Finally, monthly heat wave risk maps were produced integrating geospatial information on the population vulnerability to heat waves calculated from socio-economic variables.

Numerical analysis of wave hazards in a harbor

Resonance may occur when the periods of incoming waves are close to the eigen-periods of harbor basin. The amplified waves by resonance in harbor will induce serious wave hazards to harbor structures and vehicles in it. Through traditional theoretical approaches, the eigen-periods of harbor basin with regular shapes can be obtained. In our study, we proposed a numerical model to simulate the behavior characteristics of the harbor waves. A finite difference numerical model based on the shallow water equations (SWE) is developed to simulate incoming tsunami and tidal waves. By analyzing the time series data of water surface wave amplitude variations at selected synthetic observation locations, we estimate the wave height and arrival time in coastal area. Furthermore, we use frequency spectrum analysis to investigate the natural frequencies from the data recorded at the synthetic observation stations.

Public versus expert knowledge and perception of climate change-induced heat wave risk: a modified mental model approach

Effects of climate change and its induced extreme environmental events have been the object of intense public debate in recent years. Extreme environmental events, such as heat waves, and their impact upon the elderly and the poor are of special concern to policy- and decision-makers. However, how the public views these issues is critical for dealing with the associated risks. Recognizing the importance of risk assessments and implementation of mitigation measures, we adopted a comparative approach to assess and extend a generic methodology to examine diverse sets of beliefs about climate change-induced heat wave hazards. Using a modified mental model approach, this study mapped existing knowledge structures about the risk associated with climate change-induced heat waves in an urban setting of Canada (Winnipeg, Manitoba). ‘Public models’ were developed from open-ended interviews with diverse community groups; ‘influence diagrams’ were formulated based on open-ended discussions with experts in the pertinent fields. An assessment of the juxtaposition of the public and experts’ knowledge and perception of heat wave risk has revealed significant gaps in the perception of: (a) the effects of climate change-induced heat wave and (b) of responsible authority for policy intervention to affect the cause or impacts. It further identifies misconceptions in public perception regarding: (a) thinning of ozone layer to cause a rise in earth’s temperature; and (b) whether precautionary measures can be taken to reduce heat wave mortality; (c) of future heat wave ‘risk estimation’ in the city of Winnipeg. Based on our results, we argue that by developing interactive risk communication tools and practicing public engagement in knowledge enhancement, heat wave risk assessment and mitigation capacity of both public and experts can be improved.

Modelling the effects of failure of pipelines transporting hydrogen

Modelling the effects of failure of pipelines transporting hydrogen The depletion of stocks of fossil fuels and the environment protection requirements increase the significance of hydrogen as a future energy carrier. The present research is focused on the development of new safe methods of production, transport and storage of hydrogen. The paper presents an analysis of problems related to the assessment of the effects of failure of hydrogen transporting pipelines. Scenarios of hazardous events connected with an uncontrollable leakage of hydrogen are discussed. The sizes of heat radiation and pressure wave hazard zones are determined.

Assessment of offshore platforms under extreme waves by probabilistic incremental wave analysis

In this study, a novel probabilistic framework named Probabilistic Incremental Wave Analysis (PIWA) is established in order to assess the performance of jacket offshore platforms under extreme waves. The PIWA can take into account the uncertainties in three main elements consisting of sea state parameters, structural response and collapse capacity. The main advantage of the PIWA approach is reflected in decoupling of the wave hazard and structural analyses via an intermediate variable known as the wave height intensity measure. Despite the fact that most of the uncertainties associated with structural response are concentrated in wave hazard, this will enable the PIWA to estimate the probability of failure accurately. Moreover, both static and dynamic wave analyses can be utilized in the PIWA procedure. In this approach, multiple incremental wave analyses are employed to estimate the distribution of structural demand for a wide range of wave height intensities. Subsequently, the mean annual frequency of exceeding a structural limit state is calculated for which this research addresses two different methodologies including demand-based and wave height-based approaches. Furthermore, a new probabilistic-based Reserve Strength Ratio (RSR) is proposed and the probability of exceeding various levels of RSR is provided. To reduce the large number of simulations and hence improving the computational effort in the PIWA procedure, a combination of Latin Hypercube Sampling and Simulated Annealing optimization technique is utilized as an efficient sampling scheme. The PIWA procedure is employed in probabilistic assessment of an existing jacket offshore platform located in the Persian Gulf as well.