Comparative Risk Assessments for the City of Cologne – Storms, Floods, Earthquakes

In this paper a methodology for a multi-risk assessment of an urban area is introduced and performed for the city of Cologne, Germany, considering the natural hazards windstorm, flooding and earthquake. Moreover, sources of the uncertainty in the analysis and future needs for research are identified. For each peril the following analyses were undertaken: hazard assessment, vulnerability assessment and estimation of losses. To compare the three hazard types on a consistent basis, a common economic assessment of exposed assets was developed. This was used to calculate direct economic losses to buildings and their contents. The perils were compared by risk curves showing the exceedence probability of the estimated losses. In Cologne, most of the losses that occur frequently are due to floods and windstorms. For lower return periods (10–200 years) the risk is dominated by floods. For return periods of more than 200 years the highest damage is caused by earthquakes.     

Storm extreme levels and coastal flood hazards: A parametric approach on the French coast of Languedoc (district of Leucate)

Coastal flooding is a significant risk on the shores of Languedoc-Roussillon. The storms that periodically hit the coast can generate strong swells and storm surges. Most beach resorts, built on a low elevation dune ridge, are periodically flooded during major storms. Although risks zoning regulations take into consideration coastal flood hazards, the delineation of vulnerable areas is still insufficient and the commonly accepted threshold is regularly exceeded during most severe storms. This paper presents a method to improve the assessment of extreme storm-related water levels. It relies on fieldwork carried out in the Leucate commune (Aude), which is particularly exposed to the risk of sea level rise. It considers both storm surges and wave phenomena that occur within the surf zone (set-up and swash), calculated from the Simulating WAves Nearshore (SWAN^®) numerical wave model and the Stockdon formula. Water levels reached during several recent storm events have been reconstructed and simulations of submerged areas were carried out by numerical modelling.     

A Spatial and Temporal Analysis of Damaging Snowstorms in the United States

Records of very damaging snowstorms, those causing more than $25 million in property losses, across the United States were assessed to define the spatial and temporal dimensions of the nation’s snowstorm activity during 1949–2000. In this 52-year period 155 snowstorms occurred and caused losses totaling $21.6 billion (2000 dollars). The northeastern U.S. had the nation’s maximum storm occurrences (79 storms), total losses ($7.3 billion), and storm intensity. Two-thirds of all U.S. losses occurred in the Northeast, Southeast, and Central climate regions, and storm occurrences and losses were least in the western U.S. The incidence of storms peaked in the 1976–1985 period and exhibited no up or down trend during 1949–2000. However, national losses had a significant upward time trend, as did storm sizes and intensity. States with the greatest number of storms were New York (62) and Pennsylvania (58) with only 2 storms in Montana, Idaho, and Utah. Storm losses in the northeastern and southeastern U.S. had U-shaped time distributions with flat time trends for 1949–2000, but losses in the western regions and Deep South had distinct upward trends in losses and storm size. More than 90% of all storm losses in the western U.S. occurred after 1980. These findings indicating increased losses over time reflect that a rapidly growing population and vulnerability of more property at risk have been major factors affecting losses, and the lack of a change over time in snowstorm incidences suggests no change in climate during 1949–2000.     

RETRACTED ARTICLE: Space and time distributions of major winter storms in the United States

Winter storms are a major weather problem in the United States and their losses have been rapidly increasing. A total of 202 catastrophic winter storms involving ice storms, blizzards, and snowstorms, each causing >$5 million in damages, occurred during 1949–2003, and their losses totaled $35.2 billion (2003 dollars). Catastrophic winter storms occurred in most parts of the contiguous United States, but were concentrated in the eastern half of the nation where 88% of all storm losses occurred. They were most frequent in the Northeast climate district (95 storms), and were least frequent in the West district (14 catastrophic storms). The annual average number of storms is 3.7 with a 1-year high of nine storms, and one year had no storms. Temporal distributions of storms and their losses exhibited considerable spatial variability across the nation. For example, when storms were very frequent in the Northeast, they were infrequent elsewhere, a result of spatial differences in storm-producing weather conditions over time. The time distribution of the nation’s 202 storms during 1949–2003 had a sizable downward trend, whereas the nation’s storm losses had a major upward trend for the 55-year period. This increase over time in losses, given the decrease in storm incidences, was a result of significant temporal increases in storm sizes and storm intensities. Increases in storm intensities were small in the northern sections of the nation, but doubled across the southern two-thirds of the nation, reflecting a climatic shift in conditions producing intense winter storms.     

Modeling the impact of land reclamation on storm surges in Bohai Sea,China

A nested model for the simulation of tides and storm surges in the Bohai Sea, China, has been developed based on the three-dimensional finite-volume coastal ocean model. The larger domain covers the entire Yellow Sea and Bohai Sea with a horizontal resolution of ~10 km, and the smaller domain focuses on the Bohai Sea with a fine resolution up to ~300 m. For the four representative storm surges caused by extratropical storms and typhoons, the simulated surge heights are in good agreement with observations at coastal tide gauges. A series of sensitivity experiments are carried out to assess the influence of coastline change due to land reclamation in recent decades on water levels during storm surges. Simulation results suggest that changes in coastline cause changes in the amplitude and phase of the tidal elevation, and fluctuations of surge height after the peak stage of the storm surges. Hence, for the assessment of the influence of coastline changes on the total water level during storm surges, the amplitudes and phases of both the tidal and surge heights need to be taken into account. For the three major ports in the Bohai Bay, model results suggest that land reclamation has created a coastline structure that favors increasing the maximum water level by 0.1–0.2 m. Considering that during the storm surges the total water level is close to or even exceeds the warning level for these ports, further increasing the maximum water level by 0.1–0.2 m has the potential to cause severe damages and losses in these ports.

     

Estimating <Emphasis Type="Italic">probable maximum loss</Emphasis> from a Cascadia tsunami

The Cascadia margin is capable of generating large magnitude seismic-tsunami. We use a 1:500 year tsunami hazard flood layer produced during a probabilistic tsunami hazard assessment as the input to a pilot study of the vulnerability of residential and commercial buildings in Seaside, OR, USA. We map building exposure, apply the Papathoma Tsunami Vulnerability Assessment Model to calculate building vulnerability and estimate probable maximum loss (PML) associated with a 1:500 year tsunami flood. Almost US$0.5 billion worth of buildings would be inundated, 95% of single story residential and 23% of commercial buildings would be destroyed with PML’s exceeding US$0.5 billion worth of buildings would be inundated, 95% of single story residential and 23% of commercial buildings would be destroyed with PML’s exceeding US116 million. These figures only represent a tiny fraction of the total values of exposed assets and loss that would be associated with a Cascadia tsunami impacting the NW Pacific coast. Not withstanding the various issues associated with our approach, this study represents the first time that PML’s have ever been calculated for a Cascadia type tsunami, and these results have serious implications for tsunami disaster risk management in the region. This method has the potential to be rolled out across the United States and elsewhere for estimating building vulnerability and loss to tsunami.     

沙尘暴灾害致灾因子三维联合分布与重现期探索

探讨多致灾因子对Copula联合分布模型在三维多致灾因子综合分析中的扩展.针对沙尘暴形成的3个基本条件:大风、丰富的沙尘源和不稳定的大气层结,以内蒙古镶黄旗1990-2008年的强沙尘暴灾害事件为案例,建立了经向环流指数、地面平均最大风速和地表土壤湿度3个基本特征变量的联合分布,计算了基于联合分布的联合重现期.研究表明,镶黄旗强沙尘暴事件的三维致灾因子符合Frank Copula函数构建条件,该函数能够很好地描述强沙尘暴灾害3个基本特征变量的联合分布,具备扩展到三维的能力.相对于二维Copula函数拟合效果,三维Frank Copula在中高尾部分的拟合有很大提高.三变量联合重现期的计算结果更加贴近实际情况.     

The tropical storm Noel and its effects on the territory of the Dominican Republic

In the period between the end of October and the beginning of November 2007, the Dominican Republic was hit by the tropical storm Noel, then turned into hurricane in its movement toward the Californian coasts. The passage of Noel was accompanied by huge precipitation especially in the south-western part of the country. In some areas, the rainfall registered in 6 days exceeded 700 mm, i.e., more than two-thirds of the mean annual precipitation. The return periods calculated for this rainfall event vary greatly from region to region: while they locally reach 200 years, such as in San José de Ocoa (50 km west of Santo Domingo), in other areas, as for instance in the territory of the capital Santo Domingo, return periods do not exceed 20 years. The tropical storm caused huge damage both in terms of human victims and economic losses, related to diffused inundations and landslide phenomena, which may be attributed only partially to the exceptionality of the event. As a matter of fact, in many regions, the inadequate answer of the territory—widely characterized by serious problems of land degradation and an almost complete lack of territorial planning—appears to be the major responsible for the occurred negative effects. The impact assessment, based on the calculation of an Impact Index, confirms this statement.     

Risk assessment on storm surges in the coastal area of Guangdong Province

The coastal area of Guangdong Province is one of the most developed regions in China. It is also often under severe risk of storm surges, as one of the few regions in China which are seriously threatened by storm surges. Based on the data of storm surges in the study area in the past 30 years, the return periods of 18 tide stations for storm surge are calculated separately. Using the spatial analysis technology of ArcGIS, combined with the topography data of the study area, the submerged scope for storm surge in the coastal area of Guangdong Province is determined, and the hazard assessment is carried out. According to the view of systematic point, this article quotes the result of vulnerability assessment which was done by the author in the previous research. Based on the hazard evaluation and vulnerability evaluation, risk assessment of storm surges in the study region is done, and the risk zoning map is drawn. According to the assessment, Zhuhai, Panyu and Taishan are classified as the highest risk to storm surges in Guangdong Province; Yangdong, Yangjiang and Haifeng are in higher risk to storm surges; Dongguan, Jiangmen, Baoan and Huidong are in middle risk to storm surges; Zhongshan, Enping, Shanwei, Huiyang, Longgang and Shenzhen are in lower risk of storm surges; Guangzhou, Shunde and Kaiping are in the lowest risk to storm surges. This study builds a complete process for risk assessment of storm surges. It reveals the risk of storm surges in the coastal cities, and it would guide the land use of coastal cities in the future and provide scientific advices to the government for the prevention and mitigation of storm surge disaster. It has important theoretical and practical significance.     

Windstorms in the United States

High winds are one of the nation’s leading damage-producing storm conditions. They do not include winds from tornadoes, winter storms, nor hurricanes, but are strong winds generated by deep low pressure centers, by thunderstorms, or by air flow over mountain ranges. The annual average property and crop losses in the United States from windstorms are $379 million and windstorms during 1959–1997 caused an average of 11 deaths each year. Windstorms range in size from a few hundred to hundreds of thousands square kilometers, being largest in the western United States where 40% of all storms exceed 135,000 km². In the eastern United States, windstorms occur at a given location, on average, 1.4 times a year, whereas in the western US point averages are 1.9. Midwestern states average between 15 and 20 wind storms annually; states in the east average between 10 and 25 storms per year; and West Coast states average 27–30 storms annually. Storms causing insured property losses >$379 million and windstorms during 1959–1997 caused an average of 11 deaths each year. Windstorms range in size from a few hundred to hundreds of thousands square kilometers, being largest in the western United States where 40% of all storms exceed 135,000 km². In the eastern United States, windstorms occur at a given location, on average, 1.4 times a year, whereas in the western US point averages are 1.9. Midwestern states average between 15 and 20 wind storms annually; states in the east average between 10 and 25 storms per year; and West Coast states average 27–30 storms annually. Storms causing insured property losses >1 million, labeled catastrophes, during 1952–2006 totaled 176, an annual average of 3.2. Catastrophic windstorm losses were highest in the West and Northwest climate regions, the only form of severe weather in the United States with maximum losses on the West Coast. Most western storms occurred in the winter, a result of Pacific lows, and California has had 31 windstorm catastrophes, more than any other state. The national temporal distribution of catastrophic windstorms during 1952–2006 has a flat trend, but their losses display a distinct upward trend with time, peaking during 1996–2006.     

Meteorological analysis of the tornado in Ciudad Acuña,Coahuila State,Mexico, on May 25, 2015

Extreme meteorological conditions favor the development of severe storms and tornadoes that may have largely impacts on the population despite its relatively short life. Tornadic severe storms have been documented around the World. In Mexico (MEX), the study of the occurrence of tornadoes and severe storms is relatively new. In this research, we have selected an event of severe tornadic storm in Ciudad Acuña, Mexico. The storm was driven by a frontal system moving southward from USA converging with a warmer moist air flux from the Gulf of Mexico. The tornado strikes on the Northeast of Mexico, in Coahuila State, on May 25, 2015. Imagery of infrared channel from GOES 13 satellite and the presence of a hook echo in radar data of May 25, 2015, indicate a supercell structure. The maximum values of radial velocity were about ?20 and 15 m s^?1. In this study, the WRF model was used in order to simulate the mesoscale meteorological conditions of the tornado. Model simulations capture atmospheric features observed in Doppler radar. The simulated storm-relative helicity values were between 400 and 500 m² s^?2. The simulated convective available potential energy values were of 3000 J kg^?1. These values were higher than values for convective storms, located over the region of Ciudad Acuña in Mexico and Del Rio in USA. The supercell was a result of high humidity and temperature gradients, conditioned by frontal activity and moisture flux intensifications from the Gulf of Mexico.

     

Coping with floods in the city of Dresden,Germany

During August 2002 and again in March 2005 as well as in April 2006 the city of Dresden was hit by floods. The flood in 2002 was an extreme event, only comparable to flooding in 1862 and 1890 in Dresden. The flood discharge in 2006 was the second highest discharge since 1940 at the Dresden gauge although its return period was only about 15 years. This special situation enables a comparison of the preparedness of authorities and households in the flood endangered city of Dresden in 2002 after a long period of relatively low flood discharges and in 2005/2006 just a few years after a severe flood event. Before August 2002, the flood risk awareness and flood preparedness of authorities and households in Dresden was low. The inundation channels and the Elbe riverbed had not been maintained well. Just 13% of the households had undertaken building precautionary measures. The severe flood situation as well as the low flood preparedness led to tremendous damage, e.g., losses to residential buildings amounted to 304 million €. After 2002, the municipal authorities in Dresden developed a new flood management concept and many households were motivated to undertake precautionary measures. Building precautionary measures had been actually undertaken by 67% of the households before the floods in 2005 and 2006. Flood damage was significantly lower, due to the less severe flood situations and the much better preparedness. It is an important challenge for the future to keep preparedness at a high level also without recurrent flood experiences.     

Earthquake disaster risk assessment and evaluation for Turkey

Turkey is the one country in which 90% of the buildings are subject to the risk of earthquake disaster. Recent earthquakes revealed that Turkey’s present residential reinforced-concrete constructions are insufficient in earthquake resistance. Many of the buildings which collapsed or were severely damaged have been rehabilitated by applying simple methods, whose adequacy is questionable. As in Japan and the United States, Turkey’s earthquake assessment studies have increased, especially after earthquakes in 1999, In US, several methodologies and standards, such as Hazard-US (HAZUS) and Applied Technology Council (ATC) 13-20-21 and 156, provide comprehensive earthquake loss estimation methodology for post-earthquake assessment. This paper provides post-earthquake assessment and disaster management for Turkey. The main aim of the post-earthquake assessment discussed is to evaluate loss and estimate damage through disaster management approach. Classification criteria for damage are essential to determine the situation after an earthquake in both the short and long terms. The methodology includes probabilistic-based analysis, which considers the magnitude of Ms ≥ 5.0 earthquakes between 1900 and 2005, for determining the probabilistic seismic hazard for Turkey.     

Regional characteristics of dust storms observed in the Alxa Plateau of China from 1961 to 2005

The Alxa Plateau has one of the highest frequencies of dust events in China and one of the greatest contributions to East Asian dust. We compiled climate and dust storm data for the Alxa Plateau based on observational data from ten meteorological stations from 1960 to 2005. Our analysis showed that Guaizihu and Minqin dust centers had >26 days per year with dust storms versus 7–13 days for other desert and Gobi regions on the plateau. Variations in dust storm frequency during the study period showed that dust storms increased during the 1960s (until 1972), decreased until the late 1990s, and then increased slightly until 2002. About 75.6% of dust storms occurred in March, April, May, June, and July. Between 78.2 and 88.1% of the dust storms occurred during the daytime and 28.9% of the dust storms occurred between 13:00 and 16:00. The mean durations of dust storms in the Alxa Plateau ranged from 715 to 3,462 min. The annual number of minutes of dust storms averaged >1,800 min in the western Alxa Plateau. Dust storm frequency was inversely related to duration: the longer the average duration, the lower the frequency of such storms.     

Operational wave prediction of extreme storms in Northern Europe

The disastrous effects of numerous winter storms on the marine environment in the North Sea and the Baltic Sea during the last decade show that wind waves generated by strong winds actually represent natural hazards and require high quality wave forecast systems as warning tools to avoid losses due to the impact of rough seas. Hence, the operational wave forecast system running at the German Weather Service including a regional wave model for the North Sea and the Baltic Sea is checked extensively whether it provides reasonable wave forecasts, especially for periods of extraordinary high sea states during winter storms. For two selected extreme storm events that induced serious damage in the area of interest, comprehensive comparisons between wave measurements and wave model forecast data are accomplished. Spectral data as well as integrated parameters are considered, and the final outcome of the corresponding comparisons and statistical analysis is encouraging. Over and above the capability to provide good short-term forecast results, the regional wave model is able to predict extreme events as severe winter storms connected with extraordinary high waves already about 2 days in advance. Therefore, it represents an appropriate warning tool for offshore activities and coastal environment.     

Salt Marsh Accretion and Storm Tide Variation: an Example from a Barrier Island in the North Sea

We reconstruct past accretion rates of a salt marsh on the island of Sylt, Germany, using measurements of the radioisotopes ²¹⁰Pb and ¹³⁷Cs, as well as historical aerial photographs. Results from three cores indicate accretion rates varying between 1 and 16 mm year⁻¹. Comparisons with tide gauge data show that high accretion rates during the 1980s and 1990s coincide with periods of increased storm activity. We identify a critical inundation height of 18 cm below which the strength of a storm seems to positively influence salt marsh accretion rates and above which the frequency of storms becomes the major factor. In addition to sea level rise, we conclude that in low marsh zones subject to higher inundation levels, mean storm strength is the major factor affecting marsh accretion, whereas in high marsh zones with lower inundation levels, it is storm frequency that impacts marsh accretion.     

An innovative micro-scale approach for vulnerability and flood risk assessment with the application to property-level protection adoptions

Economic damage assessment for flood risk estimation is established in many countries, but attentions have been focused on macro- or meso-scale approaches and less on micro-scale approaches. Whilst the macro- or meso-scale approaches of flood damage assessment are suitable for regional- or national-oriented studies, micro-scale approaches are more suitable for cost–benefit analysis of engineered protection measures. Furthermore, there remains lack of systematic and automated approaches to estimate economic flood damage for multiple flood scenarios for the purpose of flood risk assessment. Studies on flood risk have also been driven by the assumption of stationary characteristic of flood hazard, hence the stationary-oriented vulnerability assessment. This study proposes a novel approach to assess vulnerability and flood risk and accounts for adaptability of the approach to nonstationary conditions of flood hazard. The approach is innovative in which an automated concurrent estimation of economic flood damage for a range of flood events on the basis of a micro-scale flood risk assessment is made possible. It accounts for the heterogeneous distribution of residential buildings of a community exposed to flood hazard. The feasibility of the methodology was tested using real historical flow records and spatial information of Teddington, London. Vulnerability curves and residual risk associated with a number of alternative extents of property-level protection adoptions are estimated by the application of the proposed methodology. It is found that the methodology has the capacity to provide valuable information on vulnerability and flood risk that can be integrated in a practical decision-making process for a reliable cost–benefit analysis of flood risk reduction options.     

Regional debris-flow distribution and preliminary risk assessment from severe storm events in the Appalachian Blue Ridge Province,USA

Storms of high-intensity rainfall, including hurricanes, occur about once every 3 years in small areas of the mountains of the eastern United States posing a high debris-flow hazard. Reported casualties and monetary losses are often an insufficient and inadequate means for comparing the impact from debris flows. A simple GIS technique was used to characterize the distribution and density of debris flows for making a preliminary assessment of risk of impact on roads. This technique was used for comparison of three major severe storms resulting in numerous debris flows: August 10–17, 1940, near Deep Gap, North Carolina; August 19–20, 1969, in Nelson County, Virginia; and June 27, 1995, in Madison County, Virginia. Based on the criteria of the number of debris flows and area covered by debris flows, the August 19–20, 1969, Nelson County, Virginia, event was the most severe of the three storms and posed the greatest risk of debris-flow impact on roads.     

Design and adoption of household tornado shelters for Bangladesh

Death tolls from tornadoes in Bangladesh are the highest in the world due to lack of storm warnings, poor communication, weak housing, and lack of shelters from strong winds in tornadoes and nor’westers. Based on surveys of housing types and designs in the Tangail district, a household tornado shelter is proposed to be placed in the elevated storage platform that is common in houses. The shelter is 2 m tall, 1.2 m wide, and 2–4 m long (4.8–9.6 m³ in volume) with the floor of the shelter placed one meter below the floor of the house. Walls are 7–10 cm thick and made of concrete or an earthen wall stabilized with cement or strengthened with bamboo or bricks. A survey of 200 residents of the region found nearly universal acceptance for the shelter design, and residents were eager for installation of the household shelters. The shelter cost is 2,500–10,000 taka (US50 to50 to 200) depending on local material and labor costs but residents were willing to pay an average of only 1,071 taka (US$21) toward the cost of the shelter. Families with greater income and land holdings and families in villages with recent tornado experience were willing to spend more for a shelter. A pilot project to install household tornado shelters in selected villages and monitor their use, along with continued efforts to issue storm warnings, communicate the warnings, and improve education about storm hazards, will prevent injuries and save lives in Bangladesh and reduce the descent into poverty that results from losses in severe local storms.