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1.
A. Curran K. M. De Bruijn M. Kok 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2020,14(1):26-40
ABSTRACTHazard analysis is a crucial step in flood risk management, and for large rivers, the effects of breaches need to be taken into account. Hazard analyses that incorporate this overall “system behaviour” have become increasingly popular in flood risk assessment. Methods to perform such analyses often focus on high water levels as a trigger for dike breaching. However, the duration of high water levels is known to be another important failure criterion. This study aims to investigate the effect of including this duration dependency in system behaviour analyses, using a computational framework in which two dike breach triggering methods are compared. The first triggers dike breaches based on water levels, and the second one based on both water-level and duration. The comparison is made for the Dutch Rhine system, where the dike failure probabilities are assumed to conform to the new Dutch standards of protection. The results show that including the duration as a breach triggering variable has an effect on the hydraulic loads and overall behaviour in the system, therefore influencing the risk. Although further work is required to fully understand the potential impact, the study suggests that including this duration dependency is important for future hazard risk analyses. 相似文献
2.
Large-scale assessment of flood risk and the effects of mitigation measures along the Elbe River 总被引：2，自引：1，他引：1
The downstream effects of flood risk mitigation measures and the necessity to develop flood risk management strategies that
are effective on a basin scale call for a flood risk assessment methodology that can be applied at the scale of a large river.
We present an example of a rapid flood risk assessment methodology for the Elbe River. A 1D hydraulic routing model is extended
by including the effect of planned (regulated and unregulated) and unintended retention (dike breaches) on the peak water
levels. We further add an inundation model for dike breaches due to dike overtopping and a macroscale economic approach to
assess the flood damage. The flexible approach to model the effects of measures by means of volume storage functions allows
for rapid assessment of combinations of retention measures of various proposed dimensions and at multiple locations. The method
allows for the comparison of the flood risk at the scale of the main river trajectory, which has not been possible for the
Elbe River to date. The model is applied to a series of exemplary flood risk mitigation measures to show the downstream effects
and the additive effects of combinations of measures on the flood risk along the river. We further demonstrate the increase
in the downstream flood risk resulting from unilateral decisions to increase the dike height at upstream locations. As expected,
the results underline the potential effectiveness of increased retention along the river. The effects of controlled retention
at the most upstream possible location and largest possible extent generate the most pronounced reduction of average annual
damage. As expected, the effect of uncontrolled retention with dike relocations is significantly lower. 相似文献
3.
In the Netherlands the current dike design policy is to design flood defence structures corresponding to an agreed flooding
probability with an extra safety board of at least 0.5 m. For river dikes a return period of 1,250 years is used to determine
the design water levels. A problem with this strategy is that it builds on assumptions with regard to the intrinsically uncertain
probability distributions for the peak discharges. The uncertainty is considerable and due to (1) the measuring records that
are limited to about 100 years and (2) the changing natural variability as a result of climate change. Although the probability
distributions are regularly updated based on new discharge data the nature of the statistics is such that a change in the
natural variability of the peak discharge affects the probability distribution only long after the actual change has happened.
Here we compare the performance of the probabilistic dike design strategy with the older strategy, referred to as the ‘self-learning
dike’. The basic principle of the latter strategy is that the dike height is kept at a level equal to the highest recorded
water level plus a certain safety margin. The two flood prevention strategies are compared on the basis of the flooding safety
over a 100-year period. The Rhine gauge station at Lobith serves as case study. The results indicate that the self-learning
dike performs better than the probabilistic design in terms of safety and costs, both under current and climate change conditions. 相似文献
4.
A comprehensive flood risk assessment should aim not only at quantifying uncertainties but also the variability of risk over time. In this study, an efficient modelling framework was proposed to perform probabilistic hazard and risk analysis in dike-protected river systems accounting for morphological variability and uncertainty. The modelling framework combined the use of: (1) continuous synthetic discharge forcing, (2) a stochastic dike breach model dynamically coupled to a stochastic unsteady one-dimensional hydraulic model (MIKE1D) describing river flows, (3) a catalogue of pre-run probabilistic inundation maps (MIKE SHE) and (4) a damage and loss model (CAPRA). The methodology was applied using continuous simulations to a 45-km reach of the Upper Koshi River, Nepal, to investigate the changes in breach and flood hazards and subsequent risks after 2 and 5 years of probable river bed aggradation. The study results indicated an increase in annual average loss of 4% per year driven by changes in loss distribution in the most frequent loss return periods (20–500 years). The use of continuous simulations and dike breach model also provided a more robust estimation of risk metrics as compared to traditional binary treatment of flood defence and/or the direct association of flow with loss return periods. The results were helpful to illustrate the potential impacts of dynamic river morphology, dike failure and continuous simulation and their significance when devising flood risk study methodologies. 相似文献
5.
地质地貌条件是长江中游洪灾形成的背景条件,近代洪水位不断上升是人-地不和谐作用下流域环境系统演化的结果.人类作用导致的多流归槽改变了长江中游河流的地貌过程和水文特性,致使洪水过程显著;大堤修筑导致堤外河漫滩出现泥沙加积,自1650年荆江大堤合拢以来,边滩总体淤积厚度为2.8～11.0m,平均淤积速率12.54～25.64mm/a;围湖造田导致江汉-洞庭平原蓄洪空间减少和"小水大灾"局面的形成;漫滩筑堤围垸严重影响了长江行洪,仅荆江段就有围筑的民垸84个,总面积为4895.95km2,民垸面积是泄洪面积的近9倍.因此,在认识自然规律的基础上,正确协调人-地-水关系,重建良性循环的流域环境系统,是解决长江中游的水患的根本出路. 相似文献
6.
洪水浸泡和水位骤降情况下黄河下游堤防堤岸稳定性分析 总被引：1，自引：0，他引：1
水库库岸边坡稳定在水位骤降工况下的研究目前已比较成熟,但对黄河下游堤防在水位骤降工况下的堤坡稳定状态却研究甚少。通过选取黄河下游标准化堤防某段堤岸边坡为研究对象,建立有限元渗流模型,提出黄河下游堤防的水位骤降速度标准,同时分析了在水位骤降速度为2、4、5 m/d时的坡内浸润线变化、堤岸稳定性变化,以及在水位骤降组合洪水浸泡最不利工况下的堤岸稳定状态。通过分析,给出水位下降情况、水位下降组合浸泡情况下的堤岸稳定状态图,并从图中可以查出在某一水位下降速度、洪水水位降至某一高程处的堤岸稳定状态,为工程人员在堤防建设中运用和推广提供了便利。 相似文献
7.
当前洪水风险分析按照典型设计标准洪水进行计算的模式难以满足实际防洪管理需要,为了提高洪水风险分析的实时性以及适应洪水演进的动态性,设计了动态实时洪水风险分析框架。在本框架中,先采用一维和二维动态耦合水动力学数值方法耦合溃堤模型,然后在樵桑联围防洪保护区建立洪水演进模拟模型,通过灵活处理模型计算边界条件以及动态设置溃堤功能,计算不同设计标准洪水发生时,堤防出现单一溃口或者组合溃口后保护区内洪水演进过程。按照上述框架开发了樵桑联围动态实时洪水风险图编制与管理应用系统,并利用历史洪水资料开展模型验证,验证结果表明,2008-06洪水马口站、三水站、大熬站、甘竹（一）站的实测最高水位和模型计算最高水位的绝对误差分别为-0.10、0.10、0.09、0.04 m,均满足洪水模拟精度要求。利用模型计算了西江发生200年一遇的洪水情况下,江根堤防出现溃口后的洪水流量及溃口内外洪水水位变化过程,模拟溃口宽度168 m,最大溃口洪水流量达到5 190 m3,分析了堤防溃决后3、6和24 h洪水漫延导致村落淹没情况,结果表明其满足合理性分析。 相似文献
8.
In this paper we provide a computational framework for evaluation of reliability and safety assessment of infrastructures. It is based on the combined application of the dynamic bounds (DB) method and a probabilistic finite element model (FEM). The DB improves the computational efficiency of the FEM when calculating time-dependent failure analyses of coastal and offshore structures, and can speed up the simulation process by several orders of magnitude. Our approach is demonstrated here for an example problem, and shown to be the most efficient method in applications with a limited number of influential variables, which is true for geotechnical and coastal flood defence systems. It is applied to the 17th Street flood wall, a failing component of the flood defence system in New Orleans during Hurricane Katrina. The variation in soil parameters is a critical input in the reliability estimation of this structure, and the calculated probability of failure depends on these assumed values. 相似文献
9.
A computational model system is proposed for the prediction of sea dike breaching initiated from the seaward side by breaking
wave impact with the focus on the application of the model system for the estimation failure probability of the defence structure.
The described model system is built using a number of existing models for the calculation of grass, clay, and sand erosion.
The parameters identified as those having the most significant influence on the estimation of the failure have been described
stochastically. Monte Carlo simulations to account for uncertainties of the relevant input parameters and the model itself
have been performed and the probabilities of the breach initiation and of the full dike breaching have been calculated. This
will form the basis to assess the coastal flood risk due to dike breaching. 相似文献
10.
Santos Pedro Pinto Tavares Alexandre Oliveira Freire Paula Rilo Ana 《Natural Hazards》2017,93(1):77-95
The assessment of vulnerability provides valuable knowledge in the risk assessment steps of a risk governance process. Given the multiscale, multilevel, and multisectorial aspects of flood risk, the diversified entities that directly and indirectly intervene in risk management require specific outputs from the assessment studies. Urban areas in estuarine margins are particularly exposed and vulnerable to flooding. Such interface conditions are found in the Old City Centre of the Seixal, located in the Tagus estuary, Portugal. Here, two distinct methodologies were applied for the assessment of territorial vulnerability. A regional, lower-scale, methodology explores the application of the statistical procedure based on the SoVI® at the statistical block level. A second, local and higher-scale, methodology is based in data collected through field matrices at the building and statistical sub-block level. Comparison of results revealed that the lower-scale assessment provides information on the vulnerability drivers at the regional and municipal level. Nevertheless, only at a higher-scale, it is possible to characterize and differentiate the smaller geographical units of analysis that compose the Old City Centre of Seixal. The lower-scale vulnerability assessment allows a strategic response, based on adaptation measures such as spatial planning, institutional capacity building and public awareness. The local level assessment provides more accurate knowledge to support local emergency planning and the allocation of operational and material resources at the urban level. Nevertheless, rather than antagonistic, both models can be considered as complementary, having in mind the requirements of an holistic flood risk governance model.
相似文献11.
The assessment of vulnerability provides valuable knowledge in the risk assessment steps of a risk governance process. Given the multiscale, multilevel, and multisectorial aspects of flood risk, the diversified entities that directly and indirectly intervene in risk management require specific outputs from the assessment studies. Urban areas in estuarine margins are particularly exposed and vulnerable to flooding. Such interface conditions are found in the Old City Centre of the Seixal, located in the Tagus estuary, Portugal. Here, two distinct methodologies were applied for the assessment of territorial vulnerability. A regional, lower-scale, methodology explores the application of the statistical procedure based on the SoVI® at the statistical block level. A second, local and higher-scale, methodology is based in data collected through field matrices at the building and statistical sub-block level. Comparison of results revealed that the lower-scale assessment provides information on the vulnerability drivers at the regional and municipal level. Nevertheless, only at a higher-scale, it is possible to characterize and differentiate the smaller geographical units of analysis that compose the Old City Centre of Seixal. The lower-scale vulnerability assessment allows a strategic response, based on adaptation measures such as spatial planning, institutional capacity building and public awareness. The local level assessment provides more accurate knowledge to support local emergency planning and the allocation of operational and material resources at the urban level. Nevertheless, rather than antagonistic, both models can be considered as complementary, having in mind the requirements of an holistic flood risk governance model. 相似文献
12.
Current flood protection policies in the Netherlands are based on design water levels. This concept does not allow for a proper evaluation of costs and benefits of flood protection. Hence, research is being carried out on the introduction of a flood risk approach, which looks into both the probability of flooding and the consequences of flooding. This research is being carried out within the framework of a major project called the Floris project (FLOod RISk in the Netherlands). To assess the probability of flooding the Floris project distinguishes different failure modes for dikes and structures within the dike ring. Based on a probabilistic analysis of both loads and resistance the probability of failure is determined for each failure mode. Subsequently the probabilities of failure for different failure modes and dike sections are integrated into an estimate of the probability of flooding of the dike ring as a whole. In addition the Floris project looks into the different consequences of flooding, specifically the economic damages and the number of casualties to be expected in case of flooding of a particular dike ring. The paper describes the approach in the Floris project to assess the flood risk of dike rings in the Netherlands. One of the characteristics of the Floris project is the explicit attention to different types of uncertainties in assessing the probability of flooding. The paper discusses the different starting-points adopted and presents an outline on how the Floris project will deal with uncertainties in the analysis of weak spots in a dike ring as well as in the cost benefit analysis of flood alleviation measures. 相似文献
13.
Flood loss analysis and quantitative risk assessment in China 总被引：9，自引：4，他引：5
Risk assessment is a prerequisite for flood risk management. Practically, most of the decision making requires that the risks and costs of all risk mitigation options are evaluated in quantified terms. Therefore, a quantitative assessment of possible flood loss is very important, especially for emergency planning and pre-disaster preparedness. This paper presents a preliminary methodology and an operational approach for assessing the risk of flood loss to the population, crops, housing, and the economy at county level in China. The present work assesses the risk of loss for each element (people, crops, and so on) under low-, moderate-, and high-intensity flood using intensity-loss curves and loss rates based on historical flood data from 1990 to 2008. Results show that the counties with high flood risk are primarily located in North, East, Central, and South China, particularly in the lower reaches of rivers. On the other hand, the risk of most counties in the western region is generally lower than that of counties in the eastern region. However, for the entire country, the high-risk regions have both a substantial amount of rainfall and low terrain, making such regions highly prone to flooding. Moreover, these high-risk regions present both high population and wealth density. 相似文献
14.
The present compartmentalization layout within the river polders in the Dutch Rhine–Meuse delta is the result of abandonment and partial removal of secondary dikes and the construction of modern infrastructure embankments. These structures will guide the flow of water in case the polder would inundate. Through the application of a 2-D flood propagation model in the polder Land van Maas en Waal this study explores whether restoration or removal of old dike remnants would contribute to a reduction of the risk and damage during an inundation. A systematic set of 28 flood scenarios was simulated and for each scenario an additional damage and risk assessment was carried out. It is concluded that a simple removal or total restoration will not reduce flood damage, but that this must be achieved by a strategic compartment plan. With such a plan old dike remnants and present embankments can be used to keep water away from vulnerable and valuable areas for as long as possible and to guide the floodwater to areas that are considered less vulnerable. 相似文献
15.
Wallrock Melting and Reaction Effects along the Higganum Diabase Dike in Connecticut: Contamination of a Continental Flood Basalt Feeder 总被引：1，自引：2，他引：1
The question of whether continental flood basalts are contaminatedwith crustal material during ascent through the lithosphereis addressed through a study of the feeder dike to the firstof the Mesozoic flood basalts in the Hartford basin of Connecticut.Faulting associated with basin formation exposed the dike, notonly where it connects with the flood basalt, but also at levelsthat may have been as deep as 10 km at the time of crystallization.Wallrocks at all levels of exposure and along the entire 250-kmlength of this 50–60 m wide dike show evidence of partialmelting and contamination of the diabase magma. Melting of the wallrocks took place on grain boundaries betweenquartz and feldspar, especially where these boundaries werefluxed with water released from the breakdown of biotite. Themelts were simple mixtures of quartz and the particular feldsparinvolved rather than equilibrium minimum compositions, probablybecause heating rates were faster than melting rates. The meltscrystallized to form granophyre. Feldspars in direct contactwith the diabase partly melted, with plagioclase developingthe fingerprint texture and orthoclase being converted to anexceptionally fine-grained mixture of plagioclase and quartz. Melts generated in the wallrocks were forced into the marginsof the dike by the volume expansion caused by melting. The earliestmelts to enter the dike are preserved as felsic wisps in thechilled margins, but at distances of more than a few centimetersfrom the edge of the dike they appear to have been assimilatedby the diabase magma. Melts that entered the dike after themargins had solidified were intruded as crosscutting granophyreveins. Chemical profiles across the dike reveal that the contaminantswere not restricted to narrow marginal zones but entered themain body of the dike. Thus, by the time this magma had risento the surface and erupted as the Talcott basalt it had assimilateda significant amount of crustal material, which accounts forthe change from olivine normative compositions in the deepestlevel exposures of the dike to quartz normative ones in thebasalt. Mass balance calculations indicate that the Talcottbasalt may have had {small tilde}6% granophyre added to it duringthe magma's ascent through the last 10 km of the crust. Theamount assimilated in traversing the entire continental crustwould therefore be greater than this. 相似文献
16.
《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2013,7(3-4):195-206
A recently developed Bayesian Monte Carlo (BMC) method and its application to safety assessment of structures are described in this paper. We use a one-dimensional BMC method that was proposed in 2009 by Rajabalinejad in order to develop a weighted logical dependence between successive Monte Carlo simulations. Our main objective in this research is to show that the extended BMC can dramatically improve simulation efficiency by using prior information from modelling and outcomes of preceding simulations. We provide theory and numerical algorithms for an extended BMC method for multi-dimensional problems, integrate it with a probabilistic finite element model and apply these coupled models to assessment of reliability of a flood defence for the 17th Street Flood Wall system in New Orleans. This is the first successful demonstration of the BMC method to a complex system. We provide a comparison of the numerical efficiency for the BMC, Monte Carlo (MC) and Dynamic Bounds methods that are used in reliability assessment of complex infrastructures. 相似文献
17.
黄河下游主槽两侧修建的生产堤通常仅能抵御中小洪水,用于保护滩区农田与村庄安全;当遭遇大洪水引发生产堤溃决时,漫滩洪水会严重威胁滩区群众的生命财产安全。当前研究溃堤洪水的传播过程与演进机理多采用数值模拟,而原型观测及模型试验成果十分有限。通过溃堤漫滩洪水的概化模型试验,模拟了生产堤溃决后主槽内的水位变化及不同程度漫滩洪水的传播过程。试验结果表明:(1)溃堤后漫滩水流以涨水波的形式向滩区迅速传播,主槽内水位具有先降低,然后维持稳定,再升高,最后趋于稳定的变化过程,且溃口上、下游水位变化速率不同;滩区水位总体表现为持续升高,最后趋于稳定的趋势。(2)漫滩洪水波的波前到达时间主要与滩区地形及距溃口的距离有关,波前首先以溃口为中心呈近似对称式椭圆形分布,而后转变为非对称分布;溃堤水流在滩区传播过程中伴有水跃发生,水跃发生的位置由距溃口较远处逐渐趋向溃口位置。(3)溃口流量与溃口内外水位差直接相关,呈先减小、然后维持稳定、再减小最后为0的变化特性。研究成果不仅可以提升对溃堤洪水在滩区演进规律的认识,丰富溃堤洪水动力学理论,还可为数学模型验证提供实测资料。 相似文献
18.
19.
Building damage characteristics based on surveyed data and fragility curves of the 2011 Great East Japan tsunami 总被引：4，自引：2，他引：2
Anawat Suppasri Erick Mas Ingrid Charvet Rashmin Gunasekera Kentaro Imai Yo Fukutani Yoshi Abe Fumihiko Imamura 《Natural Hazards》2013,66(2):319-341
A large amount of buildings was damaged or destroyed by the 2011 Great East Japan tsunami. Numerous field surveys were conducted in order to collect the tsunami inundation extents and building damage data in the affected areas. Therefore, this event provides us with one of the most complete data set among tsunami events in history. In this study, fragility functions are derived using data provided by the Ministry of Land, Infrastructure and Transportation of Japan, with more than 250,000 structures surveyed. The set of data has details on damage level, structural material, number of stories per building and location (town). This information is crucial to the understanding of the causes of building damage, as differences in structural characteristics and building location can be taken into account in the damage probability analysis. Using least squares regression, different sets of fragility curves are derived to demonstrate the influence of structural material, number of stories and coastal topography on building damage levels. The results show a better resistant performance of reinforced concrete and steel buildings over wood or masonry buildings. Also, buildings taller than two stories were confirmed to be much stronger than the buildings of one or two stories. The damage characteristic due to the coastal topography based on limited number of data in town locations is also shortly discussed here. At the same tsunami inundation depth, buildings along the Sanriku ria coast were much greater damaged than buildings from the plain coast in Sendai. The difference in damage states can be explained by the faster flow velocities in the ria coast at the same inundation depth. These findings are key to support better future building damage assessments, land use management and disaster planning. 相似文献
20.
Floods in Malaysia have been increasing in frequency and magnitude as reflected in the Kelantan Flood event in 2014 that resulted in a huge loss of lives and properties. Whereas remote sensing (RS) and geographical information system (GIS) tools have been extensively applied in flood disaster management, there are few reports and studies on the impact of floods on the land use/land cover environment in a post-disaster assessment. In this study, an integrated modelling approach was developed that used Landsat 8 OLI TIRS (Operational Land Imager (OLI) and Thermal Infrared Sensor) data, flood indexing and classification processes to estimate the impact of flood on the environment. The Normalized Difference Flood Index-3 (NDFI3) is an improvement on NDFI2 that takes into account the effects of cloud shadow in the images when extracting flood index areas. The flood model developed showed good agreement when compared with flooded areas shown in SAR (synthetic-aperture radar) image. The results of the flood extent as a proxy for damage estimation showed that the total flooded area was 502.34 km2 for the Kelantan Flood event in 2014, with plantation and built-up area accounting for 43 and 34.6% respectively. The least affected land uses/land covers were deforested area and forest, which accounted for 12.2 and 10.2% respectively. The RS and GIS technique developed in this post-disaster damage assessment is effective, relatively inexpensive and simple to implement by local authorities in support of post-flood disaster planning and decision-making. 相似文献