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1.
分别用耿贝尔(Gumbel)极值分布和广义(GEV)极值分布拟合五华县降水极值 总被引：1，自引：0，他引：1
以五华县19 a(1995—2013年)夏季(4—9月)逐日降水资料为研究对象,分析五华县年小时极端降水量变化趋势可得:从1995—2013年,五华县的小时极端降水量呈上升趋势,最大值出现在2010年,为103.5 mm/h。分别用耿贝尔(Gumbel)极值分布和广义(GEV)极值分布拟合该地降水极值,进而对两者的拟合效果进行比较,结果表明GEV的拟合效果要优于Gumbel。 相似文献
2.
Flood events of the Pachang River, one of the major rivers in Taiwan, are modeled by extreme value distributions. Flood events
are characterized by its peak, volume, duration and the time of peak. Flood volume and peak are fitted to a generalized extreme
value distribution. Flood duration and the time of flood peak are incorporated into the model to detect possible trends. The
results show that flood volume exhibits an upward trend with respect to flood duration, but flood peak exhibits a downward
trend with respect to flood duration. There appears to be no significant trends with respect to time. Among other results,
we provide estimates of return period for flood peak and flood volume, which could be used as measures of flood protection.
This paper provides the first application of extreme value distributions to flood data from Taiwan. 相似文献
3.
J. G. Williams 《河流研究与利用》2013,29(3):399-401
The bootstrap can be used to estimate confidence intervals for complex statistics such as weighted usable area, the habitat index calculated by the Physical Habitat Simulation System (PHABSIM) and related models. Use of the bootstrap entails sampling with replacement from the original sample, such as a set of PHABSIM transects. Because the method has been improperly applied to PHABSIM transects in several instances, I explain in detail why bootstrap sampling is with replacement. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
4.
In the UK, increased use of non‐structural responses (NSRs) in integrated urban flood risk management has been recommended since the flood of autumn 2000. Paralleling this change, the UK government are now strongly promoting a Whole Life Cycle Costing approach (WLCC) to flood risk management economic appraisals. However, due to a relative lack of economic knowledge in relation to NSR, costing non‐structural responses is still in its infancy. Thus, the feasibility of the WLCC approach to costing non‐structural strategies has been brought into question. This paper describes a qualitative method to assess the feasibility of WLCC approach, i.e. a method designed to assess if enough expert‐based knowledge and/or economic data are available to support an effective, robust economic appraisal for a scheme that includes NSRs. This conceptual method allows flood risk managers to identify if, and when, further efforts are required in relation to obtaining better cost data to underpin a cost–benefit test. A user‐friendly interface has been developed to support decision makers faced with these new challenges. A schematic project has been presented in the text to illustrate the potential application of the method. 相似文献
5.
The devastating effects of floods, combined with scarce data sets, have stimulated the development of hydrological regionalisation techniques. The present study proposed an evaluation of the L‐moments based index‐flood procedure, coupled with watershed grouping based on geographical convenience for regionalisation of maximum streamflows. A pioneer analysis for South America, addressing the geographical classification method adopted by National Water Agency of Brazil (ANA), was conducted considering over 100 watersheds in southern Brazil. Nonstationary and discordant maximum annual streamflow (MAS) series were removed with the aid of the Mann–Kendall test and discordancy measure, whereas the heterogeneity measure was used to check regional homogeneity. The best regional distribution was identified by the Z DIST goodness‐of‐fit measure. Finally, multiple nonlinear regressions, considering morphological and meteorological watershed characteristics, were performed to obtain better index‐flood estimates. It was concluded that: (a) the proposed methodological strategy provided satisfactory estimation of design floods; (b) area, mean slope, stream gradient, and flow length, were the most satisfactory explanatory variables; (c) the fitted equations stand out as a state‐of‐art alternative for the scarce hydrological monitoring in southern Brazil; and (d) the hydrological boundaries defined by ANA might not be the most adequate approach from a regional point of view. 相似文献
6.
Flood management activities require development of flood maps that depict the spatial and temporal extent of floods with the help of hydrodynamic models. Two-dimensional (2-D) hydrodynamic models are frequently employed for flood inundation modeling and mapping with the help of high-end computational resources and high-resolution terrain information such as LiDAR (light detection and ranging) data. However, LiDAR data are either unavailable or not freely accessible in many parts of the world, especially in nations belonging to Global South. Hence, one-dimensional (1-D) models are still in practice owing to their lesser computational cost and data requirement. Nonetheless, the successful application of a 1-D model depends mainly on the representation of the natural river and floodplain geometry, which is the primary input in the form of discrete cross-sections. The assumed flow directions on floodplains while orienting the cross-sections in 1-D models induce some uncertainty in the model simulations. This study aims to evaluate the variability in the model simulations caused by the cross-sectional orientations. Flood simulations were performed using a 1-D hydrodynamic model for six different cross-sectional realizations for three river reaches, having distinct morphological and topographical characteristics, and were compared with the simulations of a 2-D hydrodynamic model and available reference inundation maps. The study suggests that the simulations of flood inundation extent and maximum flow depth variation are influenced by the cross-sectional orientation on flood plains in river reaches characterized by broad flood plains with complex local topographical variations. In contrast, for reaches with relatively less wide and complex terrains, 1-D models can generate robust simulations of flood inundation extent and spatial variation in maximum flood depth (R2 and NSE greater than 0.89) for high flood events. 相似文献
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8.
两变量设计洪水估计的不确定性及其对水库防洪安全的影响 总被引：5，自引：0，他引：5
在两变量水文频率分析中,样本系列容量一般较小,使得水文设计值估计具有不确定性。本文基于Copula函数和Parametric Bootstrap方法,并考虑联合设计值的最可能组合模式,建立可描述两变量设计洪水估计不确定性的C-PBU(Copula-based Parametric Bootstrap Uncertainty)模型,同时提出了定量评价两变量不确定性的度量指标,分析了联合设计值估计不确定性对水库最高调洪水位的影响,并对比了不同典型洪水选取模式下的水位不确定性。以隔河岩水库为例,推求了两变量设计值估计的95%置信区域;比较了不同样本容量对不确定性的影响。结果表明:设计洪水估计和典型洪水选择具有较大的不确定性,可采用C-PBU模型推求置信区间,来考虑设计洪水估计不确定性对水库防洪安全的影响。 相似文献
9.
王青兰 《广东水利电力职业技术学院学报》2009,7(2)
通过相关文献资料的收集及各水利行业部门意见的征集,对流域洪水的风险分析与预测进行概括总结,并对当前国内与国际上较为常用的"洪水风险图"预测洪水方法进行简要论述,供今后的研究工作参考。 相似文献
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11.
《Journal of Flood Risk Management》2018,11(Z2):S805-S816
Chachoengsao province is a prime shrimp producing area for domestic consumption and exports. The province, however, is often threatened by floods. Improving the effectiveness of current flood damage protection is a major challenge. This research developed a flood risk map by combining the probability of flood events and a vulnerability map based on physical characteristics of the area and socio‐economic conditions of shrimp farmers (victims). Analysis of current risk reduction measures was performed by comparing the net benefits and costs of different strategies. Damage costs to shrimp farming from flooding were also estimated for the base case (a case with no change in actions). The flood risk map shows that two‐thirds of shrimp farms are highly vulnerable to flooding when a 10‐day accumulated rainfall is greater than 250 mm which is likely to occur every 2 years. Increasing dike heights could yield higher net benefits than other flood adaptation measures. Non‐structural flood controls such as early harvesting and shifting the crop calendar are alternative measures for shrimp farmers who lack financial supports. The results show that cost‐benefit analysis based on various scenarios can help in selecting an appropriate mitigation practice especially for shrimp farms located in a high risk area. 相似文献
12.
The Gumbel Mixed Model Applied to Storm Frequency Analysis 总被引：4，自引：0，他引：4
A bivariate extreme value distribution, namely theGumbel mixed model constructed from Gumbel marginaldistributions is employed to analyze the joint distributionof correlated storm peak (maximum rainfall intensity) andamount. Based on its marginal distributions, the jointdistribution, the conditional probability distribution, andthe associated return periods can be deduced. Parameters ofthe bivariate distribution model are estimated based on itsmarginal distributions by the method of moments (MM). Theusefulness of the model is demonstrated by using it torepresent multivariate storm events at the Niigatameteorological station in Japan. 相似文献
13.
《Journal of Flood Risk Management》2018,11(Z2):S916-S929
In Europe, floods are among the natural catastrophes that cause the largest economic damage. This article explores the potential of two distinct types of multivariate flood damage models: ‘depth‐damage’ models and ‘rainfall‐damage’ models. We use survey data of 346 Flemish households that were victim of pluvial floods complemented with rainfall data from both rain gauges and weather radars. In the econometrical analysis, a Tobit estimation technique is used to deal with the issue of zero damage observations. The results show that in the ‘depth‐damage’ models flood depth has a significant impact on the damage. In the ‘rainfall‐damage’ models there is a significant impact of rainfall accumulation on the damage when using the gauge rainfall data as predictor, but not when using the radar rainfall data. Finally, non‐hazard indicators are found to be important for explaining pluvial flood damage in both ‘depth‐damage’ and ‘rainfall‐damage’ models. 相似文献
14.
Duncan Faulkner Sarah Warren Peter Spencer Paul Sharkey 《Journal of Flood Risk Management》2020,13(1)
The Environment Agency in England is investing £2.5 billion with the aim of reducing flood risk to at least 300,000 homes by 2020/21. Several of the schemes being considered are on rivers that have experienced an upsurge of flooding over recent years. Decisions on whether to invest and how high to build are usually made on the basis of stationary methods of flood frequency analysis that assume the probability of flood flows is unchanging over time. Following successive severe floods in Cumbria, trend tests and non‐stationary flood frequency analysis techniques have been applied. These allow parameters of the frequency distribution to change over time or with some other covariate. The resulting estimates of flow, for the present day, were up to 55% higher than the stationary estimates at river gauges in north‐west England. The results have been incorporated into the scheme appraisal process. A national analysis indicates that there is evidence of upward trends in peak flows at nearly a quarter of river flow gauges across Great Britain. Many rivers show an abrupt increase in flood flows in the late 1990s. Trends tend to occur in upland areas but they are also seen on some rivers across south‐east England. 相似文献
15.
Reliable estimation of flood loss is crucial for flood management. Since this estimation relies on models that are prone to uncertainty, it is vital to clearly understand how the uncertainties affect the appraised flood loss. This paper presents a coupled probabilistic hydrologic and hydraulic modelling framework to estimate the uncertainty of anticipated loss. A hydrologic model performs rainfall‐runoff transformation and a two‐dimensional unsteady hydraulic model simulates flood inundation. The outputs of the latter are fed into a loss estimation tool. Two sources of uncertainty—rainfall depth and antecedent moisture condition—are used to illustrate the framework on the Swannanoa River watershed in North Carolina, United States. The impact of the uncertainty of these two sources is tracked over the hydrologic model, hydraulic model and loss estimation tool. Our case study results illustrate that the estimations on the percent affected people can be four times more uncertain than the rainfall depth and two times more than the flood extent, but its uncertainty is comparable to hydrograph attributes. The appraised structural damages are nearly two times more uncertain than the affected people. These findings, however, may only be valid for a case study with hilly topography and should be cautiously extrapolated to other areas. 相似文献
16.
In this paper, a nonstationary extreme value analysis approach is introduced in order to determine coastal design water levels for future time horizons. The nonstationary statistical approach is based on the generalized extreme value (GEV) distribution and an L‐moment parameter estimation. It is shown that to derive future design water levels, a parametric approach is required for the extrapolation of the time‐dependent parameters. The results are compared with common stationary methods. In addition, some definitions and methods for testing on stationarity or nonstationarity are discussed. All the methods introduced are applied to the annual maximum water levels from 1849 to 2007 at the German North Sea gauge at Cuxhaven. The nonstationary results for the year 2007 are in the range of NN+507 cm (NN: German reference datum), and for the time horizon, 2100 the results vary from NN+542 to NN+546 cm for the 100‐year event. The results show that the nonstationary GEV approach is suitable for determining coastal design water levels. 相似文献
17.
为了探讨环境变化前后雅砻江流域的水文极值演变特征及不确定性,以雅砻江流域雅江水文站和洼里水文站为代表站,基于年极大值和超门限阈值样本,结合序列变异理论、多种极值统计模型(GEV、GPD、P-III)和轮廓似然函数参数估计及不确定性分析方法,分析了变化环境下雅砻江水文极值序列演变特征。结果表明:受气候变化和人类活动的影响,雅江水文站和洼里水文站环境变化前后的最优分布线型由P-III型分布转变为GEV分布。环境变化后的水文极值序列相应设计流量增大,重现期变小。设计值估算中,重现期越长,相应设计流量的不确定性也越大,其中参数的不确定性对于设计值的影响最为显著,但极值选样及分布函数的不确定性也不容忽视。轮廓似然函数法的使用可有效降低设计值不确定性,基于极值理论与轮廓似然函数估计法进行变化环境下水文极值演变分析可提高设计值的可靠性。研究成果可为雅砻江流域水库设计管理及防洪规划等提供参考。 相似文献
18.
The identification of flood‐prone areas is a fundamental component of rational urban planning and proper natural disaster management policy. The aim of the present study is to introduce a framework for the identification of flood‐prone areas using geographical information systems techniques and decision‐making, based on a comparative evaluation for various scenarios. As a case study, the Attica region in Greece is selected, which is occasionally affected by heavy rainfall, the main cause of flooding in the region, coupled with the fact that human activities and urbanization of recent years play a significant role in flood occurrence. In this context, the development and application of a GIS‐based multi‐criteria analysis method for the determination of areas susceptible to flood events is initially presented. The entire spatial analysis is performed using SAGA 6.3.0 and ArcMap 10.2 Desktop, by applying a number of alternative modifications and, finally, by evaluating different scenarios regarding methods for the criteria standardization, criteria hierarchy and factors' weighting estimation. The proposed framework has an advantage among other approaches, since it takes into account mainly static data that are linked to flooding, such as the topography and land cover distribution and it can be easily customized in ungauged catchments. 相似文献
19.
针对P-Ⅲ型分布参数的不确定性问题,提出了应用抽样分布理论进行研究的方法。引入抽样分布及特征函数的概念,推导了P-Ⅲ型分布样本均值的分布函数,构造辅助随机变量并推导了其分布函数,在总体的离势系数和偏态系数已知情况下,结合上下概率分位点得到了总体均值的置信区间;方法应用于上犹江流域,计算得到了其设计洪峰的置信区间。理论推导表明,样本均值和辅助随机变量仍服从P-Ⅲ型分布,且辅助随机变量的分布参数仅与总体的离势系数和偏态系数有关。将该方法应用于上犹江流域,设计洪峰的置信区间合理,说明基于抽样分布理论研究P-Ⅲ型分布均值的不确定性是可行的,且分析结果受总体离势系数影响较大而受偏态系数影响较小。 相似文献
20.
根据山东省已发生的实测和调查暴雨资料,编制了五种标准历时的暴雨极值分布图,分析了山东省各历时暴雨极值的分布规律和特点,并简要分析了其影响因素,对山东省设计暴雨洪水分析计算、有关工程规划设计、防洪减灾等工作具有重要意义。 相似文献