MULTIVARIATE EXTREME VALUE DISTRIBUTION WITH MIXED GUMBEL MARGINALS1

ABSTRACT: Bivariate and trivariate distributions have been derived from the logistic model for the multivariate extreme value distribution. Marginals in the models are extreme value type I distributions for two-component mixture variables (mixed Gumbel distribution). This paper is a continuation of the previous works on multivariate distribution in hydrology. Interest is focused on the analysis of floods which are generated by different types of storms. The construction of their corresponding probability distributions and density functions are described. In order to obtain the parameters of such a bivariate or trivariate distribution, a generalized maximum likelihood estimation procedure is proposed to allow for the cases of samples with different lengths of record. A region in Northern Mexico with 42 gauging stations, grouped into two homogeneous regions, has been selected to apply the models. Results produced by the multivariate distributions have been compared with those obtained by the Normal, log-Normal-2, log-Normal-3, Gamma-2, Gamma-3, log-Pearson-3, Gumbel, TCEV and General Extreme Value distributions. Goodness of fit is measured by the criterion of standard error of fit. Results suggest that the proposed models are a suitable option to be considered when performing flood frequency analysis.     

MULTIOBJECTIVE REAL‐TIME RESERVOIR OPERATION WITH A NETWORK FLOW ALGORITHM1

ABSTRACT: A network flow algorithm has been developed for the optimization of real‐time operation of a multiple reservoir system. Two purposes have been considered in the operation: flood control and hydropower generation. A special network structure was developed which allows the consideration of river routing. A multiobjective formulation is utilized thus allowing generation of a non‐dominated curve. The effect of imperfect forecast on the performance of the real‐time operation model is also evaluated. An application is made to a subsystem of the Brazilian hydroelectric system, located in the Paranapanema river basin. In this case study, the model showed good performance under the largest flood of the historical records.     

FLOODPLAINS AND HOUSING VALUES: IMPLICATIONS FOR FLOOD MITIGATION PROJECTS1

ABSTRACT: The hedonic valuation method was used to quantify the impact of floodplain location on housing values in Fargo‐Moor‐head. Being located in the 100‐year floodplain lowered the home values by $8,990, and such homes were worth $10,241 less than similar homes located outside the floodplain before the major flood event of 1997. Required flood insurance premiums for these homes were determined to account for approximately 81 percent of this price depreciation. In contrast, homes in the 500‐year floodplain were worth $3,100 more than similar homes not in the floodplain. It was concluded that more disclosure is needed regarding the location of the 500‐year floodplain, and that the hedonic valuation method can be used to calculate the economic gains and losses associated with flood mitigation projects or floodplain remapping efforts that result in the reclassification of the legal floodplain status of individual homes.     

The impact of tidal flooding on a coastal community in Semarang, Indonesia

The article presents household vulnerability, local community adaptive capacity, and government’s response to tidal flood hazard in the Semarang coastal area, Central Java Province, Indonesia. Using data gathered from a survey of households, the study revealed a number of important factors about the interaction between people and flood. The coastal community has been experiencing problems related to tidal floods. They have adapted to tidal flooding with structural measures, such as increasing the floor level, making small dams in front of houses, increasing yard and street levels in the neighborhood area, and creating dykes around residential areas. Tidal flood mitigation in the Semarang coastal area should incorporate governmental action and local community capacities for proper protection of the population.     

A Framework to Develop Nationwide Flooding Extents Using Climate Models and Assess Forecast Potential for Flood Resilience

The methods used to simulate flood inundation extents can be significantly improved by high‐resolution spatial data captured over a large area. This paper presents a hydraulic analysis methodology and framework to estimate national‐level floodplain changes likely to be generated by climate change. The hydraulic analysis was performed using existing published Federal Emergency Management Agency 100‐year floodplains and estimated 100‐ and 10‐year return period peak flow discharges. The discharges were estimated using climate variables from global climate models for two future growth scenarios: Representative Concentration Pathways 2.6 and 8.5. River channel dimensions were developed based on existing regional United States Geological Survey publications relating bankfull discharges with channel characteristics. Mathematic relationships for channel bankfull topwidth, depth, and side slope to contributing drainage area measured at model cross sections were developed. The proposed framework can be utilized at a national level to identify critical areas for flood risk assessment. Existing hydraulic models at these “hot spots” could be repurposed for near–real‐time flood forecasting operations. Revitalizing these models for use in simulating flood scenarios in near–real time through the use of meteorological forecasts could provide useful information for first responders of flood emergencies.     

北京市北沙河上游典型小流域水环境治理措施的生态效益分析

北京市属于资源型重度缺水地区,水资源紧缺严重制约其可持续发展,加之水质恶化,造成了全市水资源和水环境形势严峻的局面.为此,北京市布设相应措施对小流域水环境问题进行治理,分析治理措施的生态效益能够为小流域水环境治理措施的合理布设提供科学依据.以北京市昌平区北沙河上游8条小流域为研究区,基于In VEST(Integrat...     

民国前期荆江两岸地区洪水灾害若干特征分析

“万里长江,险在荆江”,民国前期(1912—1927)荆江两岸地区水灾频仍。在荆江两岸地区1912—1927年洪水灾害相关资料的基础上,运用一般统计方法和理论分析了这一时期洪水灾害的若干特征,即普遍性、连续性、积累性和区域性四个特征。对洪水灾害基本特征及其规律的探讨至今对于有效的进行水患治理与防治仍有着深远的影响。     

A HYDROCLIMATOLOGICAL ANALYSIS OF THE RED RWER OF THE NORTH SNOWMELT FLOOD CATASTROPHE OF 19971

ABSTRACT: The flood hydroclimatology of the Grand Forks flood of April 1997, the most costly flood on a per capita basis for a major metropolitan area in United States history, is analyzed in terms of the natural processes that control spring snowmelt flooding in the region. The geomorphological characteristics of the basin are reviewed, and an integrated assessment of the hydroclimatological conditions during the winter of 1996 to 1997 is presented to gain a real‐world understanding of the physical basis of this catastrophic flood event. The Grand Forks flood resulted from the principal flood‐producing factors occurring at either historic or extreme levels, or at levels conducive to severe flooding. Above normal fall precipitation increased the fall soil moisture storage and reduced the spring soil moisture storage potential. A concrete frost layer developed that effectively reduced the soil infiltration capacity to zero. Record snowfall totals and snow cover depths occurred across the basin because of the unusual persistence of a blocking high circulation pattern throughout the winter. A severe, late spring blizzard delayed the snowmelt season and replenished the snow cover to record levels for early April. This blizzard was followed by a sudden transition to an extreme late season thaw due to the abrupt breakdown of the blocking circulation pattern. The presence of river ice contributed to backwater effects and affected the timing of tributary inflows to the main stem of the Red River. Only the absence of spring rains prevented an even more catastrophic flood disaster from taking place. This paper contributes to our understanding of the flood hydroclimatology of catastrophic flood events in an unusual flood hazard region that possesses relatively flat terrain, a north‐flowing river, and an annual peak discharge time series dominated by spring snowmelt floods.     

云南高原楚雄市降水分布与旱涝灾害分析

运用楚雄市1961~2009年的降水量资料,通过统计检验、五点三次滤波法并计算了楚雄降水距平百分率,分析了楚雄市旬、侯、月﹑季、年际降水量变化特征及旱涝灾害的时间分布特征,得出楚雄市49年平均降雨量为867.77 mm,2000~2009年来年平均降雨量为935.57 mm,比49年均值偏高67.8 mm,呈上升趋势。降水主要集中在5~10月,干湿明显,楚雄市冬春干旱年年都有发生,只是程度不同,初夏干旱如遇大气环流异常发生的机率较大,干旱发生连续性较强,洪涝灾害偶有发生。并对旱涝灾害成因进行了分析,提出了旱涝灾害防治基本对策。     

德国环境损害赔偿法律制度研究及对中国立法的启示

环境损害赔偿法律制度包括私法责任和公法义务.德国立法上私法层面要以《环境责任法》为中心,以私权益的救济为首要价值取向,以第三方的实际人身和财产损失为主要赔偿范畴;公法层面以《环境损害和预防法》为核心,强调企业和个人经营者的预防义务,注重环境修复和风险预防,赔偿范围主要包括预防措施费用和环境的恢复费用.德国的环境损害赔偿制度并不强调对污染企业的苛责,旨在通过合理的赔偿金额设置,让企业能够改善生产模式,保证私权益得到及时救济.