福建省主要流域的暴雨洪涝特征

利用1989-1999年近11年的水文、气象资料分析了福建省6个主要流域主控站水位与降水量的关系和洪涝的时间变化规律,进而分析了暴雨致洪的特征,结果表明:(1)福建省6个主要流域洪峰水位与上游有关气象站前期平均总降水量相关显著,暴雨是福建省洪涝发生的主要原因;(2)根据闽江(竹歧站)、九龙江(浦南)、交溪(白塔)、木兰溪(濑溪)4个站的达警戒水位或危险水位的降水指标,可利用暴雨预报作为洪涝预警预测的依据。(3)上世纪80年代后,洪水的高低变化有增大的趋势,应进一步完善抗洪防洪预警系统,提高抗洪防洪的应变能力。     

LONG‐TERM CHANGES IN REGIONAL HYDROLOGIC REGIME FOLLOWING IMPOUNDMENT IN A HUMID‐CLIMATE WATERSHED1

ABSTRACT: We analyzed the type of hydrologic adjustments resulting from flow regulation across a range of dam types, distributed throughout the Connecticut River watershed, using two approaches: (1) the Index of Hydrologic Alteration (IHA) and (2) log‐Pearson Type III flood frequency analysis. We applied these analyses to seven rivers that have extensive pre‐and post‐disturbance flow records and to six rivers that have only long post‐regulation flow records. Lastly, we analyzed six unregulated streams to establish the regional natural flow regime and to test whether it has changed significantly over time in the context of an increase in forest cover from less than 20 percent historically to greater than 80 percent at present. We found significant hydrologic adjustments associated with both impoundments and land use change. On average, maximum peak flows decrease by 32 percent in impounded rivers, but the effect decreases with increasing flow duration. One‐day minimum low flows increase following regulation, except for the hydro‐electric facility on the mainstem. Hydrograph reversals occur more commonly now on the mainstem, but the tributary flood control structures experience diminished reversals. Major shifts in flood frequency occur with the largest effect occurring downstream of tributary flood control impoundments and less so downstream of the mainstem's hydroelectric facility. These overall results indicate that the hydrologic impacts of dams in humid environments can be as significant as those for large, multiple‐purpose reservoirs in more arid environments.     

DEVELOPMENT OF A GIS‐BASED FLOOD INFORMATION SYSTEM FOR FLOODPLAIN MODELING AND DAMAGE CALCULATION1

ABSTRACT: This work presents a flexible system called GIS‐based Flood Information System (GFIS) for floodplain modeling, flood damages calculation, and flood information support. It includes two major components, namely floodplain modeling and custom designed modules. Model parameters and input data are gathered, reviewed, and compiled using custom designed modules. Through these modules, it is possible for GFIS to control the process of flood‐plain modeling, presentation of simulation results, and calculation of flood damages. Empirical stage‐damage curves are used to calculate the flood damages. These curves were generated from stage‐damage surveys of anthropogenic structures, crops, etc., in the coastal region of a frequently flooded area in Chia‐I County, Taiwan. The average annual flood damages are calculated with exceedance probability and flood damages for the designed rainfalls of 2, 5, 10, 25, 50, 100, and 200 year recurrence intervals with a duration of 24 hours. The average annual flood depth in this study area can also be calculated using the same method. The primary advantages of GFIS are its ability to accurately predict the locations of flood area, depth, and duration; calculate flood damages in the floodplain; and compare the reduction of flood damages for flood mitigation plans.     

SHOULD DAMS BE MODIFIED FOR THE PROBABLE MAXIMUM FLOOD?1

ABSTRACT: The probable maximum flood (PMF) currently serves as the design standard for many U.S. dams. Floods used for design have increased and currently thousands of dams in the U.S. would be overtopped and possibly fail using the latest calculated PMF at each dam site. Some researchers have suggested that modifying dams to accommodate the PMF could be wasteful. Objections to using the PMF for dam modification include: (1) larger spillway capacity may increase annual downstream flood losses, (2) benefit‐cost ratios may be low, (3) construction accidents associated with dam modification may cause fatalities, and (4) the dollar amount spent to save lives by making dams safer is often very high. Based on these objections, a procedure is presented for evaluating the effectiveness of a proposed dam modification. A change in spillway design policy is recommended. Accepting the status quo at a dam that cannot accommodate the PMF may be the best course of action.     

河南水旱灾害危险性时空特征研究

河南省地处南北气候过渡带,水旱灾害频发。综合利用灾害数据资料及信息扩散模型,从致灾和承灾两个层面对河南省水旱灾害进行风险评估与时空特征研究,为加强水旱灾害的风险评估和管理提供理论依据。结果表明:①1988-2007年间发生水灾的年份主要是2003、2000、1998、1996、 2005,旱灾年份是1997、2001、1999、1992、1988;②当降水距平百分率为20%、30%、40%时,发生水灾的概率分别为0.10、0.06、0.04,当降水距平百分率为-20%、-30%、-40%时,发生旱灾的概率分别为0.13、0.07、0.03;③水灾在5%、10%和15%受灾率时的风险概率分别为0.81、0.54、0.35,即1~3 a一遇之间,当受灾率大于20%时,风险概率为0.22,大约4.5 a一遇;而旱灾在5%、10%、15%、20%、25%受灾率时的风险概率分别为0.87、0.72、0.58、0.47和0.38,即1.2 a、1.4 a、1.7 a、2.1 a和2.6 a一遇;④旱灾发生频率大于水灾,空间上具有较大的区域差异,水旱灾害高风险区主要是驻马店、南阳、平顶山一带,旱灾大于水灾的区域主要是三门峡、洛阳、郑州、焦作、安阳、许昌,水灾大于旱灾的区域主要是信阳、漯河、开封、商丘、周口、濮阳,水旱灾害均较小的是济源和鹤壁。     

UNCERTAINTY OF EXTREME FLOOD ESTIMATES INCORPRATING HISTORICAL DATA1

ABSTRACT: The ability to predict extreme floods is an important part of the planning process for any water project for which failure will be very costly. The length of a gage record available for use in estimating extreme flows is generally much shorter than the recurrence interval of the desired flows, resulting in estimates having a high degree of uncertainty. Maximum likelihood estimators of the parameters of the three parameter lognormal (3PLN) distribution, which make use of historical data, are presented. A Monte Carlo study of extreme flows estimated from samples drawn from three hypothetical 3PLN populations showed that inclusion of historical flows with the gage record reduced the bias and variance of extreme flow estimates. Asymptotic theory approximations of parameter variances and covariances calculated using the second and mixed partial derivatives of the log likelihood function agreed well with Monte Carlo results. First order approximations of the standard deviations of the extreme flow estimates did not agree with the Monte Carlo results. An alternative method for calculating those standard deviations, the “asymptotic simulation” method, is described. The standard deviations calculated by asymptotic simulation agree well with the Monte Carlo results.     

黑龙江省洪水资源化探讨

洪水是可利用的宝贵资源,科学、合理的开发利用洪水是解决水资源短缺的重要途径.要加大宣传力度,提高认识,统一规划,协调发展,充分利用森林、草原、湿地的生态功能保护洪水资源.     

MATHEMATICAL SIMULATIONS OF THE TOCCOA FALLS,GEORGIA, DAM-BREAK FLOOD1

ABSTRACT: Four dam-break models were selected for testing with an observed data set from the November 6, 1977, disaster at Toccoa Falls, Georgia. The Kelly Barnes Dam failure occurred with a 35-ft head of water and produced a peak discharge of 23,000 ft³/s. The selected models included: (1) Modified Puls (MP), (2) U. S. Army Corps of Engineers Gradually Varied Unsteady Flow Profiles (USTFLO), (3) National Weather Service's Dam-Break Flood Forecast (DBFF), and (4) U. S. Geological Survey's method of characteristics (MOC) coupled with a general purpose streamflow simulation (J879DB). Achieving a successful simulation was easiest with the MP model. The DBFF model required a moderate effort while the MOC-J879DB models required some data alterations and considerable effort. The USTFLO model failed to simulate this test case. In the stream segment near the dam, the computed peak stages were generally within 5 feet of the observed high water marks. Elsewhere, the peak stage results were much better, generally within 2 feet. The peak discharges computed by the models were generally within 20 percent of discharges estimated by slope area and contracted opening measurements, except near the dam where the MOC-J879DB model's results was 80 percent too high.     

A UNIFYING SET OF PROBABILITY TRANSFORMS FOR STOCHASTIC HYDROLOGY1

Abstract: An ordered set of probability sensity functions was derived form transforms of the normal distribution. Variate transforms are based on orders of exponentiation. The set of distributions includes the log-normal. a partial basis for use of these functins in hydrology is demonstrated by establishing some required properties. A concept of mixed samples of zero and nonzero elements forming nonseparable sets of virtual and real elements is introduced to establish a physical lower limit of sampled diata independent of functional bounds.     

ESTIMATING PROBABLE MAXIMUM FLOOD PROBABILITIES1

ABSTRACT: Methods of computing probabilities of extreme events that affect the design of major engineering structures have been developed for most failure causes, but not for design floods such as the probable maximum flood (PMF). Probabilities for PMF estimates would be useful for economic studies and risk assessments. Reasons for the reluctance of some hydrologists to assign a probability to a PMF are discussed, and alternative methods of assigning a probability are reviewed. Currently, the extrapolation of a frequency curve appears to be the most practical alternative. Using 46 stations in the Mid-Atlantic region, the log-gamma, log-normal, and log-Gumbel distributions were used to estimate PMF probabilities. A 600,000-year return period appears to be a reasonable probability to use for PMFs in the Mid-Atlantic region. The coefficient of skew accounts for much of the variation in computed probabilities.