Conincident Risk Analysis Of Inconsistent Flood And Its Impact Assessment For River Flood Control

The consistency of hydrological series is the precondition for flood frequency analysis in the traditional sense.In fact,owing to the effects of frequent human activities,the hydrological series has lost their their consistency.This phenomenon appears particularly significant in arid and semi-arid regions.So the hydrological series must be tested,and appropriate should be taken to ensure those meet the consistency before flood frequency analysis.River flood risk research has developed from flood frequency analysis of a single river to comprehensive analysis of multiple rivers in the whole river basin level.In reaction to this,some scholars start using Copula functions to build multivariate joint distribution and conjointly analyzing the flood coincidence risk of multiple rivers.But the number and correlation of variables determine the number of correlation parameters and Copula functions construction.For the flood disasters,more attention are paid to less frequent flood and its influence to the flood-protected area,and the influence of medium flood to bench land and partial scour to the embankment project.But following the development of the bench land and the regulation project of dike becoming frequently,the impact assessment of medium flood seem more and more important.Yellow River and Qingshui River in NingXia Hui Autonomous region were selected in this study.For the above problems,there are mainly about research and analysis:(1)Domestic and overseas diagnosis methods of flood series inconsistency have been comprehensive compared.The hydrological meteorological conditions and water conservancy project construction have been analyzed.The hydrological alteration diagnosis systems have been selected to diagnose the hydrological series of Xia Heyan station and Quan Yanshan station,and alteration points and degree have been determined.The mixed distribution method and the probability distribution method were chosen to fit the mutational hydrological series.(2)The basic theory of Copula functions and Von Mises distribution has been explained,and multiple mixed Von mises distribution was selected to fit the date of flood occurrence.The constrained maximum likelihood estimation was selected to estimated parametes.The Gumbel Copula function was chosen to build the joint distribution of flood occurrence dates,and coincidence probabilities were calculated.Depending on flood occurrence date,four-dimensional joint dietribution of flood peak level has been developed to calculate the coincidence probabilities of flood peak level.(3)Hypothetically,10-year flood of two rivers have been coincidence.And combining with operation scheduling rules of Qing Tongxia reservoir,one-dimensional and two-dimensional have been developed to simulate the flood scour influence for the bench land.