The Effects Of Inconsistency Flood On Flood Control Capacity Of Nanning Flood Control Engineering System

Due to the influences of climatic variations and human social activities, Yujiang River Basin has occurred remarkable changes on the underlying surface and the observed flood time series are no longer satisfying consistent assumption. Taking Nanning Flood Prevention Project System as research object, this paper discusses the influences of inconsistent flood on the flood prevention ability of Nanning Flood Prevention Project System so as to provide technical support for the flood-prevention dispatching rule adjustments of Nanning Flood Prevention Project System under the condition of underlying surface changes.Firstly, if the observed flood time series of Baise Hydrology Station and Nanning Hydrology Station satisfy consistency is inspected. The trend components and jump components of the time series are separately inspected. Integrating each method to inspect the performance and analyzing with physical factors of each area, this paper confirms that Baise’s flood peak discharge, maximum 7 days’flood volume and Nanning’s maximum 7 days’ flood volume as well as the time series of Baise-Nanning interval maximum 7 days’ flood volume occur trend variability; Nanning flood peak and Baise-Nanning interval flood peak time series occur jump variability and the variability points are both in 1986.Secondly, in accordance with the inspect result of variability, the decomposition and synthesis method based on random time series is adopted toward trend variability and the method based on Mixture Distribution Hypothesis is adopted toward jump variability forms to conduct the frequency calculation and analysis of inconsistent flood time series separately. The obtained results are compared with the original time series frequency regardless of variability. The result indicates that the flood reducing phenomenon is relatively obvious as the river basin is influenced by the inoculation condition variation of underlying surface.Finally, through Copula-SAR (1) Model, the inconsistent flood process of the consistent Baise and Baise-Nanning interval peak discharge is simulated and is combined randomly by establishing Baise and interval flood Copula joint distribution function. To conduct joint regulating on Baise Reservoir and Laokou Reservoir obtains that Nanning’s flood prevention capacity is about once in 260 years, which is higher than the planning and design standard of once in 200 years. If the flood prevention standard of once in 200 years designed by Nanning is still as the objective, the flood control level of Baise Reservoir may be raised appropriately so as to increase the reservoir’s benefit of generating electricity in storage period and realize resource utilization of flood. The calculation demonstrates that the flood control level of Baise Reservoir in major flood period may be adjusted from 214m to 215.2m.