热带岛屿南渡江洪水归槽影响下防洪能力分析

An Analysis of Flood Returning to Main Channel Influence on the Flood Control Ability of Nandu River

流域内修建堤防可以抵御洪水侵害,但堤防修建易引发洪水归槽,导致用于洪水灾害风险评估的洪水序列失去一致性,防洪堤的防洪能力受到影响。采用水文变异诊断系统和变化环境下基于小波分析的非一致性水文频率计算方法,结合南渡江三滩站1956-2013年的实测年最大流量序列,对受归槽洪水影响下南渡江的堤防防洪能力进行分析。结果显示,洪水归槽影响下,引起下游断面涨水过程和洪峰流量增大、水位增高,洪水发生的频率和量级发生了较大的变化,南渡江上游龙州河堤防的防洪能力有所降低。当安全超高在1.0~2.0 m变化时,其堤防可以抵御的洪水标准从过去条件下的10~18年一遇,降到现状条件下的3~6年一遇。

Levee construction is important to prevent from flood disaster. With the increasingly higher levees, the volume of flood lagging in the main channel generally becomes much less than the past owing to the effects of flood returning to the main channel, and the increasing flood peak and flood volume leave the defense ability of levees under challenge and doubt. The Nandu River Basin has special geographical features and this returning influence on its defense ability of levees is quite notable, but few studies are focused on it. This paper calculates the levees＂ defense ability of the river under the flood returning influence, using a hydrological alteration diagnosis system and non-stationary hydrological frequency analysis method in changing environments, based on an annual peak runoff series for the period of 1956-2013 of the Santan Hydrological Station. The results show that the flood frequency and volume have been changed under the flood returning influence and hence resulted in considerable losses in flood control ability. There is a decrease in the levee＇s flood standard from the past 10- 18-yd to the present 3- 6-yd under safe superelevation of 1.0-2.0 m.