珠江河口口门洪水分流比变化及成因

Variations and Driving Forces of Flood Flow Allocation Ratio in Pearl River Estuary

河口泄洪情势的变化关系到地区经济发展和灾害防治。基于珠江河口八大口门在1998年和2005年实测洪水资料及洪水发生前后河口实测地形资料,计算口门洪水分流比变化,分析口门泄洪分配特征变化及典型泄洪断面演变特征。在此基础上计算各个口门泄洪能力变化百分比。研究发现:河口典型泄洪断面宽度基本不变,河槽冲刷加深,有利于口门洪水宣泄;除横门外,其余口门泄洪能力增加;人类大规模的采砂活动引起的口门不平衡下切是导致珠江河口泄洪能力变化的主要原因,同时上游来沙显著减小背景下的河道冲刷也对此具有一定影响。

The pattern of flood release is highly related with the economic development and disaster prevention in estuarine regions.Based on the measured flood data in 1998 and 2005 and the topographic data in 1999 and 2007 at the eight river mouths of the Pearl River Estuary,we investigated into the variations of flood flow allocation ratio among the mouths,and then analyzed the changes of flow allocation as well as the evolution of typical cross sections for flood release.According to the empirical equation,we further calculated the variations of the flood release ability of different river mouths.Our findings unveiled that the width of typical cross section for flood release of river mouth remained relatively stable while the depth tended to increase,beneficial for flood release.Apart from Hengmen mouth,the flood release ability was obviously enhanced due to the increased area of cross sections.The uneven downcutting of channel due to intensive sand mining is the main driving force of the changing flood flow allocation ratios,and meanwhile the significant decline of sediment supply also exert some influence.