Abstract

The phenomenon ‘secondary perched river’ brings a disadvantageous influence about the controlling flood and producing in the floodplains of the lower Yellow River in recent years. The authors choose the typical reach of the ‘secondary perched’ river from Dongbatou to Gaocun, and suppose six types of boundary conditions and two types of designing flood (1958-flood and 1982-flood) for two-dimensional numerical simulation of water. The authors apply two-dimensional numerical model to analyze the influence of different transverse elevation dispersion, including the diffluent discharge ratio of channel and floodplain, velocity distribution, unit discharge distribution, flood propagation along levees and so on. According to the simulated results, we make two suggestions: One is that the transverse elevation dispersion of secondary perched river surely affects the diffluent ratio between channel and floodplain and velocity along the levees, so the transverse slope of floodplain should be relevantly improved. Secondly, in view of controlling flood, by compared the two improved methods, we propose that filling and leveling up ditch abut on levees and dropping the elevation of lip floodplain should be combined.

Keywords: secondary perched river, transverse elevation dispersion, flood propagation along levee, diffluent ratio, bank-full discharge