Analysis on Characteristics of Scour and Fill of Floods and Critical Discharge of No Sedimentation at the Lower Weihe River

The paper analyzes the relationships of sediment delivery ratio and peak discharge of more than 200 events of floods with different discharge and sediment concentration of the lower Weihe River during 1974-2005 period.The outcomes show that a) the floods of the river can be divided into lower sediment concentration flood of less than 100 kg/m3,medium sediment concentration flood of 100-200 kg/m3 and high sediment concentration flood of greater than 200 kg/m3;b) the scour and fill of the lower Weihe River mainly occur in flood season,usually it scours in big discharge of flood and deposits in small discharge of flood in flood season and;c) the critical discharge of no sedimentation at the lower river is about 2 000 m3/s.When the average sediment concentration of flood is less than 100 kg/m3 and greater than 200 kg/m3,the critical flood discharge of no sedimentation is 1 000 m3/s and 1 700 m3/s respectively.