SCOUR-FILL ADJUSTMENT OF THE TRUNK OF QINGSHUIGOU CHANNEL AND THE RESPONCE TO FLOW-SAND REGIME

Daily observation data on river flow and sediment charges at Lijin hydrological station during 1950-2006,and fixed cross-section measurement data between Lijin and Qing 7 from 1976 to 2006 were employed to address the erosion/deposition pattern of the mouth channels of the Huanghe River and its relationship with water and sediment inputs since the Qingshuigou course was established.Results show that since then the incoming flow and sediment charges have remained in a lower level,with more sediment discharge concentrated in flooding season.Meantime,the accumulative dopositional amount in the main channel between Lijin and Qing 7 comes up to 3.15×10⁸m³,of which 1.11×10⁸m³ occur in flood season and 2.03×10⁸m³ in dry season,and most sediment load deposit in the reach between CS7 and Qing 7.The scour and fill process of the mouth channel is roughly experienced four stages,i.e.strong fill in flood season and slight adjustment in dry season(1976-1979),strong scour in flood season and strong fill in dry season(1981-1985),continuous fill in whole year(1986-1996),and scour in flood season and fill in dry season(1996-2006).There are two-year cycle of memory effects.Sediment amount of scour or fill in the mouth channel partially exhibited linear and/or rank correlation with runoff,sediment discharge and incoming sediment coefficient. However,water and sediment flux and water/sediment coefficients are not the major determinating foctor of the scour/fill pattern at the main channel.Flow and sedimentation process,riverbed boundary conditions and human activities play vital roles in scouring and filling process of the mouth channels.