Adjusting the water-sediment matching relationship to reduce sedimentation in the flow rate constraint reach of the Lower Yellow River, China

Abstract

The bank-full discharge along the Dongbatou-Aishan river reach of the Lower Yellow River is significantly lower than that of the upper reach and is the flow rate constraint reach that dictates the flood safety of the Lower Yellow River. The water and sediment matching relationship is the important factor that affects scour and siltation along this reach. It is necessary to control the relationship between water and sediment by retaining a portion of sediments in the upper reach in order to increase the overflow capacity in this reach. We first analyse the relationship between the water and sediment processes of the Lower Yellow River and the scouring and siltation of the constraint reach and verify the water and sediment conditions that require sediment retention in the upper reach. By analysing the characteristics of the river, we determined the area of sediment retention to be the reach that stretches from Xiaolangdi to Huayuankou. The relationship between the incoming sediment coefficient at Huayuankou Station and the percentage of sediment discharged and deposited in the lower reach is analysed. The results showed that when the incoming sediment coefficient is more than 0.04 kg.s/m6, sediment should be retain in the Xiaolangdi-Huayuankou river reach to maintain non-siltation in the constraint reach. Using bank-full discharge in the river reach from Xiaolangdi to Huayuankou and the channel stability as constraints we propose that the sediment retention in this river reach should be less than 0.144 billion m3.