Influence of flow and sediment inputs on channel sediment delivery ratio: An example of the Yichang-Hankou Reach, Yangtze River, China

The channel sediment delivery ratio (SDR) of the Yichang - Wuhan reach in the middle Yangtze River has been determined using the concept of sediment budget at channel-reach scale, based on which the variation in SDR from 1956-1997 has been studied in response to the variation in sediment load and flow inputs. The SDR showed a increasing overall trend, but its variation can be divided into 4 stages: (1) increased rapidly from 1955 to 1962; (2) still increased from 1963 to 1975, but the rate of increase became slower; (3) rapidly decreased from 1976 to 1979; and (4) increased rapidly from 1980 to 1997. Some indices describing flow and sediment load characteristics have been related to the SDR, and then a multiple regression equation has been established between SDR and these influencing factors. The multiple regression equation indicates that channel sediment delivery ratio of the Yichang-Hankou# river reach increases with the increases in river flow and the ratio of the sediment diverted from the three outfalls, and decreases with the increases in the suspended load at Yichang station, the ratio of the flow diverted from the three outfalls and the flood discharge at Yichang station.