Suspended sediment-discharge hysteresis characteristics and controlling factors in a small watershed of southern China.

• The 209 rainfall events were classified by hysteresis index and hysteresis loop. • The figure-of-eight and complex are the main hysteresis types in small watershed. • The peak rainfall intensity have significant impact on hysteresis types. • The main contributions types to soil erosion are figure-of-eight and complex. Suspended sediment concentration and discharge (SSC-Q) hysteresis characteristics during storm events can be used to indicate water–sediment response relationships. Evaluating SSC-Q hysteresis characteristics and their controlling factors is critical for watershed sediment management and the development of effective soil erosion control strategies. In this study, rainfall-runoff-sediment characteristics were analyzed under 209 flood events based on observed data from 2016 to 2022 to assess the sediment sources and hysteresis characteristics of a watershed in southern China. Principal component analysis was employed to further explain the control of antecedent rainfall conditions, conventional rainfall characteristics, rainfall fluctuation in the peak zone, and runoff characteristics on sediment transport under different hysteresis types. The results indicated that the figure-of-eight and complex was the predominant hysteresis patterns, accounting for 60.76 % of all events. Hydrological variables such as rainfall and runoff exerted different controls and explanations on the four hysteresis patterns: clockwise, anticlockwise, figure-of-eight, and complex. Water-sediment characteristics under different hysteresis types were more strongly correlated with the peak rainfall intensity, compared to the conventional rainfall intensity (I 30 , I ave). Peak rainfall intensity and runoff coefficient were the main factors controlling the clockwise and anticlockwise hysteresis patterns, respectively; the figure-of-eight was mainly affected by rainfall intensity and discharge, and the peak rainfall intensity and the antecedent precipitation mainly controlled the complex hysteresis patterns. Figure-of-eight and complex events were usually characterized by long duration, heavy rainfall, and high rainfall intensity, and produced runoff and sediment loads that accounted for 70.40 % and 80.88 % of all events in 7 years, respectively. Therefore, in the management and regulation of water and sediment in small watersheds, soil erosion brought about under figure-of-eight and complex flood events needs to be emphasized. [ABSTRACT FROM AUTHOR]