Figures 3–9 show the regression relationships between sediment concentrations and runoff amount under different rainstorm events. Correlations between runoff and sediment yield are diverse under different rainstorm events. Generally, sediment concentrations increase with increased flow rate, but when sediment concentration reaches a certain value, the change of sediment concentration is very small, even if the flow continuously increases. The value eventually tends to stabilize. It also shows that the influence of flow rate on sediment concentration has different effects during different rainfall erosion events. Therefore, the corresponding curve fitting can also be changed in different rainstorm events45. In all rainstorm erosion events, there is not always a strong correlation between runoff and sediment yield. Statistical analysis of 17 rainstorm events found that the regression relationships of 4 May 1997, 6 May 1997, 12 July 1998 and 26 July 2001 were weak, R2 (coefficient of determination) were all <0.5 and p values were all >0.05. The values of R2 for the rainstorm events on 18 August 2010 and 21 May 1998 are both <0.8, but there were three rainstorm events when R2 values were all >0.95 and p values were all <0.01 (23 June 1998, 26 August 2001 and 7 July 2000).Figure 3Relationships between sediment concentration (0–800 kg/m3) and runoff (0.002–0.022 m3/s) under different rainstorm events.Figure 4Relationships between sediment concentration (0–600 kg/m3) and runoff (0–18 m3/s) under different rainstorm events.Figure 5Relationships between sediment concentration (0–250 kg/m3) and runoff (0–8 m3/s) under different rainstorm events.Figure 6Relationships between sediment concentration (0–200 kg/m3) and runoff (0.004–0.016 m3/s) under different rainstorm events.Figure 7Relationships between sediment concentration (0–160 kg/m3) and runoff (0–7 m3/s) under different rainstorm events.Figure 8Relationships between sediment concentration (0–120 kg/m3) and runoff (0–0.7 m3/s) under different rainstorm events.Figure 9Relationships between sediment concentration (0–25 kg/m3) and runoff (0–0.01 m3/s) under different rainstorm events.