Fig.1 Tectonic and topographic distribution map of the upper Minjiang River

Fig.2 Slope-break knickpoints on the main stream of the Minjiang River and the geomorphic differences between the upper and lower reaches

Fig.3 Chi-plot and slope-area double logarithmic graph for identifying knickpoints. Modified after [12].

Fig.4 Distribution of slope-break knickpoints in the upper reach of the Minjiang River

Fig.5 Longitudinal profile and distribution of knickpoints in the main stream and major tributaries of the Minjiang River

Fig.6 (a) Chi-plot and slope-basin area map of the main basin of the Heishui River; (b) Longitudinal profile and distribution of knickpoints in the Heishui River and its tributaries

Fig.7 (a) Reference concavity and optimal chi value when the concavity is 0.45 and the chi interval is 1.6, the chi-plot of all channels in the upper reaches of the Minjiang River (the red line represents the average curve of the study area); (b) The elevation deviation between the channel chi-plot and the actual channel under different chi value intervals

Fig.8 (a) Dimensionless uplift history (t* represents the chi value in Fig. 7b); (b) Dimensioned uplift history simulated according to different K values

Fig.9 Optimal combination of erosion coefficient and area index and time interval (a) The optimal combination of K and m in the 20 groups of Heishui river (red dots represent the optimal combination of K and m); (b) The optimal parameter combination values for knickpoints formed at different formation times at the estuary

Fig.10 Simulated migration rate of knickpoints formed at different times

Fig.11 Fitting degree of the Heishui River Basin (a) Residual sum of squares under different formation times of knickpoints; (b) The fitting degree between the actual position and simulated position of knickpoints formed at 1.3 Ma estuary

Fig.12 Spatial distribution map of the actual and simulated positions of knickpoints formed at 1.3 Ma