This is an interesting paper about the Beida River, North Qilian Shan. Based on geomorphometric analysis and the geochronology of fluvial terraces, the authors infer a climatic origin of phases of fluvial incision and knickzone formation. Overall, the authors offer convincing arguments for their interpretation. Yet, I have a few questions and comments that should be addressed in a revised version of the manuscript.

1. The three rivers shown in Fig. 2 have in common that they have a prominent knickzone as well as that they incise into the foreland-basin. The along-river distance of the knickzone to the mountain front is in all cases similar. According to the stream power incision model, however, slope patches should move upstream at a velocity dictated by upstream area. Hence, the three rivers should have similar upstream areas. However, looking at the map, the three sites seem to have very different areas. A way to address the effect of variabe drainage areas is to calculate chi as a horizontal along-river distance. This might be very helpful because it would provide additional evidence for (or against) a common base level drop, if all three knickzones should have similar chi values measured from the mountain front. 

2. It is interesting to note that some of the rivers draining the North Qilian Shan have steeply incised in the foreland while others have not, at least those that seem to have smaller drainage areas (I have not investigated this in detail, though, so this may be a bit speculative). Looking at GEarth, it seems that in particular those rivers with small catchments upstream the hanging wall are rather accumulating and form large fans with no (at least to me) obvious trend towards incision. Where these rivers drain into the gorges carved by the Beida river (and the other larger rivers), these smaller rivers are fluvial hanging valleys and show signs of headward erosion. How is it possible that under a general increase in precipitation, there are such different patterns in river incision? Or are there other processes responsible for the incision? For example, could a lack of sediment connectivity and increased sediment storage behind terminal moraines in the higher areas drained by the major rivers be a possible explanation for sediment starvation of the main rivers and thus incision? At least, this explanation would not be at odds with the data as well as your interpretation of the other terraces, as well.

3. As noted in the previous comment, I think that the paper could benefit from some more geomorphometric analysis. So far, the authors mainly looked at the trunk streams of the rivers, and focussed this analysis on the Baida River. In order to generalize their findings, however, some additional work is required that shows that the findings are consistent with the other drainage basins having these knickzones. One interesting observation that could shed additional light on these river systems is the analysis of the tributaries to these rivers. Looking at the DEM in Google Earth reveals numerous fluvial hanging valleys tributary to the river downstream of the knickzone while they are missing upstream of the knickzone. Finally, comparison with incision rates measured elsewhere would help to judge the plausibility of the incision rates which are extremely high.

4. A short comment on the supplements: The quality of the pictures in the supplements is relatively bad. Consider storing the pdf with images in higher resolution.

5. A short comment on the figures: I partly found it difficult to read these figures. Perhaps I am getting old, but some of these figures (in particular photos) are very small.

All in all, I think that the paper should be considered for publication in ESURF after moderate revisions. I hope that my comments are helpful to improve the manuscript.

Wolfgang Schwanghart

This manuscript studies the river terraces of the Beida River in the northern Qilian Shan. The authors survey and date the terraces and use this information to reconstruct changes in incision rate through time. The authors then discuss the origin of a steeper segment within the channel profile and link it to an increase in precipitation during the mid-Holocene. I think the manuscript has potential, but a more thorough analysis would make this a much stronger contribution.

My pain point is that a more thorough morphometric analysis would benefit the manuscript. The authors argue for a precipitation increase which should be regional. Therefore, it would be good to have chi-plots of the Beida and neighboring rivers, including tributaries, for the lower river section where the knickzones are located. Are the knickzones migrating up the tributaries, too? Are they at the same chi-distance compared to the trunk rivers? If, e.g the knickpoints do not manage migrate up the tributaries as fast the trunk (in chi-space), this could be an indication that glacial melt is indeed the controlling factor, whereas an even increase in precipitation should affect all streams in the region in the same way.

I would appreciate more clarity in the way tectonic drivers controlling the profile geometry are ruled out. The first argument presented is that the current channel is carved in bedrock and not just an excavation of the old alluvial fill. I do not see the connection between this argument and incision due to a period of increased uplift. I would appreciate some clarity on this point. The second argument about incision rates being higher as uplift rates is good but it would be far more convincing if you present it in terms of total uplift since the abandonment of T1 versus total incision. This point would come across a lot better with more visual support within some figure. Also, there’s no figure that visualizes where the folding happens. Figure 3 would also benefit from having the locations of faults (active and now inactive) on the map, similar to Wang et al. 2020.

This might be more of a side note, but judging from Wang et al. 2020, the knickzone is located just above a thrust fault that became recently inactive, correct? Maybe it should be pointed out that this fault has been inactive for a time exceeding the age of the terraces studied here.

Line 60: Please, highlight the Hexi Corridor in figure 1. I had to look up the name.

Line 89: Seems like either a word is missing or something else is wrong with the sentence.

Line 118: What grain size was the measurement performed on?

Line 180-2: The Loess was dated to 3.2kyrs, therefore this is a minimum age and not the age of the terrace, correct? And same would apply to the incision rates.

Line 192-3: This is weird. Why would the river cut through bedrock instead of the soft alluvium?

Line 234-243: This sounds good to me, but I feel like the whole paragraph could be a lot shorter if there was somewhere a geologic map of the Beida and the neighboring rivers, with the steep segments highlighted. Could also be in the supplement.

Figure 1: I have two points that are more of a suggestions. It would be good if the color map could be changed to something that is perceptually uniform (e.g. https://www.fabiocrameri.ch/colourmaps/), and please add an underlying hillshade to improve visibility of the topography.

Figure 3: The label of Fig. 2C needs to be changed to 3C. I find it very confusing that the samples are indicated by alphabetical labels, because intuitively I would think that the letters indicate the locations of the picture panels. Please, use numbers or something else instead. Also, please highlight the geologic contacts. I cannot see the contact between alluvial fill and bedrock in figure 3D.

Richard Ott

Please see the attached pdf for my review.

Please see the attached pdf.