Dear Dr. De Biagi,

The subject of your manuscript is quintessential to rockfall protection. As rockfall models improve, there will be a strong need to establish rock volume/frequency relationships based on field observations. For this reason, we need to push forward with the manuscript.

Although the topic of your paper is quite mathematical I do not recommend extending the size of the publication. It should remain short and a "Brief communication". I tried to find ways to make the introduction and conclusions more readable, more general, but there too, I think you manage to present a good overview without too many technical details. The introduction is very clear.

Dear Dr. De Biagi,

Many thanks for your revisions. I had the reviewers look at your revised manuscript and they were very happy with modifications.

I want to stress that I believe your paper handles an important problem in rockfall science and I am hoping that your work will attract some attention. The introduction to the paper I believe is very well written and summarizes a fundamental problem in rockfall engineering. I also want to thank you for submitting your paper in the form of a Brief Communication. I believe we will see more and more authors use Brief Communications as a way to present significant results.

Many thanks again, Perry Bartelt