Review comment for "CRHyME (Climatic Rainfall Hydrogeological Model Experiment): a new model for geo-hydrological hazard assessment at the basin scale" by Andrea Abbate et al.

The authors present a new software that combines hydrological modeling with landslide and sediment transport modeling. With its distributed approach and physics-based modeling, CHRyME is a necessary complement to existing software.

This manuscript is an impressive paper that, because of its cross-disciplinary nature, addresses several very different topics. However, the sentence structure and the English do not always reach an adequate level, which, coupled with the vocabularies specific to the different themes, sometimes makes the text very difficult to understand. I would recommend checking the structure and meaning of each sentence using a translation tool. Furthermore, this article would benefit from additional references. I have made suggestions in this regard in the attached text.

Here are the main points:

1) The connection between the different modules is not as clear as it should be in Figure 3. For example, the amount of sediment available for transport is not determined, as I would have expected, by the number and size of landslides triggered, but by the Gavrilovic equation. Similarly, the link between the hydrologic model and the water-dependent variables in the stability equations of the landslide module is also not clearly established. It is therefore difficult to assess the degree of novelty of the model as a whole.

2) I am not very convinced by the 9-pixel buffer, nor by your validation using ROC curves (usually the area under the curve is calculated to quantify the quality of the indicator), for example. However, I think all these points would be much easier to accept if you developed a good "Model Limitations" section in your discussion.

3) Also, you sometimes write assertions that are too strong or are not well supported by references. I have highlighted some of these in the text. Try to be more nuanced and explain more your modeling decisions.

4) It is very easy to get lost in the names of different watersheds, subwatersheds, rivers, and stations. So I would recommend having a very clear map showing all the names and referring to it often. In addition, I would suggest referring to stations with the river names in parentheses afterwards, and always specifying the type of thing you are referring to: "Nure rivers" not "Nure".

I would recommend this article to be accepted under Major revisions, since its content is very interesting, but the way it is presented does not put it to its advantage. However, I also think that Rejecting it would be a good option, notably because I think that the GMD (Geoscientific Model Development) journal could be a (more) appropriate fit for a resubmission. Indeed, this manuscript could be of interest for audiences in natural hazard, but also for more fluvial geomorphology or hydrology publics.

Abbate et al. (2023) presented a modeling tool that simulates various surface processes, including landslides, debris flow, sediment transport, and erosion. The purpose of their paper is to present the structure of this model, along with some verifications conducted at multiple field sites across Italy. While the paper is interesting and offers an approach that contributes to closing the gap in our understanding and toolsets for landslide estimations, I have some concerns that must be addressed before its publication to improve the overall clarity of the manuscript. Although these are not fundamental modifications, addressing them could be time-consuming. Therefore, I recommend this paper for publication after a major revision or rejection at this time to provide the authors sufficient time for resubmission.

Here are the issues that need to be addressed:

1. The language in multiple places is unclear. I recommend proofreading to improve clarity.
2. The introduction should include a clear statement about the novelties of this newly proposed model to motivate readers. The authors should answer questions such as what CRHyME brings to the table that other models are incapable of doing and why landslide researchers should consider adopting this model instead of others.
3. More elaboration on the interactions of different model layers and within-layer processes is needed. Although some of the model components that solve hydrological processes were inherited from another model, providing the full picture of such processes is essential within this paper. For example, the formulations of how groundwater is handled and how percolation/exfiltration processes achieve communications between the soil layer and groundwater layer are not available.
4. The equations are difficult to follow. Although the nomenclature of the terms is provided in the appendix, explanations of some terms are still missing (e.g., Fds in Eq. 8). Furthermore, some symbols explained in the text, are not found in the equations, such as the temperature coefficient, T, not being present in any of the equations (Eq. 12, 13, 14). I recommend that the authors review each symbol in the equations and explain them clearly right after the equation.
5. In Figure 7, please use consistent units. For example, m3/s is used in the plots, but mm is used in the error metrics table, which makes it difficult to evaluate the errors. Moreover, the RMSE values for cumulative water volumes in the error metrics table do not offer any useful information. They might be removed.
6. The same figure indicates that the model predictions of river discharge are overestimated during the rainy seasons predominantly when using the MERIDA dataset, and all model predictions underestimate the discharge during the non-rainy periods (potentially due to the lack of baseflow). This result suggests that more water is partitioned as surface runoff in the model simulations, causing less infiltration. This may be an important issue causing underestimation of the landslides due to the reduced pore pressure in the subsurface. If the authors observed such model bias, please state it in the discussion section.
7. In Figure 10c, the model performed weakly during the initial year. The authors stated in the caption that this is due to initial condition uncertainties. I am curious why no spinup simulations were employed to minimize the impact of initial conditions on the model simulations.
8. In section 4.1, the hydrological performance of the model was discussed. While I agree that simulating the water cycle correctly in such basins is challenging due to the complexity of subsurface lithology and highly variable topography, the validity of the hydrological part of the proposed model may be more easily verified in a small, heavily monitored, less complex basin to ensure that the model performs satisfactorily. The authors should consider adding such model verification on top of existing test sites to verify the model's performance hydrologically.