|The manuscript discusses advantages and disadvantages of alternative flood protection systems to sandbags, the so-called Sandbag Replacement Systems (SBRS), taking into consideration their functionality, stability and handling. Sandbags or SBRS are also compared in terms of costs, helpers and logistics for installation and dismantling in three different cases:|
temporary flood dam, load drain in the case of a saturated dyke over an extensive area
and ring dike for reinforcement against heavy punctual exit of seepage on the inner embankment of the dyke.
The manuscript is well written and structured and it improved a lot since the previous version, mainly due to the merging of the two previous manuscripts and the clarification of many concepts.
Although I think that it doesn't add so much in terms of scientific knowledges (especially the first part, that is little more than a summary of Masolle et al., 2018), it addresses an interesting and rarely explored topic in the literature, and it can be interesting for decision makers and stakeholders, in order to improve the management of extreme events.
I will suggest to the author some modification more, in order to improve the scientific side even more and make the manuscript more suitable to be published in NHESS (I will refer to pages and lines of the version without track changes).
Concerning the introduction, I would try to be more clear in saying exactly what is the state of the art, which are the gaps and which are the aims of the study. For example, at P2L7-8, authors say "SBRSs are suitable fo flood protection and can be equated with sandbagging in terms of functionality"... It seems to be a conclusion based on the results of the study, it is not clear what author refer (if necessary, add citations). Similarly, there are other sentences that seem to be already a conclusion, while they should present the topic to be assessed in the study (e. g. P3L8-10, or consideration about costs and functionality. I think the reference to Fig. 7 is too far in the Introduction (P2L9), please revise this part. Statements at P3L13-14 and P4L16-17 need references. P5L11: ")." is missing, after 2019b. Please revise also sentence at P6L12-13.
I strongly suggest to add, before actual chapter 2, a chapter with the description of all flood defense methods considered in the study, included a brief description of sandbags and their construction, installation and possible reuse. This is useful, in my opinion, to better merge the two parts coming from the two previous manuscripts.
My main concern is about actual chapter 2: after having described a lot of SBRSs, tests are performed just on a few of these (or they are only partially performed) because of different reasons (accessibility conditions, avoidance of damages, difficulties in sand fillings, uneveness of the basin floor, particular condition of the floor with consequent neglection of underground failure risk, short duration of the tests, to mention some of them). In this case, are the results really valid? Can we talk about functionality, stabilty and handling of SBRSs in general? I think some clarification from the beginning are needed, in order not to expect results that are valid in general terms. In addition, I think a comparison with the performance of sandbags could give more coherence with the title and the rest of the manuscript (at the moment, functionality is a comparison term for only the different type of SBRSs, while costs and logistic are compared also with sandbags). Concerning the results part, I would only focus on those results, that can be quantify, in the scientific term. There are too many sentences that are too general and can be stated also before performing the tests (e.g. P12L8-11, P12L16-21, and others). I would better describe Fig. 10, included what the red line means. In Table 1, I wonder how can authors state results about wind influence or similar, when at P8L10-11, it is written that current, waves, wind flotsam and vessel impact cannot be investigated in the test facility. P15L19: please specify (with examples) what "authors' consideration" means.
Chapter 3: I would shorten this chapter a bit, also moving some part in the new descriptive chapter, e.g. the duration of sandbags and SBRSs (P20L19-29)
Conclusion: in general, I would avoid numbers, costs and percntages in this chapter, moving them in the results' chapter. P25L17: please specify the precautions you cite. P25L17-P26L2: how can you speak about subsoil failure risk if you didn't consider it in the tests?