Review of “Impacts of Barrier-Island Breaching on Mainland Flooding During Storm Events applied to Moriches, NY” written by Catherine R. Jeffries, Robert Weiss, Jennifer L. Irish, and Kyle Mandli and submitted to Natural Hazards and Earth System Sciences.

This paper describes the modelled breaching behavior of a 1938 Hurricane that made landfall in Moriche Bay, New York, USA, to gain a better appreciation of how hurricanes can initiate and generate breaches in barrier islands for future coastal community protection in these areas. This paper is a timely and important contribution to the literature examining the impacts of hurricanes on these environments with significant implications for the communities and infrastructure developed in these regions. The technique applied is sound and can be translated to other geomophologically-similar sites around the world to improve coastal hazard management and adaptation. As such, the paper would be of interest to a wide audience.

The paper is generally well written (but see minor comments below). The introduction, methods and results are clear and conclusive (but see minor comments below). However, the paper is not acceptable in its current form based on the Discussion.

The Discussion is a very well written interpretation of the results, but lacks any connectivity to other research. It is unbelievable that not a single reference is cited in the Discussion! I urge the authors to compare their results and interpretations with the work of others who have conducted similar analyses in coastal barrier island systems. The authors could also compare their findings with the findings from other sandy coastal systems, and from other types of coastal hazards.

In addition, it would be very useful to practitioners, industry, policy-makers, decision-makers and the local community if the authors could extrapolate their findings to articulate what the impacts on the community and infrastructure would be if a repeat of this storm occurred today.

Minor comments:

L12: Please rephrase “we’ve”

L50: space between ‘),’ and ‘these’

Throughout: Referencing not in correct format, e.g. L51 “by (Visser” – this is likely a software issue, but please correct.

L80: What is the difference between Moriches and Moriches Bay? Could these be labelled in Figure 1?

L81: What is the population?

L81: Please provide some details on this damage

Figure 1: Is this a LiDAR image? What is the vertical scale? The storm track in the inset could be more pronounced. Could you please label the features ie. the Moriches Bay and the various islands, in the main image. What is that weird cross hatching in the barrier island between b and c?

L91-92: What is the evidence for this? How quickly did they close after the Hurricane? Please explain how significant these breaches were for flooding? Please show where these breaches occurred on Figure 1.

L100: In what case? Recommend deleting

L102: Please spell out “ADCIRC” and use acronym in future.

Figure 5: Hanging sentence “(west” – Should there be something following this?

Overall, I believe the above changes are easily addressed by the authors and I look forward to seeing the next iteration of this manuscript.

General comments

The study presents convincing evidence and modelling for breaching of a barrier island during a hurricanes on the US East coast that impact inundation mainland. They demonstrate that the number, location, and size of the breaches can significantly change the inundation potential for the coastline.

The authors create a framework that allows breaching to develop during a simulation and imposes a breach in an approximation of a Gaussian bell-curve that deepens over time. They then simulate storm events by varying the size, location, and number of breaches in the barrier island and examining the storm surge and inundation is affected by breaching; total inundation has a logarithmic relationship with total breach area which tapers off after the entire island is removed. Breach location is also an important predictor of inundation and bay surge.

The work is important as understanding vulnerable areas and examining how breaching impacts barriers can provide opportunities for shoring up infrastructure (or perhaps the authors could add a stronger suggestion of not building or rebuilding in these locations). The work will also allow planning that minimizes hurricane disruption to coastal communities.

Specific Comments

Lines 30-33      Awkward sentence

Line 40 and 44  Check referencing format

Line 46 at and at in same sentence

Line 53 just geological mapping no need for the ‘a’

Line 83 change especially to a real word like particularly

Line 88 add more details maximum winds

Line 159 should be computation time

Line 282 awkward sentence

Figures

 I suggest you unify fonts and scales. The size of the text in figs 8,9 and 10 also seems a little odd. The lat longs are in larger font size then the scale and features. You may also want to annotated the figures to highlights the key features you want the reader to be drawn to.