| 04 Dec 2025
Morphological Response of Vegetated and Urbanized Barrier Islands to Hurricane Ian
Abstract. Barrier islands are vulnerable to extreme storm events which cause erosion and deposition of sediment. These morphological changes pose risks to both the built environment and natural habitats but are also affected by them. This study investigates the morphological impacts of Hurricane Ian (2022) on two barrier islands along Florida's Gulf Coast: the urbanized Fort Myers Beach, and Lovers Key, a naturally vegetated island and State Park. Using high-resolution pre- and post-storm topo-bathymetric datasets, we quantify patterns of erosion, sediment deposition and dune crest change. In addition, we investigated the morphological response of the developed and natural barrier islands by integrating spatially varying land cover data into the numerical model XBeach. Results show that the built environment on Fort Myers Beach significantly affects sediment transport pathways, causing localized erosion and deposition patterns distinct from those observed on the vegetated Lovers Key Island where dune crest lowering, landward migration, and storm-induced breach were prominent. Model simulations that incorporated detailed spatial variability of vegetation and built environment, replicated observed morphological changes with reasonable Brier Skill Scores, including the location of breach formation. Sensitivity analyses demonstrated that relatively small changes in roughness coefficient, wave skewness and asymmetry factor, morphological acceleration factor, and boundary water levels influence erosion intensity and sediment deposition patterns. Additionally, introducing supplemental vegetation patches in the model showed less dune erosion on vegetated barrier island, indicating that revegetation of islands may be beneficial. The findings provide insights into the complex interplay between storm forcing, land cover variability, and barrier island morphodynamics, and emphasize the importance of incorporating detailed land use and vegetation data in morphodynamic models to better assess barrier island responses to future storms under evolving climatic conditions, ultimately aiding efforts to enhance coastal resilience and adaptive management.
General Comments:
Review of article titled “Morphological Response of Vegetated and Urbanized Barrier Islands to Hurricane Ian” by Ilyas et al., submitted to Natural Hazards and Earth System Sciences:
This manuscript describes the morphologic responses of two barrier islands to the extreme conditions produced by Hurricane Ian. This manuscript uses a combination of multiple scenarios that incorporate different landcover classifications to determine which of the modeled scenarios most accurately replicates the observed morphological responses.
The manuscript makes a couple of important points. First, spatially variable bed roughness elements are important to include to best simulate the morphodynamic response of barrier islands during large storm events. Second, increased secondary vegetation densities can reduce erosion along dune environments.
However, this manuscript is limited in that it focuses only on dune response, instead of incorporating multiple morphological responses (i.e., changes in shoreline position, beach volume, beach slope, barrier-island interior volume, etc.) within the analyses. This study would benefit by incorporating more details about the total morphologic changes, instead of only focusing on impacts to dune crest height and dune crest cross-shore position.
Additionally, this manuscript fails to contextualize the results within the body of existing literature in the discussion. The discussion section could benefit by adding two different sections:
I think that the results presented in this manuscript are sufficiently important to publish, but the manuscript will need substantial revisions before it is suitable for publication.
Specific Comments:
*indicates more important/significant comments to be addressed
[40-45] – There is a lot of information on global mean sea level, which is not carried through the rest of the manuscript. I would suggest either limiting the amount of info about sea level, or carry it throughout the rest of the manuscript.
[70–71] – There should be more information about measured (or modeled) conditions produced by Hurricane Ian, including storm track, duration, wind speeds, water levels, etc. These conditions are published and available through Bucci et al. (2022), but should be included to provide context for the storm.
[80–99]* – There are a lot of different data sources that were used for the “observed changes” resulting from Hurricane Ian. These datasets are presented here but there are no specific details or information about the spatial uncertainties (both horizontal and vertical) of the different datasets, and the specific methodologies used to collect those data. For example, the authors discuss “LiDAR surveys” accessed by NOAA’s Digital Coast and different LiDAR surveys provided by Florida Gulf Coast University. Were these surveys collected using the same methods? Do they have the same uncertainties? Clarification and increased specificity for each of the datasets is needed here. Additionally, CEC transects extend up to 1km into the nearshore, were those collected by a total station, as noted in the manuscript, or was it done using bathymetric surveying (i.e., single beam sonar)?
[116] – The continuously updated digital elevation model that is cited through the NOAA (2018) reference is a 1/9 arc second DEM, which has a 3m pixel resolution.
[121] – How do the modeled wave and water levels compare to the measured total water levels during Hurricane Ian on Fort Myers Beach and Lovers Key? I think this should be addressed to validate the modeled water levels during the storm. These are accessible through the USGS Flood Event Viewer (https://apps.usgs.gov/fev/event/2022-ian)
[150–152] – Can the authors speculate as to why there were differences in the land cover classifications? Was it the result of differences in cell size or a different reason?
[167–170] – How did the authors differentiate beach berm crests from primary dune crests in Equation 3 at locations where beach berms (or berm ridges associated with ridge and runnel morphologies) existed following the storm?
[175–225]* – This whole section does a nice job of comparing the modeled outputs to the observed changes but only considers dune crest height and dune position as “morphological responses”. With many other morphologic responses (including changes in shoreline position, beach volume, beach slope, barrier-island interior volumes, etc.) excluded from this section (and excluded from the entire manuscript), this section should either be renamed to be focused only on dune responses, or expand it significantly to encapsulate more of the morphologic responses resulting from Hurricane Ian.
[Figure 6] – Why are the observed Pre- and Post-storm profiles labeled as NOAA+CEC? I thought those were two different datasets, with varying spatial scales and data collection methods (i.e., one is LiDAR and one is a total station survey)?
[230–275]* – See above comment ([175–225]) about morphological responses. Additionally, there is no section here about lateral or vertical changes in dune crest. Was this section excluded due to a lack of prominent primary dunes on Fort Myers Beach, or a different reason? A short explanation for why this was excluded from the Fort Myers Beach section should be included.
[261–263] – The observed deposition within the nearshore was a trend found in other field-based studies on Hurricane Ian (cited in the general comments section and next comment). Could you provide hypotheses as to why this is not seen in the modeled output of this study?
[278–282]* – How do your results fit into the bigger context of the growing body of literature already published on Hurricane Ian, as well as the modeled results from other previous large storm events from around the US and the World? The sensitivity analyses should still be a part of the discussion section, but the authors do not address how their work fits into the existing body of literature. For example, the authors could compare the modeled water levels from Hurricane Ian to the findings of McCann et al. (2024) and the modeled morphologic changes to the results of McCormick et al. (2025), Hauptman et al. (2024), and Wang et al. (2024). Additionally, the authors could provide more context for how their approach to incorporating variable bed roughness values for vegetation and built environments could have improved the results of previous studies that focused on other large storm events that impacted developed islands, such as Hurricane Michael or Sandy.
[294–303] – Are these examples of available datasets collected frequently enough, or at a fine enough resolution, to be useful for coastal managers?
[303–305] – This claim seems to be a bit of a stretch for the scope of this manuscript. Also, “vegetation restoration” is a little ambiguous and could use some clarification.
[308–309] – This statement is not well supported in this context. This paper shows that the XBeach model can “reasonably” approximate the results of the inundation regime during Hurricane Ian, and does not provide citations to support that the model can accurately approximate the three other regimes. Please provide citations of other studies that have successfully replicated the three other impact regimes.
[320–334] – This section would be better suited in the results section, as it is presenting new results relating to a different land cover scenario. The results of this then could be elaborated on within the discussion and include appropriate references that corroborate the results.
Technical Corrections:
[75] – “Lovers Key State Park comprises…”
[141] – Incorrect citation; should be “Salgano (2023)”
[Figure 3] – Need scale bars and North arrows on both sets of maps with different spatial extents and different rotations; maps of Fort Myers Beach are too small to determine the differences in landcover classification
[194–195] – Elevations should include the vertical datum (NAVD88?)
[203] – What do you mean by “waning flows”? Decreased flow velocities or ebbing flows, or both?
[Figure 5] – Dashed lines and shading are difficult to distinguish in greyscale, you may want to consider making these colored lines (in addition to the different dash types) to make them more distinguishable; may want to put orientation indicator to show which direction is North/South along the x-axis to orient reader.
[212–213] – Elevations should include the vertical datum (NAVD88?)
[230] – “Hurricane Ian”
[241–244] – “A noticeable effect…”: This sentence is awkwardly worded and redundant, and should be revised.
[259] – “4.2.1 Model Versus…”
[324] – Elevations should include the vertical datum (NAVD88?)
[350–353] – “Three model scenarios… Scenario 2 is based on…”: Need to reword these two sentences as there are typos and could be combined into one sentence.
[364] – “(waves and surge)”