the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 27 Jan 2025
Measurements of aeolian sediment transport in the vicinity of coastal dunes on Spiekeroog Island, Germany, and extrapolation to annual transport volume
Abstract. This work presents a field study measuring aeolian sediment transport and wind profiles across a dune, and provides an approximation of the annual volume of aeolian transport into the dune systems of the East Frisian island of Spiekeroog, using commonly available meteorological data. Aeolian sediment traps were positioned along a transect aligned with the general wind direction during the measurement, starting on the open beach and ending on the back site of a selected dune. Wind profiles were temporarily measured next to four aeolian traps. Using a recent version of an aeolian sediment transport model, the total annual aeolian sediment transport into the dune systems is approximated. Input variables for this model are the time series of shear velocity and surface moisture. These are derived from the wind velocity measured at a height of 10 m and the amount of precipitation in combination with potential evaporation calculated using radiation intensity. The results are compared to volume changes of the beach and dune systems, which are derived from geospatial data. Data from the field study shows, that sediment transport occurs even behind twenty metres of vegetation on top of a dune. Further, the study indicates that the impact of precipitation on aeolian transport reduction can be lower within vegetated areas on a dune compared to the open beach. The approximation of the total annual aeolian transported sediment surpasses the actual volume changes of the dune systems as expected, however this difference varies depending on the compared beach section almost by a factor of five.
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RC1: 'Comment on egusphere-2024-4120', Anonymous Referee #1, 11 Mar 2025
General Comments:
The authors introduce a study on aeolian sediment transport over a coastal dune system in Spiekeroog Island, Germany.
The Introduction is carefully presented with appropriate and updated references, providing relative context to aeolian sediment transport and the challenges associated with measuring and modeling it.
The authors introduce five goals of the study, focused on the quantification of aeolian sediment transport and potential to extrapolate transport rates and trends over larger and longer spatial and time scales. I found the Materials and Methods to be well described and visualized, with appreciation for the figures in the Appendix (e.g., Wind roses of region).
Their experiment results are then compared to accretionary and erosional trends calculated through DEMs of Difference (DoDs) for three sections of the beach on Spiekeroog alongside meteorological data. Results introduce wind profiles that introduce spatial variance along the cross-shore of the coastal dune, extrapolated transport rates, and trends when extending results to larger spatiotemporal scales.
The discussion that follows focuses on challenges with aeolian transport extrapolation, challenges in field (and morphologic/vegetation) conditions, and how results from this field experiment compare to extant models. I found the work to be straightforward, concise, and had more specific comments for the discussion and conclusion, provided below.
Specific Comments:
Figure 5 – I would suggest standardizing the x-axis across the plots for AT1, AT4, and AT6. Right now, the transport rates look misleading as if AT4 and AT6 have similar rates between 0.2-0.4 m, yet they are a magnitude different.
Discussion – The discussion introduces challenges faced in the field, and how these challenges (alongside assumptions) could be responsible for variability throughout the instrument. I believe the discussion could be lengthened and serve to relate the findings introduced her back into the literature more heavily, which was explored further in the Introduction. (e.g., Relate to other field experiments exploring wind flow over a dune, scarp, vegetated dune, etc.) Even if many experiments are at the “event/episodic scale” across the literature, they would be applicable for this discussion. Further, I would restructure the conclusion to move relativity to previous experiments/papers to the discussion (right now the conclusion feels more like a discussion than a summary of main findings).
Line 304 – How much precipitation? Consider adding time series of local rainfall into Figure 6.
Line 436 – To quantify “sunshine duration” I would advise to include a time series for precipitation, especially given the relevance for surface crusting and resulting impact on aeolian transport potential. This is of critical importance when estimating yearly transport given local meteorological conditions.
Technical Corrections:
Line 19 – Is that the correct format for the Bagnold reference?
Line 67 – von Karman constant; check spelling
Line 68 – check formatting on Nikuradse reference, I believe it should be “by Nikuradse (1931),”
Line 111 – Sentence beginning with “Jackson and Nordstrom (2011)” is a bit confusing. Consider reframing or splitting sentence.
Line 151 – Remove italics from “1.5 m” for consistency.
Line 153 – check for consistency throughout; use of space between value and unit (9.45m or 9.45 m).
Line 156 – Be consistent with units/degrees of measurement. Should be 3.50 to 12.00 m following text above which provides measurement down to the ten’s unit.
Line 166 – Check consistency with units (italics or not)
Line 167 – maintain units (0.2 to 4.0).
Line 180 – Replace extents with extends.
Line 190 – Consider quantifying “half a day” into hours of data recording.
Line 194 – Incomplete sentence “The resulting shear velocities…”. Refinement needed.
Line 321 – Grammatical error – exceptionally (should this be exceptional?)
Line 332 – Grammatical error “This work simplifying assumes”; consider rewording start of sentence.
Line 343 – Confusion on where “The bottom row” is referencing. Please include figure and panel reference.
Line 346 – Grammatical error: “Table 2 lists is the annually” – Remove “is”.
Line 350 – Consider replacing “grow up” with “increase”
Line 356 – Add reference to LIDAR.
Table 3 – remove units from values throughout table; units are defined in top row.
Line 367 – Bathymetry data, or topographic LIDAR?
Line 415 – “aeolian transport [rate] exceeding the dune growth”
Line 416 – Remove comma after “could be”
Line 419 – “not considered [with/in] this approximation.”
Line 438 – Consider checking for consistency throughout on the reference for federal LiDAR DEMs. It seemed to be referenced differently throughout the manuscript which can lead to confusion (LiDAR, bathymetry, terrain models). Include reference to the dataset each time it is referenced.
Citation: https://doi.org/10.5194/egusphere-2024-4120-RC1 - RC2: 'Comment on egusphere-2024-4120', Anonymous Referee #2, 16 Mar 2025
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EC1: 'Comment on egusphere-2024-4120', Andreas Baas, 25 Mar 2025
Dear Authors,
We have received two peer-review reports and the open Discussion phase is now closing. The comments from referee #1 are supportive and suggest a minor revision. The review from referee #2, however, raises many significant concerns regarding the methods, data, and analysis and suggests a major revision, likely involving further/new analysis and a re-framing of the study results.
If you wish to proceed, please consider a major revision that addresses the concerns particularly of referee #2, together with a detailed author-response that explains how the issues were addressed. Please do not hesitate to let me know if you need more time for this work, as we can easily extend the revision period.
With best wishes,
Andreas Baas, handling editor, King's College London
Citation: https://doi.org/10.5194/egusphere-2024-4120-EC1
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