The author appreciates the issue raised in the response regarding the negative assessments of artificial nourishment’s effectiveness that are skewed by insufficient attention to the sedimentological aspects of the issue.
Two data bases were used in this review paper for beach nourishment projects in the United States—Western Carolina University (WCU, 2024) and American Shore and Beach Preservation Association (ASBPA, 2024)—and include 2482 and 3633 episodes of beach nourishment, respectively. An investigation of the relationship between grain size and nourishment lifespan at a significant number of these thousands of nourishment episodes would require a massive time commitment, if, in fact, the project reports included data on grain size and its variation for both the target beach and the imported sand. However, these data bases are limited to location, number of nourishment events, dates of first and last nourishment episodes, total volume of sand, known maximum length of project, and known total cost.
Broad agreement supports that if sand finer grained than the native sand is placed on a beach, then it will almost certainly have a short lifespan. Thus, it is desirable to use sand for nourishment or replenishment that is of similar grain size or a grain size coarser than the native sand (Campbell and Benedet, 2004).
This raises two additional issues. Beach nourishment costs are already very high and increasing, and for most U.S. Atlantic coast projects, the imported sand is typically what is conveniently located immediately offshore. Searching and importing coarser grained sand, if such sand were available, along the Atlantic coast would add significantly to nourishment costs. The question is also asked whether beach nourishment is primarily intended to restore (or build) a surface for tourism and recreational use, or whether it is predominantly a coastal defense measure. The author further states that it can be both. I would argue that although gravel or cobble beaches will generally be much more stable and would last longer than sandy beaches, recreational uses of gravel or coarser beaches are more limited and much less desirable than sandy beaches, at least in the United States, and preclude many uses (e.g., walking, jogging, volleyball, soccer) other than sitting because of their coarseness and slopes (Figures 1A, 2A, and 3A). Many stable gravel or cobble beaches are certainly found along European coastlines, some of which may have been nourished, that are used by default when no sandy beaches are available ( Appendix Figures 1A–3A).
Three statements in the introduction to the discussion of this paper also provide critical context to the discussion:
“… beach nourishment is nevertheless considered a suitable strategy to counteract the advancing sea, even though it will pose serious problems because, considering the volumes already extracted annually, sand is a scarcely renewable resource,” (UNEP, 2019).
“Most of the scientific community agrees that strategic retreat is the more economically sustainable solution when taking a long-term perspective and considering future generations, at least for areas not densely urbanized,” (Brown et al., 2021; Hinkel et al., 2014; Jonkman et al., 2013).
“It will not be possible to live along low coastlines solely by defending against the waves, and the adaptation or relocation of coastal settlements will become a pressing necessity”
I agree and would add that the most valuable conclusions from this paper, which is focused on beach nourishment in the United States, are that the short life spans and the need to continually nourish most beaches (Elko et al., 2021)—along with the environmental effects (Woodbridge, Henter, and Kohn, 2016), occurrence of short-term extreme events, and accelerating rise in sea level (Parkinson and Ogurcak, 2018)—provide a strong rationale for terminating federal expenditures and dependence in the United States on short-term and repeated beach nourishment and planning for the inevitable long-term necessity of moving back from the shoreline.
LITERATURE CITED
APPENDIX
Steep coarse-grained gravel beach on the Jurassic coast of the United Kingdom.
Steep coarse-grained gravel beach on the Jurassic coast of the United Kingdom.
Steep coarse-grained gravel beach on the Jurassic coast of the United Kingdom.
Steep coarse-grained gravel beach on the Jurassic coast of the United Kingdom.
