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Beach nourishment has many positive aspects: Wide sandy beaches protect uplands, provide habitat and a place to nest and rest, and are a vital economic resource for coastal communities and the country as well.
However, there are some consequences associated with beach restoration which scientists and regulatory agencies watch closely. One of them is the impact of dredging and sand placement on a beach on the bottom rungs of the marine food chain – the worms, clams, crabs and other tiny animals generally referred to as benthic infaunals and typically found either on the beach near the wave zone or on the bottom in the nearshore or offshore areas. You may have dug up mole crabs or the tiny clams (Donax) while building a sand castle as the water rushes in and out.
The potential for impact is obvious, since these animals either live offshore (where the sand is taken from) or on the active beach (where the sand typically ends up). Therefore, beach restoration projects are often required to monitor the impact the project has on these creatures, the time it takes them to recover and what conditions help (or hinder) that recovery.
Why should we care? Aside from striving to minimize the environmental impact of an otherwise beneficial activity, benthic infaunals fulfill a number of ecologically valuable roles:
- They are an important link in the marine food web, converting phytoplankton into food that’s accessible to higher levels in the chain.
- They offer a valuable snapshot into overall environmental conditions in the given marine ecosystem, both as early warnings of larger disasters and continuous monitoring of a given area (since they move around a lot).
- They are particularly valued for their ability to flag pollution, low oxygen and excess sediment, and the impacts those have on an overall ecosystem over time.
- They can also break down waste and other natural organics for food, further augmenting their role in the food web.
“In general, best management practices of nourishment during the appropriate time of year with similar sand to the native beach sand will help minimize impacts,” said Nicole Elko, the American Shore & Beach Preservation Association (ASBPA) Vice President of Science & Technology (S&T). The ASBPA S&T committee looked at the findings amassed so far, and has drawn some initial conclusions as to “best management practices” for such projects:
- Beaches nourished with sand that matches what is already there shows better recovery rates than those where the sediment is a mismatch – because the organisms find a compatible home on a properly restored beach and will return to good health faster.
- Avoiding active nourishment efforts during the period when these organisms are at “peak larval recruitment” – meaning when new organisms are being established.
- Beaches that were restored during the warmer months showed a better recovery than those finished in colder months. They posit that the organisms have a chance to begin recovery if the waters are still warm enough to encourage repopulation before the weather turns cold – rather than having to wait all winter to begin their recovery.
- Organisms at offshore borrow sites (the places where sand is dredged to be placed on the beach) overall tend to recover pretty well, particularly if there are compatible sites nearby where they can move until the sand removal process is complete.
- Borrow sites in active shoal areas (where natural in-filling is likely to be quicker) recover better than sites in less active bottom areas. This can help guide the engineers to certain areas of a shoal to be used as a borrow site, where the natural forces moving sediment around will expedite in-filling and, thus, recovery.
- How sand is removed also affects recovery. Shallow cuts, leaving areas of undisturbed sand between borrow site strips and avoiding deep steep-sloped pits all can expedite recovery
“Understanding and implementing best practices for beach nourishment projects are critical for the future health and stability of coastal communities,” said Tiffany Roberts Briggs, Ph.D. Assistant Professor for Geosciences at Florida Atlantic University. “Through the synthesis of recent, relevant literature and summarizing recommendations for maximizing recovery times of benthic infaunal communities after dredging, the committee has provided what we hope to be a useful document facilitating efforts for holistically successful coastal projects.”
Providing project managers and researchers with this background should enable them to make choices that will expedite recovery after a beach nourishment project, as well as to make the permitting and regulatory monitoring aspect of those projects quicker and more beneficial to the overall beach ecosystem.
If we can minimize the inevitable impacts of beach restoration, it will further maximize the overall benefits such projects can bring to all the creatures who rely on the coast for their lives and livelihood.
NOTE: The committee’s complete white paper is available at https://asbpa.org/publications/educational-resources/
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ABOUT ASBPA: Founded in 1926, the American Shore & Beach Preservation Association (ASBPA) is a 501(c)3 nonprofit that advocates for healthy coastlines by promoting the integration of science, policies and actions that maintain, protect and enhance the coasts of America. For more information on ASBPA, go to www.asbpa.org, Facebook or www.twitter.com/asbpa. For information, to change your email address or to unsubscribe from this list, contact us at managing@asbpa.org. A complete collection of Beach News Service articles is available for media access online at https://asbpa.org/publications/american-beach-news-service/.