Beach Renourishment

The Problem: Beach renourishment consists of dredging and digging up sand from offshore or from inland sand deposits and pumping, trucking or otherwise depositing sand on a beach to replace what has been lost to erosion. While beach renourishment is almost always preferable to coastal armoring, it can negatively impact sea turtles in a number of ways. If the sand is too compacted for turtles to dig in or if the sand imported is significantly different (different color or sand grain size or if there is too much clay or gravel in the sand) from native beach sediments, it can negatively affect nest-site selection, digging behavior, incubation temperature and the moisture content of nests. If renourishment is allowed to proceed during nesting season, nests can also be buried far beneath the surface or run over by heavy machinery. In addition, a very flat and wide beach can cause turtles to nest lower on the beach and too close to the water where they can be covered or washed out during high tides and storms.

Dredging can also cause direct threats to sea turtles and their nearshore marine habitats. Hopper dredges that suck up the sand from offshore have been directly responsible for the incidental capture and death of many sea turtles in the US. Also if the sand is too fine or silty it can wash back out and cover near shore rocky bottom habitats that are used by many marine species and sea turtles.

However, when done correctly and in accordance with all laws to protect sea turtles and other natural resources, beach nourishment can add nesting habitat where erosion had washed it away. It is worth noting that a very wide beach resulting from nourishment is generally only beneficial to sea turtles in those areas where limited or degraded nesting habitat had previously existed.

Species Affected: All species of sea turtles are affected by beach nourishment and dredging.

The Solution:
  * Don't build structures too close to the active beach and mean high water line;
  * Promote coastal construction set-back policies;
  * Ensure that the renourishment project is in compliance with all environmental safeguards and regulations;
  * Avoid relying on sea walls to stop erosion;
  * Help re-plant native dune vegetation to reduce coastal erosion and protect nesting habitat.

Case Study: A multi-year study of a four-mile long renourishment project in Martin County revealed much of what we now know about the impacts of beach nourishment to the nesting beach and sea turtle nesting. The study consisted of collecting extensive nesting data on the nesting beach before the nourishment project and comparing it with data after the project and with another beach that had not been nourished. The study concluded that there was a significant reduction in nesting success (turtles that come ashore and successfully nest) and an increase in false crawls in the year following the renourishment. Also a higher percentage of nests are laid closer to the water (since the new beach is so wide and flat) and are prone to being washed out during high tides and as the beach begins to naturally recede to a more normal configuration. Most of these negative impacts were greatly reduced in year two and by year three nesting returned to normal.

Related links:
  * Beach Renourishment and Loggerhead Turtle Reproduction: A Seven Year Study at Jupiter Island, Florida
  * Indian River County Study

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