Beach Nourishment and Turtles – Can They Get Along?

Issue 2, 2004 Articles:

* Money Talks and Turtles Prosper, CCC’s Tortuguero Efforts Have Global Impact
* Beach Nourishment and Turtles – Can They Get Along?

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Beach Nourishment and Turtles – Can They Get Along?

By Gary Appelson

The tracks of a female loggerhead can been seen along the side of a pipe used during a renourishment project on Florida’s Gulf Coast.

Florida’s beaches host over 90% of all sea turtle nesting in the U.S. How the state manages its beaches has a profound impact on the long term protection and recovery of sea turtle populations. CCC monitors coastal policies and advocates for policies that improve the long-term outlook for sea turtle survival.

Almost 40% of Florida’s sandy beaches are in a state of “critical erosion.” In order to protect upland structures and recreational, cultural, or environmental interests, state and local governments look to beach nourishment (renourishment if a beach has previously been nourished), a costly, and often controversial engineering solution.

Depending on sand sources, beach design parameters, monitoring protocols, and surf conditions, nourishment projects can adversely impact sea turtles in many ways. These dredging projects can also impact or bury offshore reefs. During the past two years, beaches in Brevard County, Fla. were nourished. The project area, just to the north of the Archie Carr Wildlife Refuge, contains beaches with nationally significant nesting densities for sea turtles. The good news is, it appears the Brevard County project had minimal long-term impacts to sea turtles and their nesting habitat.

The Brevard County Shore Protection Project (BCSPP) contained 2 phases. Phase 1, The North Reach (9.4 miles) was constructed from November 2000 to April 2001. Phase 2, the South Reach (3.8-miles) was built from February to April 2002, before construction was stopped for turtle nesting season. The last mile was completed in April 2003. The project area is expected to need renourishment on a smaller scale every six years.

Sea turtles were given high priority by county officials and state regulators in the design, construction and monitoring of the BCSPP. Close attention was paid to the selection of the off shore borrow areas where sand was obtained to ensure that the sand was compatible with native beach sand and suitable for turtle nesting. The county monitored the constructed beach for excessive sand compaction and scarp formation that could be problematic for nesting.

As the project proceeded, the county and state regulators provided input into the design of the project. In the South Reach for example, construction began during high spring tides. Consequently the constructed beach could be overtopped by waves, resulting in ponding on the beach. The design was modified during the project to allow an increase in beach elevation, resulting in a more natural slope and reducing the risk of sea turtle nests becoming flooded by high tides.

State regulation in Florida requires three years of post-construction monitoring to look at the new beach’s impacts to sea turtles. Results from the Brevard County project show nesting numbers in the first season after construction dipped slightly, but by the second season nesting was at least equal to historical figures. However, the total number of nests laid does not provide adequate information on overall possible impacts to turtles.

The University of Central Florida’s Marine Turtle Research Group (UCF) was contracted to study sea turtle reproduction during the 2002 and 2003 nesting seasons. The UCF team monitored three key indicators of sea turtle nesting beach success: overall nest production; nesting success (ratio of nests laid to number of false crawls); and reproductive or hatching success (percentage of eggs hatching and producing hatchlings that emerge).

Nest Production- Loggerhead nest production in 2002 only totaled 972 nests, slightly more than half the pre-nourishment average of 1,794. In 2003, loggerheads laid 1,798 nests, slightly above average.

Nesting success- In 2002 the rate was 0.31, below the average rate. In 2003 loggerhead nesting success was 0.54, reflecting a return to the long term average rate.

Reproductive success- In 2002 the rate was 60.8%. In 2003 the hatching success returned to normal for the project area with a hatching success of 67.9%.

Disorientations- A possible consequence of raising the beach profile is that upland light sources can become more visible to nesting turtles and hatchlings, resulting in increased lighting disorientations. The pre-nourishment average number of disorientations was about 2 per year, far less than the 179 disorientations documented in 2003. It is not possible to prove this dramatic increase was a direct result of the elevated new beach. Nonetheless, the county stepped up enforcement of its lighting ordinance and identification of lighting violations. It also sent lighting information flyers to every beachfront property owner.

The overall assessment of this project’s impacts to sea turtles is summed up by comments from Dr. Lew Ehrhart contained in UCF’s final monitoring report. “We attribute this quick return to normal nesting success to the equilibration of the beach profile (the process by which the new beach adjusts to wave and wind action). In addition, we are convinced that the relatively high hatching success rates demonstrate that good quality sand and beach construction has resulted in normal to high success rates for marine turtle egg incubation.”