Since 1918, numerous efforts to establish and stabilize Sebastian Inlet for navigation have occurred over the years resulting in the construction of jetties and a sand trap. The current structural configuration consists of a north jetty approximately, 1,600 feet in length, and a southern jetty of approximately 1,200 feet. The sand trap has a design capacity of 180-190,000 cubic yards.
The inlet channel, sand trap and associated structures are maintained by the Sebastian Inlet District Commission. Maintenance dredging of the channel and sand trap occur periodically, with placement of suitable material on the downdrift beaches located south of the inlet.
Previous studies of the inlet suggest the need to bypass between 70,000 and 75,000 cubic yards of material annually to offset the impacts of the inlet. In an effort to meet the bypassing objective, the District places material from an upland source on the downdrift beaches when sufficient material is not available from the sand trap.
The Sebastian Inlet District completed its review with a Technical Advisory Committee (TAC) over a period of one year to better define sand bypass needs and bypass alternatives through the development of a new inlet management plan. The recommendation from the TAC is to increase the sand bypass target to 90,000 cubic yards on an average annual basis. The Inlet District worked cooperatively with Indian River County to achieve a renourishment of the Ambersand Beach Project following the 2004 hurricanes. Approximately 85,000 cubic yards of sand was removed from the District’s sand trap to enhance the 158,00 cubic yards of sand that was dredged from offshore by Indian River County in 2007-2008. In 2010 the District partnered with Indian River County to renourish the beaches south of the inlet. The District’s fill template immediately south of the inlet was healthy, not requiring more sand. Due to the state mandate of beach renourishment, the District is obligated to place sand on the beach to maintain its annual beach fill quota. The Indian River County project placed 267,182 cubic yards of sand from upland sand mines starting approximately 5 miles south of the inlet to north of John’s Island. The upland sand source was significantly less expensive than previous offshore dredging costs by nearly $10 per cubic yard which helped stimulate the local economy by using local sand mines. The District contributed $4,184,070.12 to the project and gained 3 years of sand credit in Phase I of the project. In 2012, the District dredged its Sand Trap, extracting 122,000 cubic yards of beach quality sand. The material was placed on the beach south of the inlet between R-4 and R-9.
The Inlet District continues to focus on the identification and implementation of more efficient sand transfer alternatives. We have constructed a material management area within the State Park. The permanently constructed disposal facility will allow the District to provide supplemental fill for projects south of R-17 in Indian River County. The facility will also provide the opportunity to dredge during summer months, managing some of the smaller shoals with good beach quality sand. The DMMA was completed in August 2011.
In February 2013 the District completed an emergency dune restoration project for erosion from Hurricane Sandy. A total of 34,614 cubic yards of sand was placed on the beach from R-8 to R-17. 16,614 cubic yards of beach quality sand came from the District’s DMMA and an additional 18,000 cubic yards of sand was purchased from Davis Mines. Total construction cost was $547,316.86 or $15,81 per cubic yard.
In 2014, Orion Marine Group out of Tampa, FL was awarded a bid for the sand trap dredging, excavation and expansion project. Over 11,000 cubic yards of beach quality sand was removed from the sand trap and placed on the south beaches prior to May 1, 2014. After May 1st, over 50,000 cubic yards of coquina rock and were dredged from the bottom of the sand trap to gain more capacity and create a more uniform trap. This material was placed in the District’s Dredged Material Management Area (DMMA). Work began in December 2014 to separate the rock and sand within the DMMA. Working in conjunction with Indian River County, the Sebastian Inlet District placed 56,126 cubic yards of sand in Sectors I and II, south of the inlet. The District pulled 31,250 cubic yards of sand from its DMMA and piggybacked onto Indian River County’s contract for Davis Mine to place an additional 24, 876 cubic yards of sand onto the down-drift beach, for a total of 56,126 cubic yards of beach quality sand. The beach placement was completed on February 17, 2015. All of the material in the DMMA was screened, leaving 4,000 cubic yards of rock that will be used to fortify roads and public areas with the Sebastian Inlet State Park. An additional 35,000 cubic yards of beach quality sand remains in the DMMA to be used for emergencies in the coming two to four years while The District awaits the newly expanded sand trap to fill to capacity with sand.