New Sebastian Inlet Report Confirms Coastal Processes Affecting Entire East Coast of Florida
In a new report citing long-term data gathered on the hydrodynamics and meteorological forces at work in the Sebastian Inlet area, scientists at Florida Tech have now conclusively linked sand volume on adjacent beaches and within the nearshore sand transport system to seasonal and inter-annual sea level change, coastal processes that affect the entire East coast of Florida.
Periods of sea level rise correlate to cumulative sand volume losses, and periods of falling sea level can be directly linked to sand volume gains. Variations in Gulf Stream flow off the coast can produce a rise and fall of up to 3 feet annually in sea level and upwards of a 20,000 cubic yard variation in sand volume.
After more than a decade of ongoing research and data collection, these finding were among those published in the 2019 State of the Inlet report. The report was funded by the Sebastian Inlet District (SID) in partnership with Florida Tech’s Dr. Gary Zarillo, professor and researcher with the Florida Tech Department of Ocean Engineering and Marine Sciences.
“It’s quite difficult to extract these findings from other coastal processes at work without long-term, continuous data sets, and we couldn’t be conclusive without it,” said Dr. Gary Zarillo, Florida Tech. “No one was studying how seasonal sea level changes, linked to Gulf Stream dynamics and multi-year variations in sea level, were affecting sand volume on our beaches. These data can be employed by all coastal communities as part of coastal resiliency planning so the reach is far broader than just our local area.”
Based on identified trends and data from late-2018 to January-May of 2019, Dr. Zarillo is forecasting the beginning of another period of sea level rise.
The first State of the Inlet report was published in 2007, after SID entered into a long-term coastal applied research agreement with Florida Tech to monitor sea level changes, natural sand transport and accumulation within the inlet system so SID could effectively manage sand resources and fulfill its mandate per the Florida Beach Management Act which requires SID to bypass sand that migrates into the inlet.
The report, published annually, quantifies the volume of sand contained within inlet reservoirs which helps determine SID’s sand bypassing budget, looks at morphological changes within the inlet system, and conducts a numerical modeling analysis of hurricane impacts and infilling patterns of the inlet’s sand trap, a 42-acre depression that accumulates sand. It is shared with the Florida Department of Environmental Protection (FDEP), and Brevard and Indian River counties.
“We are one of the most data rich inlets on the East Coast of the U.S., and it’s important we continue to collect this type of scientific data to refine District projects and the Commissions’ management of the inlet system,” said SID Executive Director and Florida Tech graduate James Gray. “Sand is in constant motion. We know how sand moves through the system, at what volumes and have trends over a long-term period that allow us to be more effective in our work. Based on the data, we know that we are bypassing sand that migrates into the system with our periodic inlet sand trap dredging and sand bypass projects.”
Per the report, the inlet cell gained on average 24,600 cubic yards of sand per year, and when combining the 2012, 2014 and 2019 SID sand trap dredging and sand bypass projects, the annualized removal rate from the inlet cell is 44,900 cubic yards per year.
Another major finding again qualified in this year’s report shows the Sebastian Inlet continues to be in a state of dynamic equilibrium – a scientific term that means sand transported into the inlet entrance by wave-induced alongshore currents and carried into the inlet channel by the flood tidal currents are equal to the sand transported back in the seaward direction by the ebb-tidal currents.
“It demonstrates inlet management is working as expressed through the data. Major changes to the current management strategy could negatively affect the balanced inlet system,” said Gray.
Dr. Zarillo’s work with the District dates back further, to 1993, starting with the installation of the submerged wave gauge, an acoustic doppler profiler with four sensor heads to measure wave energy and currents. These data are critical to Dr. Zarillo’s modeling, reporting and forecasting work. Located just North of the inlet and 1,500 feet offshore, it transmits readings to an onshore data-logger every 3 hours.
Data from the meteorological station at the tip of the North Jetty installed in 1997, topographic data dating back to 1989 and semi-annual hydrographic survey data collected by SID, feed into the complex modeling being conducted by Dr. Zarillo and his graduate student team.
In addition to monitoring sea level changes, sediment transport and accumulation within the inlet system, the report also includes a shoreline change analysis. Annual aerial imaging of the shoreline 7 miles North and South of the Sebastian Inlet with an archive dating back to 1958 is combined with hydrographic survey data. The report identifies alternating sections of receding and advancing shoreline in both Brevard and Indian River counties that are divided into three northern and three southern sections. From 2008-2018, the widest contiguous section of landward migration or receding shoreline was found to be in two of the southern sections, measuring -126 feet approximately 2,000 feet South of McLarty Treasure Museum. The exception; specific stretches of southern beaches that are advancing and stable as a direct result of SID sand bypass and beach placement projects completed between 2006 and 2019.
“Beyond helping us employ a science-based approach to precisely manage sand resources within the inlet system per our charter and formal Inlet Management Plan submitted to FDEP, the data sets and analyses inform all of the other projects the District undertakes,” said Gray. “As an example, we will be mobilizing to repair the inlet’s northern shoreline due to some scouring damage from Hurricane Dorian armed with valuable data on how best to do that, and it’s also helped us adjust our sand placement areas on the beaches to the South for maximum benefit.”
The report also details Dr. Zarillo’s development of a new real-time model application that will be able to forecast water levels and circulation 72 hours in advance, and will include predictions of sand transport, salinity and water temperature. Model results will be updated daily and posted to a public website for general access.
The full, technical State of the Inlet report is available here.
38 Years of Partnership
The report is published as Florida Tech and SID mark 38 years of partnership during SID’s centennial. SID was established by the Florida State Legislature in May 1919 with the charter of maintaining the navigable channel connecting the Indian River Lagoon to the Atlantic Ocean.
The partnership began in 1981 with a $3,000 grant to a Florida Tech graduate student to study the feeding ecology of fish at Sebastian Inlet and in subsequent years, several additional grants to graduate students were made. In 1985-1986, Florida Tech conducted all permit-required monitoring associated with SID’s dredging, sand bypass and beach placement project.
More formal research partnerships and contracts would follow. In 1989 and under the direction of Drs. Randall Parkinson and Walter Nelson, scientists with Florida Tech’s Department of Ocean Engineering and Marine Sciences, a team of graduate students conducted biological and physical monitoring of reefs, seagrass beds and fishing populations, and completed physical monitoring of turbidity conditions near Sebastian Inlet as part of a 13-year study that concluded in 2002.
During the decades long partnership, Florida Tech has studied the effects of beach renourishment on sea turtle nesting and hatchling success, water quality, seagrass beds and benthic organisms. Scientists have conducted numerical modeling for hydrodynamics and sand transport at Sebastian Inlet that pre-dates Dr. Zarillo’s work, and shoreface sediment distribution patters, measuring grain size, beach temperature, compaction, moisture and mineral content. When SID received federal and state approval to collect data on the environmental impact of creating a navigational channel connecting the inlet to the IntraCoastal Waterway (ICW), Florida Tech completed several biological field studies in advance of the project to assess what environmental impact creating the channel might have on plant and animal species in the Sebastian Inlet area.
“We see this shift in the Sebastian Inlet District Commission’s approach to science and forging partnerships with higher education start to occur in the 1980s,” said SID Commission Chair Jenny Lawton-Seal . “Relative not only to sand management, the littoral transport along our coast and how it moves through the inlet system, but also as an acknowledgement of the important habitat surrounding the inlet – the nearshore hardbottom reef to the South, the seagrass beds on the flood shoal West of the inlet and along our beaches with some of the highest sea turtle nesting densities for loggerhead and green sea turtles in the U.S. We see a lot of the biological studies come to fruition in the early 90s.”
“Unique to Florida Tech is the interdisciplinary approach that combines oceanography, coastal engineering and environmental monitoring when studying complex systems like Sebastian Inlet,” said Dr. Zarillo. “It gives us a more complete understanding, produces data that are incorporated into our modeling work and ultimately enables us to come to better conclusions in managing the entire system.”
Florida Tech has one of 34 ocean engineering programs worldwide. Dr. Zarillo has been recognized by peers worldwide as a leading coastal modeling expert, and in the 30-year relationship between Florida Tech and SID, more than 100 Florida Tech students who have worked on Sebastian Inlet-related projects are now active worldwide as coastal engineering and marine science professionals.
Regional Benefits of Sebastian Inlet
Our region sees both economic and environmental benefits from the Sebastian Inlet. Cardno ENTRIX economists quantified the total annual impact of Sebastian Inlet as $149M, in a report commissioned in 2013 with an update planned. The Sebastian Inlet is bordered on both sides by Sebastian Inlet State Park, which is managed by the Florida Department of Environmental Protection (FDEP), and is among the top three most visited state parks each year welcoming 750,000 visitors and bringing in $1.8M in revenue between July 2018 and June 2019.
The water exchange between the Indian River Lagoon and the Atlantic Ocean or flushing, has a positive impact on water quality within the lagoon, and has promoted an accelerated resurgence of seagrass beds on the western flood shoal at the inlet as compared to other parts of the lagoon. Those seagrass beds are home to a highly diverse group of plants and animals, including; microscopic bacteria to copepods, shrimp, blue crab and juvenile fish, and 70% of Florida’s marine recreational fish depend on seagrass communities at some point in their lives.
Nearshore hardbottom reef to the South of the inlet is prime grazing ground for juvenile, endangered Green sea turtles, provides rest and refuge for nesting females and supports our fisheries.
The Sebastian Inlet sits between two segments of the Archie Carr National Wildlife Reserve – 20.5 miles of beach in Brevard and Indian River counties that has the highest nesting densities of Loggerhead and Green sea turtles in the Western Hemisphere.
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About the Sebastian Inlet District
The Sebastian Inlet District was created in 1919 as an independent special district by act of the Florida State Legislature, and chartered to maintain the navigational channel between the Atlantic Ocean and the Indian River. The Sebastian Inlet District’s responsibilities include state mandated sand bypassing, erosion control, environmental protection and public safety. The Sebastian Inlet supports a rich and diverse ecological environment that is unparalleled in North America. The Inlet is vital not only to the ecological health of the Indian River Lagoon, but it is also an important economic engine for local communities in the region. Known as the premier surfing, fishing, boating and recreational area on the east coast of Florida, the inlet is one of only five navigable channels that connect the Indian River lagoon to the Atlantic Ocean.
About Florida Institute of Technology
Florida Tech was founded in 1958 at the dawn of the Space Race that would soon define the Atlantic coast of Florida and captivate the nation. Now the premier private technological university in the Southeast, Florida Tech is a Tier 1 Best National University in U.S. News & World Report and one of just nine schools in Florida lauded by the Fiske Guide to Colleges. Florida Tech is ranked among the top 5 percent of 18,000 degree-granting institutions worldwide in the 2018-19 World University Rankings and has been named a Top College and Best Value University for 2019 by Forbes. Florida Tech offers bachelor’s, master’s and doctoral degrees in aeronautics and aviation, engineering, computing and cybersecurity, business, science and mathematics, psychology, education and communication. Learn more about our relentless pursuit of greatness at www.fit.edu.