Florida Gulf Coast Marsh Response to Sea Level Rise

By

LADNER, LUCIEN, and HoEnstine, Ron

Florida Geological Survey,

Cross, Brian

Florida State University

Florida Gulf Coast marshes along the Big Bend are experiencing sea-level rise and an insufficient sediment supply to maintain the marshes surface elevation. Local mean sea level is rising at an approximate rate of 1.5 to 2.4 millimeters (mm) per year and the spring-fed or controlled (dammed) rivers of the Florida Gulf Coast do not provide sufficient sediments to maintain long-term health of the marshes. Marsh health is determined by several factors; sediment supply, sea-level rise, storm events, erosion rate of waves and marsh subsidence. The Florida Geological Survey’s Coastal Research Group installed Sediment Elevation Tables (SET) at a number of sites along the Florida Gulf Coast (St. Joe Bay, Apalachicola River, Ochlockonee River, St. Marks River, Aucilla River, Rocky Creek, Cedar Key area and Waccasassa River area) to measure elevation changes of the marsh surface. SET measurements were combined with feldspar marker horizon measurements to quantify changes in marsh topography. Due to the sediment starved nature of these marshes (-0.3 to -15.0 mm/year) and the inability to keep pace with sea level rise, the Big Bend coastal areas are at risk, documenting the dynamic and mobile nature of coastal environments.