Reich, C. D., Swarzenski, P. W., Greenwood, W. J., Wiese, D. S.

Investigation of coastal hydrogeology utilizing geophysical and geochemical tools along the Broward County coast, Florida

2009

Reston, VA

U.S. Geological Survey

Land-Based Sources of Pollution Project 27

21

USGS Open-File Report 2008-1364

"Geophysical (CHIRP, boomer, and continuous direct-current resistivity) and geochemical tracer studies (continuous and time-series radon-222) were conducted along the Broward County coast from Port Everglades to Hillsboro Inlet, Florida. Simultaneous seismic, direct-current resistivity, and radon surveys in the coastal waters provided information to characterize the geologic framework and identify potential groundwater-discharge sites. Time-series radon at the Nova Southeastern University National Coral Reef Institute (NSU/NCRI) seawall indicated a very strong tidally modulated discharge of ground water with Rn-222 activities ranging from 4 to 10 disintegrations per minute per liter depending on tidal stage. CHIRP seismic data provided very detailed bottom profiles (i.e., bathymetry); however, acoustic penetration was poor and resulted in no observed subsurface geologic structure. Boomer data, on the other hand, showed features that are indicative of karst, antecedent topography (buried reefs), and sand-filled troughs. Continuous resistivity profiling (CRP) data showed slight variability in the subsurface along the coast. Subtle changes in subsurface resistivity between nearshore (higher values) and offshore (lower values) profiles may indicate either a freshening of subsurface water nearshore or a change in sediment porosity or lithology. Further litho-logic and hydrologic controls from sediment or rock cores or well data are needed to constrain the variability in CRP data."

Southeast Florida Coral Reef Initiative

Funded by the Broward County Environmental Protection Department

Broward County Environmental Protection Department