Turbidity Monitoring Projects
   Miami River and Key West

Overview
Turbidity is a measure of light-scattering that occurs in water and is an important parameter for understanding impacts to plants and the potential for particulates to settle on marine live bottoms. Turbidity monitoring in the Miami River was performed to determine if ship traffic, particularly opposing tugboats wrestling ships through tight bridges and turns, mobilized contaminant-laden sediment, creating adverse turbidity plumes. Little was known about natural and ship-traffic related levels of turbidity in and around Key West Harbor, until a 5-day monitoring effort in 2001 and a subsequent 1-month effort in October 2003 was performed by Water & Air field teams. Data were collected at 15-minute intervals at six stations in 2001 and 10 stations in 2003.

Details

• Turbidity monitoring stations were established at appropriate locations on boats in the Miami River or on fixed structures including navigational buoys, with Coast Guard approval at Key West.
• Data were downloaded daily or every other day to facilitate data reduction and graphing to expedite data interpretation and reporting.

Results
Pulses of turbid water associated with ship traffic were found to flow through the Miami River channel. In Key West, natural levels of turbidity were found to be between 1 and 3 NTUs during calm weather (<5 mph wind) and near 40 NTUs during severe weather conditions. Short-lived spikes in turbidity were found to be associated with cruise ship traffic. South and east winds of 10 to 20 mph were found to be associated with incoming tidal water masses with turbidity increases of 5 to 10 NTUs. Findings were useful in designing a monitoring program for channel dredging.