Raymond W. Schaffranek¹, Judson W. Harvey¹, Gregory B. Noe¹, Ami L. Riscassi¹, Daniel J. Nowacki¹ and Laurel G. Larsen^2
1 U.S. Geological Survey, Reston, VA, USA
² University of Colorado, Boulder, CO, USA

Land drainage and water impoundment stemming from decades of managed water-level controls have altered sheet flow behavior in the Everglades. The National Research Council (2003) reports a general lack of understanding of the role of flow as a factor contributing to landscape changes in the Everglades. Sheet flow conditions were monitored continuously during the latter part of the 2005-2006 wet season at a remnant ridge and slough site in Everglades water conservation area 3A (WCA-3A). Flow velocity, water level, water temperature, and conductivity were monitored at two locations 14 meters apart in a Cladium jamaicense ridge and adjacent Nymphaea odorata slough. At the monitoring site, the ridge and slough have a predominant north-south alignment with the ridge being about 20 cm higher in elevation. Water level and temperature were monitored at 15-minute intervals; flow velocity and conductivity were monitored at 30-minute intervals; and wind speed and direction were monitored every 15 minutes. Flow velocities were measured at common fixed depths in the water column, adjusted to account for a decrease in water depths on the ridge from 53 to 16 cm through the August 2005 to January 2006 monitoring period. For periods of concurrent data, mean velocities were 0.27 and 0.36 cm/s and mean water depths were 43 and 63 cm at the ridge and slough, respectively. These results do not include data during Hurricane Wilma. Flow directions were southerly in both the ridge and slough at the onset of monitoring and gradually shifted to the southeast at the ridge and to the south-southeast at the slough by the end of the monitoring period. Ninety percent of all sheet flow velocities were between 0.07 and 0.54 cm/s on the ridge and 0.08 and 0.58 cm/s in the slough. By contrast, ninety percent of the daily means of all sheet flow velocities measured at five wetland sites in Shark River Slough, Everglades National Park, from July 1999 to July 2003 were between 0.46 and 2.29 cm/s (Schaffranek, 2004).

Preliminary monitoring results indicate that mean flow speeds in the slough were approximately 33 % faster than on the ridge. Resultant unit discharges in the slough were nearly double (95 % greater than) discharges on the ridge. These flow differences were accentuated as water levels declined. Measured flow velocities in WCA-3A were generally much slower than flow velocities previously measured in the free flowing part of Shark River Slough within Everglades National Park. Implications of this reduced flow velocity on flux and particulate transport in WCA-3A and its relation to landscape maintenance are under investigation in this collaborative study.

References:
National Research Council, 2003, Does water flow influence Everglades landscape patterns, Washington, DC, National Academies Press, http://books.nap.edu/catalog/10758.html, 41 p.

Schaffranek, R.W., 2004, Sheet-flow velocities and factors affecting sheet-flow behavior of importance to restoration of the Florida Everglades, U.S. Geological Survey Fact Sheet 2004-3123, http://pubs.er.usgs.gov/pubs/fs/fs20043123, 4 p.

Contact Information: Raymond W. Schaffranek, U.S. Geological Survey, 430 National Center, Reston, VA 20192, Phone: 703-648-5891, Fax: 703-648-5484, Email: rws@usgs.gov

(This abstract is from the 2006 Greater Everglades Ecosystem Restoration Conference.)

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