TY - JOUR
T1 - Hydrologic measurements and implications for tree island formation within Everglades National Park
AU - Bazante, Jose
AU - Jacobi, Gary
AU - Solo-Gabriele, Helena M.
AU - Reed, David
AU - Mitchell-Bruker, Sherry
AU - Childers, Daniel L.
AU - Leonard, Lynn
AU - Ross, Michael
N1 - Funding Information:
This project was funded through the National Park Service and Everglades National Park (Contract No. H 5000 00 0494 CIF NPS). Partial support was also provided by the Florida Coastal Everglades LTER Program through the National Science Foundation Grant No. 9910514. We gratefully acknowledge the assistance received from representatives of the USGS, SFWMD, SonTek, and AMJ Equipment who were very generous with their knowledge and time. We also thank Pablo Ruiz, Adam Wood, Alex Croft, Tomoyuki Shibata, Jean Chery, Mary Durbin, and David Jones for their help during our field trips. We also thank Natalia Zürcher, Robert Gawley, John Berry, Lilian Custals, Matthew Lynn, and for their assistance in the laboratory.
PY - 2006/10/15
Y1 - 2006/10/15
N2 - Tree islands in the Shark River Slough of the Everglades National Park (ENP), in the southern state of Florida in the United States, are part of a wetland system of densely vegetated ridges interspersed within relatively open sloughs. Human alteration of this system has had dramatic negative effects on the landscape of the region and restoration efforts will require adjusting the hydrology of the region to assure the preservation of these important ecologic features. The primary objectives of this study were to document the hydrology in the vicinity of tree islands in ENP by measuring velocities in time and space and by characterizing suspended sediments. The results of such measurements were interpreted with respect to factors that may limit tree island growth. The measurements were conducted in the vicinity of three tree islands known as Black Hammock (BH), Gumbo Limbo (GL), and an unnamed island that was named for this study as Satin Leaf (SL). Acoustical Doppler Velocity (ADV) meters were used for measuring the low velocities of the Everglades water flow. Properties of suspended sediments were characterized through measurements of particle size distribution, turbidity, concentration and particle density. Mean velocities observed at each of the tree islands varied from 0.9 to 1.4 cm/s. Slightly higher mean velocities were observed during the wet season (1.2-1.6 cm/s) versus the dry season (0.8-1.3 cm/s). Maximum velocities of more than 4 cm/s were measured in areas of Cladium jamaicense die-off and at the hardwood hammock (head) of the islands. At the island's head, water is channelized around obstructions such as tree trunks in relatively rapid flow, which may limit the lateral extent of tree island growth. Channelization is facilitated by shade from the tree canopy, which limits the growth of underwater vegetation thereby minimizing the resistance to flow and limiting sediment deposition. Suspended sediment concentrations were low (0.5-1.5 mg/L) at all study sites and were primarily of organic origin. The mean particle size of the suspended sediments was 3 μm with a distribution that was exponential. Critical velocities needed to cause re-suspension of these particles were estimated to be above the actual velocities observed. Sediment transport within the water column appears to be at a near steady state during the conditions evaluated with low rates of sediment loss balanced by presumably the release of equivalent quantities of particles of organic origin. Existing hydrologic conditions do not appear to transport sufficient suspended sediments to result in the formation of tree islands. Of interest would be to collect hydrologic and sediment transport data during extreme hydrologic events to determine if enough sediment is transported under these conditions to promote sufficient sediment accumulations.
AB - Tree islands in the Shark River Slough of the Everglades National Park (ENP), in the southern state of Florida in the United States, are part of a wetland system of densely vegetated ridges interspersed within relatively open sloughs. Human alteration of this system has had dramatic negative effects on the landscape of the region and restoration efforts will require adjusting the hydrology of the region to assure the preservation of these important ecologic features. The primary objectives of this study were to document the hydrology in the vicinity of tree islands in ENP by measuring velocities in time and space and by characterizing suspended sediments. The results of such measurements were interpreted with respect to factors that may limit tree island growth. The measurements were conducted in the vicinity of three tree islands known as Black Hammock (BH), Gumbo Limbo (GL), and an unnamed island that was named for this study as Satin Leaf (SL). Acoustical Doppler Velocity (ADV) meters were used for measuring the low velocities of the Everglades water flow. Properties of suspended sediments were characterized through measurements of particle size distribution, turbidity, concentration and particle density. Mean velocities observed at each of the tree islands varied from 0.9 to 1.4 cm/s. Slightly higher mean velocities were observed during the wet season (1.2-1.6 cm/s) versus the dry season (0.8-1.3 cm/s). Maximum velocities of more than 4 cm/s were measured in areas of Cladium jamaicense die-off and at the hardwood hammock (head) of the islands. At the island's head, water is channelized around obstructions such as tree trunks in relatively rapid flow, which may limit the lateral extent of tree island growth. Channelization is facilitated by shade from the tree canopy, which limits the growth of underwater vegetation thereby minimizing the resistance to flow and limiting sediment deposition. Suspended sediment concentrations were low (0.5-1.5 mg/L) at all study sites and were primarily of organic origin. The mean particle size of the suspended sediments was 3 μm with a distribution that was exponential. Critical velocities needed to cause re-suspension of these particles were estimated to be above the actual velocities observed. Sediment transport within the water column appears to be at a near steady state during the conditions evaluated with low rates of sediment loss balanced by presumably the release of equivalent quantities of particles of organic origin. Existing hydrologic conditions do not appear to transport sufficient suspended sediments to result in the formation of tree islands. Of interest would be to collect hydrologic and sediment transport data during extreme hydrologic events to determine if enough sediment is transported under these conditions to promote sufficient sediment accumulations.
KW - Everglades
KW - Restoration
KW - Suspended solids
KW - Tree islands
KW - Water velocity
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U2 - 10.1016/j.jhydrol.2006.03.011
DO - 10.1016/j.jhydrol.2006.03.011
M3 - Article
AN - SCOPUS:33748929479
SN - 0022-1694
VL - 329
SP - 606
EP - 619
JO - Journal of Hydrology
JF - Journal of Hydrology
IS - 3-4
ER -