Post on 19-Jan-2016
Water Velocity and Suspended Solids Concentrations in the Proximity of Tree Islands in Everglades National Park
Water Velocity and Suspended Solids Concentrations in the Proximity of Tree Islands in Everglades National Park
ABSTRACT OBJECTIVES METHODS
• Water velocity measurements along the transects varied between less than 1 Water velocity measurements along the transects varied between less than 1 cm/s to more than 4 cm/s. The highest velocities occurred at those stations cm/s to more than 4 cm/s. The highest velocities occurred at those stations where there is an opening (due to sawgrass die-off) in transects 1 and 3. where there is an opening (due to sawgrass die-off) in transects 1 and 3. Relatively high velocities are observed inside the tree line in the areas closer Relatively high velocities are observed inside the tree line in the areas closer to the head of the island. Low velocities were recorded inside the tree line at to the head of the island. Low velocities were recorded inside the tree line at the tail of the island (Figure 1). the tail of the island (Figure 1).
• Wind velocity and direction are highly variable. Water flow is shielded from Wind velocity and direction are highly variable. Water flow is shielded from wind influences inside the tree line at transects 1 and 2 but not at transect 3 wind influences inside the tree line at transects 1 and 2 but not at transect 3 (Figure 2). (Figure 2).
• Water depth was variable in all transects but there is a clear tendency for Water depth was variable in all transects but there is a clear tendency for water depth to decrease as the center of the island is approached in transects water depth to decrease as the center of the island is approached in transects
1 and 2. This tendency was not observed for transect 3. 1 and 2. This tendency was not observed for transect 3.
• Turbidity was relatively low along all 3 transects with most values being in the Turbidity was relatively low along all 3 transects with most values being in the 0.45 NTUs to 0.55 NTUs range (Figure 2). 0.45 NTUs to 0.55 NTUs range (Figure 2).
• The particle size distribution of most samples was exponential in nature with The particle size distribution of most samples was exponential in nature with the largest number of particles having a smaller average diameter. Mean the largest number of particles having a smaller average diameter. Mean particle size was relatively constant, varying from 2.5 to 4.0 microns(Figure particle size was relatively constant, varying from 2.5 to 4.0 microns(Figure 3).3).
•Total suspended solids were measured at 7 stations at transect 1 using an in- Total suspended solids were measured at 7 stations at transect 1 using an in- line filtration system. Total suspended solids were in the order line filtration system. Total suspended solids were in the order of 1.0 mg/L and of 1.0 mg/L and were relatively constant between stations. As were relatively constant between stations. As expected, most of the total expected, most of the total suspended solids were volatile due to the high suspended solids were volatile due to the high organic content of suspended organic content of suspended solids in a marsh environment (Figure 4). solids in a marsh environment (Figure 4).
RESULTS
• Spatially intensive velocity data are being taken along 3 transects that are Spatially intensive velocity data are being taken along 3 transects that are perpendicular to the main North-South axis of each island, using a Sontek handheld perpendicular to the main North-South axis of each island, using a Sontek handheld device (Picture 2). The first and northern-most transect is located by the island’s device (Picture 2). The first and northern-most transect is located by the island’s tropical hardwood hammock (head), the second transect is located near the middle tropical hardwood hammock (head), the second transect is located near the middle and the third is located close to the tail of the island. Each transect has its origin to the and the third is located close to the tail of the island. Each transect has its origin to the
west of the tree island and has a station every 5 meters. west of the tree island and has a station every 5 meters.
• One Sontek Argonaut ADV autonomous velocity meter has been installed near each One Sontek Argonaut ADV autonomous velocity meter has been installed near each tree island to obtain temporally intensive velocity in three dimensions (Picture 3) tree island to obtain temporally intensive velocity in three dimensions (Picture 3)
• Suspended sediments are characterized along the transects. Samples are collected Suspended sediments are characterized along the transects. Samples are collected without filtration for turbidity, particle size distribution and number of particles per ml without filtration for turbidity, particle size distribution and number of particles per ml analyses. The latter two are performed with a Coulter Counter Particle Size Analyzer analyses. The latter two are performed with a Coulter Counter Particle Size Analyzer (Picture 4). The gravimetric analysis of total suspended solids, volatile suspended (Picture 4). The gravimetric analysis of total suspended solids, volatile suspended solids and non- volatile suspended solids is being conducted by sampling with an in- solids and non- volatile suspended solids is being conducted by sampling with an in- line filtration system (Picture 1) line filtration system (Picture 1)
• The experimental procedure for the suspended sediment density analysis requires the The experimental procedure for the suspended sediment density analysis requires the
collection of at least 1 gram of suspended sediment, with up to 5 grams as ideal. In collection of at least 1 gram of suspended sediment, with up to 5 grams as ideal. In order to collect this amount of suspended sediments we will need to filter order to collect this amount of suspended sediments we will need to filter approximately 1000 gallons of water through a yarn wound filter. approximately 1000 gallons of water through a yarn wound filter.
• Tests using dyes and tracers will be conducted in order to test if the acoustic Doppler Tests using dyes and tracers will be conducted in order to test if the acoustic Doppler systems are underestimating water velocity through vegetation, since the Doppler systems are underestimating water velocity through vegetation, since the Doppler system requires that an area be cleared of vegetation between the sampling volume system requires that an area be cleared of vegetation between the sampling volume and the transducers. and the transducers.
The overall goal of this study is to determine the The overall goal of this study is to determine the importance of water flow in the formation and importance of water flow in the formation and preservation of tree islands in the Florida preservation of tree islands in the Florida Everglades. In the process we intend to measure Everglades. In the process we intend to measure suspended sediment properties and develop suspended sediment properties and develop methods for measuring water velocity in the unique methods for measuring water velocity in the unique environments of the Everglades. environments of the Everglades.
This study quantifies water velocities and determines suspended sediment characteristics in the vicinity of 3 tree islands situated in the Shark Valley Slough in Everglades National Park. The three islands are known as Black Hammock, Gumbo Limbo and Satin Leaf. Spatially intensive velocity data are being taken along 3 transects that are perpendicular to the main North-South axis of each island, using a handheld Sontek Acoustic Doppler Velocity Meter. An autonomous Sontek Argonaut ADV velocity meter deployed at each tree island will continuously record temporally intensive data. Suspended sediments are also being characterized along the transects. Gravimetric analysis of total suspended solids, volatile suspended solids and non-volatile suspended solids is being conducted by sampling with an in-line filtration system. The suspended particle density analysis will be performed by filtering approximately 1000 gallons of water through a yarn wound filter in order to collect at least 1 gram of suspended sediment. Additionally, we plan to develop a method to evaluate the affect of wind on water flow and to evaluate the use of the acoustic Doppler meters for measuring flow in the Everglades. We expect to find important correlations between the variables under study that will allow us to model and understand the relationship between water flow and the creation and preservation of tree islands.
Map of Everglades National Park
Area of Study
Picture 1. Picture 2.
Picture 3 Picture 4
CONCLUSIONS
• The fact that transects 1 and 2 have hard wood tree cover that The fact that transects 1 and 2 have hard wood tree cover that does not allow underwater vegetation to grow, appears to play does not allow underwater vegetation to grow, appears to play a major role in the relatively rapid flow in areas with dense tree a major role in the relatively rapid flow in areas with dense tree cover. Although water flow is obstructed under the canopy due cover. Although water flow is obstructed under the canopy due to the presence of tree trunks, roots, and ferns, water is to the presence of tree trunks, roots, and ferns, water is generally canalized around these obstructions. In contrast, generally canalized around these obstructions. In contrast, water velocities are relatively low inside the tree line at transect water velocities are relatively low inside the tree line at transect
3, which is located at the tail of the tree island. In the tail the 3, which is located at the tail of the tree island. In the tail the trees are sparser and do not significantly impede light trees are sparser and do not significantly impede light penetration towards the water, thereby permitting underwater penetration towards the water, thereby permitting underwater vegetation to flourish. This underwater vegetation impedes flow vegetation to flourish. This underwater vegetation impedes flow
thereby decreasing water velocities in this area. thereby decreasing water velocities in this area.
• The Acoustic Doppler Velocity Meters work by generating a The Acoustic Doppler Velocity Meters work by generating a narrow beam of sound. The sound is then reflected by narrow beam of sound. The sound is then reflected by particulate matter suspended in the water. The equipment then particulate matter suspended in the water. The equipment then measures the frequency change of the received signal and measures the frequency change of the received signal and calculates the water velocity. Unfortunately the amount of calculates the water velocity. Unfortunately the amount of suspended solids in the Shark Valley Slough is so low that the suspended solids in the Shark Valley Slough is so low that the measurements have not been reliable unless suspended solids measurements have not been reliable unless suspended solids
are added by stirring the bottom or by adding particulates to the are added by stirring the bottom or by adding particulates to the
water (Figure 5). water (Figure 5).
• However, it was also noted that even with acceptable values of However, it was also noted that even with acceptable values of
sound to noise ratio (SNR) which is achieved by adding sound to noise ratio (SNR) which is achieved by adding sediments to the water, some of the high velocity magnitudes sediments to the water, some of the high velocity magnitudes were primarily caused by the velocity reading in the “z” were primarily caused by the velocity reading in the “z” direction. We believe that the high Vz values are created by the direction. We believe that the high Vz values are created by the
addition of sediments and the release of gases when the addition of sediments and the release of gases when the bottom is stirred. Some sediments settle at a high pace and bottom is stirred. Some sediments settle at a high pace and this this is interpreted by the equipment as the vertical component of is interpreted by the equipment as the vertical component of velocity. Gas is released from the bottom and rises to the velocity. Gas is released from the bottom and rises to the surface also at a high pace, again affecting Vz. All data have surface also at a high pace, again affecting Vz. All data have been revised and, for the sake of consistency, incorporate only been revised and, for the sake of consistency, incorporate only the x and y components of velocity (Figure 6). the x and y components of velocity (Figure 6).
• Velocity measurements were taken with a dye and a ruler in Velocity measurements were taken with a dye and a ruler in areas with dense sawgrass vegetation. The dye and ruler areas with dense sawgrass vegetation. The dye and ruler measurements can be made with more certainty than the measurements can be made with more certainty than the acoustic Doppler measurements. Our data indicate acoustic Doppler measurements. Our data indicate Acoustic Acoustic Doppler Velocity meter water velocities are likely being Doppler Velocity meter water velocities are likely being underestimated. Further testing has to be performed to confirm underestimated. Further testing has to be performed to confirm
these preliminary findings. If it is confirmed, a different method these preliminary findings. If it is confirmed, a different method (other than use of the Sontek Flowtracker) will have to be (other than use of the Sontek Flowtracker) will have to be developed to measure water velocity in areas that are densely developed to measure water velocity in areas that are densely
vegetated. vegetated.
Enlarged Area
X - Tree Islands Under Study
XX X
Figure 6
Gumbo Limbo Transect 1 - West SideTree Line Starts at G1 + 30 (021018)
0
1
2
3
4
5
6
G1 +
00
G1 +
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G1 +
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G1 +
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G1 +
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G1 +
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G1 +
80
Station No.
Ve
loc
ity
(m
/s),
(c
m/s
)
Water Vel Magnitude (cm/s)
Vel. Mag. w/o Vz (cm/s)
Tree line
Gumbo Limbo Argonaut LocationFebruary 14, 2003
-5
-4
-3
-2
-1
0
1
2
3
4
0 5 10 15 20 25 30 35 40 45 50 55
Time (min)
Vx,V
y,V
z (
cm
/s)
0
2
4
6
8
10
12
14
16
18
20
SN
R (
dB
)
Vx Vy Vz SNRx SNRy SNRz
Bottom was stirred to addsuspended sediments
Bottom was stirred to addsuspended sediments
Figure 5
Figure 3
Gumbo Limbo T1 + 00October 4, 2002
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
2 3 4 5 6 7 8 9 10 20 30 40 50
Particle Diameter (um)
Nu
mb
er
of
Part
icle
s p
er
ml
Figure 1
Gumbo Limbo Transect 3 - West SideTree Line Starts at G3 + 175
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
4.50
5.00
G3
+ 0
0
G3
+ 1
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G3
+ 2
0
G3
+ 3
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G3
+ 4
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G3
+ 5
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G3
+ 6
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G3
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G3
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+ 1
00
G3
+ 1
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G3
+ 1
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+ 1
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+ 1
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G3
+ 1
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G3
+ 1
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G3
+ 1
70
G3
+ 1
80
G3
+ 1
90
G3
+ 2
00
Station No.
Sp
ee
d (
cm
/s)
Oct 01/02 Oct 04/02 Nov 08/02
Tree Line
Sawgrass Open area with small patches of sawgrass. Speed depended on the location of the patches.
SparseButtonBush
ButtonBushbecomesThicker
Button Bush is thicker as we approach theisland's tail. Sparse sawgrass. Underwater plants abundant inside "tree line"
Speeds w/o considering Vz and omitting data with SNR values equal to or less than 5
Figure 2
Gumbo Limbo Transect 3 - West SideTree Line Starts at G3 + 175 (November 8, 2002)
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
4.50
G3
+ 0
0
G3
+ 0
5
G3
+ 1
0
G3
+ 1
5
G3
+ 2
0
G3
+ 2
5
G3
+ 3
0
G3
+ 3
5
G3
+ 4
0
G3
+ 4
5
G3
+ 5
0
G3
+ 5
5
G3
+ 6
0
G3
+ 6
5
G3
+ 7
0
G3
+ 7
5
G3
+ 8
0
G3
+ 8
5
G3
+ 9
0
G3
+ 9
5
G3
+ 1
00
G3
+ 1
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G3
+ 1
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G3
+ 1
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G3
+ 1
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G3
+ 1
25
G3
+ 1
30
G3
+ 1
35
Station No.
Sp
ee
d (
cm
/s),
(m
/s)
0
5
10
15
20
25
Oth
ers
Speed w/o Vz (cm/s) Avg Wind Speeed (m/s) WaterD (m)Number of Particles/mL (x 10 4̂) Mean Particle Size (um) Turbidity (NTU) (x 10 1̂)
sawgrass Open area with small patches of sawgrass Sparse Button Bush
Button Bush becomes thicker
Water speeds w/o Vz, data with SNR values equal to or less than 5 are omitted
Figure 4
Gumbo Limbo Transect 1 - West SideOctober 18, 2002
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
G1 +
00
G1 +
05
G1 +
10
G1 +
15
G1 +
20
G1 +
25
G1 +
30
Station No.
So
lid
Co
ncen
trati
on
(m
g/L
)
Total SuspendedVolatile Fixed
Tree Line
LegendOpen Area: oaSawgrass: sgSpikerush: srButtonbush: bb
sr oa Inside tree line - nounderwatervegetation
sg sg/sr sr sr
Gumbo Limbo
Satin Leaf
Black Hammock
Jose Bazante and Helena M. Solo-GabrieleUniversity of Miami, Dept. of Civil, Arch., and Environmental Engineering,, Coral Gables, Floridajbazante@bellsouth.net hmsolo@miami.edu
CONTACT
GEER ConferencePalm Harbor, Florida
April 16-18, 2003
Jose Bazante M.S., M.B.A. and Helena M. Solo-Gabriele, Ph.D., P.E.University of Miami, Dept. of Civil, Arch., and Environmental Engineering,, Coral Gables, Florida
Sherry Mitchell, Ph.D. Everglades National Park, Homestead, Florida
Michael Ross, Ph.D. and Daniel L. Childers, Ph.D.Southeast Environmental Research Center,Florida International University, Miami, Florida
Lynn Leonard, Ph.D.University of North Carolina at Wilmington, Department of Earth Science and Geology, Wilmington, North Carolina