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9. FY07 RRPP “F David Fugate_ FGCU Dr. David Fugate_ will

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9. FY07 RRPP “F David Fugate_ FGCU Dr. David Fugate_ will Powered By Docstoc
					9. FY07 RRPP “FATE AND TRANSPORT OF CALOOSAHATCHEE ETM SEDIMENT” RESULTS –
David Fugate, FGCU

Dr. David Fugate, will present the results of the FY07 RRPP project “Fate and Transport of
Caloosahatchee ETM Sediment”. The “Fate and Transport of Caloosahatchee ETM Sediment”
Final Draft Report is available on the CHNEP website in the TAC 4-8-09 Meeting Folder at:
       Address for CHNEP ftp site: ftp://ftp.swfrpc.org
       User name: chnep
       Password: chnepaccess
       Folder: TAC 4-8-09

Estuaries trap sediment in high concentrations at localized regions called estuary turbidity
maximums (ETMs), which change location relative to river flows. ETMs provide habitat for
planktonic and larval fish and affect dissolved oxygen, mixing and stratification. The
Caloosahatchee River has a well developed ETM which migrates many kilometers, flushing into
San Carlos Bay during heavy river discharges. The purpose of this project was to investigate the
fate and transport of ETM associated suspended sediment in the Caloosahatchee Estuary during
heavy freshwater flow. Project objectives were: 1) determine at what freshwater flow ETM is
flushed out of the Caloosahatchee River; 2) monitor salinity, temperature, stratification and
suspended sediment levels over a tidal cycle in San Carlos Bay during high flow; and 3) estimate
the settling velocity of suspended particles in the water column.

Sampling occurred in San Carlos Bay in August 27 and September 5, 2008 before and just after
tropical storm Fay and the first a large release of water through the river for the season.
Sampling occurred over an entire tide cycle along transects throughout the bay. Measurements
were made using an Acoustic Doppler Current Profiler (ADC), a sonde for conductivity,
temperature and depth (CTD) and Laser In Situ Scattering Transmissometer (LISST)
instruments. Salinity and flow discharge data from SFWMD programs was incorporated.
Vertical and horizontal estimates of net sediment flux across the 4 passes surrounding San Carlos
Bay were produced. Salinity conditions over time temporal and location were mapped, and
sediment settling velocity was estimated. Two empirical methods were used to estimate the
freshwater discharge necessary to flush saline waters out of the Caloosahatchee River. Results
show stratification varied by location and river flow. After tropical storm Fay and high river
flows, the most important pathway for suspended sediment transport from the Caloosahatchee
River was from the mouth through the channel towards the Sanibel causeway. Sediments were
resuspended along this route from a mobile pool of sediments. Within days of the storm,
relatively small suspended sediment concentrations occurred, indicating that a strong pulse of
high concentrations suspended sediments didn’t likely occur during the storm.

              Recommendation:        Recommend that Management and Policy Committees
                                     approve FY07 RRPP “Fate and Transport of
                                     Caloosahatchee ETM Sediment” final report.

              Attachments:           ”Fate and Transport of Caloosahatchee ETM Sediment”
                                     Final Draft Report on ftp site
                    The Fate and Transport of Caloosahatchee ETM Sediment

               A Final Report to the Charlotte Harbor National Estuarine Program

                                           David Fugate

                                        February 23, 2009




Project Description




Suspended sediment concentrations and the associated light attenuation in the Charlotte Harbor
Estuarine System are important factors affecting the health of a variety of organisms, including
oysters, clams and seagrasses (e.g. Lawson et al., 2007, Wilber and Clarke, 2001). Estuaries
typically trap sediment in high concentrations at localized regions within the estuary called the
estuarine turbidity maximum (ETM). The primary mechanism by which estuaries trap sediment
and passive organisms is the convergence of landward flowing salty bottom currents from the
ocean end of an estuary and seaward flowing fresh water bottom currents from the head of the
estuary. Consequently, ETMs usually develop near the upper extent of the salinity intrusion. In
areas with extreme freshwater outflow, such as the Mississippi R. and the Amazon R., ETMs are
found outside the mouth of the river, where the confluence of fresh and saltwater occur (e.g.
Trowbridge and Kineke, 1994). The ETM is a unique dynamic habitat in itself, providing
protection and nutrients to planktonic and larval fish (Roman et al., 2005; North and Houde,
2003). The physical factors of mixing and stratification that contribute to the dynamics of the
ETM also affect the level of dissolved oxygen (DO) in the water column. Physical stirring by
tides or winds mix DO to the bottom. Conversely, stratification isolates the bottom from the
surface water and prevents new DO from reaching the bottom waters. The fate and transport of
particulate material associated with the ETM have an important impact on the biological
processes in the estuaries from the microbial to the macro-organism scale. Ongoing studies of
the Caloosahatchee River have shown that it has a well developed ETM and that the ETM
migrates many kilometers over timescales of a few weeks. The data also suggest that during
heavy freshwater discharges, the ETM can be completely flushed out of the river and introduce
large pulses of suspended sediment into San Carlos Bay.

The artificial discharge of large amounts of freshwater from Lake Okeechobee is likely to
increase the frequency of flushing of the ETM relative to natural conditions. While the
Caloosahatchee River is much smaller than the Amazon River, it has the potential to create
similar dynamics during high flow periods. One might expect that during very high discharge
conditions, turbidity outside of the mouth of the Caloosahatchee should increase dramatically
from at least two processes. The first, as mentioned above is the advection or flushing of the
ETM that is typically inside of the river to outside of the mouth. The other process is the
continued trapping of sediment by the hydrodynamics of the system which may resemble a salt
wedge estuary during high flow conditions, such as the Mississippi and the Amazon.

This project investigates the fate and transport of ETM associated suspended sediment during
heavy freshwater flow. The first objective is to determine under what level of freshwater flow is
the ETM likely to be flushed out of the Caloosahatchee. The next objective is to monitor the
salinity, temperature, stratification, and suspended sediment levels over a tidal cycle in San
Carlos Bay during a high flow event to relate the density structure to the position of suspended
sediment concentrations. An added benefit from this project is the estimation of the settling
velocity of suspended particles in the water column, which is a key parameter that is necessary to
numerically model sediment transport, but is difficult to obtain.




Site Description and Methods:

Site and Environmental Conditions

San Carlos Bay in SW Florida is shown in Figure 1. The numerous inlets and shallow
bathymetry create a complex hydrodynamic system. For example, in less than 10 miles, between
the Cape Coral Bridge and the Sanibel Light, tides are lagged as much as 3 hours. Two field
trips were carried out for this study, the first on August 27, 2008 shortly after the passing of
tropical storm Fay, and September 5, 2008, the first day in the year of a large release of
freshwater through the Franklin Locks. Figure 2 shows the wind speed and direction around the
time of the two field trips from NOAA CO-OPS data. The winds were relatively calm and from
the north on the first field day, but higher, around 14 knots with heavy chop, on the second field
day. River discharge through the Franklin Locks was about 330 m3 s-1 (5584 ft3 s-1) on the first
field day and about 160 m3 s-1 (5584 ft3 s-1) on the second field day. Tidal heights and current
speeds at the mouth of the Caloosahatchee for each day are shown in Figures 3 and 4
respectively.




Cast Procedure and Instrumentation

During each field trip a number of transects were made that roughly circled around the perimeter
of San Carlos Bay. A typical transect consists of a run from the mouth of the Caloosahatchee,
towards the Sanibel Causeway, southwesterly across the Sanibel Causeway, then north across the
lower end of Pine Island Sound, then following the Intracoastal Waterway back across to the
Caloosahatchee mouth. The first field trip covered an entire tidal period. The results from this
trip along with previous analyses (see Results section below) suggested that it would only be
possible for the ETM to be flushed out during ebb tide, so the transects for the second field day
were started shortly after slack after flood and made through the rest of the ebb phase. Data
was to be collected from a towed downward looking ADCP in order to determine current
profiles. The ADCP experienced various problems during both field trips and the data was not
suitable for analysis. However, regular profiles were made with an SB19+ CTD and a Laser In
Situ Scattering Transmissometer (LISST). Additionally, a total of 76 bulk water samples were
collected and analyzed for Total Suspended Solids (TSS) concentrations and percent of organic
material. Overall, these data provided excellent insights into the behavior of the suspended
material in the bay.




Total Suspended Sediment

Total suspended sediment concentrations were determined gravimetrically from the bulk water
samples. First, 47 mm glass fiber filters were baked at 525 C then pre-weighed. Approximately
1 l of the bulk water sample was vacuum filtered, dried at 80 C for 24 hours, weighed, then dried
another 24 hours and weighed again. Once the weight stabilized, these values were used to
derive the TSS concentrations. In order to estimate the organic content of the suspended
sediment, the filters were then baked in a muffle furnace at 525 C for 4 hours. Subsequently, the
filters were weighed to determine the loss on ignition from volatile carbon.




Aggregate Settling Velocity

Stokes law for mineral grains predicts the settling velocity, ws :




     D 2 (ρ s − ρ )
ws =    g
     18      µ



where D is the diameter of the particle, g is acceleration due to gravity, ρs is the density of the
mineral, ρ is the density of the water and µ is the molecular viscosity of the water. The settling
velocity of aggregates is more difficult to estimate than solid mineral particles, since the density
of aggregates changes with the size of the aggregate; larger, loosely packed aggregates tend to be
less dense than smaller more compact aggregates. Because of the fragile nature of aggregates
and their size dependence on ambient turbulence, isolation of aggregates in bulk water samples
can change their size distribution, excess densities, and fall velocities from the in-situ state.
Therefore, an in-situ method of measuring the aggregates is called for. In this study, the Sequoia
Science LISST100X was used to provide in-situ estimates of particle sizes and volume
concentrations.




The density of an aggregate, denoted ρa, is determined by the relative volume amounts of solid
material and interfloc water, the density of the water, and the dry density of the material, ρs:




        ρ a = ρ sφ + ρ (1 − φ )
where φ is the unitless volume fraction of the solid material of the aggregate to the total
aggregate volume. If the dry density of the aggregate material is known, then the volume
fraction of the material may be estimated by using the total volume concentration of aggregates
obtained by the LISST, Va (a volume of aggregates to volume of water concentration), and the
total suspended sediment (TSS) mass concentration (mass of dry sediment to volume of water
concentration):




             TSS
        φ=         .
             ρ sVa




The density of the aggregate may then be calculated and substituted into the Stokes equation
along with the particle size diameter determined by the LISST to get an estimate of the settling
velocity of the aggregate (Fugate and Chant, 2006).




Data Presentation

The data that is presented from the field is generally provided in the following format. First a
site figure presents the location and chronological order of the casts made during each transect.
For each transect, planar contours of surface and bottom salinity, temperature, and optical
backscatter are calculated. An additional contour plot shows the difference between bottom and
surface salinity to provide a planar view of stratification in the region. A final depiction of the
data shows high resolution depth profiles of suspended sediment, salinity, and particle size by
distance along each transect. During the first field trip it became apparent that saltwater would
not be completely flushed from the Caloosahatchee. Therefore, the last two transects were
longitudinal transects going upstream in the Caloosahatchee in order to find the extent of the
salinity intrusion.
Results and Discussion:




Freshwater Discharge and Salinity

Data from the South Florida Water Management District (SFWMD) salinity monitors and data
on discharge at the Franklin Locks from the Army Corp of engineers were used to estimate the
freshwater discharge that would be necessary to flush out all of the marine water in the river.
Figure 5 shows the sites from which SFWMD data were compiled and processed. Hourly data
were obtained of surface and bottom salinity at each of the sites for approximately ten years,
from 1992 to 2002. Figure 6 shows near bottom salinity at 4 sites in the Caloosahatchee plotted
against the freshwater discharge coming through the Franklin Locks. An estimate of the
discharge necessary to flush saline water out of the estuary can be made from the results from the
Marker H site at the mouth of the river. From the available data it isn’t possible to precisely
separate flood and ebb tide values. Nevertheless, a general pattern can be seen in which the
higher values of salinity tend to be associated with flood tides, and the lower values tend to be
from ebb tides (red circles in diagram). It appears that at low tides the salt water is completely
flushed out of the estuary when the salinity at the mouth is zero, starting around 100-150 m3 s-1.
It also appears from this data that the salt water is rarely flushed out completely during high
tides. Since the ETM is usually located near the extent of the salinity intrusion, the data suggest
that the ETM may be flushed out during ebb when freshwater discharge is greater than 150 m3 s-1
(about 5300 ft3 s-1). However, analyses of ETM locations in the Caloosahatchee River by river
discharge (Fig. 7) suggest a much higher discharge may be necessary, up to 250 m3 s-1 (about
9000 ft3 s-1). A final insight into the amount freshwater discharge necessary to flush the
saltwater intrusion can be made from using a Froude number, F, which quantifies the balance
between freshwater flow and the density driven force that moves the saltwater upstream:


                                                ∆        /



where Ur is the river velocity, ∆ρ is the density difference between fresh and salt water,   is
mean density, g is gravity, and h is the depth of the estuary (e.g. Geyer et al., 2004). Assuming a
mean depth of 3 m, the Froude number suggests that a combined river flow and ebb tidal flow of
about 0.8 m s-1 is necessary to balance the force of the saline intrusion.




Results from August 27, 2008

The locations of the casts for the first transect on August 27, 2008 are shown in Figure 8. The
first transect at slack after ebb revealed a very high degree of stratification near the mouth of the
Caloosahatchee River. Surface salinity was around 4 ppt and bottom salinity was around 20 ppt
(Figs 9-11). The degree of stratification reduced markedly from the mouth into San Carlos Bay;
the southwest portion of the bay had only a 6 ppt difference between surface and bottom
compared to near 20 ppt around the mouth. Near bottom and surface temperatures were
relatively uniform, indicating that changes in salinity are more responsible for changes in density
than temperature (Figs. 12-13). Surface OBS values showed relatively little suspended sediment
near the mouth, and higher values in the southwest region of the bay where the water was less
stratified (Fig. 14). Near bottom OBS showed a clear ETM like signature with high suspended
sediments near the mouth of the river and extending along the channel towards the Sanibel
causeway (Fig 15). This is especially evident in the longitudinal plot (Fig. 16). Particle size
distributions do not show any particular pattern (Fig. 17).




The very shallow bathymetry on the northwest side of the Sanibel causeway significantly slowed
the completion of the first transect. Therefore, subsequent transects were made in the deeper
waters to the south of the causeway. The locations of the casts for the second transect are shown
in Figure 18. Between the time of the first and second transects, the water became significantly
more well mixed with the flooding tide in most of the site locations. The exception is at the site
in the Intracoastal Waterway where outside of the channel, the bathymetry is exceptionally
shallow. Elsewhere, surface and bottom salinity differences were mostly less than 10 ppt (Figs.
19-21). Temperature patterns showed that somewhat cooler water was present in the
Caloosahatchee River and the two sites bordering the entrance to Pine Island Sound (Figs. 22-
23). This is roughly the same distribution of surface temperature during the first transect, and
since both surface and bottom temperatures are similar during the second transect, this is further
evidence of strong mixing of the water column. The localized high surface and bottom turbidity
at the stratified site in the Intracoastal Waterway produce an unlikely interpolation in the OBS
planar views (Figs. 24-25). A more revealing view is shown in the longitudinal section (Fig. 26).
Although the water level was rising at the mouth, ebb currents likely persisted after the first cast
was made (Fig. 3a), since there is a lag in the tidal phase of one to two hours between the mouth
and the Sanibel Causeway. The continuing ebb currents advected the ETM at the mouth of the
river downstream through the channel towards the Causeway. Current speed decreased and
reversed to flood by the beginning of the second transect. Much of the suspended material
settled at the mouth, however, near the well mixed region along the channel from the mouth of
the river to Sanibel Causeway, turbulence resuspended sediment to the surface of the water.
Thus, the turbidity maximum was relocated downstream in the channel and was maintained by
turbulent mixing in the water column, rather than by convergence of density gradients. Particle
sizes appear to be larger in the north and west region of the bay, where the water is fresher and
cooler (Fig. 27).




Subsequent to the second transect, a short transect was made across the mouth of the
Caloosahatchee River, from the deeper main channel of the Intracoastal Waterway northwest
through a channel that cuts through the shallow shoals at the mouth (Fig. 28). This transect was
to investigate whether there was a significant difference in the physical parameters laterally
across the river mouth. Contrary to expectations, the water was less stratified in the deeper
channel, and more stratified in the channel through the shallower shoals (Fig. 29). There was a
strong vertical salinity gradient in the shoal area, from 3 ppt at the surface to 23 ppt at the
bottom, in only 2 m of water. There was also a strong lateral salinity gradient; surface salinity
was near 3 ppt in the shoal, and 14 ppt in the deeper channel. The slower moving currents over
the shoals may contain less turbulent shear, thus allowing a more stratified water column to
persist, especially in the channel that cuts through the shoals, while the stronger currents in the
main channel mixed the water column. There is also a mild temperature gradient across the river
with warmer water in the deep channel and cooler water in the shoal (Fig. 30). Suspended
sediment concentrations were uniformly low across the river. (Fig. 31) and particle sizes were
uniformly large (Fig. 32).




Cast sites for the third transect around the bay are shown in Figure 33. The transect locations are
presented in the planar figures in slightly different order, with the easternmost site outside of the
Causeway being the first represented, and the site at the mouth of the river, the last (i.e. sites 2-
6). There was a delay because of instrument problems before the site outside of the Causeway
was sampled, so the transect was reordered to preserve the most synoptic view of the physical
parameters. Surface, bottom, and surface-bottom differences show that the water was
considerably fresher and much less stratified throughout most of the region (Figs. 34-36).
Temperatures were very well mixed across the region with the coolest water still coming from
the western portion near the entrance to Pine Island Sound (Fig. 37-38). The turbidity maximum
was nearly in the same location along the channel between the mouth of the river and the Sanibel
causeway, however, the particles had settled and were mostly in the lower part of the water
column (Figs. 39-41).




After completion of transect 3, the water level was near the minimum ebb level, and it was
apparent that the saltwater would not be completely flushed out of the river. It was expected that
the ETM would be located near the 0 ppt contour and there was no way of realizing that the
instruments had already located high turbidity regions downstream of the 0 ppt contour, since the
data was logged in internal memory on the equipment. Consequently, it was decided to conduct
longitudinal surveys upstream in the Caloosahatchee to determine exactly how far the 0 ppt
contour had been advected and to record the location and strength of the ETM which was
expected to still be upstream in the river. The cast sites of the first longitudinal transect are
shown in Figure 43. While the onboard real time YSI indicated that the transect had reached
freshwater, the more accurate CTD shows that we had not quite reached it. However, the fine
scale structure of the salinity is interesting and shows that the water was well mixed with higher
turbidity at surface and bottom up to about 1 ppt (Figs 44, 46). Further upstream there was one
sited with very slight stratification and increased turbidity near the bottom. This site was
probably an anomaly where higher salinity and turbidity water was trapped in a localized area.
The subsequent transect did not show this feature. Temperature was well mixed along the entire
transect (Fig. 45).




The second longitudinal transect started in the channel just north of the Sanibel causeway and
proceeded towards the Caloosahatchee R and then upstream (Fig. 47). A similar pattern to the
first longitudinal transect of well mixed water with high turbidity around the 0.5 ppt contour is
apparent (Figs. 48- 50) However, the slight stratification and near bottom turbidity feature is
absent. The additional extent of this transect past the river mouth reveals the upstream edge of
the turbidity maximum that was tracked throughout the “circular” transects.




Figures 51-53 show time series of salinity, temperature, and OBS at the mouth of the river. The
stratified water column at slack after ebb at the beginning of the survey evolves to a well-mixed
water column at the end of ebb at the end of the survey. High turbidity persisted in the lower
stratified water column for several hours, until near the end of flood. The data from this time
series and earlier transects show that the suspended material in the ETM at the mouth was
dispersed throughout the subsequent tidal cycle by settling slowly, by advection downstream
away from the mouth, and by resuspension to the surface in the turbulent flood current.




Forty bulk water samples were collected throughout this survey day. Total suspended solids
(TSS) concentrations were relatively low, ranging from around 0.004 g l-1 to 0.016 g l-1.
Although the OBS tends to work better in higher concentrations, there was a good correlation
between TSS and OBS values (Fig. 54). The overall correlation coefficient was 0.68, the
correlation amongst only bottom samples was 0.79, and amongst only surface samples was 0.52.
The relationship between percent organic matter (from loss on ignition) and TSS was also typical
(Fig. 55). Lower values of TSS were associated with higher percentages of organic matter (up to
65%) and higher values of TSS were associated with lower percentages of organic matter
(around 30 %). The estimated settling velocities were relatively low for estuarine aggregates, but
not surprising for the low TSS concentrations that were present (Fig. 56).




Results from September 5, 2008

A week after the first survey, a second survey on September 5, 2008 was added to the project to
take advantage of the season's first pulsed release of water through the Franklin Locks, when
turbidity and freshwater flow could potentially be high. The transects were similar to those of
August 27th, 2008, but included additional cast sites in the interior of the bay. These sites were
monitored in order to further increase the spatial resolution of the sampling, and additional sites
were added when a distinct front was observed during the survey.

The cast locations for the first transect are shown in Fig. 57. Salinities at the surface ranged from
17 to 25 and near bottom salinities ranged from 22 to 29 (Figs. 58-59). Salinity was lower and
stratification was much stronger near the mouth of the river. Conversely, the water was saltiest
and the water was very well mixed across the mouth of Pine Island Sound (Fig. 60). Surface
temperatures varied less than 1 degree C (28.2-28.8); bottom temperatures were also within
about 1 degree C (28.5-29.5) (Figs. 61-62). OBS results show the strongest turbidity outside of
the bay, across the Sanibel Causeway and across the mouth of Pine Island Sound (Figs. 63-65).
There was no clear pattern in particle size (Fig. 66).

The cast locations of the second transect are shown in Fig. 67 and include extra sites very close
to each other, but straddling a clearly observable front in the water that stretched across the
interior of San Carlos Bay. The front separates fresher cooler Caloosahatchee River water from
saltier warmer water coming from Pine Island Sound and communicating with the waters on the
western side towards the Sanibel Causeway (Figs. 68-72). The front also divides relatively clear
river water from much more turbid water in the saltier region (Figs. 73-75). There was still no
clear pattern in particle size (Fig. 76).

By the time that the third transect was completed (Fig. 77) the water had freshened and the front
was not as clearly defined (Figs. 78-82). Turbidity was also reduced, although still higher in the
western side of the bay (Figs. 83-86). The fourth transect (Fig. 87) continued these trends of
freshening and decreasing turbidity (Figs. 88-96).

The time series of salinity, temperature, and OBS (Figs. 97-99) show that the water column at
the mouth was relatively well mixed with low turbidity during most of ebb. However, near the
end of surface ebbing currents, near bottom salty and turbid water can be seen to start flooding
upstream. This stratified the water column dampening mixing, and suggesting that the increased
turbidity comes from advection of material outside of the river, rather than from resuspension.
This is further evidence of a pool of easily resuspended material located outside of the mouth and
in the channel towards the Sanibel Causeway.

Thirty six bulk water samples were taken during this survey day. TSS concentrations were
somewhat higher than on August 27 but were still relatively low. The values ranged from
around 0.007 g l-1 to 0.034 g l-1. There was a relatively good correlation between TSS and OBS
values (Fig. 100). The overall correlation coefficient including 3 outliers from bottom samples
was 0.57, the correlation amongst only bottom samples was 0.36, and amongst only surface
samples was 0.84. The relationship between percent organic matter (from loss on ignition) and
TSS was also typical (Fig. 101). The percent of organic material was lower than the August 27
survey; almost all of the samples had less than 45% organic material. The estimated settling
velocities were consistent with the previous survey (Fig. 102); settling velocity ranged from
about 5*10-2 to 4*10-1 mm s-1.




Conclusions




Two empirical methods were employed to estimate the freshwater discharge necessary to flush
saline waters completely out of the Caloosahatchee River Observations of salinity and
freshwater discharge data suggested that a discharge of 100-150 m3 s-1 would be necessary to
flush out the salinity intrusion. Observations of the locations of the ETM in the river by
freshwater discharge suggest a higher discharge is necessary, up to 250 m3 s-1. Based on these
estimates, the freshwater discharge of 350 m3 s-1 at the time of the first survey should have been
enough to freshen the entire river, however the salinity front just barely persisted in the river,
although very near the mouth. A rough Froude number estimation suggests that ebb directed
currents need to be greater than 0.8 m s-1 to move the salinity front. During the study period,
peak ebb velocities at the mouth did reach 0.8 m s-1, and so should have been able to hold the
front steady temporarily. However, flood velocities counteracted that balance and the front was
not completely flushed out of the river. Despite the fact that the salt water did not completely
leave the river, many insights into the sediment transport during and after the passage of a storm
were achieved.

Provisional data from the USGS suggest that the strongest flush of freshwater and sediment
occurred during and in the hours after the passing of Tropical Storm Fay. The patterns of
resuspension during this survey show that most of the sediment was deposited in the region
between the mouth and the Sanibel Causeway, rather than across the entire San Carlos Bay. It
remained as a mobile pool of sediment that is constantly reworked and dispersed by the tides and
continued freshwater runoff. The sediments and current are mostly confined to the southeastern
channel by the very shallow bathymetry in the middle of the bay.

The pattern of stratification implies that the depth, salinity gradients, and currents are near the
critical balance required for stratification. When the tidal currents were slightly lower, such as in
the ebb cycle just before the survey, the water column became stratified. When the tidal currents
are stronger, such as the ebb recorded during the survey, there was sufficient energy to mix the
water column. This significant fluctuation of stratification on a tidal time scale is an important
result with regard to sediment transport and needs to be modeled correctly to predict long term
sediment transport. These results also suggest that that the water column was well mixed during
the peak storm currents and did not create a salt wedge as hypothesized.

The currents near the mouth are strongly ebb dominant during high discharge and produced a net
transport of sediment out of the mouth and into San Carlos Bay. However, the level of
suspended sediment concentration was surprisingly low, ranging from 0.004- 0.016 g l-1. It
remains for further research to discover whether these levels are sufficient to stress seagrass,
oysters, and other organisms. Low concentrations of suspended sediment are often associated
with relatively high levels of organic content. This association is supported by the low values of
settling velocities found during this survey, ranging from 4*10-3 to 7*10-1 mm s-1. Estuarine
aggregate settling velocities are usually on the order of 1 mm s-1. A higher percentage of organic
content would reduce the density and consequently the settling velocities. Another reason for
this low settling velocity may be the result of the relatively higher calcium carbonate content
than in other temperate estuaries and a different level of cation exchange when reaching marine
waters. This hypothesis warrants further investigation.

Sediment concentrations were also very low during the second survey when the first of the year
controlled release of water through the Franklin Locks occurred. The concentrations may have
been low because the easily resuspended material in the river had already been flushed out by
the storm, and because the total discharge was also low relative to storm induced discharge. The
highest turbidities during this survey were found in the marine waters across a front formed by
the convergence of the river water and marine water, while the riverine water turbidity was much
lower.

The turbidity maxima found during the first survey developed through two mechanisms. The first
mechanism is from the classical convergence of near bottom residual currents; the second is from
increased resuspension in localized regions of well mixed water, compared to lower resuspension
in stratified regions where turbulence and mixing is damped. The high turbidity near the mouth
at the first slack after ebb in well stratified water, suggests a classical ETM resulting from the
convergence of residual currents. Further along in the tidal cycle, this ETM settles in the
stratified waters near the mouth, and more sediment is resuspended higher in the water column
near the Sanibel Causeway. At the location of this new turbidity maximum, the water column is
well mixed and turbulence and mixing is enhanced. The final slack after ebb shows elevated
turbidity associated with the well mixed head of salinity, but not nearly as strong as at the
beginning of the day. This turbidity maximum is probably a result of resuspension of the mobile
pool of sediment that was previously deposited in the region. The rapid (i.e. on a tidal scale)
change of the location, strength, and forcing mechanism of the ETMs suggest that it is unlikely
that the ETM maintained its integrity outside of the mouth of the river as do ETMs in high
discharge areas such as the Mississippi and the Amazon.
In summary, the results show that after the passing of tropical storm Fay, the most important
pathway of suspended sediment from the Caloosahatchee River was from the mouth through the
channel towards the Sanibel Causeway. Although there were occasional regions of localized
high turbidity elsewhere, the most consistent pattern of resuspension appeared to come from a
mobile pool of easily resuspendable sediment lying along this route. This mobile pool of
sediment was likely deposited during and in the hours after the storm and high discharge abated.
The water column was likely well mixed during the storm and subsequent hours after its passing,
and probably did not form a well defined salt wedge. If there were high concentrations of
suspended sediment during the storm, they settled and consolidated rapidly or were advected far
from the mouth of the river. More likely, there was not a strong pulse of sediment, since the pool
of sediment that was resuspended only days after the storm produced relatively small suspended
concentrations. Also, freshwater currents near the bottom where suspended sediment
concentrations are the highest were not likely strong enough to push saline water far from the
bay.
References:



Fugate, D.C., R.J. Chant, 2006, Aggregate settling velocity of combined sewage overflow.
       Marine Pollution Bulletin 52, pp 427-432

Geyer, W.R., P.S. Hill, and G.C. Kineke, 2004, The transport, transformation and dispersal of
       sediment by buoyant coastal flows, Continental Shelf Research 24, pp 927-949.

Lawson, S.E., P.L. Wiberg, K.J. McGlathery and D.C. Fugate, 2007, Wind-driven sediment
      suspension controls light availability in a shallow coastal lagoon, Estuaries and Coasts.

North, E.W., E.D. Houde, 2003, Linking ETM physics, zooplankton prey, and fish early-life
       histories to striped bas Morone saxatilis and white perch M. americana recruitment,
       Marine Ecology Progress Series, 260, pp. 219-236.

Roman, M., X. Zhang, C. McGilliard, W. Boicourt, 2005, Seasonal and annual variability in the
     spatial patterns of plankton biomass in Chesapeake Bay, Limnology and Oceanography,
     50(2), pp. 480-492.

Trowbridge, J.H. and G.C. Kineke, 1994, Structure and dynamics of fluid muds on the Amazon
      continental shelf, Journal of Geophysical Research, 99(C1), pp. 865-874.

Wilber, D.H. and D.G. Clarke, 2001, Biological effects of suspended sediments: a review of
       suspended sediment impacts on fish and shellfish with relation to dredging activities in
       estuaries, North American Journal of Fisheries Management, 21: 855-875.
Fig. 1. San Carlos Bay, Southwest Florida
                                 16
                                 14


              Wi Speed (knots)
                                 12
                                 10
                                  8
                                  6
               ind




                                  4
                                  2

                                  08/24                        08/31                       09/07




                                 350
                 egrees)




                                 300
Wind Direction (de




                                 250
                                 200

                                 150

                                 100
                                 50

                                  08/24                         08/31                      09/07

                                                        Month / Day / 2008

                                   Fig. 2. Wind speed and direction at Fort Myers during the
                                   survey days, marked with red circles.
                         2.4
             m)

                         2.2
         Ht (m




                           2   a.
                          00:00     06:00          12:00   18:00   00:00
   Current Speed (m/s)




                          0.8
                          0.6
                          0.4  b.
                          0.2
                            0
         t




                         -0.2
                           00:00    06:00          12:00   18:00   00:00


                                            Time 8/27/08


Fig. 3. USGS Provisional data at the mouth of the Caloosahatchee 8/27/08 a)
                                            positive).
relative water height b) current speed (ebb positive) Blue shading shows the
duration of the field effort.
                          2.3
                                    a.
          Ht (m)
             (




                          2.2

                          2.1

                           00:00         06:00         12:00   18:00   00:00
    Current Speed (m/s)




                          0.5


                            0
          t




                          -0.5
                                b.
                            00:00        06:00         12:00   18:00   00:00




                                                 Time 9/5/08
Fig. 4.
Fig 4 USGS Provisional data at the mouth of the Caloosahatchee 9/5/08
a) relative water height b) current speed (ebb positive). Blue shading shows
the duration of the field effort.
                                      C

                                                 D
                         B




           A




Fig. 5.  Site map of SFWMD stations A) Marker H B) Fort Myers C) Bridge 31 
                         D) S79 (Franklin Locks)
                                                    High Tide Values




                                  Low Tide Values
Fig. 6. Near bottom salinity (ppt) by discharge levels (cms) at A) 
Fig. 6. Near bottom salinity (ppt) by discharge levels (cms) at A)
  S79 (Franklin Locks) B) Fort Myers C) Bridge 31 D) Marker H 
           40



           35
                 Km=5.2 * Q0.21
                 R2=0.81
           30



           25
River Km
      K




           20



           15



           10



           5
             0          1              2               3             4
           10          10             10              10            10



                 3 Day Avg of Discharge from Franklin Locks (cfs)



Fig. 7. Location of ETM by Caloosahatchee Discharge. Fitted curve
suggest that the ETM will reach the mouth around 9000 cfs (~250 m3 s-1 )
           26.54

           26.53

           26.52
           26 52                                        81
           26.51
                                                         2
            26.5                            7
Latitude




                                                             3
           26.49
                               6                4
           26.48

           26.47
                                   5

           26.46

           26.45


                   -82.08   -82.06     -82.04       -82.02       -82   -81.98   -81.96
                                                Longitude

                   Fig. 8. Cast locations of transect 1, August 27, 2008
Latitude




                                      Longitude

           Fig. 9. Transect 1 August 27, 2008, Surface Salinity (ppt)
Latitude




                                      Longitude

           Fig. 10. Transect 1 August 27, 2008, Bottom Salinity (ppt)
Latitude




                                         Longitude

           Fig. 11. Transect 1 August 27, 2008, Bottom-Surface Salinity (ppt)
Latitude




                                  Longitude

     Fig. 12. Transect 1 August 27, 2008, Surface Temperature (ºC)
Latitude




                                 Longitude

     Fig. 13. Transect 1 August 27, 2008, Bottom Temperature (ºC)
Latitude




                                      Longitude

           Fig. 14. Transect 1 August 27, 2008, Surface OBS
Latitude




                                       Longitude
           Fig. 13 Transect 1 August 27, 2008, Bottom OBS
            Fig. 15. Transect 1 August 27, 2008, Bottom OBS
Cast 1   2    3      4         5     6         7          8
                                                                     +




                       Km along transect
Fig. 16. Along transect series of OBS and salinity (red contours).
Triangles denote cast locations. Transect 1 August 27, 2008.
Cast 1   2    3      4         5    6        7          8




                         Km along transect
Fig. 17. Along transect series of median particle size. Triangles
denote cast locations. Transect 1 August 27, 2008.
           26.54

           26.53

           26.52
           26 52                                              1
           26.51                                       82
            26.5                          7
Latitude




           26.49
                               6
           26.48
                                                              3
           26.47                 5
           26.46
                                              4
           26.45


                   -82.08   -82.06   -82.04        -82.02         -82   -81.98   -81.96
                                                  Longitude

                   Fig. 18. Cast locations of transect 2, August 27, 2008
Latitude




                                      Longitude

           Fig. 19. Transect 2 August 27, 2008, Surface Salinity (ppt)
Latitude




                                      Longitude

           Fig. 20. Transect 1 August 27, 2008, Bottom Salinity (ppt)
Latitude




                                       Longitude

           Fig. 21. Transect 2 August 27, 2008, Bottom-Surface Salinity (ppt)
Latitude




                                      Longitude

           Fig. 22. Transect 2 August 27, 2008, Surface Temperature (ºC)
Latitude




                                      Longitude

           Fig. 23. Transect 2 August 27, 2008, Bottom Temperature (ºC)
Latitude




                                      Longitude

           Fig. 24. Transect 2 August 27, 2008, Surface OBS
Latitude




                                     Longitude

           Fig. 25. Transect 2 August 27, 2008, Bottom OBS
Cast 1   2    3      4         5     6         7          8
                                                                     +




                       Km along transect
Fig. 26. Along transect series of OBS and salinity (red contours).
Triangles denote cast locations. Transect 2 August 27, 2008.
Cast 1   2          3       4        5      6     7       8




                        Km along transect
Fig. 27. Along transect series of median particle size. Triangles
denote cast locations. Transect 2 August 27, 2008.
             26.54

             26.53

             26.52                       3       2
             26.51                                          1
              26.5
  Latitude




             26.49

             26.48
             26 48

             26.47

             26.46

             26.45

                     -82.08   -82.06   -82.04        -82.02     -82   -81.98   -81.96
                                                Longitude
Fig. 28. Cast locations of across-river transect , August 27, 2008
Cast 1                         2                         3




Fig. 29. Across River Transect August 27, 2008, Salinity (ppt)
Cast 1                         2                         3




 Fig. 30. Across River Transect August 27, 2008, Temperature. Black
 contours are salinity
   Cast 1                        2                       3




                          Km along transect
Fig. 31. Along transect series of OBS and salinity (red contours).
Triangles denote cast locations. Cross mouth transect August 27, 2008.
Cast 1                                 2              3




                       Km along transect
Fig. 32. Along transect series of median particle size. Triangles
denote cast locations. Across mouth transect, August 27, 2008.
           26.54
           26 4

           26.53

           26.52
                                                            6
           26.51                                             1
    tude




            26.5
Latit




           26.49
                               5
           26.48
                                                                 2
           26.47                   4
           26.46
                                                 3
           26.45


                   -82.08   -82.06     -82.04        -82.02          -82   -81.98   -81.96
                                                Longitude

                   Fig. 33. Cast locations of transect 3, August 27, 2008
Latitude




                                     Longitude

           Fig. 34. Transect 3 August 27, 2008, Surface Salinity (ppt)
Latitude




                                      Longitude

           Fig. 35. Transect 3 August 27, 2008, Bottom Salinity (ppt)
Latitude




                                      Longitude

           Fig. 36. Transect 3 August 27, 2008, Bottom-Surface Salinity (ppt)
Latitude




                                     Longitude

           Fig. 37. Transect 3 August 27, 2008, Surface Temperature (ºC)
Latitude




                                     Longitude

           Fig. 38. Transect 3 August 27, 2008, Bottom Temperature (ºC)
Latitude




                                     Longitude

           Fig. 39. Transect 3 August 27, 2008, Surface OBS
Latitude




                                     Longitude

           Fig. 40. Transect 3 August 27, 2008, Bottom OBS
  Cast 1       2     3          4              5       6
                                                              +




                       Km along transect
Fig. 41. Along transect series of OBS and salinity (red contours).
Triangles denote cast locations. Transect 3 August 27, 2008.
Cast 1                 3            4              5        6




                       Km along transect
  Fig. 42. Along transect series of median particle size. Triangles
  denote cast locations. Transect 3 August 27, 2008.
              26.54

              26.53
                                                                        5 6 7 89
                                                                  2 3 4
              26.52
                                                              1
              26.51

               26.5
   Latitude




              26.49

              26.48

              26.47

              26.46

              26.45


                      -82.08   -82.06   -82.04       -82.02         -82    -81.98   -81.96
                                                 Longitude

  g                           g                       g
Fig. 43. Cast locations of longitudinal transect 1, August 27, 2008
Fig. 44. Longitudinal transect 1 August 27, 2008, Salinity (ppt)
Fig. 45. Longitudinal transect 1 August 27, 2008, Temperature.
Black contours are salinity.
Cast 1   2   3    4        5     6        7       8




                      Km along transect

   Fig. 46. Longitudinal transect 1 August 27, 2008, OBS. Red
   contours are salinity.
               26.54

               26.53                                                          10      11
                                                                        89
               26.52
                                                                  7
                                                              6
                                                             5
               26.51                                        4
                                                            3
    Latitude




                26.5                                          2
                                                             1
               26.49

               26.48

               26.47

               26.46


               26.45


                       -82.08   -82.06   -82.04    -82.02             -82    -81.98   -81.96
                                              Longitude
  g                           g                       g
Fig. 47. Cast locations of longitudinal transect 2, August 27, 2008
Fig. 48. Longitudinal transect 2 August 27, 2008, Salinity.
Fig. 49. Longitudinal transect 2 August 27, 2008, Temperature.
Black contours are salinity.
     Cast 1 2 3      4     5   6     7      8   9      10    11




                            Km along transect
Fig. 50. Longitudinal transect 2 August 27, 2008, OBS. Red contours are salinity.
Fig. 51. Time Series of Salinity at mouth of Caloosahatchee,
August 27, 2008.
Fig. 52. Time Series of Temperature at mouth of Caloosahatchee,
August 27, 2008. Black contours are salinity
Fig. 53. Time Series of OBS at mouth of Caloosahatchee, August 27,
2008. Red contours are salinity, triangle denote time of each cast.
              18



              16



              14



              12
TSS (m l-1)



              10
     mg




              8



              6


                                                  bot
              4                                   sfc


              2
                   0   2   4       6     8   10         12


                           OBS (Volts)

Fig. 54. Correlation of median OBS values with TSS
A 27 2008 R 0 68 b tt            l   0 79     f    l
Aug.27 2008, R=0.68, bottom only r=0.79, surface only
r=0.52
            70


            65


            60
% Organic


            55


            50
  O




            45


            40


            35


            30
            0.002   0.004   0.006    0.008   0.01   0.012   0.014   0.016   0.018


                                    TSS (g l-1)

              g                 p         percent organic and TSS,
            Fig. 55. Relationship between p         g
            August 27, 2008
               0.8



               0.7



               0.6




               0.5
w_s (mm s-1)




               04
               0.4



               0.3




               0.2



               0.1




                0
                 50   100          150           200          250           300


                               Median Particle Size (µm)
    Fig. 56. Relationship between settling velocity and median particle size,
    August 27, 2008
           26.54

           26.53

           26.52
                                                          121
           26.51

            26.5
            26 5
Latitude




           26.49
                                         11                   2
                               10
           26.48                              8               3
           26.47                     9             7
                                                              4
           26.46                              6
                                                    5
           26.45

                   -82.08   -82.06       -82.04      -82.02       -82   -81.98   -81.96
                                                  Longitude

              Fig. 57. Cast locations of transect 1, September 5, 2008
Latitude




                                     Longitude

           Fig. 58. Transect 1 September 5, 2008, Surface Salinity (ppt)
Latitude




                                     Longitude

           Fig. 59. Transect 1 September 5, 2008, Bottom Salinity (ppt)
  Latitude




                              Longitude

Fig. 60. Transect 1 September 5, 2008, Bottom-Surface Salinity (ppt)
Latitude




                          Longitude

Fig. 61. Transect 1 September 5, 2008, Surface Temperature (ºC)
Latitude




                          Longitude

Fig. 62. Transect 1 September 5, 2008, Bottom Temperature (ºC)
Latitude




                          Longitude

Fig. 63. Transect 1 September 5, 2008, Surface OBS
Latitude




                         Longitude

Fig. 64. Transect 1 September 5, 2008, Bottom OBS
Cast   1     2   3 4    5 6 7 8       9    10 11      12
                                                              +




                       Km along transect
Fig. 65. Along transect series of OBS and salinity (red contours).
Triangles denote cast locations. Transect 1 September 5, 2008.
Cast 1      2    3 4    5 6 7 8       9 10 11         12




                       Km along transect
Fig. 66. Along transect series of median particle size. Triangles
denote cast locations. Transect 1 September 5, 2008.
                      Transect 2
           26.54

           26.53

           26.52
                                                               15 1
                                                              26.48
           26.51                                                                                                9
                                                                                                               10
            26.5                                                                                             11
Latitude




                                                             26.475
                                                                    2
                                       14
           26.49
                                 13                                                                                              8

           26.48                                                        12                                                       7
                                               9
                                              10
                                              11                    3
                                      12            8
                                                    7         26.47
           26.47
                                                                    4
           26.46                                6
                                                       5     26.465
           26.45


                   -82.08    -82.06        -82.04          -82.02       -82        -81.98        -81.96
                                           Longitude          26.46
                                                                                                                   6



                                                             26.455
                                                                              -82.05        -82.045       -82.04       -82.035       5
                                                                                                                                     -82.03   -82.025


                            Fig. 67. Cast locations of transect 2, September 5, 2008
Latitude




                                     Longitude

           Fig. 68. Transect 2 September 5, 2008, Surface Salinity (ppt)
Latitude




                                     Longitude

           Fig. 69. Transect 2 September 5, 2008, Bottom Salinity (ppt)
  Latitude




                              Longitude

Fig. 70. Transect 2 September 5, 2008, Bottom-Surface Salinity (ppt)
Latitude




                          Longitude

Fig. 71. Transect 2 September 5, 2008, Surface Temperature (ºC)
Latitude




                          Longitude

Fig. 72. Transect 2 September 5, 2008, Bottom Temperature (ºC)
Latitude




                          Longitude

Fig. 73. Transect 2 September 5, 2008, Surface OBS
Latitude




                         Longitude

Fig. 74. Transect 2 September 5, 2008, Bottom OBS
Cast   1   2   3 4   5 6 7 8    9 10 11      12 13 14 15
                                                               +




                       Km along transect
Fig. 75. Along transect series of OBS and salinity (red contours).
Triangles denote cast locations. Transect 2 September 5, 2008.
Cast   1   2    3   4    5   6   7 8 9-11 12   13   14    15




                        Km along transect
Fig. 76. Along transect series of median particle size. Triangles
denote cast locations. Transect 2 September 5, 2008.
           26.54

           26.53

           26.52
                                                              121
           26.51

            26.5
            26 5
                                                                2
                                     11
Latitude




           26.49
                               10
           26.48                             8                  3
           26.47                     9               7
                                                                4
           26.46                             6
                                                     5
           26.45


                   -82.08   -82.06       -82.04        -82.02       -82   -81.98   -81.96
                                                  Longitude

               Fig. 77. Cast locations of transect 3, September 5, 2008
Latitude




                                     Longitude

           Fig. 78. Transect 3 September, 2008, Surface Salinity (ppt)
Latitude




                                     Longitude

           Fig. 79. Transect 3 September 5, 2008, Bottom Salinity (ppt)
  Latitude




                              Longitude

Fig. 80. Transect 3 September 5, 2008, Bottom-Surface Salinity (ppt)
Latitude




                          Longitude

Fig. 81. Transect 3 September 5, 2008, Surface Temperature (ºC)
Latitude




                          Longitude

Fig. 82. Transect 3 September 5, 2008, Bottom Temperature (ºC)
Latitude




                          Longitude

Fig. 83. Transect 3 September 5, 2008, Surface OBS
Latitude




                         Longitude

Fig. 84. Transect 3 September 5, 2008, Bottom OBS
Cast   1    2   3 4     5 6 7 8     9 10 11         12
                                                            +




                        Km along transect
 Fig. 85. Along transect series of OBS and salinity (red contours).
 Triangles denote cast locations. Transect 3 September 5, 2008.
  Cast 1     2    3   4     5 6 7 8     9 10 11        12




                          Km along transect
Fig. 86. Along transect series of median particle size. Triangles
denote cast locations. Transect 3 September 5, 2008.
           26.54

           26.53

           26.52
                                                              121
           26.51

            26.5
            26 5
                                                                  2
Latitude




           26.49
                                         11
                                         10

           26.48                              8                   3
           26.47                     9               7
                                                                  4
           26.46                              6
                                                     5
           26.45


                   -82.08   -82.06       -82.04          -82.02       -82   -81.98   -81.96
                                                  Longitude

            Fig. 87. Cast locations of transect 4, September 5, 2008
Latitude




                                     Longitude

           Fig. 88. Transect 4 September, 2008, Surface Salinity (ppt)
Latitude




                                     Longitude

           Fig. 89. Transect 4 September 5, 2008, Bottom Salinity (ppt)
  Latitude




                              Longitude

Fig. 90. Transect 4 September 5, 2008, Bottom-Surface Salinity (ppt)
Latitude




                          Longitude

Fig. 91. Transect 4 September 5, 2008, Surface Temperature (ºC)
Latitude




                          Longitude

Fig. 92. Transect 4 September 5, 2008, Bottom Temperature (ºC)
Latitude




                          Longitude

Fig. 93. Transect 4 September 5, 2008, Surface OBS
Latitude




                         Longitude

Fig. 94. Transect 4 September 5, 2008, Bottom OBS
Cast 1      2   3 4    5 6 7 8       9   10 11       12
                                                             +




                       Km along transect
Fig. 95. Along transect series of OBS and salinity (red contours).
Triangles denote cast locations. Transect 4 September 5, 2008.
Cast 1      2    3 4      5 6 7 8      9     10         12




                       Km along transect
Fig. 96. Along transect series of median particle size. Triangles
denote cast locations. Transect 4 September 5, 2008.
Fig. 97. Time Series of Salinity at mouth of Caloosahatchee,
September 5, 2008.
Fig. 98. Time Series of temperature at mouth of Caloosahatchee,
September 5, 2008. Black contours are salinity.
Fig. 99. Time Series of OBS at mouth of Caloosahatchee,
September 5, 2008. Black contours are salinity.
               35
                                                          bot
                                                          sfc


               30




               25
TSS (mg l-1)




               20




               15
T




               10




               5
                    2   4   6        8        10   12           14

                                OBS (Volts)
    Fig. 100
    Fig 100. Correlation of median OBS values with TSS Sep
    5 2008, R=0.57, bottom only r=0.36, surface only r=0.84
                 55



                 50

Percen Organic
                 45



                 40
     nt




                 35



                 30



                 25



                 20
                 0.005
                 0 005   0.01
                         0 01   0 015
                                0.015      0 02
                                           0.02       0.025
                                                      0 025   0.03
                                                              0 03   0 035
                                                                     0.035


                                        TSS (g l-1)
  g                  p         p         g
Fig. 101. Relationship between percent organic and TSS,
September 5, 2008
                  0.45


                   0.4


                  0.35
                  0 35


                   0.3
    ws (mm s-1)




                  0.25


                   0.2


                  0.15


                   0.1


                  0.05


                         50   100    150    200    250      300


                                Median Particle Size (µm)
Fig. 102. Relationship between settling velocity and median particle size,
September 5, 2008. Outlier at D50=74.6 and ws =0.70 not shown.

				
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