EFFECT OF ORGANIC MATTER ON WAVE-INDUCED RESUSPENSION OF FINE SEDIMENT
Jan 16, 2016
EFFECT OF ORGANIC MATTER ON WAVE-
INDUCED RESUSPENSION OF FINE SEDIMENT
Newnans Lake
Fine sediment aggregate constituents
Clay mineral
Non-clay mineral
Wood fragmentWorm tube
Biopolymer
Pore water
Diatom
N
0 100 kmGulf of Mexico
AtlanticOcean
Cedar/Ortega Rivers
Rodman Reservoir
Newnans Lake
Lower Kissimmee River Basin
Lake Okeechobee
Lake Bonnet
Loxahatchee River
Florida
Extended Agricultural Area
Variation of wet bulk density with organic content
Organic content, OC (%)
Bu
lk d
ensi
ty,
(kg
m-
3)
100 20 30 40 50 60 70 80 901000
1500
2000
2500
= 1136exp(-0.32OC)-0.9OC+1110
Rodman Reservoir (Mehta et al., 1994)Lower Kissimmee River (Rodriguez et al., 1997)Loxahatchee River (Ganju, 2001)Cedar/Ortega River (Mehta et al., 2000; Gowland, 2002a)Lake Bonnet (Gowland, 2001)Newnans Lake (Gowland, 2002b)
Variation of dry density with organic
content; data from six sites
Organic content, OC (%)
Dry
den
sity
, D (
kg m
-
3)
100 20 30 40 50 60 70 80 90
500
1000
1500
2000
0
Rodman ReservoirLower Kissimmee RiverLoxahatchee RiverCedar/Ortega RiverLake BonnetNewnans Lake
D = 1900exp(-0.156OC) + 80
Variation of free settling velocity with organic content
Organic content, OC (%)
Sett
ling
vel
ocit
y, w
0 (m
/s)
10 20 30 40 50 60 70 80 90010-7
10-6
10-5
10-4
Wind Induced Wave Sediment Re-suspension
NEWNANS LAKE
Shannon-Brezonik Trophic State Index (TSI):
T = turbidity (JTU), CD = conductivity [(μΩ)-1/cm =μS/cm], TN = total organic nitrogen (mg/l), TP = total phosphate (mg/l), PP = primary productivity (mg-C/m2-hr), CL = chlorophyll-a (mg/m3) cation ratio CR = [Ca++]+[Mg++]/[Na+]+[K+]. TSI: 0-3 oligotrophic, 3-7 mesotrophic, 7-10 eutrophic, 10 hypereutrophic Newnans Lake = 15.3
0.18 0.008 1.1 4.2 0.01 0.044 0.39 0.26TSI T CD TN TP PP CL CR
Newnans Lake zones based on bathymetry. Suspended sediment concentration was
measured at Sites A and B
Outer open water area
Inner open water area
Exposed area
1 km N
-1.5 m
-0.5 m
-0.3 m
0.0 m
Site B
Site A
Stage variation in Newnans Lake, 1995-2001
Date (y)
Stag
e (m
NG
VD
)
February 1998El Niño high
Typical 1995-98 level
August 2001 low
1.1 m
1995 1996 1997 1998 1999 2000 2001
19
20
21
Wind Record Maximum 2-minute Maximum 5-second
Mean Speed Direction Speed Direction Speed Direction(m/s) (degrees) (m/s) (degrees) (m/s) (degrees)
Jan 3.1 310 16.1 250 19.2 270Feb 3.4 270 14.8 240 18.3 240Mar 3.6 270 17.9 250 23.2 320Apr 3.3 270 13.9 330 17.9 330May 3.1 250 13.4 250 16.5 250Jun 2.8 250 20.1 240 23.2 220Jul 2.5 270 20.1 290 28.6 290
Aug 2.4 240 13.4 120 19.2 120Sep 2.6 90 13.0 120 17.4 160Oct 2.9 40 10.7 40 13.4 20Nov 2.8 40 11.6 320 14.8 320Dec 2.7 300 13.0 270 15.2 280
Yearly 3.0 270 20.1 240 28.6 290
Wind speed(m/s)
Wave amplitude, a
(m)
Wave period, T(s)
Peak wave-induced velocity,
um(m/s)
8 0.10 1.85 0.11
9 0.10 1.90 0.12
10 0.11 2.00 0.14
Bulk density, (kg m-3)
-1.4
-1.2
-1.0
-0.8
-0.6
-0.4
-0.2
0.0
Dep
th b
elow
bed
sur
face
(m
)
1030 1040 1050 1060 1070 1080
10 y
20 y30 y
40 y50 y
60 y70 y
80 y
Initial Densityprofile
Brenner and Whitmore (1998)
Gowland (2002)
Bed surface
Bed density variation due to consolidation and data from Newnans Lake
Erosion flux versus bed shear stress with lines of constant OC; data from Newnans
Lake
Shear stress, b (Pa)
0
0.1
0.2
0.3
0 0.05 0.1 0.15 0.2 0.25 0.3
OC (%) 60 50 40 30 20 10
Ero
sion
flu
x,
(kg
m-2
s-1)
Settling velocity variation with
concentration for Newnans Lake sediment
Concentration, c (kg m-3)
Sett
ling
vel
ocit
y, w
s (m
s-1)
10-1
10-2
10-3
10-4
10-5
10-6
10-2 10-1 100 101 102
OC = 10%; b = 1.6
20%; 2.4
30%; 3.7
40%; 5.8
50%; 7.9 60%; 10
10%≤OC≤30%30%<OC≤60%
Concentration Profiles at Sites A in Newnans Lake
0.05
0.10
0.15
0.20
0.25
0.000 0.5 1.0 1.5
Ele
vati
on, z
(m
)
Lutocline
30 min
60 min
90 min
Data
Concentration, c (kg m-3)
Concentration profiles at Sites B in
Newnans Lake
Lutocline
0.05
0.10
0.15
0.20
0.000 1 2 3
Ele
vati
on, z
(m
)
Concentration, c (kg m-3)
30 min60 min90 min
Data
4
120 min
0.25
0.30
Wind-induced re-suspension simulation
in Newnans Lake
0200 4000
2
1
3
100 300Time, t (min)
Con
cen
trat
ion
, cm (
kg m
-3)
8 m s-1
9 m s-1
7 m s-1
Accelerometer
Pore pressure sensor