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 km Gulf of Mexico Atlantic Ocean 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 (%) Bulk density,  (kg m -3 )  = 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 density,  D (kg m -3 ) Rodman Reservoir Lower Kissimmee River Loxahatchee River Cedar/Ortega River Lake Bonnet Newnans Lake  D = 1900exp(-0.156OC) + 80

Variation of free settling velocity with organic content Organic content, OC (%) Settling velocity, w 0 (m /s)

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/m 2 -hr), CL = chlorophyll-a (mg/m 3 ) cation ratio CR = [Ca ++ ]+[Mg ++ ]/[Na + ]+[K + ]. TSI: 0-3 oligotrophic, 3-7 mesotrophic, 7-10 eutrophic, 10 hypereutrophic Newnans Lake = 15.3

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, Date (y) Stage (m NGVD) February 1998 El Niño high Typical level August 2001 low 1.1 m

Wind Record

Wind speed (m/s) Wave amplitude, a (m) Wave period, T (s) Peak wave- induced velocity, u m (m/s)

Bulk density,  (kg m -3 ) Depth below bed surface (m) y 20 y 30 y 40 y 50 y 60 y 70 y 80 y Initial Density profile 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) OC (%) Erosion flux,  (kg m -2 s -1 )

Settling velocity variation with concentration for Newnans Lake sediment

Concentration Profiles at Sites A in Newnans Lake Elevation, z (m) Lutocline 30 min 60 min 90 min Data Concentration, c (kg m -3 )

Concentration profiles at Sites B in Newnans Lake Lutocline Elevation, z (m) Concentration, c (kg m -3 ) 30 min 60 min 90 min Data min

Wind-induced re-suspension simulation in Newnans Lake Time, t (min) Concentration, c m (kg m -3 ) 8 m s -1 9 m s -1 7 m s -1

Accelerometer Pore pressure sensor