Valdosta State University Students (1993-1999)
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While at Valdosta State University I was fortunate to have worked with several talented undergraduate students on a variety of research projects including rill erosion, lacustrine sedimentology, sinkhole development, and digital elevation modeling. I have thoroughly enjoyed working with Jay, Nancy, Holly, Buck, Brent, and Jeff on these projects. Although I am very proud of the research that each has done, I should mention that both Jay Winkler and Holly Wilkes received outstanding paper in geography awards for their presentations at the Georgia Academy of Sciences meetings in 1996 and 1998 respectively. 

Abstracts given below are taken either from the student's final report, or from published abstracts in the Georgia Journal of Science. 

Rill Erosion Along an Exposed Embankment of Interstate 75 Near Valdosta, GA. 
Jack L. Winkler. R
This study examines the effectiveness of vegetation (grass) at reducing soil erosion on an embankment of Interstate 75 near Valdsota, GA. Three soil erosion plots were established downslope from vegetated and non-vegetated portions of a uniformly sloping (13% grade) earthen embankment. Plot 1 was mapped photographically at the beginning and end of the study to assess changes in preexisting rills between September 22 and November 17, 1995. Plot 2 (no vegetation upslope) and plot 3 (vegetation upslope) were graded at the start of the study, and were surveyed weekly using a rill meter to note the development of new rills and measure changes in surface elevation. 
      Twelve of 17 pre-existing rills at Plot 1 were lengthened by headward erosion increasing the total length of rills by 16 m (9% of the total rill length for plot 1). This lengthening occurred nearly equally downslope from vegetated and non-vegetated areas, and was in part controlled by a hard silty-clay layer at 15 to 20 cm depth (mean bulk density = 1.75 g/cm3). This layer inhibited vertical erosion and promoted sapping and headward erosion. Results from plots 2 and 3 show that most new rills form during the first rainstorm. Based on estimates of elevation change, nearly 4 times more erosion occurred at plot 2 (no vegetation upslope) than at plot 3. However, much of this difference was due to the deposition of an coluvial fan at plot 3. These findings imply that erosion on embankments will be minimized if vegetation is established quickly following completion of embankment construction (i.e. before the first major rainfall). Even small amounts of protective vegetation will greatly reduce the development of rills. 

Reference: Winlker, J. L., and Hyatt, J. A. 1996. Georgia Journal of Science, Vol 54, p. 49.


Spatial Variation of Inorganic Sediment and Implications for Human-Induced Trace Metal Loading at Lake Louise, Ga. 
Nancy F. Ekstrom

Near-surface sediments within Lake Louise, Georgia, form a 15 to 20 cm thick layer of light gray sediment that is enriched relative to underlying sediment in inorganics (by a factor of 2.5) and trace metals (e.g. Ti by 28, Ba by 3, Pb by 36). This enrichment has previously been attributed to the influx of clastic sediments to the lake during construction of near-by interstate 75 in 1957. In this study we examine the spatial variability of inorganic sediment within this surface layer (SL). Our purposes are: (1) to infer controls on sedimentation, (2) to estimate how much sediment and metal has entered the lake because of highway construction, and (3) to discuss implications of observed spatial trends to trace metal loading in the lake. Sixteen Eckman grab samples of the SL were recovered at 10 m intervals across the lake. Volumetric subsamples from the top, middle, and bottom of the SL were analyzed to determine moisture content, dry bulk density, and inorganic content (by LOI). The middle (M) and top (T) sample groups are statistically indistinguishable from one another. However, the bottom sample group (B) has significantly higher inorganic sediment content, dry bulk density, and lower moisture content than the combined M-T sample group. In addition, simple linear regression indicates a statistically significant trend (r2=0.54, p<0.001) of increasing inorganic content with increasing water depth. This trend is strongest for B samples and likely reflects an initial focusing of construction-derived clastic sediment into the deepest parts of the lake by turbidity flows. Subsequent bioturbation and a diminished post-construction influx of sediment to the lake may be responsible for the reduced focussing trend apparent in the M-T sample group. Using these trends together with bathymetric data we estimate between 7.1 and 10.1 x 105kg of dry sediment and significant quantities of trace metals (e.g. 6540 kg Ti, 270 kb Ba, 60 kg Pb) were introduced to the lake by highway construction. In addition, sequential extractions performed on SL sediments indicate that the majority of trace metals reside within the inorganic sediment fraction. Consequently, the observed focussing of inorganic sediment to the deep parts of the lake basin implies a similar concentration in trace-metals within Lake Louise. 
Reference: Hyatt, J. A., Ekstrom, N. F., and Tepper, J. H. 1997. Georgia Journal of Science, Vol 55, p. 82.

The Distribution of Inorganic Sediment in Lake Louise, Georgia. 
Andrew B. Bearden
Near-surface sediments from Lake Louise, GA, a 5 ha blackwater sinkhole lake near Valdosta, are examined to evaluate spatial variability of inorganic material within the lake. A light gray inorganic-rich layer of sediment, 10 to 20 cm in thickness, occurs throughout the lake. This layer is attributed to the influx of inorganic sediments during construction of Interstate 75 in 1957 across the lake's only inflow channel. Inorganic content is most concentrated at the bottom of this "highway layer" and steadily decreases upwards in the sediment column. A descriptive model is developed to explain three trends in changing inorganic content in the lake. At depths less than 3.35 m (near the shoreline), inorganic content is low because of a high contribution of organic material from shoreline vegetation. At intermediate depths (3.35 to 4.95 m), inorganic content decreased because of the existence of steep side slopes which permit sediment flows to by-pass these sections of water depth. At depths greater than 4.95 m, inorganic content increases linearly with water depth. This increase is greatest at the bottom of the highway layer, reflecting the initial influx of sediment in 1957. Finally, inorganic sediment contents are highest in the northern basin of the lake near the inflow channel.  

Reference: Bearden, A. B., and Hyatt, J. A. 1998. Georgia Journal of Science, Vol 56, p. 54.

Distribution and Analysis of Sinkholes in Albany, Georgia Prior to Tropical Storm Alberto. 
Holly P. Wilkes
In 1994, precipitation released by Tropical Storm Alberto caused extensive flooding of the Flint River at Albany, GA triggering the collapse of more than 300 new sinkholes. Previous studies have examined the form and distribution of these new sinkholes (Hyatt and Jacobs, Geomorphology, 1996). However, the influence of preexisting or "old" sinkholes on new sinkhole development has not been considered. This study analyses the size, location, and morphology of old sinkholes that were present in Albany prior to Tropical Stoorm Alberto. These characteristics are compared to the new sinkholes, and are used to identify important geologic and hydrologic controls on the development of sinkholes at this site. Old and new sinkhole locations were compared to determine (1) the number of new sinkholes inside each old sinkhole, (2) the number of old sinkholes inside and outside the limits of flooding that followed Tropical Storm Albert, and (3) the type and thickness of overburden for each sinkhole as determined from maps of the lithology and overburden thickness. Old sinkholes occur in nearly equal numbers inside and outside flood limits. They are most prevalent within sandy overburden inside the limits of flooding and within clayey overburden outside the limits of flooding. Clustering of new sinkholes within old sinkholes only occurs inside the flood limits, near the flood limit boundary, and along a large-scale lineation. Overall, old sinkholes apparently have had little influence on the development of new sinkholes at Albany.  

Reference: Wilkes, H. P., and Hyatt, J. A. 1998. Georgia Journal of Science, Vol 56, p. 54.

Digital Elevation Modeling and Color Analysis of Lake Louise, GA. 
Brent A. Collier
Located approximately 15 miles south of Valdosta, Lake Louise is a blackwater, limesink lake. Water in and around the lake has a dark, tea-like color. Decaying vegetation surrounding the lake produces fuluvic, humic, and tannic acids, and gives the water its distinctive color. 
   Water color and change in water volume for Lake Louise are of particular interest because they give insight to past changes in regional hydrology. Previous studies of lake core suggest that water levels were higher, lake volume was greater, and water color was less dark prior to 4000 years before present than it is today. This study tests this hypothesis by (1) analyzing the color of water in lake-side swamps and in the open lake, and by (2) constructing digital elevation models (DEM) to determine changes in the volume of swamp and open lake for various water levels. Color data indicate that swamp water is more than twice as dark as lake water. Data also show an increase in water color with an increase in water depth. Little difference is noted between open water in the center of the lake and open water around the lake margin that has abundant algae. DEM data show that as water levels rise the ratio of swamp volume to open lake volume increases. These data also reveal a critical water level that joins together the Lake Louise and Browns Pond drainage basins. At this critical water level, swamp volume increased by a factor of 80. 
    Color and volumetric data suggest either that previously higher water levels were not substantially lighter in color than present, as presumed, or that factors other than just the size of the swamp should be considered when inferring paleohydrology for the site.  

Reference: Collier, B. A., 1998. Final Report, GLY 499, 17 pp.