KARST GEOMORPHOLOGY RESEARCH IN SOUTH GEORGIA
my page
Since 1993, I have conducted collaborative studies that examine the geomorphology of sinkholes on the southeast coastal plain of Georgia. The first project, coauthored with Peter Jacobs, examines the morphology, distribution, and geomorphic significance of  >300 new sinkholes that formed in response to flooding  in 1994 at Albany, Ga. The second paper in this series (coauthored with Holly Wilkes, a VSU undergraduate student, and Peter Jacobs) examines spatial relationships between the new sinkholes and pre-flood (old) sinkholes. This paper, which is currently in review, uses digital elevation modeling techniques to evaluate the influence that topography has had on sinkhole development. Finally, in collaboration with Robert Gilbert (Queen's University, Kingston, Ontario, Canada), we have recently conducted several subottom acoustic surveys of sinkhole lakes near Valdosta. Although this project has only just begun, Bob and I are excited by the results that we have obtained from surveys at Lake Balboa which indicates in excess of 25 m of sediment infill beneat the lake.  
 
 
 
 
 
 
 
 
 
Distribution and morphology of sinkholes triggered by flooding following Tropical Storm Alberto at Albany, Georgia, U.S.A.

Flooding of the Flint River in July 1994 triggered the collapse of at least 312 sinkholes in the karstic Dougherty Plain at Albany, Georgia.  We examined the distribution and morphology of these new sinkholes to evaluate the mode of formation, to characterize early stages of the evolution of sinkhole form, and to estimate the lowering of the surface associated with the development of new sinkholes. 

Eighty-eight percent of sinkholes occur inside the limits of flooding, especially in areas of sandy overburden, and they often follow joint-controlled linear trends.  Sinkhole dimensions are log-normally distributed with median values of circumference = 5.7 m, length = 1.8 m, width = 1.6 m, and depth = 0.7 m; asymmetry (L:W) = 1.2.  Cross-sectional forms range from narrow cylinders to large bowls, with many sinkholes having undercut sides. 

Flooding triggered the formation of sinkholes by saturating and liquefying overburden, which caused soil arches to collapse and flow into cavities in bedrock.  The prevalence of sinkholes near the periphery of flooding suggests that drainage and loss of buoyant support as flood waters subsided may also have contributed to failure.  A volume ratio index is used to quantify the three dimensional geometric form of sinkholes.  Initially, small cylindrical shafts open over a bedrock joint, followed by progressive slumping that leads to widening and increases in volume to a final bowl form.  Estimates of the aggregate volume of overburden transported underground in flooded areas range from 7,990 to 11,130 m3.  Averaged over flooded areas, this accounts for 0.26 to 0.37 mm/km2 lowering of the surface.  Based on a 500 year recurrence interval for the flood event, values for lowering of the surface range from 0.52 to 0.74 mm per 1,000 years.  These values are an order of magnitude less than estimates of carbonate dissolution and suggest that transport of overburden underground is limited by triggering events. 

Reference: Hyatt, J. A., and Jacobs, P. M. 1996. Geomorphology, Vol. 17:305-316.