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Title: SEDIMENT TRANSPORT MODEL FOR SEEPAGE EROSION OF STREAMBANK SEDIMENT

Author
item FOX, G. A. - UNIV. OF MISSISSIPPI
item Wilson, Glenn
item PERIKETI, R. K. - UNIV. OF MISSISSIPPI
item Cullum, Robert

Submitted to: Journal Hydrologic Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2006
Publication Date: 12/1/2006
Citation: Fox, G.A., Wilson, G.V., Periketi, R.K., Cullum, R.F. 2006. Sediment transport model for seepage erosion of streambank sediment. Journal Hydrologic Engineering, 11(6): 603-611, ASCE 1084-0699.

Interpretive Summary: Subsurface flow through permeable layers above impermeable layers is known to undercut streambank by seepage erosion. The role of seepage erosion on the collapse of streambanks is not well understood. The objective of this research was to investigate erosion by seepage and develop a mathematical model that describes the movement of sediment by seepage erosion. Laboratory experiments were performed using a constructed streambank setup packed with three different soil layers to mimic seepage erosion occurring at Little Topashaw Creek (LTC) in Northern Mississippi. Soil samples from LTC streambanks indicated large differences in permeability between the silt loam top soil, a loamy sand permeable layer, and a clay loam impermeable layer. Laboratory experiments were conducted with a variety of water table heights, top soil depths, and layer slopes. Bank failure occurred before the SiL top soil layer had positive pressure suggesting that saturation of the bank was not necessary for bank collapse due to seepage erosion. A model was developed based on a sediment proeprties that described the seepage erosion.

Technical Abstract: Erosion by lateral, subsurface flow is known to erode streambank sediment in numerous geographical locations; however, the role of seepage erosion on mass failure of streambanks is not well understood. The objective of this research was to investigate the mechanisms of erosion by concentrated, lateral subsurface flow and develop a sediment transport model for seepage erosion. Laboratory experiments were performed using a two-dimensional soil lysimeter of a reconstructed streambank profile packed with three different soil layers to mimic seepage erosion occurring at Little Topashaw Creek (LTC) in Northern Mississippi. Soil samples from LTC streambanks indicated considerable hydraulic conductivity contrast between an overlying silt loam layer (SiL), highly permeable loamy sand (LS), and confining clay loam (CL) layer. Lysimeter experiments were conducted with various upstream water table heads, overburden heights, and lysimeter slopes. Bank failure occurred prior to the removal of negative pore-water pressures in the SiL layer suggesting that such a mechanism was not critical for bank collapse due to seepage erosion. A sediment transport model was derived based on a dimensionless sediment discharge and dimensionless seepage flow shear stress.