Incorporating seepage processes into a streambank stability model

Maria Librada Chu-Agor, Garey A. Fox, Glenn Wilson

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Seepage processes are usually neglected in bank stability analyses although they can become a prominent failure mechanism under certain field conditions. This study incorporated the effects of seepage (i.e., seepage gradient forces and seepage erosion undercutting) into the Bank Stability and Toe Erosion Model (BSTEM) and evaluated the importance of the seepage mechanisms on bank stability. The effects of the seepage force were incorporated into BSTEM by modifying the force balance. Seepage erosion undercutting was simulated using a recently proposed sediment transport function. The modified BSTEM was then used to evaluate the stability of a streambank along Little Topashaw Creek under different scenarios: (1) without seepage forces and undercutting, (2) with seepage forces only, (3) with seepage undercutting only, and (4) with both seepage forces and undercutting. For a condition where the bank was fully saturated, the factor of safety (FS) decreased by as much as 66% (i.e., FS decreased from 2.68 to 0.91) from that of a dry condition due to the decrease in the factional strength of the soil as the pore-water pressure increased. Incorporating the effects of the seepage force resulted in an average decrease in the FS of approximately 30 to 50% for all water table depths. Seepage erosion undercutting reduced the FS by approximately 6% for a 5 cm undercut (i.e., 2% of the bank height) and 11% for a 10 cm undercut (i.e., 3.3% of the bank height) due to the loss of supporting material in the conductive layer. Seepage erosion undercutting required 15 to 20 cm of seepage undercut to become the dominant failure mechanism over seepage forces and pore-water pressure effects. The cumulative effects of seepage reduced this streambank's FS by up to 63% when the water table reached the entire bank height. The development of a bank stability model capable of simulating seepage processes was necessary in order to better understand site-specific failure mechanisms.

Original languageEnglish (US)
Title of host publicationAmerican Society of Agricultural and Biological Engineers Annual International Meeting 2009, ASABE 2009
Pages1769-1779
Number of pages11
StatePublished - Dec 1 2009
Externally publishedYes
EventAmerican Society of Agricultural and Biological Engineers Annual International Meeting 2009 - Reno, NV, United States
Duration: Jun 21 2009Jun 24 2009

Publication series

NameAmerican Society of Agricultural and Biological Engineers Annual International Meeting 2009, ASABE 2009
Volume3

Other

OtherAmerican Society of Agricultural and Biological Engineers Annual International Meeting 2009
CountryUnited States
CityReno, NV
Period6/21/096/24/09

Keywords

  • Erosion
  • Groundwater flow
  • Sediment transport
  • Seepage
  • Streambank stability

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)

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  • Cite this

    Chu-Agor, M. L., Fox, G. A., & Wilson, G. (2009). Incorporating seepage processes into a streambank stability model. In American Society of Agricultural and Biological Engineers Annual International Meeting 2009, ASABE 2009 (pp. 1769-1779). (American Society of Agricultural and Biological Engineers Annual International Meeting 2009, ASABE 2009; Vol. 3).