Mass Bank Failure Analysis of Selected Yazoo Basin Streams

Abstract

ABSTRACT IN the streams studied, bank instabilities occurred as a result of channel entrenchment and local scouring of the outerbank in bendways. Banks retreated primarily by mass failures of overheightened and oversteepened banks. Failures usually followed periods of heavy precipitation that increased the bank material weight and decreased its strength. These failures were generally associated with banks with extensive tension cracks. Slope stability analyses were used to assess the stability of streambanks and to predict limiting values for the bank height and slope angle. In this study, the limit analysis for a logarithmic spiral toe failure was used. This analysis required data on the strength properties and distribution of the bank materials which were ob-tained from a borehole survey of bank materials and from in situ strength tests. The applicability of the stability analyses was evaluated using field observations of bank geometry. Observations of bank failures showed good agreement with the analyses suggesting that the logarithmic spiral method of analysis can be used with confidence as an aid in redesigning unstable banks in the Yazoo Basin in northern Mississippi.