Genesis of channel bank overhangs in the Niger Delta and analysis of mechanisms of failure

The instability of channel banks carries a significant economic implication because of its effect on navigation and channel commercial development. The impact of bank instability in the Niger Delta is accentuated by the dense network of rivers and creeks. The occurrence of overhangs in channel banks is not restricted to stratified banks in which clay overlies sand. Field observation and analysis indicate that factors such as stratigraphy, local climate, bio-technical and fluvio-tidal processes act singly or in combination to generate overhangs in channel banks. The failure of channel banks with overhangs involves one of four mechanism, namely; rotation, beam, shear, and tension failure. A mathematical basis for the discrimination of these failure mechanisms is described. gnificance of identifying the critical location of tension cracks for the failure of the overhang is discussed. Although the study is based on experience in the Niger Delta, the principles applied and the conclusions reached undoubtedly apply to areas of similar geological and environmental conditions.