Bank Processes on the Red River Between Index, Arkansas and Shreveport, Louisiana

摘要

The aims were to determine: the nature of the bank materials and the dominant mechanisms of bank failure; the role of outer bank type in affecting the scour depth of meander bends; and the possible impact of bank stabilization schemes on scour depth. The results show that the banks are formed in materials of four different origins: meander belt alluvium and clay plug materials associated with the present flood plain; back swamp deposits in a terrace left from the nineteenth century flood plain; and Pleistocene/Tertiary materials in the valley walls. Slab failures and rotational slips are the dominant failure modes. The Osman-Thorne analyses of bank stability were found to be useful in predicting critical geometry for failure of banks formed in the different materials. A relationship between outer bank type and bend scour depth was found. Generally, scour depth increases as outer bank resistance to erosion and failure increases, especially for tight bends of low radius of curvature to width ratio. Maximum scour pool depths for revetted bends are 5 to 20% greater than those in the equivalent free, alluvial meander. These results suggest that some additional bed scour should be expected as a consequence of stabilizing the remaining free meanders in the study reach, but reducing sedimentation in the lock chambers and behind the dams. (fr)