Approaches to the Design of Biotechnical Streambank Stabilization: Volume III—Design Guidelines

A conceptual framework for the design of biotechnical streambank revetment is proposed. It is intended to be simple in practice, flexible in being widely applicable, familiar in retaining cer­tain aspects of current practice while being patterned after other aspects, and encouraging a more environmentally sensitive approach to reliable streambank protection for INDOT projects. It distinguishes between a toe zone, where traditional hard armoring techniques such as those already included in the INDOT standard designs are more appropriate, and an upper bank zone where vegetation-based techniques would typically be applied. Default techniques are identified to simplify the choice of measures for \u27routine\u27 problems, but more case-specific techniques may also be selected. Primary techniques that offer immediate protection on their own are also distin­guished from supplementary techniques that are used only in combination with other (primary) techniques. The boundary between the toe zone and the upper bank zone is proposed to be the maximum of the ordinary high water mark (or bankfull elevation), the elevation corresponding to the 2-year discharge, and the elevation corresponding to the point that is one third up the slope from the bank toe at the design discharge (for streambank protection). For the upper bank zone, for bank slopes up to 2H:1V, regrading and revegetation with herbaceous species together with the use of rolled erosion control products (RECPs) is proposed as the default. The other (non-default) main primary technique for the upper bank zone is the vegetated mechanically stabilized earth (VMSE, or vegetated reinforced soil slope VRSS, or soil lifts) option (where revegetation with herbaceous species is also considered standard). This requires more engineering and construct­ion effort but is appropriate for those projects where a more vertical (up to maximum bank slope of 1H:1V) solution is desired. The supplementary techniques to be included are live staking to be used with the regrading option, and brush-layering to be used with the VMSE option