Establishing Native Grasses on Soil Faced with Retaining Walls

In 1998 the Western Federal Lands Highway Division (WFLHD), a department within the Federal Highway Administration (FHWA) that works primarily on improving roads on federal lands, developed a plan for public review that proposed improvements to the Agness-Illahe Road by realigning the curves to increase visibility of on-coming traffic and adding inter-visible turnouts. This was a challenge, considering that on one side of the existing road is the renown Rogue River, a federally designated “Wild and Scenic River” and on the other, the base of a steep, unstable slope. Cutting into the unstable slope was not an and long term visual objectives. The short term goal spanned 5 to 10 years and would screen the walls by establishing a stand of grasses on the nearly vertical wall surfaces. The long term objective would be to establish shrubs and trees in front of the walls to blend the walls into the surrounding forested landscape. We agreed on a design that would place a foot of topsoil covering the front of the walls from which grasses would grow. Simple enough, but just how does one establish grasses on walls that rise 6 to 26 feet above the natural ground line? We began to answer that question by setting up a set of simple experiments.

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Author(s): David E. Steinfeld, Scott Blower, George Fekaris, Mike Miller

Section: Diverse Species