Vegetated Geogrids

Brush MattressApproachConstruction CostSoft Hard Low HighMaintenance CostAdaptabilityLow High Low HighDescriptionA brush mattress incorporates livestakes, live fascines, and branch cuttingsto create one comprehensive protectivecover over a stream bank. This coverserves to slow the velocities of thestream as it runs against the shore and iscapable of capturing sediment duringflood conditions. The structure issupplemented with a rock base in orderto prevent scouring. The materials of themattress are held in place with wire, livestakes, and dead stout stakes. Oncedeveloped the mattress turns into astrong network of interlocking roots.conditions. For a brush mattress toproperly develop the site beingconsidered must be moist enough tosupport growth during the growingseason. Most woody plants howeverhave a limited tolerance for water thatcannot be exceeded. The amount ofavailable sunlight must also beconsidered depending on the type ofmaterial being used in the brushmattress. Willow and alder areparticularly sensitive to the amount ofsunlight. Soil conditions are importantbecause the roots must be able topenetrate the substrate.DRAFTFigure 29: Brush mattress installation.Figure 28: Brush mattress cross-section.Design and ConstructionImportant site considerations for a brushmattress project include moisture level,exposure to sunlight, and subsurfaceThe design of a brush mattress typicallyincorporates the followingconsiderations; the elevation of the bankwith respect to the level of water, thecurrent velocity and shear-stressthresholds (4 ft/sec and 0.4 lb/sf to 4.1lb/sf for a new placement and 12 ft/secand 3.9 lb/sf - 8.2 lb/sf for an establishedproject according to Fischenrich, 2001),