Riprap's gaps make it flexible, but those same gaps let soil wash out from underneath if nothing stops it — filter fabric is that stop. This guide explains why nonwoven geotextile fits over 90% of riprap projects, breaks down the three specs that actually matter (AOS, permittivity, puncture resistance), and covers installation practices that prevent the fabric from tearing during stone placement.
There's no universal Class 1/2/3 riprap standard — a "Class I" stone can weigh under 25 lb under an FAA spec or up to 200 lb under a state DOT spec, with the identical class name. This guide proves that variance with real agency comparisons, explains how our light/medium/heavy commercial naming relates (and doesn't equate) to DOT systems, and covers how to correctly use a specific agency's gradation table.
Loose riprap self-heals because its stones settle and adjust independently — grouting trades that flexibility for extra strength, and by FHWA's strict definition, fully grouted rock technically isn't even "riprap" anymore. This guide compares loose, partially grouted (matrix), and fully grouted riprap directly, explains why engineers often avoid full grouting on critical structures, and covers when grouting genuinely makes sense.
A 12-18 inch stone can be sold as "Class I riprap" for $30-60 a ton, or as a "landscape boulder" for $100-600 a ton — the rock itself is often nearly identical. This guide explains what actually drives that price gap (selection and placement, not size), compares coverage and cost between bulk functional riprap and individually placed landscape boulders, and helps match the right product to a functional versus decorative project.
Gravel and riprap aren't really competing for the same job — gravel handles moderate runoff at a fraction of the cost, while riprap exists for the conditions gravel simply can't survive. This guide compares both by velocity threshold, cost, and application, gives a simple decision framework, and covers the aesthetic and habitat trade-offs worth weighing wherever velocity leaves room for either choice.
Riprap size scales with velocity cubed — a small increase in flow speed can require a much bigger stone. This guide covers the FHWA HEC-23 formula with concrete velocity-to-D50 figures, compares it against other professional sizing methods (Isbash, USACE, HEC-14, USBR), and explains two often-missed corrections: a 40% increase for steep slopes and a 25% increase for rounded river stone.
Riprap can genuinely extend a retaining wall's life, but only in a supporting role — toe and scour protection, drainage assistance, and front-face erosion control — not as a substitute for the wall's actual engineered structure or leveling pad. This guide clarifies that distinction, covers toe protection sizing using the standard keyway rule, and walks through worked examples for dry-land and waterfront applications.
A culvert outlet needs a riprap apron sized directly off the pipe's own diameter — length at 3 or 4 times the diameter depending on tailwater depth, width flaring outward from a 3x-diameter minimum, and thickness at 1.5 times the median stone size. This guide walks through the standard HEC-14 design rules, explains why tailwater condition matters so much, and covers three full worked examples across different pipe sizes.
A drainage ditch is trapezoidal, not flat — a bottom plus two sloped sides — and flow velocity, not just area, determines what stone size actually survives there. This guide covers the trapezoidal lining-area formula, matches velocity ranges to rock classes, explains the 3:1 side slope stability limit, and shows why channel bends need upsized stone compared to straight runs.
Pond riprap calculates differently from a shoreline — it's a ring around a round or oval water edge, not a linear strip, and often just needs to protect a liner rather than stabilize a full sloped bank. This guide covers the ring-area formula, why underlayment matters to protect a pond liner from puncture, and how to design a wildlife-friendly edge that avoids a solid "necklace" of rock.