Category Blog

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.

A ton of riprap covers less ground the thicker it's spread — light riprap covers about 17.4 sq ft per ton, medium about 11.1, heavy about 8, each at its own standard thickness. This guide breaks down coverage by class and thickness independently, shows why doubling thickness always halves coverage, and warns against thinning a layer just to stretch a fixed tonnage further.

Riprap density figures vary by source because "density" can mean solid rock weight or placed bulk weight — two genuinely different numbers due to the 20-40% void space between stones. This guide explains that distinction, gives density tables by both material and rock class, and covers full bidirectional conversion between tons and cubic yards with worked examples.

Riprap's weight and stone size often call for bigger delivery trucks than standard gravel work uses — tri-axle and quad-axle trucks are common specifically for heavy riprap loads. This guide compares truck capacity by axle configuration, explains why actual loads often run below rated maximums, and covers site access considerations before committing to a larger truck.

Riprap thickness starts with a simple base rule — 1.5 to 2 times the stone size — but wave attack, ice, floating debris, and the slope's toe all call for their own adjustments on top of it. This guide covers the base rule by rock class, exactly how much to add for exposed conditions, the separate toe keyway calculation, and how to verify thickness after placement.