Skip to main content
CalcStack

Riprap Gabion Mattress Sizing Calculator

Wire-mesh enclosed gabion mattresses protect stream banks and spillway channels against erosive high-velocity tractive shear stresses with smaller stone sizes than dumped riprap.

Mean cross-sectional stream velocity during design peak flood.

Energy grade line or bed slope (e.g. 0.01 for 1% grade).

Maximum hydraulic flow depth over the mattress during peak discharge.

Relative density of aggregate rock fill (standard granite/limestone = 2.65).

Commercial mattress thickness (0.17m, 0.23m, 0.30m, or 0.50m).

Calculated Result
1.92

Mattress Stability Factor of Safety

Safety Factor

1.92:1

Hydraulic Bed Shear (τ₀)

117.7 Pa

Mattress Critical Shear (τ_c)

226.1 Pa

Recommended Mattress Thickness

300 mm

Minimum Stone Fill D₅₀

115 mm

Revetment Status

ADEQUATE: Stable mattress revetment (Safety Factor ≥ 1.3)

Calculation Breakdown

  1. Tractive Bed Shear Stress Computationτ₀ = γ_w × y × S = 9,810 N/m³ × 1.2 m × 0.01 = 117.7 Pa
  2. Agostini / Maccaferri Enclosed Stabilityτ_c = 0.10 × ((2.65 - 1) × 9810) × 0.115 + 40 Pa = 226.1 Pa
  3. Safety Factor CheckFS = τ_c / τ₀ = 226.1 / 117.7 = 1.92

Shear Stress Comparison (Pa)

Interactive visualization based on your current inputs

Shear Stress
0.057113170226Bed Shear (τ₀)Critical Shear (τ_c)Stress ComponentShear Stress (Pa)

What Is the Riprap Gabion Mattress Sizing Calculator?

The Riprap Gabion Mattress Sizing Calculator designs flexible wire-enclosed rock blankets for lining drainage channels, bridge scour aprons, and riverbanks.

How Does the Riprap Gabion Mattress Sizing Calculator Work?

It computes hydraulic tractive shear force from depth and energy slope, comparing it to the Agostini critical shear resistance of the rock-and-wire composite.

Riprap Gabion Mattress Sizing Calculator Formula & Variables

The core mathematical equation utilized by this calculator is expressed as:

\tau_0 = \gamma_w y S, \quad \tau_c = 0.10 (\gamma_s - \gamma_w) D_{50} + \tau_{mesh}, \quad FS = \frac{\tau_c}{\tau_0}

Tractive force hydrodynamic shear stress balanced against wire-confined rock matrix critical shear resistance.

How to Use the Riprap Gabion Mattress Sizing Calculator

  1. Input design flood velocity, water depth, and channel slope.
  2. Specify stone specific gravity and select candidate mattress thickness.

Step-by-Step Example Calculation

High Velocity Riverbank Channel Protection

Input Values:

channelFlowVelocityMs:3
channelBedSlopeMPerM:0.01
waterDepthM:1.2
stoneSpecificGravity:2.65
mattressThicknessM:0.23
Worked Steps: Generates 117.7 Pa bed shear stress with a 1.92 factor of safety using a 230 mm mattress.

Understanding Your Result

Safety Factor: Ratio of mattress critical resistance to hydrodynamic tractive force.

Bed Shear Stress: Maximum fluid drag exerted by flowing water on the mattress surface.

Recommended Thickness: Standard commercial mattress gauge.

Factors That Affect the Result

  • Steeper bed slopes and higher water depths linearly multiply the tractive shear stress.

When Should You Use This Calculator?

  • Steep stormwater channel linings, weir downstream aprons, bridge pier scour blankets, and reservoir shorelines.

Assumptions & Limitations

  • Assumes uniform steady open channel flow and proper geotextile underlayment to prevent subsoil piping.

Frequently Asked Questions

Calculation Accuracy & Reference Note

Based on Maccaferri River Training and Agostini hydraulic design criteria.

Related Calculators

Explore more tools and calculators in Math Calculators

Soil Nail Wall Pullout & Tendon Sizing Calculator

Calculates ultimate and allowable pullout resistance along the grout-ground interface, steel tendon yield strength, and governing limit state per FHWA GEC 7.

Helical Screw Pile Ultimate Axial Capacity Calculator

Calculates ultimate and allowable compressive axial capacity of multi-helix screw anchors using individual plate bearing method in cohesive and frictional soils.

Culvert Outlet Riprap Apron Erosion Protection Calculator (HEC-14)

Calculates median stone size (D₅₀), apron length, downstream width, and blanket thickness for culvert outlet scour protection per FHWA HEC-14.

Dry Extended Detention Basin Drawdown Orifice Calculator

Calculates the required release orifice diameter, average discharge rate, and drawdown velocity for stormwater dry extended detention basins.

Broad-Crested Rectangular Weir Discharge Calculator (ISO 3846)

Calculates open channel discharge capacity, critical depth, crest flow velocity, and discharge coefficient for broad-crested rectangular weirs.

SWMM Urban Catchment Peak Runoff & Infiltration Calculator

Calculates peak stormwater runoff, Horton infiltration abstraction, depression storage losses, and composite runoff coefficients for urban subcatchments.