Silt Trap & Detention Basin Design Calculator – Sediment Settling for Erosion Control

Silt Trap & Detention Basin Design Calculator

Stokes' law · Settling velocity · Basin dimensions (L×W×H) · 2D profile · PDF report · Batch CSV

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📐 1. Silt Trap / Detention Basin – Why Proper Design Matters

Silt traps (detention basins) are used to capture sediment from construction runoff, agricultural drainage, and urban stormwater. They prevent erosion, protect downstream water bodies, and comply with environmental regulations. This calculator uses Stokes' law to determine particle settling velocity, then computes basin dimensions (length, width, depth) and settling time based on inflow rate and target particle size.

Stokes' law: v_s = (g·(ρ_p-ρ_w)·d²) / (18·μ)
Basin area: A = Q / v_s
Basin length (rectangular): L = A / W (user sets width or aspect ratio)

🚀 2. Live Silt Trap Design Calculator

Inflow rate Q (m³/s)

Particle diameter d (mm)

Water temperature (°C)

Particle specific gravity (ρ_p/ρ_w) – typical sand 2.65

Basin width (m) – user defined

Safety factor (SF) – multiply settling time

Batch CSV (Q, d, temp, sg, width)

Get PDF Report via Email

CSV Template

📊 3. Basin 2D Profile (Top view & Cross-section)

📈 4. Settling Velocity vs Particle Size & History

📘 5. How to Use the Calculator

1. Enter design flow rate (Q in m³/s), target particle size (d in mm).
2. Set water temperature and particle specific gravity (default 2.65 for sand).
3. Provide basin width (or use recommended aspect ratio).
4. Click "Compute Basin" – settling velocity, required area, length, depth, and retention time are calculated.
5. The 2D canvas shows basin dimensions schematically.
6. Batch CSV: upload multiple designs; output table with basin dimensions.
7. PDF report includes the basin sketch and all parameters.

❓ Frequently Asked Questions

❓ What particle size should I target?

For construction silt traps, target 0.05–0.1 mm (fine sand/silt). Regulatory guidelines often specify D50 = 0.05 mm.

❓ Why use a safety factor?

Turbulence, short-circuiting, and non-ideal flow reduce efficiency. A factor of 1.5–2.0 is common.

❓ Can this be used for stormwater detention?

Yes, with appropriate design flow (peak discharge). For extended detention, consult your local guidelines.

🌐 Standards & References

Stokes' Law for Sedimentation | USEPA Stormwater BMP Guidance | Construction Site Sediment Control

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© ERH Silt Trap Design Calculator – Based on Stokes' law and sedimentation theory. All data processed locally.