Calculator Inputs
Example Data Table
These values illustrate typical inputs and the kinds of outputs you get.
| Scenario | B (m) | y (m) | S | n | d50 (mm) | Result type |
|---|---|---|---|---|---|---|
| Temporary diversion channel | 5 | 1.2 | 0.002 | 0.030 | 2.0 | Bedload rate |
| Settling basin outlet monitoring | 3 | 0.8 | 0.001 | 0.028 | 0.5 | Mass transport |
| Storm bypass with field velocity | 4 | 0.9 | 0.003 | — | 3.0 | Shear and Shields |
Formulas Used
- Geometry: A = B·y, P = B + 2y, R = A/P.
- Manning velocity mode: V = (1/n)·R2/3·S1/2.
- Discharge: Q = V·A (if you do not enter Q).
- Bed shear stress: τ₀ = ρw·g·R·S.
- Shields parameter: θ = τ₀ / ((ρs − ρw)·g·d50).
- Bedload (Meyer-Peter Müller): qᵦ = 8(θ − θc)3/2·√((s−1)·g·d503), for θ > θc.
- Bedload rate: Qᵦ = qᵦ·B; solid-only volume ≈ Qᵦ·(1 − porosity).
- Concentration-based load: mass rate ṁ = Q·C, with unit conversions to kg/m³.
How to Use This Calculator
- Select a transport method: bedload theory or measured concentration.
- Choose how velocity is provided: computed or direct entry.
- Enter channel width, flow depth, slope, and grain size.
- Provide discharge if measured; otherwise it is computed.
- For measured load, enter concentration and the correct unit.
- Press Calculate to show results above the form.
- Download CSV or PDF for sharing and recordkeeping.
Professional Guidance Article
1) Why sediment transport matters on jobsites
Sediment movement influences pump sizing, diversion stability, and downstream turbidity. Even short storm events can mobilize fines that bypass controls and raise discharge readings. Tracking transport rates helps prioritize controls, schedule maintenance, and document responsible water management.
2) Bedload and suspended load are different signals
Bedload is the coarse fraction that rolls and hops along the bed, often dominating channel change. Suspended load is carried within the flow and is usually measured as concentration. This tool offers a bedload theory option and a concentration-based option to match field data.
3) Hydraulic drivers: depth, slope, and roughness
Hydraulics control shear stress. Increasing slope or depth raises boundary stress; increasing roughness can reduce velocity for a given slope. When velocity is unknown, the calculator estimates it from width, depth, slope, and roughness, then computes discharge from area times velocity.
4) Shear stress and the Shields parameter
Bed shear stress is computed as τ₀ = ρw·g·R·S. The Shields parameter normalizes τ₀ by grain size and submerged weight, producing θ. When θ exceeds the chosen critical θc, bed particles are likely to move and bedload transport may increase rapidly.
5) Bedload estimate for gravelly channels
The Meyer‑Peter Müller relationship uses excess Shields (θ − θc) to estimate volumetric bedload per unit width. It is commonly applied for coarse beds where traction transport is important. Use realistic d50 values and a defensible θc, and treat results as planning estimates.
6) Concentration method for monitoring and compliance
When sampling provides concentration, the calculator converts mg/L, ppm, g/L, or kg/m³ to kg/m³ and multiplies by discharge to obtain mass rate (kg/s) and daily tonnage. This supports reporting, treatment verification, and comparing performance between events.
7) Converting to volumes for hauling and storage
Mass rates can be converted to solid volume using sediment density, producing m³/day. For bedload, porosity can be applied to approximate solid-only volume. These outputs help estimate bin capacity, dewatering duration, and the number of truckloads required for disposal or reuse.
8) Practical workflow and quality checks
Start with measured geometry, confirm units, and enter either measured velocity or roughness. Compare computed discharge with gauge readings. For bedload, check whether θ is near θc; small changes can swing results. Export CSV/PDF to keep calculation snapshots tied to field notes. Record rainfall intensity, upstream controls, and material type so assumptions remain transparent during reviews and audits.
FAQs
1. What does this calculator estimate?
It estimates sediment transport indicators for open-channel flows: hydraulic variables, shear stress, Shields parameter, and either bedload rate (theory) or mass rate from measured concentration.
2. When should I use bedload versus concentration?
Use bedload for coarse, gravelly beds where particles roll or hop. Use concentration when you have sampling data for suspended fines or turbidity-based monitoring and need mass transport rates.
3. How do I pick the roughness coefficient?
Select a value consistent with lining, vegetation, and bed material. Smoother finished channels have lower values; rough riprap or vegetated ditches have higher values. If possible, calibrate using measured velocity or discharge.
4. What if Shields θ is less than θc?
Transport predicted by the bedload method becomes zero because motion is unlikely at the selected threshold. In the field, occasional movement can still occur from bursts, local turbulence, or grain-size variability.
5. How are concentration units converted?
The calculator converts to kg/m³ before multiplying by discharge. For example, 1 mg/L is approximately 0.001 kg/m³, and 1 g/L equals 1 kg/m³. PPM is treated as roughly mg/L for water.
6. Can I use this for culverts or closed conduits?
It is designed for open-channel hydraulics with free-surface flow. For full pipes, energy slope and hydraulic radius differ. Use it only as a screening estimate and prefer a conduit-specific hydraulic model.
7. Why might results differ from site measurements?
Equations assume steady, uniform flow and a representative grain size. Real channels have bends, unsteady hydrographs, mixed gradations, and changing beds. Verify inputs, compare computed discharge to gauges, and treat outputs as planning ranges.
Always verify site data before making final decisions independently.