Canal Sedimentation Rate Calculator

• Convert concentration: SSC(kg/m3) = SSC(mg/L) × 0.001
• Sediment load: Load(kg/s) = Q(m3/s) × SSC(kg/m3)
• Incoming mass: Min(kg) = Load × (Days × 86,400)
• Deposited mass: Mdep(kg) = Min × (Trap efficiency/100)
• Deposited volume: V(m3) = Mdep / rhobulk(kg/m3)
• Average thickness: t(m) = V / (Canal length × Effective deposition width)

1. Measure canal section dimensions and select the correct section type.
2. Enter average discharge for the same monitoring period.
3. Enter suspended sediment concentration from tests or monitoring.
4. Set trap efficiency based on past surveys or a sensitivity range.
5. Enter bulk density representing deposited material in-place.
6. Press Calculate Sedimentation, then export CSV or PDF.

Sedimentation is one of the most common performance risks in irrigation and drainage canals. When fine particles and sand enter a reach, flow velocity may be insufficient to keep them in suspension. The material then settles on the bed and margins, reducing hydraulic capacity, increasing water levels, and raising overtopping and seepage risks. A practical sedimentation rate estimate helps you plan desilting windows, allocate equipment, and justify maintenance budgets with traceable assumptions.

This calculator uses a mass-balance approach. First, the suspended sediment concentration is converted from mg/L to kg/m3, then multiplied by discharge to estimate the incoming sediment load (kg/s). Over the chosen period, the load is integrated to obtain total incoming mass. A user-defined trap efficiency represents the fraction of that incoming mass that deposits within the reach. Finally, deposited mass is converted to volume using the in-place bulk density, and spread across a specified effective deposition width to estimate average thickness.

For planning, focus on three outputs: deposited volume, deposition rate (m3/day), and average thickness (mm). The thickness metric connects directly to serviceability. For example, if the reach operates with 2.0 m water depth and your allowable depth loss is 10%, then a 200 mm average deposit already consumes 10% of available depth and may justify immediate desilting before peak demand.

The example table demonstrates seasonal sensitivity. In the dry-season case (Q=5.0 m3/s, SSC=220 mg/L, 55% trap, 30 days), the deposited volume is about 1,570 m3 and thickness is roughly 63 mm across a 5 m deposition width and 1,000 m reach. Under monsoon conditions (Q=10.0 m3/s, SSC=600 mg/L, 70% trap, 30 days), deposition rises sharply to about 10,886 m3 with around 435 mm thickness, reflecting higher loads and stronger settling within low-velocity zones.

Use the tool iteratively: run separate scenarios for dry season, monsoon, and shoulder months, then compare results against measured silt levels from cross-section surveys. Adjust trap efficiency to match observed deposition trends. Once calibrated, the calculator becomes a reliable decision aid for prioritizing reaches, estimating dredging quantities, and documenting maintenance rationale for project stakeholders.

1) What does trap efficiency represent here?

It is the fraction of incoming suspended sediment that deposits within the selected reach during the period. Use survey history, hydraulic judgment, or sensitivity ranges when field calibration is unavailable.

2) How do I choose sediment bulk density?

Use an in-place (wet) deposit density from site data when possible. If unknown, test a reasonable range (for example, 1100–1700 kg/m3) and see how deposited volume changes.

3) Why can thickness be different from observed local silt depths?

The calculator reports an average thickness spread across your chosen deposition width. Real canals deposit unevenly, forming bars and pockets. Use surveys to identify hotspots and treat thickness as a planning average.

4) Should I use rectangular or trapezoidal section type?

Choose trapezoidal when side slopes affect flow area and wetted perimeter. If the canal is lined or behaves like a near-rectangular section, rectangular is acceptable for quick planning.

5) Can I use variable discharge or SSC?

Yes. Run multiple scenarios (weekly, monthly, or seasonal) using average values for each period, then compare totals. This is often more realistic than forcing a single annual average.

6) Does this include bed load transport?

No. The method is based on suspended sediment concentration. If bed load is significant, treat this result as a minimum and consider adding separate bed-load estimates from field measurements or local guidance.

7) What is a good way to validate the outputs?

Compare predicted deposited volume against measured dredged quantities or cross-section survey differences over the same reach and time window. Adjust trap efficiency until predictions align with observed deposition.