What This Solves
Calculates energy losses at channel transitions (contractions, expansions, drops) using standard loss coefficients for various transition geometries.
Best Used When
- You are designing a channel width change and need to estimate the head loss
- You need to evaluate energy losses at a bridge approach or culvert inlet transition
- You want to compare head losses between abrupt, gradual, and warped transition geometries
Do NOT Use When
- You need to calculate the full water surface profile through a reach of varying geometry — Use Gradually Varied Flow Calculator
- You need to calculate uniform flow capacity in a constant-section channel — Use Manning's Channel Calculator
Key Assumptions
- Head loss coefficients are empirical values from FHWA HDS-4 and USACE EM 1110-2-1601
- Flow is subcritical through the transition (no hydraulic jumps)
- Energy equation applies between upstream and downstream sections
- Velocity distribution is approximately uniform at each section
Input Quality Notes
Loss coefficients vary with transition angle and geometry. Use published values for the closest matching transition type. For unusual geometries, physical or numerical modeling may be needed.
Contraction Coefficients (Cc)
| Geometry | Cc |
|---|---|
| Abrupt | 0.5 |
| Gradual (typical) | 0.2 |
| Warped | 0.1 |
| Cylindrical Quadrant | 0.15 |
| Wedge (1:4) | 0.3 |
Expansion Coefficients (Ce)
| Geometry | Ce |
|---|---|
| Abrupt | 1 |
| Gradual (typical) | 0.5 |
| Warped | 0.2 |
| Cylindrical Quadrant | 0.25 |
| Wedge (1:4) | 0.5 |
Ready to Calculate
Select transition type and enter velocities to calculate head loss.
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Last verified: February 2026