Hydraulic Design Tool
Broad Crested Weir + Undersluice Calculator
Enter the weir geometry, undersluice configuration, downstream rating constants, and flood discharges. The calculator automatically solves the former Goal Seek cases, prepares rating curves, and summarizes DFL/CFL design checks.
Flood Discharge Table
Editable return periods for the final summary.
| Return Period | Flood Q (m³/s) |
|---|
Stage–Discharge Rating Curve
Total, weir, and undersluice contribution.
Return Period Water Levels
Interpolated upstream and downstream levels.
Discharge Split at Flood Events
Weir and undersluice capacity contribution.
NWL Gate Opening Capacity
Undersluice-only capacity for gate-opening cases.
Design Summary
Interpolated results for each return period.
DFL / CFL Checks
Flow classification and undersluice capacity.
Rating Table
Computed at the selected water-level step.
NWL Gate Opening Table
Automatic solution for gate-opening cases.
Calculation Notes
Q = Cd × L × H3/2. Cd is evaluated row-by-row from the reference H/B–Cd coefficient relationship.
Free flow when h₀ ≥ 0.81h₂(h₂/a)0.72. Otherwise, the submerged-flow Swamee form is applied.
Former manual Goal Seek cases are solved automatically by bisection in the browser.
D/S depth above end sill is y = A × QC. A and C are editable input constants taken from the downstream rating-curve trendline equation in the reference workbook.