What Is the USBR Ogee Spillway Crest Profile & Discharge Calculator?
An ogee crest is hydraulically shaped to conform precisely to the lower nappe profile of a ventilated thin-plate weir under design overflow head.
This profile guarantees maximum discharge coefficient efficiency (C0 ≈ 2.18) while preventing cavitation-inducing negative pressures along the crest boundary.
This calculator applies the US Bureau of Reclamation (USBR) Design of Small Dams guidelines to calculate discharge capacity, downstream power curve equation, and upstream radii.
How Does the USBR Ogee Spillway Crest Profile & Discharge Calculator Work?
The calculation evaluates user-provided measurements using recognized domain equations, converts between measurement units, and adjusts for real-world efficiency factors.
USBR Ogee Spillway Crest Profile & Discharge Calculator Formula & Variables
The core mathematical equation utilized by this calculator is expressed as:
USBR empirical profile power function reproducing the lower nappe of a ventilated rectangular weir jet.
How to Use the USBR Ogee Spillway Crest Profile & Discharge Calculator
- Enter your primary measurements in the input fields above.
- Select your preferred units (e.g. metric or imperial) if applicable.
- Review or adjust operational assumptions such as field efficiency.
- Click Calculate to instantly generate the full results breakdown and visual chart.
- Use the Reset button at any time to clear the form and test a new scenario.
Step-by-Step Example Calculation
Gravity Dam Spillway (Hd = 4.0 m, Le = 25 m)
Input Values:
Understanding Your Result
Your calculated result represents the realistic operational capacity or baseline output under the specified conditions. Comparing theoretical and effective outputs reveals the direct impact of turns, overlap, and practical downtime.
Factors That Affect the Result
Field terrain, operator experience, equipment maintenance, overlap margin, and weather conditions can significantly influence real-world output.
When Should You Use This Calculator?
Use this calculator whenever you need quick, verified estimates for job planning, budgeting, equipment sizing, or project timelines.
Assumptions & Limitations
- Discharge Capacity: Q = C0 · Le · Hd^(1.5).
- Deep approach (P/Hd ≥ 3.0) yields maximum standard SI discharge coefficient C0 = 2.18 m^(0.5)/s.
- Downstream USBR profile equation: y = -x^1.85 / (2.0 · Hd^0.85).
Frequently Asked Questions
Calculation Accuracy & Reference Note
This calculator implements verified, deterministic mathematical equations based on published standards. Results should be treated as professional engineering estimates; always verify critical operations with local equipment manuals and site inspections.