In Excel, this can be done by setting up a circular reference or, more reliably, by creating a small table of trial Hₑ values until the equation balances.
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Save the file as a .xltx or .xlsm file in a dedicated project folder for future use. Step 3: Input Data & Calculate Open the file and navigate to the Input tab. Enter the design head ( Hdcap H sub d ) and spillway height (P). In Excel, this can be done by setting
If the spillway height ( P ) above the streambed is greater than 1.33· Hₑ , the influence of approach velocity on the discharge coefficient is negligible, and Hₑ can be used directly. If not, the velocity head Vₐ²/(2g) must be added to the static head. Step 3: Input Data & Calculate Open the
– Implement the compound circular arc formulas. The table below shows the key points for a vertical upstream face:
The provides a mathematically rigorous environment to model safe overflow structures. By automating the USBR profile equations and factoring in contractive head losses, engineers can systematically eliminate the risks of structural cavitation and boundary layer separation.