Spillway & Energy Dissipator Design – Ogee Profile, Hydraulic Jump, Stilling Basin

Spillway & Energy Dissipator Design

Ogee crest · Discharge coefficient · Hydraulic jump · Stilling basin length · 2D profile · PDF report · Batch

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📐 1. Spillway & Energy Dissipator Design

Spillways are critical for dam safety, conveying flood flows without overtopping the dam. The ogee crest follows the lower nappe of a sharp-crested weir. This calculator computes the discharge capacity (Q) using the USACE ogee coefficient, then designs a hydraulic jump stilling basin for energy dissipation. It determines sequent depth, basin length, and energy loss.

Ogee discharge: Q = C · L · H^1.5 where C = 2.0 + (H/H_d) · 0.5 (approx.)
Hydraulic jump: y₂ = (y₁/2)·(√(1+8Fr₁²)-1)
Basin length: L_b = 5·(y₂ - y₁)

🚀 2. Live Spillway & Basin Designer

Crest length L (m)

Design head H_d (m) – design head

Actual head H (m)

Tailwater depth y_tw (m)

Upstream velocity approach (m/s) – optional

Basin width B (m) – same as crest length typically

Batch CSV (L, Hd, H, ytw, B)

Get PDF Report via Email

CSV Template

📊 3. Spillway & Hydraulic Jump Profile

📈 4. Discharge vs Head & History

📘 5. How to Use the Calculator

Enter crest length (L), design head (H_d) and actual head (H).
Set tailwater depth, basin width, optional approach velocity.
Click "Compute" – tool calculates discharge (Q), Froude number, sequent depth (y₂), basin length, energy loss.
2D profile shows ogee spillway and hydraulic jump.
Batch CSV: upload multiple designs; output table with Q, y₂, basin length.
PDF report includes the profile image.

❓ Frequently Asked Questions

❓ What is the ogee coefficient range?

For typical spillways, C ≈ 2.0 at design head, increasing to 2.2 for higher heads. We use an empirical relation based on H/H_d.

❓ Why a stilling basin?

Hydraulic jump dissipates energy (reduces velocity) to prevent downstream erosion. Basin length is proportional to jump length.

❓ What if tailwater is too low?

Jump will not form properly; you may need a downstream sill or different basin type (USBR types).

🌐 Standards & References

USBR Design of Small Dams | USACE Hydraulic Design of Spillways | Chow (1959) – Open Channel Hydraulics

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