Spillway Designer

Design an ogee (overflow) spillway: relate the discharge, crest length and design head through the weir equation Q = C·L·H^3/2, optionally account for pier & abutment end contractions, and generate the WES ogee crest profile.

⭐ Free to use · Balance … EP

① What do you want to solve for?

Enter the crest length L and design head H; the app finds the discharge Q.

② Spillway data

Discharge Q (m³/s)

Crest length L (m)

Design head H_d (m)

Discharge coefficient C

Q = C·L_eff·H^3/2 (SI). Ogee crest at design head C ≈ 2.0–2.2; sharp-crested ≈ 1.84. L is the net crest length.

Account for end contractions (piers & abutments)

No. of piers N

Pier coeff K_p

Abutment K_a

L_eff = L − 2(N·K_p + K_a)·H. Typical round-nosed pier K_p ≈ 0.01, rounded abutment K_a ≈ 0.10.

🌊 Spillway design

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Ogee overflow spillway

Hydraulics

Discharge Q

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Crest length L

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Design head H_d

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Effective length L_eff

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Unit discharge q

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Coefficient C

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Ogee crest profile (downstream quadrant: x^1.85 = 2·H_d^0.85·y)

Worked solution

⚠️ Study/estimating aid. The coefficient C varies with the head-to- design-head ratio, the upstream face slope and the approach depth; the WES profile here assumes a vertical upstream face and neglects approach velocity. Verify C, the upstream quadrant radii and energy dissipation against USBR/your course references.