Rainwater Ditch Design
Rectangular rainwater ditch, full flow, n=0.013. Intensity q = 1825·(1+0.774·logP)/(8+t)^0.724.
| No. | Start | End | Length L (m) | Local F (ha) | Concent. Qj | Width B (m) | Height H (m) | Slope i (‰) | Invert ↑ (m) | ΣF (ha) | m·t2 (min) | t (min) | q (L/s·ha) | Qs (m³/s) | v (m/s) | Q (m³/s) | ΔH (m) | Invert ↓ (m) | ΔQ |
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Max velocity
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m/s
Design flow ΣQs
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m³/s
Capacity ΣQ
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m³/s
Flow time t = t1 + m·t2, m·t2 = Σ(L/vs)/30; ΣF accumulates down the chain. Design flow Qs = Qj + Ψ·ΣF·q/1000 (m³/s). Full rectangular velocity v = (B·H/(2B+2H))^(2/3)·√(i/1000)/0.013; capacity Q = B·H·v. Velocity ≥ 0.7 m/s is self-cleaning; capacity must be no less than design flow.