🌧️
Stormwater Retention Sizing
FreeSize your retention basin based on impervious area, runoff coefficient and design rainfall.
📊Retention sizing
💧Retention volume
30,7m³
🌊Peak flow
8,8L/s
📏Avg. runoff coefficient
0,79
Total area
1,000m\u00b2
Weighted active area
790m\u00b2
Rainfall depth
Intensity : 40 mm/h, duration : 60 min
40mm
Incoming volume
31,6m\u00b3
Discharged volume (leak)
Discharge rate : 3 L/s/ha
0,9m\u00b3
🏗️ Recommended structure
Retention basin or swale
Active surfaces
Roof (slope > 5%) (500 m\u00b2, C=0.95)475 m² active
Asphalt / concrete (300 m\u00b2, C=0.95)285 m² active
Flat lawn (200 m\u00b2, C=0.15)30 m² active
📐 Calculation method
Surface active = Σ(S × C)
Q_pointe = C_moy × i × A / 360 (m³/s)
V_rétention = V_entrant − V_fuite
V_entrant = S_active × h_pluie / 1000Simplified rational method. C = runoff coefficient, i = rainfall intensity (mm/h), A = area in ha.
Standards & regulations
- NF EN 752Réseaux d’évacuation et d’assainissement — Dimensionnement
- Instruction technique 77/284Méthode de calcul des réseaux d’assainissement pluvial
- Loi sur l’eauArt. L.214-1 à L.214-6 du Code de l’environnement — Loi sur l’eau
This tool provides indicative estimates. Results do not substitute professional advice. Always verify with current regulations.
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