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Techniques de l’eau et calcul des réseaux

Techniques de l’eau et calcul des réseaux. le calcul hydrologique proprement dit Michel Verbanck mikeverb@ulb.ac.be 2015. 1: Rainfall is transformed by the hillslopes into a hydrograph which is delivered throughout the network.

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Techniques de l’eau et calcul des réseaux

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  1. Techniques de l’eau et calcul des réseaux le calcul hydrologique proprement dit Michel Verbanck mikeverb@ulb.ac.be 2015

  2. 1: Rainfall is transformed by the hillslopes into a hydrograph which is delivered throughout the network . 2: Hydrographs from A take longer to travel to the outlet than those from B, and those from C arrive sooner still. 3. When these are combined, the outlet hydrograph is more drawn out, and the peaks from A, B, C do not coincide Routing a hillslope hydrograph through the network

  3. Loss Rate Method:Initial and Uniform Loss Rate Method • Initial Amount Lost to Infiltration (in) • Uniform Loss at a Constant Rate (in/hr) Inches/Hour Example: Initial Loss = 0.5 in, Uniform Loss = 0.05 in/hr

  4. Traitement d´un événement de pluie intensité de pluie, l s-1 ha-1 pluie mesurée 400 300 pluie cumulée sur 10 min 200 100 0 0 5 10 15 20 25 Durée de pluie, minutes

  5. Rainfall and Conversion to Runoff • Use either design rainfalls or historical events • Spread uniformly over a given basin area • Use Unit hydrograph to compute response for relatively large basins - 10 to 100 km² The unit hydrograph is defined as the hydrograph of direct runoff that results from 1 inch (25.4mm) of excess rainfall generated uniformly over the watershed at a constant rate during a specified time.

  6. The unit hydrograph is defined as the hydrograph of direct runoff that results from 1 inch (25.4mm) of excess rainfall generated uniformly over the watershed at a constant rate during a specified time. In practice, a large number of actual watersheds are evaluated and then made dimensionless by dividing all discharge ordinates by the peak discharge and the time values by the time to peak.

  7. Rainfall and Conversion to Runoff • Use either design rainfalls or historical events • Spread uniformly over a given basin area • Use Unit hydrograph to compute response for larger basins - 10 to 100 km² • Use Rational Method to compute peak flow for small basin area – a few hectares

  8. calcul des réseaux Qav

  9. isohyètes 24-Jul-1969 étude des inondations dans le bassin de la Woluwe, Min.Trav.Publics

  10. Storm event 16 June 2011 Maximal intensityat 16:05 Rainfall 16.3 mm / 15 min

  11. inégale répartition spatiale des pluies

  12. Méthode rationnelle intensité i Aire A Q = i × A × Y av Débit à l´exutoire Y = coefficient de ruissellement

  13. ò Q × dt = V av produit V produit V précipité intensité des précipitations et des flux instantanés ò A × i × dt = V précipité 0 0 Durée de pluie & d´écoulement Coeff de ruissellement moyen: = Probabilité de récupération d´eaux Y = m

  14. averse de référence d’orage pour la région bruxelloise période de retour décennale L’intensité i (l / ha . s) de l’averse d’orage de durée ≤ 120 min est donnée par tp : durée de la pluie (minutes) Cette expression, sous sa forme la plus générale, est appelée formule de Talbot. Il s’agit de l’intensité moyenne pendant l’épisode, appliquée au centre du bassin technique considéré. NB. Au delà d’une durée de 120 minutes, on considère qu’il s’agit d’une pluie de longue durée (dans ce cas le coefficient 6000 est porté à 8000).

  15. Texture du sol

  16. toiture verte en intérieur d’ilôt

  17. modèle du réservoir linéaire

  18. Le modèle du réservoir linéaire

  19. linear reservoir cascade

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