4. Effluents: quantitative aspects

4.1 Principles of flow estimation

Determining the dimensions of drainage structures requires calculating the flow to be evacuated.

In a combined system, where stormwater and wastewater are collected in the same pipe, wastewater flow is often considered negligible compared to stormwater flow, except in certain situations such as when calculating outfalls.

In a segregated system, water from pavement washing does not normally contribute to increased flows in the stormwater pipes. In a pseudo-separated system, on the other hand, it is necessary to combine wastewater flows with the small amount of rainwater collected in the wastewater network.

• Two types of water flow used

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