Sewer network calculation
The dimensioning and recalculation of sewer systems are the means against the effects of extreme precipitation. Therefore no dimensioning without the corresponding proof that a duct system offers certain overflow protection. The relevant regulations are Worksheets A118 and DIN-EN 752.
The proof of the frequency of flooding is the only way to show the risk of flooding in a mathematical way. It is up to the person who evaluates the calculation result to decide whether this is associated with an event of damage, i.e. flooding. The better alternative is certainly the simulation of urban flash floods.
When simulating a precipitation event, the hydrodynamic sewer system calculation always starts in a dry state, i.e. the sewer system and all retention spaces are emptied. In addition to the individual events (Euler II, model rain group, heavy rain series), the simulation of the precipitation continuum is therefore increasingly taking place. Effects that otherwise cannot be mapped, such as half empty basins and the next precipitation event again provides runoff, can be displayed and hydrodynamically simulated over a long period of time.
If the catchment definition also contains the use/pollutants, not only the discharge volume but also the corresponding pollution loads can be determined. In contrast to the hydrological models, the hydrodynamic simulation takes the retention behaviour of the sewer system into account and calculates realistic dirt loads.
Due to the wealth of calculation results, apart from dimensioning, a graphic-based evaluation in the site plan and longitudinal section (hydrographs, theme plans, etc.) is highly recommended as a basis for decision-making.
Our software recommendation
The programs GraPS (graphic system for sewer and water supply networks) and HYKAS (stationary and transient sewer network calculation, pollution load simulation) offer you the methods discussed above.