Variations par temps de pluie des débits dans les réseaux d'eaux usées de type séparatif : identification des composantes et modélisation des infiltrations

The present concern about urban storm drainage and pollution control should not apply to separate foul water sewerage. However, flowrates that can be monitored at the outlets of such sewerage display huge variations along with rainfall, very much alike the ones related with combined systems. Inappropriate connexions of runoff water are not the sole explanation for such a behaviour, and infiltration is to be considered. Leaking defects, included the ones located on private properties, involve rather complex mechanisms which result in drainage of large flows into the collection pipes. These flows can reach high values whatever timescale is considered (yearly, daily and even hourly flowrates). But these flowrates cannot be easily quantified, because they depend not only on rainfall events, but also on what happened before, and on the season. So we developed a mathematical model to simulate these flowrates, and validated this model using field data and sensibility analysis. This model should be a valuable tool for sewer evaluation studies.