Stormwater drainage systems are designed to operate in a free surface flow regime, however, transition into a pressurized flow regime may occur during intense rain events as the inflow exceeds the transport capacity of the system in free surface flow mode. The air phase within the sewers may then become pressurized, significantly altering the dynamics of the flow. Mixed flows, also referred to as flow regime transitions, have been linked to the occurrence of serious operational problems in stormwater systems, such as geysering and structural damage of sewers. While such flow conditions have...