Stormwater tanks in the form of continuous basins discharge excess water volumes via a sewage overflows (KÜ) and a basin overflows (BÜ). The overflows are usually designed and built as fixed, overflowing weir barriers. Depending on the amount of inflow mixed water at the overflows, overflow heights are correspondingly set.
When designing the sewage overflows, however, it is imperative to ensure that the maximum surface loading or the desired sedimentation capacity is achieved. To limit the overflowing water volumes at the maximum capacity of the basin, the treatment overflows are often throttled or designed as dimensioned openings. Furthermore, mechanical control devices, in some cases, are provided in the basin to regulate the throttling openings, depending on the overflow height of the basin overflow or the resulting water level.