Lonsee flow monitoring survey Following a number of historic overflow and flooding issues, Wassermüller Engineering commissioned Detectronic GmbH to deliver a flow monitoring survey in and around the town of Lonsee in the district of Baden-Württemberg in Germany. Objective To improve the performance of a sewer network during rainfall events. Planning and implementation Wassermüller Engineering initially identified and selected 24 locations for specific monitoring. 17 of those sites were part of the sewer network itself and seven sites were valve-controlled outlets of stormwater tanks or storage sewers that also formed part of the local sewer network. After several site visits and ongoing consultation with Wassermüller Engineering, the Detectronic GmbH site team installed 24 monitors and four rain gauges to cover the whole catchment and gathered and analysed data over a six week period before creating a comprehensive report of findings which was presented to Wassermüller Engineering. Results The flow survey revealed that most of the stormwater tanks and storage sewers had faulty valves which meant that retention capacity was being lost. This, in turn, was causing flooding and overflow in the sewer network. As a result of the monitoring, Wassermüller Engineering have been able to improve performance across the sewer network in Lonsee.