Flood early warning system on the Đetinja river Basin in Serbia

The Đetinja river basin, in Užice, western Serbia, is ungauged. Many torrential floods have occurred there over the past decades. In the city of Užice, there are no rainfall intensity gauges, and it is impossible to provide the data needed to monitor torrential floods or make a timely response, which is a precondition for successful defense from them. An early warning system for torrential floods was designed, with three key elements: measuring devices in the basin and river, a server application and a web-client application. A hydrologic study was made to assess multiple scenarios, focusing on the analysis of real data to determine alarm criteria for oncoming floods. Alarm criteria were proposed, based on analysis of previous floods and measurements. Using the direct relationship between runoff, rainfall depth and intensity, the alarm criteria are based on precipitation and river stage. There are three levels: the first level ‘warning’, the second ‘regular flood defense’, and the third ‘emergency flood defense’. The earliest possible warning is of great importance, due to the nature and speed of onset of the process. The system plays a key role in active flood control and prevention, by providing the lead time to secure and strengthen the flood defense system, thereby minimizing the adverse impacts of torrential floods.