The procedure of the rainfall–runoff (R-R) model, based on the instantaneous unit hydrograph (IUH) method and used to calculate the probable flows in 8 profiles of the Losse river (on the stretch from 5+476 to 7+596 km) for three flood scenarios (Qextreme, Q1% and Q10%), has been presented in this work. A computer program developed by the author was used to conduct the analyses, enabling the flows to be simultaneously calculated for each of the analyzed profiles in response to 10 rainfall events of varying duration and a given exceedance probability.
The obtained values of probable flows were recalculated into corresponding water table levels using the WSP-ASS program (Water Level Program). The extent of the flooding and water depths for three flood scenarios were calculated based on the levels of the water table and terrain elevation data ("Digital Terrain Model"). As a final effect of the analyses, flood hazard maps for the analyzed stretch of the Losse River were constructed, enabling the consequences of flooding to business activities, the infrastructure, the environment, and human health and life to be assessed.