Impact of polder flood plain of the Cisowska Struga on the transformation of flood waves between Gdynia and Rumia

Abstract

Aim of the study The paper presents the results of hydraulic calculations (numerical simulations), which were conducted in order to investigate the role of floodplain (polder) adjacent to the left bank of Cisowska Struga in Gdynia downstream of Hutnicza street in the process of retention and transformation of flood waves occurring in this river due to heavy rainfall. The paper also addresses the issue of the impact of potential changes in the development of the retention area under consideration for the flood risk in Rumia. Material and methods In order to perform hydraulic calculations, mathematical modelling was used. All hydraulic calculations of flood wave transformation in channels and floodplains were performed using the HEC-RAS software and the data on characteristic flows obtained from the available hydrological calculations. Results and conclusions In the light of the obtained results, it should be stated that the analysed retention area between Hutnicza street in Gdynia and the railway line is of high hydrological significance. Potential reduction of the retention capacity of this area will negatively affect the transformation process of flood waves in the Cisowska Struga on the analysed section. At the outlet section in the area of Dębogórska street and further in Rumia, the water level will be elevated, and flood waves will reach there faster. Due to the potential increase of the flood risk in Rumia, this is undesirable.

Keywords

• mathematical modelling
• flood wave transformation
• retention
• flood risk
• Gdynia
• Rumia
• Cisowska Struga (stream)