The aim of the study was to determine an effective variant of operation of the Golina
polder to reduce flood hazard in the Warta River valley. We implemented a trial-and-error
method for the development of computational variants. Our approach was based on staged
analyses of alternatives, which took into account different locations and parameters
of the inlet and outlet-controlling structures. Various control scenarios for flooding
and draining the polder were also considered. A hybrid hydrodynamic model consisting
of a 1D part for the main river area and a 2D part for the polder area was used for
calculations. The model was built based on a digital elevation model (1 m resolution)
and channel sections of the Warta River. The calibration was based on data collected
during the flood in 2010 from the water gauge Slawsk (located directly at the Warta
River) and water surface elevation measurements carried out in the polder area. Alternatives
in subsequent stages were determined based on the results of previous stages, as well
as experiences from the 2010 flood and consultations with the Regional Water Management
Board in Poznan. The performance of the alternatives was evaluated according to six
criteria that described the effectiveness of the polder operation in terms of its
practical use and effectiveness in reducing flood hazard. The results showed that
our approach made it possible to identify an effective variant of polder operation.
Additional calculations were also performed to determine the magnitude of flows for
which flooding of the polder should be considered to reduce downstream flooding.
