The Kalanjevac retention basin is located in Sisak-Moslavina County, near the municipality of Topusko. Its purpose is to provide flood protection for the area downstream of Topusko.
The lowest elevation of the retention basin at the dam profile is 129 m a.s.l., while the spillway crest is set at 135.5 m a.s.l.; this configuration allows for the retention of a 100-year flood wave with controlled release through the bottom outlet, creating a storage volume of approximately 22,600 m³. The surface area of the retention basin at an elevation of 136 m a.s.l. is approximately 12,000 m².
The design provides for a maximum discharge of 0.7 m³/s through the bottom outlet, a rate that ensures no water overflows the channel banks downstream of the dam.
The body of the dam is expected to be made of selected clayey material from the deposits that will be formed in the area of the future reservoir. The slope of the upstream slope is 1:2.5, and the slope of the downstream slope is 1:2. The crown of the dam was selected with a width of 5.0 m. For the construction of the embankment dam, it is necessary to install about 5,500.00 m3 of suitable material from the site.
The bottom outlet is located at the lowest point of the dam, offset to the south of the Kalanjevac stream channel axis. The purpose of the bottom outlet is to ensure continuous flow during normal conditions and to regulate outflow from the retention area during flood events.
A central spillway over the dam crest has been designed, featuring a chute and a stilling basin. The spillway crest is situated at an elevation of 135.5 m a.s.l. and has a width of 10 m. The transition between the spillway crest and the dam crest is constructed with 1:5 slopes, resulting in a trapezoidal cross-section for the spillway.
