Sisak is situated on the banks of rivers Sava, Kupa and Odra. Therefore, its sewer system consists of several individual subsystems. The main objective of this project is creation of representative mathematical model, of sufficient safety, data and results for all subsystems (building stage 1998-1999).
Regarding the project task and available details three separate mathematical models of Sisak sewer system were created:
1. mathematical model “F-G” represents a sewer system model for the area of Zeleni Brijeg and Stari Sisak. This model is made of 18.7 km of main collectors and catchment channels. It contains 292 ha of the catchment area and has a population of 15000 inhabitants.
2. Mathematical model “I1” represents a sewer system model for the area of Novi Sisak. The length of main collectors and catchment channels in this model is app. 5 km, the volume of urban catchment area is 57 ha and the population is 2500 inhabitants.
3. mathematical model “J1” represents a sewer system model for the area of Novog Siska located by existing roads: Strossmayerova, Petrinjska and Školska street. This model is made of 6.1 km of main collectors and catchment channels, 80 ha of catchment area and has 6100 inhabitants.
Based on hydrology-hydraulic simulations with ITP rain events from different recurrence periods in these three mathematical models the following analyses were done:
- all collector sections that are subject to flooding are identified
- collector sections that are subject to back-water effect, pressure flow or any other flow except gravitational are identified
The results of hydrology-hydraulic simulations show the following:
At subsystem “FG” for ITP rain event from half a year recurrence period, pressure flow occurs together with water on field sometimes. At subsystem “I1” for recurrence period rain event of one year pressure flow occurs, but there is no record of water on the field. Only for rain events for three year recurrence period there is flooding of one collector, and in one part of subsystem there is pressure flow.
At subsystem ”J1” there is no recorded flooding for half a year rain event recurrence period, but there is recorded pressure flow. Flooding is recorded one year rain event recurrence period, and for three year recurrence period it is increasing in logical sequence.
Flow problems that occur in Sisak sewer system will be solved through urgent remedial measures in project continuance.
