Rain water management and flood protection for suburbs of the city of Sisak (sub-system of the residential areas of Zabno, Odra Sisacka, Stupno, Staro Pracno and Sela)

In recent years the city of Sisak and its suburbs have been hit repeatedly by flooding due to rainfall events.

igr d.o.o. was commissioned by the city authorities to develop the first phase of a design for rainwater management  and flood protection in Sisak – Rural residential areas, a sub-system for the suburbs of Zabno, Odra Sisacka, Stupno, Staro Pracno and Sela.

The reasons for the flooding are complex.  Flooding following extreme rainfall events is also the result of unregulated water management on the wide upstream catchment area of the Sava, Odra and Kupa rivers.

Current situation

Sewage disposal:

There is no public sewage disposal system in the study area.

Rain water disposal:

In most residential areas rain water is channelled through open, partially or fully enclosed street sewers/ditches, sometimes with an unclear flow direction.  Rain water disposal is characterised by individual technical solutions, which have not been coordinated with each other.

Image 1 – Study catchment area

As the rain water disposal is not being financed through EU funds, innovative technical solutions, which could be borne by the municipality or regional authorities, were explored in the study.

In the course of the study a network of 34.5 km of predominantly open public sewers were recorded within the construction areas.

The main aim of this study is the preparation of an optimal design for sewage disposal and rainwater management.

Rain water management design

11 "critical flood zones" were identified, amongst them a critical zone on a part of the D36 main road (in the vicinity of Odra Sisacka, Stupno and Sela).

Image 2 – Aerial view of area KZ 10 (February 2014 flooding)

The aim of the study was to prepare a sustainable rain water management system (Sustainable Urban Drainage System (SuDS)).

Image 3 – Depiction of the critical zone 10

Sustainable Drainage Systems use drainage solutions, which represent an alternative to the direct channelling of surface water through pipe and sewage networks into nearby waterways.

Image 4 – One of the suggested rain water drainage technical solutions using surface infiltration tank technology.

This project was completed working together with colleagues from our head office in Rockenhausen.

Suzana Josipović und Robert Zelić