Łódź: Stormwater retention and ecological quality improvement The River Sokołówka is a small, urban stream running through the northern part of the city of Łódź, the third largest city in Poland. The catchment spans urban, as well as agricultural and natural areas. In the early 1930s, the upper reaches of the river were straightened, deepened and partially canalized. The main channel of the urban stream was converted into a collector for 50 stormwater outlets. These developments resulted in adverse effects on the urban and surrounding ecosystems, and the Sokołówka and adjacent rivers were polluted with discharge from combined sewage and stormwater overflows several times per year. Most of Łódź rivers work as a part of a combined sewerage system of the city. During heavy rains, rivers intercept waters from overflows and rain water. Shortage of stormwater retention reservoirs is one of the reasons for pollution of the biggest river of the city, the River Ner, which receives combined sewage from the entire city. The repeating problems related to pollution, overflows and ecological degradation made the city look for possibilities of stormwater retention, and for improving the ecological quality of the rivers, thus creating friendlier and healthier public space. The city of Łódź has implemented a comprehensive urban development programme on water and river restoration, part of which has been the restoration of the River Sokołówka . For the River Sokołówka, a sequential stormwater sedimentation-biofiltration system was implemented, which prevents the influx of pollutants into the river during high flows (Zalewski et al. 2012). Five retention reservoirs were constructed in order to increase river retention and pollution absorption capacity. These measures went hand in hand with development plans for a further rehabilitation of the river valley (Wagner and Breil, 2013). As a result of the measures taken, the river and its valley have turned into an attractive residential and recreational area which has contributed to the positive economic development in the wider area (Wagner et al. 2007). The creation of new green areas as part of the restoration activities has had positive influence on the quality of the inhabitants’ life and their health.The restoration of the Sokołówka River has been used as a demonstration case to gather experience that can then be used for further replication on other streams and rivers crossing the city. The demonstration projects implemented by the city of Łódź have played an important role in creating visibility, interest and cooperation, and as such have been vital in the scaling-up strategy of the project. Zgierska pond in the urban catchment of the Sokolowka River after restoration. (Photo: ©Anita Waack-Zając) |
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