flash floods

On one hand, I know the Strzyza from its positive side. Together with my grandfather during summer we visited its lush riparian forest and slowly flowing current. On the other hand, my grandmother, as a municipality worker, had to deal with the flooding. She walked from one house to the next, meeting people who had lost their entire possessions. After the catastrophic floods she was involved in calculating the material losses of people whose houses were flooded.

As a result of urbanization and heavy rainfalls during hot summers, the floods keep on reappearing in the Gdansk city. But why are floods happening? We have destroyed the natural riparian ecosystem of the Strzyza, which was able to naturally absorb rainwater. River vegetation is able to absorb and store enormous amounts of water. Healthy soil is able to absorb and store water for long periods of time, and then slowly give it back to the atmosphere. The creek used to flow naturally, but today it has been straightened to fit geometrical shapes. The canalized riverbed speeds up the water flow. On top of that, rainfall will only get stronger in the coming years, due to progressing urbanization and climate change, which brings more weather extremes.

1. kiepinek 59063 m3

2. jasien 48487 m3

3. nowiec 8336 m3

4. gorne mlyny 2630 m3

5. ogrodowa 1500 m3

6. potokowa-slowackiego 6700 m3

7. srebrniki 65 000 m3

8. kilinskiego 16000 m3

9. wilenska 7070 m3

Fig. 48: Govermnent fights the floods by designing retention basins. The total amount of the retention capacity in all of the basins is 217 686 m3, while the m3 of the most extreme rainfall is about 4 mln m3 during few hours. Fig. 49: When the technical solutions (retention basins) fail to collect all the rainwater, the Strzyza stream floods the lower laying part of the city.

‘‘An estuary demands gradients not walls, fluid occupancies, not defined land uses, negotiated moments not hard edges. In short, it demands the accommodation of the water not a war against it which continues to be fought by engineers and administrators as they carry walls inland to both channel the rain runoff and keep the river out.‘‘

Flash floods effected the interiors of the houses, as seen on the images above. This is an apartment of Dorota and Wieslaw Borys, who live in the floodplein of Strzyza stream. The walls were destroyed by the flooding waters. Source: Trojmiasto.Wyborcza.pl