Large-scale flooding in Warsaw prevented

The problem

The Vistula, or Wisla as it's known in Polish, stands as Poland's most majestic river, stretching an impressive 1,047 kilometres (651 miles) and holding the title of the country's longest river.

In 2010, the Vistula witnessed one of its most challenging periods. A combination of torrential rain and swift snowmelt from the mountains triggered large-scale floods. Cities situated along the river's course scrambled to fortify their defenses, with sandbags lining streets and structures adjacent to the river. Krakow, one of Poland's most iconic cities, was thrust into a state of emergency.

The Vistula's waters there surged to alarming levels, first reaching 74 cm above the average, and then, in a mere day, it swelled to a staggering 300 cm above the flood stage. 

Yet, Krakow's robust stone barriers, which lined the river, stood resilient. They not only held back the deluge but also directed the bulk of the floodwaters downstream. While Krakow was spared the worst, other cities weren't as fortunate. They faced extensive flooding, revealing the oversight of local authorities who had permitted extensive construction in areas that were now submerged - the floodplains. It was a month-long ordeal before the waters retreated and normalcy was restored.

But the scars of the flood remained, etching a lasting memory in the minds of the locals and amplifying their concerns about potential future threats.

A significant issue exacerbating the flooding was the numerous stormwater outfalls that emptied into the Vistula. Under normal conditions, these outfalls channel stormwater from the suburbs into the river.

However, during floods, the roles reverse. The engorged river forces water back up these stormwater pipes, effectively turning them into conduits that channel floodwaters into the heart of the suburbs. Instead of alleviating flooding, these stormwater systems inadvertently amplify it, leading to widespread inundation.