Heavy rain and climate change: How places can protect themselves

Heavy rain and climate change: How places can protect themselves

The number of extreme heavy rain events is increasing significantly - with serious consequences such as flooded streets, evacuations and billions of dollars in damage. A look at Upper Austria shows the dimension: in 2002 and 2013 there were floods on the Danube and Inn with discharge peaks that, statistically, should only occur every 100 to 300 years. And the series continues: in 2023, two storms led to significant flooding - once in Vorarlberg, Tyrol and Salzburg, and again in Carinthia, southern Styria and southern Burgenland.

From water shortages to heavy rain

September 2024 was followed by long-lasting heavy rain, which caused widespread flooding from Salzburg across Upper Styria to northern Burgenland. Lower Austria and Vienna were particularly badly affected, with water levels that are otherwise only reached once in a hundred years. "This shows that current standards are no longer sufficient. Comprehensive flood protection and climate-resilient urban planning are crucial for the future of cities and communities," emphasizes Gregor Grassl, associate partner and expert for climate-adapted building and urban development at Drees & Sommer.

While rising temperatures lead to water shortages in some regions, other areas are repeatedly faced with heavy rain. The latter is particularly treacherous because it occurs spontaneously and selectively and is therefore difficult to plan, explains Grassl. “The good news: with the right know-how, cities can adapt and become more resilient.”

Five areas of action to stay dry

Grassl names five areas of action with which cities and communities can significantly increase their resilience to heavy rain:

1. Analysis of local risks
Heavy rain can also cause flooding that is difficult to predict, even away from rivers. Regular risk analyzes and tests of the existing protection systems are therefore important. “Overloaded sewage systems are one of the most common causes of urban flooding,” explains Gregor Grassl. It is also crucial to ensure access to emergency routes, fire stations and hospitals at all times.

2. Promote blue-green infrastructure
Green areas and urban open spaces act as natural retention areas and buffer precipitation. “We also speak of sponge cities because the areas act like a sponge and absorb rainwater,” says Grassl. In addition, they offer protection from heat, improve air quality and biodiversity and increase the quality of life in cities.

3. Unseal surfaces
Asphalt and concrete prevent rainwater from seeping away. “To counteract this, you have to unseal large areas and replace them with water-permeable alternatives,” says Grassl. In this way, backwaters and flooding can be avoided and the microclimate can be improved at the same time.

4. Avoiding counterproductive dams
Rigid dams often drain water too quickly, exacerbating flooding elsewhere. “Instead of discharging water at an accelerated rate, it is important to slow it down and buffer it.” Retention areas and natural designs help to retain water on site for longer.

5. Integration into urban planning and land use planning
Protective measures should be integrated into construction projects at an early stage. “Retention areas can also be used as parks, playgrounds or lounges.” This creates functional protection with additional added value.

"Instead of reactively reacting to events, cities and communities should proactively invest in climate-resilient infrastructure. Solutions that combine security, sustainability and quality of life can already be implemented today," concludes Gregor Grassl.