Climate change fuels increased flood risks
Critical infrastructure failures resulting from rainfall-induced floods pose substantial risks to society, public health, economies and the environment. Recent heavy flooding in Europe proves that rainfall can shut down cities, leading to enormous damage and costs.
Studies show that more intense and frequent heavy precipitation will hit European cities in the future. This emphasises the need for comprehensive risk assessment and management, also in relation to critical infrastructure. The European Union’s new Critical Entities Resilience Directive (CER) mandates measures to ensure uninterrupted essential services across 11 critical sectors.
Increase in heavy rainfalls
On the night of July 14, 2021, a devastating catastrophe struck multiple areas in Europe, including Germany, Belgium and the Netherlands. It disrupted essential services, such as hospitals and fire departments, and caused extensive damage to roads, railways, bridges and utility systems. It soon became clear that the recovery process would take months or even years.
This disaster was not triggered by seismic activity but rather by an unprecedented force of nature: extreme rainfall. The affected regions experienced an astonishing 100-200 millimetres of rain in a short timeframe, exacerbating the situation as the land was already saturated from prior rains. This event served as a stark reminder of the threat of climate change.
An international team of experts, known as the World Weather Attribution (WWA), conducted a comprehensive analysis of how climate change influenced extreme summer rainfall, like the events in July 2021 across Germany, the Netherlands and Belgium. Researchers predict that such extreme rainfall will become a once-in-400-years occurrence in specific areas in the region between the North Sea and the Alps. Climate models indicate that these heavy summer downpours may increase by up to 6 per cent by 2040.
Extreme precipitation has been on the rise in Europe, with further increases in frequency and intensity expected due to climate change. High emissions scenarios are likely to see the most significant increase in heavy rainfall, especially in Northern Europe. By 2050, extreme summer rainfall events are projected to bring about approximately 25 per cent more rainfall than they do today.
Expensive bills
Such extreme rain events lead to substantial direct and indirect damage, as evidenced by the 2021 summer floods in Europe, which resulted in damages exceeding €38 billion.
These examples highlight the immense damage that rain-induced floods can inflict on cities. In a warming climate, Europe must contend with heavier rainfall, which current drainage systems are ill-equipped to handle.

As the examples in the figure show, rain-induced floods can cause an enormous amount of damage to cities. One thing is clear: whatever the exact statistics, a warming Europe must deal with heavier rainfall that current drainage and critical infrastructure systems were not always designed to manage.
Critical infrastructure and the CER directive
In response to these challenges, the European Union recently adopted the Critical Entities Resilience (CER) directive, effective from January 16, 2023. While this directive primarily targets national critical infrastructure, it also addresses city officials tasked with maintaining local critical infrastructure.
“We face increasing hybrid attacks and climate-change impacts. Being prepared and resilient requires collective action. With today’s adoption, we are taking another step to ensure that our societies and industries are prepared to face security challenges and disruptions in the provision of essential services,” said Ylva Johansson, EU Commissioner for Home Affairs, July 25, 2023 on the adoption of the CER on July 25, 2023.
In a recent Urban Insight report, Sweco delves into cities’ preparedness to withstand the impact of rainfall-induced floods on critical infrastructure. The report explores how cities can prepare for unforeseen events and proactively plan to enhance both urban and critical infrastructure resilience. Extreme rainfall serves as a prime example of a risk that can strike anywhere and at any time, underscoring the importance of readiness even in the face of unidentified risks.
Our study therefore underscores the necessity of being prepared for unexpected challenges and safeguarding critical infrastructure within cities. Rainfall events are localized but can trigger cascading failures that affect entire cities and societies. These localized incidents have far-reaching impacts on society.
Sweco conducted interviews with representatives from eight European cities and assessed the policies of 26 others to gain insights into their approaches to managing and preparing for extreme rainfall events. By sharing the perspectives and findings from these cities, along with our research outcomes, we aim to provide valuable insights into bolstering critical infrastructure resilience against increasingly frequent and severe rainfall events.