Copenhagen Sponge City Flooding Solutions
- Copenhagen, consistently ranked among the world's most livable cities, is proactively confronting the increasing threat of climate change, specifically the growing risk of flooding.A pivotal moment arrived on...
- The University of Copenhagen's research demonstrated that global warming doubled the risk of such an extreme weather event.
- The "sponge city" concept, pioneered by Chinese landscape architect Kongjian Yu in the late 1990s, draws inspiration from traditional Chinese irrigation methods and the natural water-retention capabilities of...
CopenhagenS “Sponge City” Initiative: A Model for Climate Resilience
Table of Contents
Published August 20, 2025
Facing the Rising Tide: Copenhagen’s Flood History
Copenhagen, consistently ranked among the world’s most livable cities, is proactively confronting the increasing threat of climate change, specifically the growing risk of flooding.A pivotal moment arrived on July 2, 2011, when a devastating cloudburst unleashed torrential rainfall – 135.4 millimeters in the Copenhagen Botanical garden alone, with 31 millimeters falling in Ishj – accompanied by over 5,000 lightning strikes within three hours. The resulting damage totaled approximately US$1 billion (billions of kroner), and brought the city to a standstill, closing roads for up to three days.
The University of Copenhagen’s research demonstrated that global warming doubled the risk of such an extreme weather event. Recognizing the need for a long-term solution, Copenhagen embarked on an aspiring plan to transform itself into a ”sponge city.”
The “Sponge city” Concept: Absorbing the Impact
The “sponge city” concept, pioneered by Chinese landscape architect Kongjian Yu in the late 1990s, draws inspiration from traditional Chinese irrigation methods and the natural water-retention capabilities of wetlands. Yu’s work, as highlighted by the World Economic Forum, focuses on creating urban landscapes that absorb, store, and reuse rainwater, rather than relying solely on traditional drainage systems. This approach not only mitigates flood risk but also replenishes groundwater supplies and enhances biodiversity.
Copenhagen formally adopted the “sponge city” approach in 2012 with the implementation of the Cloudburst Management plan. The plan’s core objective, according to Interlacehub, is to minimize the impact of increasingly frequent and intense rainfall events driven by climate change.
A 20-Year, €1.5 Billion Investment
The Cloudburst Management Plan is a comprehensive, 20-year undertaking involving 300 individual projects. It’s a collaborative effort funded by the City of Copenhagen, the Greater Copenhagen Utility Company, and private landowners. The total investment is estimated at €1.5 billion, allocated as follows:
| Category | Investment (Euros) |
|---|---|
| Surface solutions | 700 million |
| Cloudburst Pipes | 358 million |
| Disconnection/Connection Outside Property boundaries | 134 million |
| Home Protection | 320 million |
These funds are being directed towards a variety of initiatives, including the restructuring of drainage systems to separate rainwater from wastewater, transforming streets into temporary waterways during heavy rainfall, and creating retention basins.
Greenscaping and Innovative Design
A key component of Copenhagen’s strategy is “greenscaping,” which involves implementing Sustainable Urban Drainage Systems (SUDS). This includes constructing green parks, green roofs, and bioswales – landscaped channels designed to slow down and filter rainwater runoff. these features prevent water from overwhelming traditional drainage infrastructure.
Lake Sankt Jørgens Sø exemplifies this approach. During the summer, it functions as a public recreational space. Though, during a flood event, over 70% of the lake’s area is designed to submerge, providing meaningful water storage capacity while allowing a central pathway to remain accessible. The water than gradually seeps into the ground, replenishing groundwater reserves.
Global Impact: from Copenhagen to Indonesia
Copenhagen’s “sponge city” model is gaining international recognition and is being adapted for use in other urban centers facing similar challenges. Notably,the concept is being integrated into the planning of Indonesia’s new National Capital (IKN) in East Kalimantan,as mandated by Law Number 3 of 2022. In 2023, representatives from the IKN Authority visited Deltares, a research institute in The Hague, Netherlands, to learn from their expertise in water management and urban planning.