About this challenge
Hungary
Challenge description
The Sponge City Initiative is a climate-adaptive urban development model designed to help cities cope with growing extremes in rainfall and drought. As climate change intensifies, many urban areas experience sudden, heavy downpours followed by long dry periods, overwhelming conventional drainage systems and stressing water supplies. The sponge city concept responds by reshaping the built environment so it can absorb, store, purify, and slowly release water, much like a natural ecosystem.
Central to the initiative is the recognition that water retention is key to microclimate stability and sustainable resource management. Instead of allowing rainwater to run off rapidly over sealed surfaces, sponge cities incorporate permeable pavements, bioswales, rain gardens, wetlands, green roofs, and restored waterways. These features allow water to infiltrate the ground, recharge aquifers, reduce urban flooding, and maintain soil moisture during dry periods. By storing water locally, cities enhance their resilience against droughts and ensure more reliable access to non-potable water for irrigation, cooling, and other uses.
Enhanced water retention also contributes to microclimate regulation. Evapotranspiration from vegetation and open water bodies reduces urban heat island effects, improves thermal comfort, and increases overall biodiversity. At the same time, decentralized water management reduces pressure on municipal infrastructure, lowering costs and improving long-term sustainability.
Overall, the Sponge City Initiative represents a shift from rapid water drainage to nature-based retention and reuse, creating urban environments that are more resilient, healthier, and better prepared for the hydrological challenges of the future.
Central to the initiative is the recognition that water retention is key to microclimate stability and sustainable resource management. Instead of allowing rainwater to run off rapidly over sealed surfaces, sponge cities incorporate permeable pavements, bioswales, rain gardens, wetlands, green roofs, and restored waterways. These features allow water to infiltrate the ground, recharge aquifers, reduce urban flooding, and maintain soil moisture during dry periods. By storing water locally, cities enhance their resilience against droughts and ensure more reliable access to non-potable water for irrigation, cooling, and other uses.
Enhanced water retention also contributes to microclimate regulation. Evapotranspiration from vegetation and open water bodies reduces urban heat island effects, improves thermal comfort, and increases overall biodiversity. At the same time, decentralized water management reduces pressure on municipal infrastructure, lowering costs and improving long-term sustainability.
Overall, the Sponge City Initiative represents a shift from rapid water drainage to nature-based retention and reuse, creating urban environments that are more resilient, healthier, and better prepared for the hydrological challenges of the future.
This city is looking for
A suitable peer city should demonstrate strong technical and planning expertise in climate-adaptive water management. This includes proven experience with integrated urban water management or sponge-city approaches and advanced knowledge of green infrastructure design, such as permeable pavements, bioswales, rain gardens, and green roofs. The city should also possess solid skills in hydrological modeling, urban flood-risk assessment, and stormwater system optimization, alongside expertise in nature-based solutions and the ecological restoration of waterways and wetlands.
Equally important are competencies in funding, cost-benefit analysis, and lifecycle management. A valuable partner city should apply best practices for financing water-sensitive projects through grants, climate funds, or innovative financing mechanisms. It should be capable of conducting economic evaluations that quantify benefits such as reduced flood damage, lower heat stress, and improved ecosystem services. Finally, it should offer guidance on developing effective long-term maintenance plans to ensure the durability and performance of green infrastructure.
Equally important are competencies in funding, cost-benefit analysis, and lifecycle management. A valuable partner city should apply best practices for financing water-sensitive projects through grants, climate funds, or innovative financing mechanisms. It should be capable of conducting economic evaluations that quantify benefits such as reduced flood damage, lower heat stress, and improved ecosystem services. Finally, it should offer guidance on developing effective long-term maintenance plans to ensure the durability and performance of green infrastructure.
City size
Small city (50k to 250k inhabitants)
Author
Péter Gajda
Hungary
mayor
Budapest Capital District XIX Kispest Municipality
