What are China’s ‘sponge cities’ and why aren’t they stopping the floods?

What are China’s ‘sponge cities’ and why aren’t they stopping the floods?

Subject: Geography

Section: Physical Geography 

China’s ‘Sponge Cities’ Initiative

• Launched in 2015 to enhance flood resilience and manage rainwater in urban areas.
• Aims to use nature-based solutions for water distribution, drainage, and storage.
• Solutions include permeable asphalt, canals, ponds, and wetland restoration.
• Intends to reduce the negative impacts of urbanization on water management.

Rationale:

• Urbanization led to impermeable concrete covering floodplains and wetlands.
• This resulted in increased flooding and waterlogging due to a lack of water absorption.
• Traditional floodplains and natural wetlands are replaced by concrete surfaces.
• Rainwater cannot infiltrate, causing surface runoff and overwhelming drainage systems.

Implementation and Challenges:

• Pilot initiatives showed positive outcomes, but implementation varies across cities.
• Lack of consistent implementation attributed to limited attention from the government.
• Researchers emphasize the need for strong national legislation to ensure widespread adoption.
• Challenges include retrofitting existing urban infrastructure and funding large-scale projects.

Limitations:

• Even if fully implemented, unable to prevent extreme events like recent floods.
  • Example: Zhengzhou allocated funds but faced overwhelming rainfall in 2021.
• Sponge City infrastructure can handle limited rainfall, around 200 mm per day.
• Extreme rainfall events exceed the capacity of sponge city measures.
• Limits of sponge cities underscore the need for comprehensive flood management strategies.

Climate Change Impact:

• Climate change adds complexity to flood management.
• Areas like northern China experience heavier rainfall due to shifting climate patterns.
• Changing rainfall patterns challenge the effectiveness of existing drainage systems.
• Climate adaptation measures must align with evolving climate conditions.

Recent Floods and Statistics:

• Devastating floods hit China recently, causing deaths, damage, and questions about the initiative.
• July floods caused 142 deaths, destroyed 2,300 homes, and economic losses of $2.19 billion.
• 641 out of 654 cities are vulnerable to flooding and waterlogging according to 2018 data.

Sponge City Concept:

• Purpose: Manage urban water challenges with nature-based solutions.
• Approach: Permeable surfaces, green spaces, sustainable drainage systems.
• Features: Permeable pavements, green roofs, rain gardens, and wetland restoration.
• Integration: Balance development with ecology for sustainable water management.

Pros:

• Flood Mitigation: Reduces runoff, minimizes flooding.
• Water Quality: Natural filtration enhances water quality.
• Climate Resilience: Adapts to changing rainfall patterns.
• Ecosystem Benefits: Increases green spaces, and biodiversity.
• Community Engagement: Creates greener, livable urban environments.

Cons:

• Complex Implementation: Retrofitting existing areas can be costly.
• Limited Scalability: Not suitable for all densely built regions.
• Maintenance: Requires ongoing care of green spaces, and systems.
• Space Constraints: Urban density may limit sponge feature availability.
• Technical Expertise: Needs urban planning, hydrology knowledge.
• Extreme Rainfall: May be overwhelmed by intense rainfall events.

Future Trends:

• Smart Integration: Monitor, manage with technology.
• Nature-Based Infrastructure: Merge with traditional engineering.
• Ecosystem Services: Utilize for energy, carbon management.
• Global Collaboration: Share experiences for adaptable models.

Countries with Adoption:

• China: Pioneered “Sponge City” initiative.
• Singapore: “ABC Waters Program” for urban water bodies.
• USA: “Green City, Clean Waters” in Philadelphia.
• Australia: “Water Sensitive Urban Design” in Melbourne.
• Malaysia: “River of Life” project in Kuala Lumpur.
• India:  “Smart Cities Mission” promotes sustainable urbanization, and cities like Surat and Pune integrate permeable pavements and flood-resilient planning to manage water effectively.