SPONGE CITY
WHY IN NEWS ?
- Recently, China has been hit by devastating floods in recent weeks, inundating cities and causing deaths and infrastructural damage.
WHAT ARE SPONGE CITIES ?
- A sponge city is a new urban construction model for flood management, strengthening ecological infrastructure and drainage systems.
- It can alleviate urban flooding, water resources shortage, and the urban heat island effect and improve the ecological environment and biodiversity by absorbing and capturing rain water.
- Rain water harvested can be repurposed for irrigation and for home use.
- It is a form of a sustainable drainage system on an urban scale and beyond.
- Sponge city policies are a set of nature based solutions that use natural landscapes to catch, store and clean water.
OBJECTIVES OF SPONGE CITIES:
There are three main facets to developing such systems: protecting the original urban ecosystem, ecological restoration, and low-impact development.
- Protection focuses on the city’s original ecologically sensitive areas, such as rivers, lakes, and ditches. Natural vegetation, soil, and microorganisms are used to gradually treat the aquatic environment and restore the damaged urban ecosystem.
- Restoration measures include identifying ecological patches, constructing ecological corridors, strengthening the connections between the patches, forming a network, and delineating the blue and green lines to restore the aquatic ecological environment.
- Mandatory measures apply to urban roads, urban green spaces, urban water systems, residential areas, and specific buildings to protect ecological patches, maintain their storage capacity, strengthen source control, and form ecological sponges of different scales.
CHINA’S SPONGE CITIES:
- China has long sought to improve the way it handles extreme weather, and make highly populated cities less vulnerable to flooding and drought.
- The “sponge city” initiative was designed to make greater use of lower-impact “nature-based solutions” to better distribute water and improve drainage and storage.
- Those solutions included the use of permeable asphalt, the construction of new canals and ponds and also the restoration of wetlands, which would not only ease waterlogging, but also improve the urban environment.
- Breakneck urbanisation has encased vast stretches of land in impermeable concrete, often along banks of major rivers that traditionally served as flood plains.
- With wetlands paved over and nowhere for surplus water to settle, waterlogging and flooding was commonplace.
- According to 2018 data, 641 out of 654 large- and medium-sized cities in China were vulnerable to flooding and waterlogging, with 180 facing flood risks every year.
CHALLENGES WITH CHINESE SPONGE CITIES:
- A total of 30 pilot sponge cities were selected in 2015 and 2016. By last year, only 64 of China’s 654 cities had produced legislation to implement sponge city guidelines.
- Zhengzhou in Henan province was one of the most enthusiastic pioneers of sponge city construction, allocating nearly 60 billion yuan to the programme from 2016 to 2021.
- But it was unable to deal with its heaviest rainfall in history in 2021.
- Experts believe sponge city infrastructure can only handle no more than 200 millimetres (7.9 inches) of rain per day.
- At the height of the rainstorms that lashed Beijing at the end of July, rainfall at one station reached 745 millimetres over three and a half days.
- In July 2021, Zhengzhou saw rainfall in excess of 200 mm in just one hour.
SYLLABUS: PRELIMS, CURRENT AFFAIRS
