Dhaka, the overburdened capital city of Bangladesh, faces severe water management challenges, such as flood and waterlogging, especially during the monsoon season. The concept of a Sponge City offers a promising solution to combat these issues. This article delves into the details of the Sponge City concept, its successful implementation in other countries, and why it should be adopted in Dhaka. The Concept of Sponge City Kongjian Yu, a Chinese landscape architect and professor, pioneered the concept of the Sponge City. A Sponge City is designed to passively absorb, clean, and utilize rainwater in an eco-friendly manner by reducing polluted runoff. Essentially, it uses landscapes and infrastructure to preserve water and promote natural retention, infiltration, and purification of drainage. Key techniques associated with a Sponge City include: ·        Rainwater Harvesting: Collecting and storing rainwater for various uses. ·        Permeable Roads: Roads designed to allow water to seep through and be absorbed into the ground. ·        Terrace Gardens: Green roofs that help absorb rainwater and reduce runoff. ·        Green Spaces and Waterbodies: Parks, ponds, and lakes that act as natural water retention and purification systems. Proper implementation of these techniques can minimize the frequency and severity of floods, improve water quality, and reduce individual water usage. Green roofs, for example, enhance the quality of life by improving air quality and mitigating urban heat islands. Overall, a Sponge City can efficiently handle excess water during heavy rains and reuse it during dry periods to combat water shortages. Read more: How to Build Dhaka as a Water Wise City How China Adopted the Concept of Sponge City In 2013, the Chinese Central Government adopted Professor Kongjian Yu’s Sponge City concept, implementing it across 30 cities. Following successful trials, China aims to transform 80% of urban areas into “sponges” by 2030. The core principle of Chinese Sponge Cities is to give water enough room and time to drain into the soil rather than quickly channeling it into large dams. Instead of fast-flowing water channels, these cities employ meandering streams without concrete walls, allowing water to spread out during heavy rains. Yu asserts that replacing concrete infrastructure with natural systems can save lives. In Sponge City designs, natural waterways and permeable soils clean water and reduce pollution. Evaporated rainwater cools the city, while collected rainwater is used for irrigation, street cleaning, and other purposes, reducing the reliance on tap water. The vegetation, sediments, and microorganisms in Sponge City water systems lessen the burden on energy-intensive urban water filtration facilities. As climate change brings unpredictable rainfall, Sponge City buildings are constructed to accommodate rising water levels during floods. Compared to traditional gray infrastructure, Sponge City designs require less energy for maintenance. They reduce the load on water treatment facilities, decrease the need for air conditioning due to heat reduction effects, and use fewer resources like concrete. Additionally, vast green spaces absorb carbon dioxide and air pollutants, promote biodiversity, and provide recreational areas for residents. China has also implemented Sponge City concepts in Ningbo, a coastal city 150 km south of Shanghai. Ningbo’s sponge infrastructure includes an eco-corridor on a post-industrial site, where channeled water flows through meandering waterways surrounded by native plants. This blue space improves water quality, provides habitat for flora and fauna, and reduces the risk of waterlogging. Read more: What Can Dhaka Learn from the Smart City Singapore Application of Sponge City Model in Copenhagen Copenhagen adopted the Sponge City concept in its Cloudburst Master Plan, developed in 2012. This plan redesigns approximately 250 public spaces to retain or redirect floodwaters, including parks, playgrounds, and the Sankt Kjelds Plads roundabout. Green spaces like trees, shrubs, and soil naturally retain water and direct it to non-destructive areas.