The widespread implementation of flood protection measures in the past has transformed rivers into concretised channels, thereby eradicating ecological resilience. Moreover, untreated sewage flowing into these waterways is a serious health risk. The proposal by Beijing’s landscape practice Turenscape effectively tackles these problems in a holistic manner.

Through a step-by-step approach, the project transforms an inefficient drainage system into a green oasis. This project and its large-scale implementation are based on Turenscape’s concept of ‘sponge cities’, a measure developed to address and prevent urban flooding due to erratic rainfall patterns, attributed to climate change.

Transforming the gray into green

The existing channel is redesigned into a wide terraced wetland by removing concrete barriers and terracing the slope. Wastewater flowing into the waterway is cleansed biologically, allowing adjacent green spaces to be fertilized and irrigated.

The approach here builds on results from past experiments. Tests showed conclusively that 10 km2 of constructed wetland can cleanse 0.8 m3 of wastewater from grade V to III. The treatment slows down the speed of surface flows, increases detention and improves flood resiliency by 36%. It also saves 70% of energy that would otherwise have been used for mechanical treatment.