Advanced drainage System in the Ancient Beijing
The flood problem in Beijing, Chinese capital situated away from coast and major rivers, becomes more severe in the recent decades.
The cause could be multifactorial: The expansion of the urban footprint, the impermeable road pavement, the lack of maintenance and repair to the underground drainage infrastructure, and the damage done to the natural and manmade water system that historically served as reservoir. All these contribute to the frequent flood in the modern Beijing.
But Beijing was not like this before, and is not everywhere in Beijing like this today.
In July 2012, a super storm lashed Beijing that saw part of the Chinese capital inundation with dozens of casualties recorded, but the Round City (Tuancheng) at the centre of the storm was not affected by the flood at all.
Beijing was constructed 600 years ago by the third Ming Emperor Yongle, based on the city planning model of old capital city Nanjing and the amendments made according to Beijing’s unique geographic setting, feng shui configuration and existing infrastructure condition.
When it came to the stormwater management, a comprehensive drainage system was set up right from the master plan stage.
In the inner city district, there were Inner City Moat, East Trench, West Trench and a water channel encircled the Forbidden City; in the outer city vicinity, Dragon Tassel Trench (longxugou) and Tiger Arch Trench (hufangqiao) along with Sanli River form a waterway network. All trenches were designed to allow the water naturally flow from higher terrain in the north towards the lower ground in the south, which reflects an advanced land survey technology, urban design skill and infrastructure construction quality.
Besides a highly effective drainage solution in the city’s microscope, most public buildings, including Altar of Heaven, Bell & Drum Terrace and various archways, have stormwater drainage pipes and gully pits installed, which efficiently prevented water from accumulating in the surrounding areas.