Underground Stormwater Storage Prove Effective – Government Should Accelerate Flood Prevention Infrastructure

Hong Kong recently experienced a series of extreme weather events, including the arrival of a super typhoon and an exceptionally heavy rainstorm described as a "once-in-500-years" event. These caused the city’s flooding across different districts, cutting off roads, and widespread traffic disruptions. In response to the government's call for action, various sectors and community organizations worked together to help restore normal operations as quickly as possible.

Typhoons are common in Hong Kong; however, it is rare for heavy rains and strong winds to cause consecutive serve disasters. This recent event has raised public concern about the city's flood prevention measures, with worries that the current stormwater storage system may not be effective enough to cope with the increasingly frequent extreme weather conditions.

In fact, the HKSAR Government began drainage improvement works many years ago. We have also participated in numerous drainage projects, including construction of large stormwater storages , such as the Happy Valley Underground Stormwater Storage Tank, which integrated the use of Movable Weir and Supervisory Control and Data Acquisition (SCADA) system, the Anderson Road Quarry underground stormwater storage ,and the respective stormwater storage tanks in Tsim Sha Tsui and Sau Nga Road which have been undergoing construction.

Underground storage tanks can temporarily store part of the stormwater collected from the upstream catchment for attenuating the peak flow through the downstream stormwater drainage systems during heavy rainstorms. For instance, Happy Valley, located in a low-lying area with aging pipelines, had faced a high risk of flooding. In 2012, The Happy Valley Underground Stormwater Storage Scheme commenced, constructing an underground storage with a gigantic volume of 6,000 cubic meters where was equivalent to the total volume of 24 standard sized swimming pools. Together with pipeline improvement works in that area, the project has successfully alleviated flooding issues in Happy Valley.

Globally, we are facing a climate change crisis. Countries such as South Korea, Japan, and the United States have also experienced heavy rainfall in recent years, leading to severe flooding and landslides, resulting in significant casualties. Fortunately, the impact of the recent torrential rainfall in Hong Kong did not exert impactful harm to the city, and each stormwater storages have made the most impact. In 2010, the Geotechnical Engineering Office launched a rolling Landslip Prevention and Mitigation Programme (LPMitP) to reduce landslide risk from the impact of extreme weather. However, residents living in some low-lying areas without stormwater storage, such as Chai Wan and Wong Tai Sin, are still threatened by the high risk of flooding due to the poor performance of drainage system.

I believe that with this memorable event, government officials have learned a lesson and will continue to explore improvement strategies to enhance drainage capacity and efficacy , such as by spotting out the blind spots of the current system,  Moreover, the government shall review the rainstorms and typhoons’ emergency response system and provide early alert to citizens before extreme weather conditions have developed maturely, making sure they evacuate on time and therefore reducing the risk of injury, casualty and property lost.