Building a Flood-Resilient Hong Kong: Lessons from the Frontline

Hong Kong is one of the most densely populated coastal cities in the world, and its Drainage Services Department (DSD) manages an infrastructure network to match: nearly 5,000 kilometers of pipeline, 370 drainage facilities, and a sewerage system serving 94 percent of the population. On this episode of Exec Exchange, host Piers Clark speaks with Ringo Mok, Director of the DSD, about why infrastructure scale alone cannot guarantee flood resilience, and what can.

A City That Can No Longer Build Its Way Out of Flooding

Mok is direct about the limits of infrastructure. Hong Kong recorded roughly 2,550 millimeters of rainfall last year, about 5 percent above normal, and extreme weather events are arriving faster than design standards anticipated. His conclusion: bigger drains and higher walls will never fully eliminate flood risk in a city as compact, coastal, and hilly as Hong Kong.

The ARM Framework: Adaptation, Resilience, Management

Drawing on economist Elinor Ostrom’s work on polycentric governance of common-pool resources, Mok’s department built what it calls the “Resilience Commons,” organized around three pillars. Adaptation pairs with public awareness: the government builds infrastructure while educating citizens on realistic protection levels rather than promising zero flooding. Resilience pairs with acknowledgment: since many flooding incidents stem from blocked drains rather than capacity shortfalls, businesses and property managers must actively maintain shared infrastructure. Management pairs with action: real-time monitoring, pre-planned deployment measures, and public tools like wading-line markings and a 24-hour flooding hotline.

Putting the Framework to the Test: Super Typhoon Ragasa

The ARM framework faced its sharpest test during Super Typhoon Ragasa in 2025. A week ahead of landfall, DSD’s flood risk prediction model identified 11 high-risk areas. Contractors distributed sandbags and erected barriers, 14 pumping robots were pre-positioned, and over 200 emergency response teams were placed on standby. When the storm escalated overnight, causing severe storm surge, the department received more than 500 service calls and confirmed 24 flooding cases, most of which were cleared within one to two hours. Hong Kong resumed normal life the following day.

The Long-Term Lesson

For Mok, the real measure of resilience is not the absence of flooding but the speed and coordination of recovery, and that depends on shared responsibility between government and communities being built well before the storm arrives.

Resilience, Mok argues, is not built by drains alone. It is built by government and communities acting together, well before the next storm arrives.