We're riding along on the crest of a wave!

Tai Wai, Shatin 1930s looking east

I’m Cassandra-like in this article. Hong Kong faces many threats, yet often overlooked is extreme weather events. These have the potential to do massive damage and even kill. Moreover, in our headlong rush to develop land, we may have made one threat much worse.

On 1st September 1937, an unnamed typhoon tracked westward over the top of Hong Kong Island. Wind speeds soon reached 125 mph. The storm was small, intense and nimble. The Observatory anemometer broke having exceeded its designed tolerance. Later assessments put the winds at up to 149 mph. 

Victoria Harbour, packed with ships, suffered the initial impact. Vessels dragged from their berths, crashed ashore. Captains gave up the battle to allow their boats to run aground. Some 600 ships report damage, as hundreds of crafts sunk. 

At the same time, a storm surge sent water crashing through Wanchai, Causeway Bay and Central. Basements flooded, as ground floor premises were overwhelmed. Food stored in waterlogged godowns are now beyond use, as streets turned into rivers. Only the steep terrain prevented further damage. 

As the storm tracked west, the back-end was to have a far more destructive effect. At around 1 am, the eye of the storm crossed to the Mainland, dragging behind it terrible winds and rain. Unfortunately, the height of the gale coincided with a high tide. The swollen waters of Mirs Bay pushed west with considerable force, swept up Starling Inlet, Tolo Harbour, and Tide Cove. 

Constrained by the terrain in the Tolo Channel, the surge gathered momentum. It stored energy. As it hit the shore, that energy was unleashed. A wave the height of two double-decker buses swept inland without mercy. The residents of Shatin and Tai Po had no warning. 

The area was much less populated than now. The Shatin valley, a narrow floodplain, hosted a farming community. Villages and hamlets sat in clusters. The Kowloon Canton Rail-line ran along the west-side following the route is uses today. There is no highrise, no concrete channels as the Shing Mun River weaved its way to the sea. No race-course existed, while Ma On Shan was a small community. The destructive wave charged inland. It devastated everything in its path.

All along the coast from Ma On Shan to Tai Po Market, roads, bridges and homes disappeared. The railway embankment swept away, then the rail tracks collapsed. At Tai Po Market 60 homes disappear with their occupants. The flood rolled to Tai Po Kau, over half a mile inland. It carried battered humans, cattle, pigs, dogs, ducks, and debris with it.

Estimates of the number killed vary from 10,000 to 12,000. And yet, this was not the first such surge. Similar events occurred in 1874, 1906 and 1923. 

The public laid the blame on the Observatory.  Working with rudimentary science, the Observatory's warning proved inadequate.  Gradually the significance of storm surge forecasting came to prominence. Indeed by 1975, it was essential. The development of new residential and industrial areas on reclaimed land increased the risks. New towns meant more folks were sitting in harm's way. 

In the 1970s the Observatory computerised the study of surges. Tide monitors, satellites and other technology fed data into the system. Modeling with computers means better predictions. The government then established a dedicated Storm Surge Unit in January 1978.  

Nonetheless, predicting the surge is one thing. It doesn’t address the question what should you tell people to do. What are the escape routes, where should people shelter and who is coordinating?
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Moreover, the scientists I’ve spoken with tell me we need to be worried. Modern developments reduced the capacity of Tolo Harbour to absorb a tidal surge. In fact, we’ve amplified the risk. The Plover Cove Dam constructed in 1968, took away space. The engineers understood this, although the link to a possible tidal surge didn’t register with the policymakers. 

Since the 1980s, developments in Shatin, Ma On Shan and Tai Po have encroached on Tolo Harbour. Reclamation and construction lowered the ability of the area to dissipate a tidal wave. The Science Park is sitting on reclaimed land, as are sections of the Tolo Highway. The small wetland area at Tai Po Kau, hemmed in by concrete, can't help absorb the impact. 

With the Shing Mun River fixed by embankments, it will act to funnel any surge inland. Research suggests that a 1937 level event taking place today could produce a wave three double-decker buses high. Amplified by the restricted space, the consequences are dire.

Pause and think about it. Imagine such a wave roaring down the Shatin valley. The first thing hit is the Marine Police Base at Ma Liu Shui. Next, it would smash through the Shatin Sewage Works picking up everything to carry it inland. A wave of toxic sewage is now thrusting inland. The Shatin Racecourse is under three feet of water. Walkers on the promenades swept away have no escape. The Tate’s Cairn Highway disappears as the surge presses through the ground floor of the Shatin Hospital.  

Shoreline properties at Siu Lek Yuen are flooded. Underground carparks fill with foul stinking water. The surge reaches Shek Mun. On it presses. Shatin City One residents get off lightly. The raised estate protected by its podium levels. Across the river, Wo Che and Lek Yuen Estates are not so lucky as ground floor flats are submerged. New Town Plaza and Sha Kok Estate are next. 

Finally, the wave barrels into the narrow streets of Tai Wai. Che Kung Temple is waterlogged. Meanwhile, power is failing as sub-stations shut down. Thousands trapped in lifts are unreachable by the Fire Services. With roads flooded, access is impossible. The sheer number of calls overwhelms the mobile telephone system, which shuts down.   

Shatin Police Station grinds to a halt with a flooded compound. Ma On Shan Police Station is higher and spared the worse. Tin Sum Police Station is likewise saved by its elevation, although operating on emergency power. 

Meanwhile, similar things are unfolding in Tai Po. The low lying industrial estate is awash. The gas plant enters automatic shut-down as fail-safe systems kick in. Parts of Tai Po Town centre are underwater. The East Rail and Ma On Shan lines come to a halt. 

Tragically residents in Providence Bay, next to the Science Park, pay a terrible price. Their waterfront homes take the full force of the surge. The ground floor flats submerge in water and debris. 

Across Shatin and Tai Po, thousands are dead. Many more injured. The receding waters leave behind a pile of untreated sewage, human remains and sludge. The risk of disease is high. Tolo Harbour filled with floating cars, bodies and assorted debris empties towards the sea. 

I’m sure these days plenty of warning would come before a surge. Thus hopefully avoiding much death and destruction. For that to happen a well-resourced, tested and executed plan must be in place.  While just under one million people are living in the Shatin, Ma On Shan and Tai Po area, not all are at risk. Many developments are on high ground and so unlikely to be directly affected. Although, they could have power outages, cut transports links and disruptions to the water supply. 

Of course, avoiding this is possible. The construction of a surge barrier across the Tolo Channel would protect the area. At its narrow point, the channel is about 1.5 km wide. A movable flood-barrier akin to the Thames Barrier should be technically feasible and indeed may be necessary as sea levels rise. 

In the interim, the government needs a robust evacuation plan. The quick extraction of citizens from low-lying vulnerable areas is crucial.  

There is no room for complacency. It’s happened before; it will happen again. Are we ready for this?

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Destroyed KCR line 1937

Shatin 1960

The Shatin Valley 1940s