By D M Wood, Cambridge University
This paper was first published in GE’s January 1981 issue
At about 9pm on June 18, 1972, after a period of heavy rainfall, a hillside above Po Shan Road, in the popular —though by Hong Kong standards not particularly populous —Mid-Levels area on Hong Kong Island collapsed, taking with it a 13-storey apartment block and killing 67 people. An eye witness described the block toppling before breaking up “like a man kneeling, then falling forward”.
On the same day a man-made slope of filled material at Sau Mau Ping in one of the newer housing estates to the east of Kowloon also collapsed forming an Aberfan-like flowslide which killed 71 people when it engulfed a densely populated hutted resettlement area.
In a colony with, effectively, no elected government, soil landslides —particularly where there are many casualties— become political events. ln the early days of the colony’s existence a landslide might block a path or track temporarily,but pedestrians, coolies, rickshaws could rapidly establish a new route over or round the debris with minimal interruption to communications and daily life.
Now, with massive commercial dependence on rail and road traffic, nature is able with a very small number of carefully placed landslides, as in 1966, to sever all transport routes in the colony. Perhaps this disruption of the trading existence on which Hong Kong clearly thrives, rather than the loss of a few lives, provides the main incentive to try and bring the slopes under control. But also, particularly in a colony with no elected gctvernment, the effect on public relations of being seen to be doing something about landslip prevention is not insignificant.
Prevention of landslips by decree is a Canute-like operation; the soil does not know about decrees and is unlikely to respond favourably to them. However, governments can buy people and expertise, and pay consulting engineers and others to tiy and identify the particular causes of slope instability, and to make recommendations of appropriate remedial oi stabilising measures.