C. O.
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17745
Surface Drainage in Hongkong.
Rece
Nullah Training.
IRES 18 MAY 07
Nullah-training in Hongkong has been almost entirely confined to the area occupied by the City of Victoria. The City, of which a plan is attached, is built on the slopes of a range of hills which rises steeply to a maximum height of 1,800 feet above sea-level. The base of the hills was at one time practically washed by the sea but, as the result of successive reclamations, a considerable area of flat land has now been interposed between them. The Colony being subject to severe rainstorms, over 3 inches per hour at times, and the hills being steep and generally of a rocky nature, it has been found necessary to construct a very extensive system of channels and culverts to intercept and discharge safely into the harbour the great volumes of storm-water flowing off them at such times.
Practically all the channels which traverse the more densely populated portions of the City are entirely enclosed, forming underground culverts, and it is only in the less densely populated parts, which occur generally on the upper levels, that the channels are open.
It is unnecessary to refer here to the culverts nor are they shown on the plan of the City, but the open channels which have been trained are indicated on it by blue and red lines. The blue lines show the work done prior to the end of 1900 and the red lines that done after that date.
The channels, or nullahs, as they are termed locally, are of varying dimensions, extending up to 234 feet in width by 12 feet in depth. A drawing showing a number of sections of them is enclosed as well as 4 photographs.