258
17. Although more or less damage occurred in almost every street and road in the Colony, the chief scenes of disaster were (1) the Albany Nullah, froin its commencement downwards (2) the Glenealy Nullah (marked respectively 4. and B. on plan) and (3) the heavy landslips which having their origin in the steep slopes above the Tytam Aqueduct, swept down the mountain side, carrying away the masonry of the Aqueduct itself in three places. In the case of the heaviest of these slips, the torrent carried the debris straight through the Public Cemetery, and landed the greater part on the race-course in the Happy Valley below. I propose in the first place to describe these principal accidents with some amount of detail, and for further particulars, and a full description of damage out- side the City and in Kowloon I beg to refer to Mr. COOPER's reports.†
Damage in the Albany or Military Nullah.
18. I have already alluded to the very serious damage which occurred on the morning of the 29th May to the service tank and filter beds of the Tytam Water-works, situated at C. on plan. On further investigation the cause was obvious. Excavations on a large scale were carried on during the past year in preparing a site for a house on the summit of the ridge above the service tank (at Ď. on plan, Rural Building Lot No. 7.). A large portion of the debris was deposited on a very steep slope immediately below the house. On the morning of the 29th (I am informed at 11.40 A.M.) a great mass of this spoil bank, amounting at the lowest estimate to 10,000 tons, became detached and was precipitated down the ravine. This mass started from an elevation of about 1,400 feet above sea level, and must have travelled with fearful velocity down slopes varying from 1 to 1, to 3 to 1, until its course was arrested by the obstruction formed by the service tank which had been constructed across the bed of the valley, a passage for storm water being provided by means of a great culvert or tunnel, carried under the bed of the reservoir or service tank. The distance traversed horizontally by the avalanche before its course was arrested was about 2,200 feet the fall vertically was about 1,000 feet. It naturally swept everything before it, clearing a passage through pine woods and scrub, from 150 to 200 feet in width and leaving the hill side, previously covered with luxuriant vegetation, as bare as a ploughed field. Huge boulders strewn in the bed of the nullahs, and on the mountain side, were swept down, and it was one of these measuring 350 cubic feet and weighing about 25 tons which effectually blocked the tunnel mouth.
·
19. At about one-third of its downward course, the path of the avalanche crossed the line of the tramway which connects the City with the Peak district. The tramway, including two bridges and other works, was swept clean away for a length of about 100 yards, and the rails and girders were twisted and contorted in a very remarkable manner. The cars could only have completed their last journey a few minutes before the catastrophe occurred. The greater part of the ironwork was subsequently recovered from the debris lodged on the upstream side of the service tank. Photograph No. 1 gives some idea of the course' of the avalanche.
4.
20. At the service tank itself this vast mass of rocks and earth first filled up the bed of the valley above the tank to the level of some 20 feet above the coping. It would then appear that the rush of water down. the nullah burst this temporary obstruction, and caused a great wave to sweep over the service tank and some of the filter beds. To this great and sudden rush of water may be attributed much of the damage sustained by the Bowen and Garden Roads, and the earthen embank- ment outside the masonry walls, on the down stream side of the tank and filter beds.
21. The yet heavier rainfall during the night and early morning of the 30th, caused a very heavy rush of water across the service tank and over the wall on the north or down stream side which had now to serve as an overfall or weir a purpose for which, it is hardly necessary to observe, it was not designed. This great flood brought down with it enormous quantities of sand and other material. During the 29th and 30th, about 18,000 cubic yards of earth were washed away from the slopes of the service tank and filter beds, and probably an equal quantity from the banks of the nullah below the tank, the bed of which has in consequence been greatly enlarged. The rush of water also carried away the bridge over the nullah on the Kennedy Road. During the night of the 29th and 30th, a formidable slip had occurred in the lower part of the nullah. A mass of earth fell from the cliff at the north west angle of the Head Quarter House, on to the open space east of the Officer's quarters at the Murray Barracks (at E. on plan). This dammed the valley, the large open masonry conduit 22 feet wide and 12 feet deep was filled up, and the flood of water carrying mud and sand spread along the Queen's Road right and left, flooding the ground floors of the barrack rooms, and leaving a solid deposit, consisting chiefly of clean quartz sand, on the roads and barrack yards adjoining, to a depth of from two to four feet. From 15,000 to 20,000 cubic yards of debris were here deposited, and a far larger quantity was carried into the Harbour, and formed a formidable bank at the mouth of the nullah. The effects of the flood in the neighbourhood of the Murray Barracks are shewn in photograph No. 3.
* Photograph No. 2 shews damage below service tank.
+ Not printed.