Report No. : GEO Report No. 330

Report Title : Factual Report on Hong Kong Rainfall and Landslides in 2015 (2017), 77 p.

Author : R.C.T. Wai, R.W.H. Lee & V.W.W. Kong

Abstract

This report presents a summary of the factual information on rainfall and landslides in Hong Kong throughout 2015. Rainfall information was obtained from the Hong Kong Observatory (HKO) to supplement the information available in the Geotechnical Engineering Office (GEO). Details of the landslides were obtained from records of landslide incidents reported to the GEO. Supplementary information was collected from the Agriculture, Fisheries and Conservation Department, Architectural Services Department, Drainage Services Department, Highways Department, Housing Department, Lands Department, Water Supplies Department, and the GEO's landslide investigation consultants, namely Fugro ACSL Joint Venture and Halcrow China Limited.

Rainfall recorded in 2015 at the HKO's Principal Raingauge at Tsim Sha Tsui amounted to 1,874.5 mm, a deficit of 22 percent comparing to the mean rainfall of 2,398.5 mm between 1981 and 2010. One Black Rainstorm Warning was issued on 26 May 2015. Four Red Rainstorm Warnings and 21 Amber Rainstorm Warnings were issued between 20 May and 15 August 2015, and between 11 May and 4 October 2015 respectively.

Two Landslip Warnings were issued on 20 May and 22 July 2015. A total of 182 incidents were reported to the Government in 2015. Of these, 161 were classified as genuine landslides and ten of them were designated as major failure (i.e. with a failure volume of 50 m3 or more, or where a fatality has occurred).

There were 12 landslides in 2015 with notable consequences. Of these landslides, one led to minor injuries of four persons due to a fallen rock block punching through the window of a tour bus and one led to permanent evacuation of a squatter dwelling. The remaining ten landslides resulted in temporary closure of roads. Other landslides in 2015 affected open areas, footpaths or minor access roads, construction site and catchwaters without any significant direct or indirect consequence. No fatality was reported as a result of the 2015 landslides.

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