Report No. : GEO Report No. 294

Report Title : Factual Report on Hong Kong Rainfall and Landslides in 2009 (2014), 76 p.

Author : C.L.H. Lam, J.W.C. Lau & H.W. Chan

Abstract

This report presents a summary of the factual information on rainfall and landslides in Hong Kong throughout 2009. 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 provided by the Agriculture, Fisheries and Conservation Department, Architectural Services Department, Drainage Services Department, Fire Services Department, Highways Department, Housing Department, Lands Department, Water Supplies Department, and the GEO's landslide investigation consultants, namely Fugro Scott Wilson Joint Venture and AECOM Asia Company Limited.

Rainfall recorded in 2009 at the HKO's Principal Raingauge at Tsim Sha Tsui amounted to 2,182.3 mm, which was about 8% below the mean rainfall of 2,382.7 mm recorded between 1971 and 2000. Two Red Rainstorm Warnings were issued on 4 June and 17 July 2009; and 20 Amber Rainstorm Warnings were issued between 5 March and 30 September 2009.

Two Landslip Warnings were issued on 19 July and 15 September 2009. A total of 102 incidents that occurred in 2009 were reported to the Government. Of these, 101 were classified as genuine landslides and two of them were designated as major failures (i.e. with a failure volume of 50 m3 or more, or where a fatality has occurred).

Ten landslides in 2009 resulted in notable consequences. Of these ten landslides, one led to temporary evacuation of a squatter dwelling. Two landslides resulted in temporary closure of roads and another seven resulted in temporary closure of pedestrian pavements, footpaths or access paths. In addition, four other landslides affected catchwaters, but none of them had any significant direct or indirect impact on the areas downhill of the catchwaters. No injury or fatality was reported as a result of the 2009 landslides.

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