Extensive flooding in Shenzhen River and Ma Tso Lung areas, Sheung Shui, during Typhoon Dot in 1993	The completed Shenzhen River Regulation Project Stages I & II

Hong Kong is on the common track of tropical cyclones and can experience very heavy rainstorms at times. The annual average rainfall is about 2200 millimeters, one of the highest among the cities in the Pacific Rim. During these rainstorms, flooding in the rural low-lying areas and natural flood-plains in the northern part of the territory and in parts of the older urban areas will not be uncommon. To quote an example, the heavy rain brought about by Typhoon Dot in 1993 flooded over 1,000 hectares of land.

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Extensive flooding in Ho Sheung Heung, Sheung Shui, during Typhoon Dot in 1993	Ho Sheung Heung during the rainstorm on 9 Aug 2002, after the completion of the river training works for Sheung Yue River

Over the years, intensive development associated with urban development has taken place in the flood-plains. This has turned large areas of natural ground into hard paved areas and rainwater, which formerly was retained, now quickly becomes surface flows. The extension of built-up areas in close proximity to the major watercourses has also reduced their flood carrying capacity and has further aggravated the flooding problem.

In the old urban areas, flooding occurs because stormwater drainage systems built decades ago to the older protection standards are becoming inadequate due to aging of the systems and the expansion of the built-up urban area.

Flooding in Mong Kok, 1997	A flood storage tank has been constructed under Tai Hang Tung Recreation Ground to solve the flooding problem in Mong Kok

* Aerial flood photographs reproduced with permission of The Director of Lands, Government of Hong Kong SAR.  Licence No. G08/2003