University of Bristol - Historical Photographs of China reference number: NA16-084. Image from an album in The National Archives referenced as ‘HONG KONG 3. Views of Hong Kong from the 1860s to the 1920s' (CO 1069-446). According to the Hong Kong Observatory, the highest record of daily rainfall ever recorded in Hong Kong, is 534.1 millimetres - the 19th July 1926 rainstorm. See https://www.hko.gov.hk/en/blog/00000135.htm. See NA16-083, NA16-085 and NA16-086 (more photographs of the effects of the 1926 rainstorm on Hill Road).
Damage caused by the 19th July 1926 rainstorm, Hill Road, Hong Kong
Black and white photograph
The National Archives, London