This two-volume set, with cd-rom, comprises the Proceedings of the 4th International Symposium on Environmental Hydraulics & the 14th Congress of Asia and Pacific Division, International Association of Hydraulic Engineering and Research held in December 2004 in Hong Kong. Volume 1 covers the selected papers presented at the 4th International Symposium, while Volume 2 features the advances outlined in papers from the 14th IAHR-APD Congress. Both volumes will be of interest to practitioners and researchers in sustainable water management and environmental science.