Hydraulic research is developing beyond traditional civil engineering to satisfy increasing demands in natural hazards, structural safety assessment and environmental research. Hydraulic Engineering IV contains 38 technical papers presented at the 4th International Technical Conference on Hydraulic Engineering (CHE 2016, Hong Kong, 16–17 July 2016), including the 5th International Workshop on Environment and Safety Engineering (WESE 2016) and the 2nd International Structural and Civil Engineering Workshop (SCEW 2016). The sections on hydraulic engineering mainly focus on river engineering and sediment transport, flood hazards and innovative control measures, complex flow modelling, dam safety, slope stability, environmental hydraulics and hydrology, while the contributions related to environmental issues focus on environmental prediction and control techniques in environmental geoscience, water pollution and ecosystem degradation, applied meteorology, coastal engineering, safety engineering and environmental pollution control. The sections on structural and civil engineering mainly focus on underground engineering, construction engineering, road and bridge engineering. Hydraulic Engineering IV will of interest to academics and engineering involved in Hydraulic Engineering and Civil Engineering.