Although chute aerators have been investigated experimentally by many researchers, only a few studies have been conducted on the comprehensive air–water flow properties of the lower jet downstream chute aerators. In this study, after eliminating the upper aeration of the jet, a complete characterization was recorded and presented for the distributions of air concentration, air–water velocity, and bubble frequency. Based on these extensive tests, a comprehensive equation to compute the air concentration distributions of each zone was presented. The velocity distribution had a shape similar to that of shear air–water flows; however, the quantitative parameters differ in each zone. In the cavity zone, the position of the maximum air bubble frequency was largely within a region of relatively high air concentration and gradually approached an equal air concentration of 0.50. The location of the maximum air bubble frequency was approximately the same as that of the section maximum air concentration at a section in the impact zone, but lower than that in the equilibrium zone. Self-similar relationships between the air concentration and bubble frequency were proposed for each zone.

Under the influence of extreme weather conditions or other unfavorable factors, if a dam break occurs in a mountain river, it will cause a great number of casualties and property losses in the affected downstream areas. Usually, early warning of the affected areas downstream of the dam depends mainly on qualitative evaluation and cannot be quantitatively evaluated. Based on the authors’ calculation of floods for many years, this study presents a quantitative assessment method for flood risk. The Ertan Hydropower Station in Southwest China and the flood-affected areas were chosen as the object of this study. Based on field surveys, research literature data, and the authors’ calculations, the basic data of the Ertan Hydropower Station and the calculation results of the dam break were obtained, and 35 representative flood-affected areas were selected to study risk assessment and early warning. The fuzzy analytic hierarchy process (FAHP) was used to build a mathematical model for quantitative analysis. The population, flood arrival time, flood level, evacuation time, and local GDP (Gross Domestic Product) were selected as five typical evaluation factors. Finally, this study calculated and counted the risk level of 35 representative flood-affected areas, and the study results were applied to Quxue and Guanmaozhou Hydropower Station.