THROUGH-FLOW CHARACTERISTICS OF GRAVEL FILTER BED OF AN ACTUAL RIVER COURSE BASED ON NUMERICAL SIMULATION OF MIKE 21: A CASE STUDY OF ECOLOGICAL RESTORATION PROJECT IN A RIVER COURSE IN HANZHONG CITY

In order to explore the through-flow characteristics of gravel filter bed (GFB) in river water restoration, a river ecological restoration project in Hanzhong, Shaanxi Province, was taken as an objective case, and the hydrodynamic model of the river was constructed by using MIKE 21 software. By simulating the flow conditions of the main channel and GFB under the designed flow rate, the velocity and water level distribution of the channel were obtained, and the flow characteristics of gravel filter bed were calculated. The results showed that according to the distribution of flow, the water flow that entered GFB only accounted for (1.00±0.25)% of the designed flow in the river. Therefore, GFB played a limited role in river water restoration in practice. The study suggested that GFB built in a real river channel was a complex system with bypass system. So, hydraulic retention time, flow times of filter bed and flow capacity of river channel should be considered comprehensively in design, which had certain significance for the similar project cases.